# Content and Bioaccumulation of Nine Mineral Elements in Ten Mushroom Species of the GenusBoletus

Authors: Xue-Mei Wang; Ji Zhang; Tao Li; Yuan-Zhong Wang; Hong-Gao Liu
Journal: Journal of Analytical Methods in Chemistry
 (2015)

---

## Abstract

Concentrations and bioconcentration potential of nine elements (Ca, Cu, Fe, K, Mg, Mn, Na, P, and Zn) in ten species of wild edibleBoletus and the corresponding underlying soils were analyzed. The analyses were performed using inductively coupled plasma atomic emission spectrophotometer. Boletus showed relative abundant contents of P, K, Fe, Mg, Ca, and Na and less of Zn, Cu, and Mn. Caps compared to stalks were enriched in P, K, Cu, Mg, and Zn, while stalks were enriched in Mn. The elements such as P and K were accumulated (BCF
>
1), while Ca, Fe, Mg, Mn, and Na were excluded (BCF
<
1) in the fruiting bodies. The correlation analysis indicated high correlations between Cu, Mn, Ca, and Fe in the mushrooms as compared to the corresponding soils. Significant correlations were also obtained between Cu-P (r
=
0.775), Fe-P (r
=
0.728), and Zn-P (r
=
0.76) for caps and Cu-Mg (r
=
0.721), Fe-Mg (r
=
0.719), Zn-Mg (r
=
0.824), and Zn-P (r
=
0.818) for stalks. The results of this study imply that ability of fungi to accumulate elements from substrate could be influenced by mushroom species and underlying soil substrates.


---

## Body

## 1. Introduction

Mushrooms are traditionally recognized as a valued source of nutrients and a popular delicacy in many countries for their rich contents in proteins, essential minerals, and low energy levels [1]. Edible wild-grown mushrooms consumption has been preferred to cultivated species for their indisputable flavor, texture, and medicinal properties [2, 3]. Proteins of wild edible mushrooms are usually high, commonly ranging between 10% and 60%, which were calculated using the conversion factor of 4.38 [1]. Mushroom gathering has been a very popular leisure and commercial activity in many European and Asian countries [4].Macromycetes in nature play a major role in biogeochemical transformation of macro- and microelements essential to humans [5]. Wild mushrooms can absorb large amounts of water and minerals within a relatively short period due to large area of mycelium overgrowing the surface layer of soil [6]. Abundance of minerals such as P, K, Ca, Mg, Na, Fe, Mn, Zn, and Cu desired in human nutrition has been reported in edible wild-grown mushrooms; meanwhile, undesired high levels of toxic elements including As, Hg, Cd, and Pb were also found in previous studies [5]. Bioconcentration factor (BCF) is the ratio of the element content in fruiting body (cap or stalk) to the content in underlying substrate, which can express the ability of fungi to accumulate elements from substrate [7]. If BCF exceeds unity (BCF > 1) it indicates the accumulation of elements in fungus, and if BCF is below unity (BCF < 1) it excludes bioaccumulation [8]. Bioaccumulation capacity of mushroom is usually affected by fungal lifestyle, age of fruiting body, specific species and element, and environment such as pH, organic matter, and pollution [5].Rich resources of wild edible fungi are distributed in Yunnan province (southwest of China) due to the mild and rainy climate. Laterite, lateritic red loam, red soil, yellow soil, and brown soil are the main agrotypes in Yunnan [9]. Contents of elements such as Cu, Fe, Pb, Cd, Co, Se, Ni, V, Tl, Sc, and Ti in soil are rather high, which would be the primary sources of elements to fungi [10]. More than 880 species of wild-grown mushrooms were identified as edible in Yunnan province, which account for 80% in China and 40% in the world [11]. Export volume of wild edible mushrooms in Yunnan was 105000 and 135000 tons, and the exports were 1.21 and 1.43 million dollars in 2010 and 2011, respectively. Species of the genusBoletus andTricholoma matsutake are the main export varieties, which account for 90% of the total export in Yunnan [12].Species of the genusBoletus are a popular food throughout the world because of their particular aroma, sensory qualities, texture, and biologically active compounds. Flavor of the favorite dried species such asBoletus edulis,Boletus aereus, andBoletus badius includes odor and marvelous taste of nuttiness, earthiness, and meatiness [13]. 199 species of Boletales were identified as edible in China, among which 144 species were distributed in Yunnan province [14].Boletus is abundant in proteins, carbohydrates, vitamins, and essential elements required in the human body. Furthermore, its history of traditional use in oriental therapies and modern clinical practice has been reported such as use as for its anti-inflammatory, antimicrobial, antioxidant, antiviral, antitumor, and immunomodulatory activities and its use for reduction of blood glucose levels [15]. However, species such asBoletus edulis,Boletus badius,Boletus griseus, andBoletus pinophilus contained high contents of toxic Cd, Hg, As, and Pb [5, 16, 17]. Also undesired Ag and Sb can be elevated in some wild-grown mushrooms [18, 19].There was little information available about bioaccumulation ability of elements inBoletus family in China. Since these mushrooms have been traditionally used for consumption by local people and trading, the aim of this study was to determine the contents of nine elements (Ca, Cu, Fe, K, Mg, Mn, Na, P, and Zn) in ten species of edibleBoletus and the underlying soil to investigate the relationship between fruiting body and habitat.


## 2. Materials and Methods

### 2.1. Sampling

Mature fruiting bodies of ten edible species of the genusBoletus were collected from Yunnan province (southwest of China) during summer and autumn in 2012. The species, habitat, and number of fruiting bodies are given in Table 1. The underlying surface layers (0 to 10 cm) were collected after removing the superficial layer of litter and organic detritus.Table 1
Families, habitat, and number of analyzed fruiting bodies.
Species
Habitat
Number
Boletus speciosus Frost
On mixed woods ground
10
Boletus griseusFrost
On needles, oak, and chestnut forest ground
10
Boletus luridusSchaeff.
On broadleaf or mixed woods ground
8
Boletus umbriniporus Hongo
On forest ground
8
Boletus tomentipes Earle
On needles and broadleaf forest ground
7
Boletus edulis Bull.
On mixed coniferous and broadleaf forest ground
10
Boletus pallidus Frost
On shaw ground
9
Boletus brunneissimus W.F. Chiu
On mixed pine tree and katue forest ground
9
Boletus rubellusKrombh.
On broadleaf or mixed woods ground
7
Boletus aereusBull.
On oak forest ground
7Fresh fruiting bodies ofBoletus were cleaned from plant and substrate debris with a plastic knife and divided into two parts (caps and stalk) and then washed with deionized water. Each sample was dried in an electrically heated oven at 65°C to constant weight. Dried samples were pulverized with laboratory mill and kept in sealed polyethylene bags in dry conditions. Substrate samples were air-dried at room temperature for several weeks and passed through a 100-mesh sieve.


### 2.2. Digestion Process

Dried mushroom samples were weighed as 0.3 g accurately and placed into the polytetrafluoroethylene (PTFE) pressure vessels. 4 mL HNO3 (65%) and 2 mL H2O2 (30%) were added to the vessel and digested under pressure in an automatic microwave digestion system, Ethos One (Milestone, Italy). The extract was further diluted to 25 mL using deionized water.Soil samples (0.1 g) were placed into the polytetrafluoroethylene beaker and digested and mixed with 6 mL HNO3 (65%) and 1 mL HClO4 (72%) on an electric hot plate at 170°C, removing and cooling the samples when they turned into paste. Then the paste was dissolved in 10 mL HF (40%) and 0.5 mL HClO4 (72%) and heated again at 210~220°C until the acid evaporated completely. Further, 10 mL HCl (38%) was added and heated until dissolved and diluted with distilled water up to 25 mL.


### 2.3. Analytical Determination

All elements (Ca, Cu, Fe, K, Mg, Mn, Na, P, and Zn) contents in dry weight (dw) of mushrooms and soils samples were determined using inductively coupled plasma atomic emission spectrophotometer (ICPE-9000, Shimadzu, Japan). The repeatability for all determined elements was less than 5%. Limits of quantitation (LOQ) for Ca, Cu, Fe, K, Mg, Mn, Na, P, and Zn were 0.04, 0.17, 0.18, 2.16, 0.04, 0.01, 1.53, 0.44, and 0.05 mg/kg dw, respectively. The efficiency of the process was validated with 94–107% recovery success using certified reference materials, namely, tea leaves (GBW07605) and soils (GBW07406), both produced by the Institute of Geophysical and Geochemical Exploration in Beijing, China.


## 2.1. Sampling

Mature fruiting bodies of ten edible species of the genusBoletus were collected from Yunnan province (southwest of China) during summer and autumn in 2012. The species, habitat, and number of fruiting bodies are given in Table 1. The underlying surface layers (0 to 10 cm) were collected after removing the superficial layer of litter and organic detritus.Table 1
Families, habitat, and number of analyzed fruiting bodies.
Species
Habitat
Number
Boletus speciosus Frost
On mixed woods ground
10
Boletus griseusFrost
On needles, oak, and chestnut forest ground
10
Boletus luridusSchaeff.
On broadleaf or mixed woods ground
8
Boletus umbriniporus Hongo
On forest ground
8
Boletus tomentipes Earle
On needles and broadleaf forest ground
7
Boletus edulis Bull.
On mixed coniferous and broadleaf forest ground
10
Boletus pallidus Frost
On shaw ground
9
Boletus brunneissimus W.F. Chiu
On mixed pine tree and katue forest ground
9
Boletus rubellusKrombh.
On broadleaf or mixed woods ground
7
Boletus aereusBull.
On oak forest ground
7Fresh fruiting bodies ofBoletus were cleaned from plant and substrate debris with a plastic knife and divided into two parts (caps and stalk) and then washed with deionized water. Each sample was dried in an electrically heated oven at 65°C to constant weight. Dried samples were pulverized with laboratory mill and kept in sealed polyethylene bags in dry conditions. Substrate samples were air-dried at room temperature for several weeks and passed through a 100-mesh sieve.


## 2.2. Digestion Process

Dried mushroom samples were weighed as 0.3 g accurately and placed into the polytetrafluoroethylene (PTFE) pressure vessels. 4 mL HNO3 (65%) and 2 mL H2O2 (30%) were added to the vessel and digested under pressure in an automatic microwave digestion system, Ethos One (Milestone, Italy). The extract was further diluted to 25 mL using deionized water.Soil samples (0.1 g) were placed into the polytetrafluoroethylene beaker and digested and mixed with 6 mL HNO3 (65%) and 1 mL HClO4 (72%) on an electric hot plate at 170°C, removing and cooling the samples when they turned into paste. Then the paste was dissolved in 10 mL HF (40%) and 0.5 mL HClO4 (72%) and heated again at 210~220°C until the acid evaporated completely. Further, 10 mL HCl (38%) was added and heated until dissolved and diluted with distilled water up to 25 mL.


## 2.3. Analytical Determination

All elements (Ca, Cu, Fe, K, Mg, Mn, Na, P, and Zn) contents in dry weight (dw) of mushrooms and soils samples were determined using inductively coupled plasma atomic emission spectrophotometer (ICPE-9000, Shimadzu, Japan). The repeatability for all determined elements was less than 5%. Limits of quantitation (LOQ) for Ca, Cu, Fe, K, Mg, Mn, Na, P, and Zn were 0.04, 0.17, 0.18, 2.16, 0.04, 0.01, 1.53, 0.44, and 0.05 mg/kg dw, respectively. The efficiency of the process was validated with 94–107% recovery success using certified reference materials, namely, tea leaves (GBW07605) and soils (GBW07406), both produced by the Institute of Geophysical and Geochemical Exploration in Beijing, China.


## 3. Results and Discussion

### 3.1. Element Concentrations

The element contents in fruiting bodies ofBoletus (cap and stalk) and underlying soil samples are presented in Table 2. As previously reported, fruiting bodies ofBoletus can be considered as rich in P, K, Na, Ca, and Mg and also abundant in trace elements such as Cu, Zn, and Mn. Among the minerals determined in this study, K, P, Fe, Mg, and Ca exhibited higher concentrations than Na, Zn, Cu, and Mn, which is in accordance with the literature [7]. WhileBoletus collected from Yunnan contained lower levels of K, Na, Ca, Mg, Fe, and Mn than other reports [20], significant differences were obtained not only among variousBoletus species but also within different part of fruiting body (Table 2). Similarly to previous studies, the ranges of concentrations spread over one to two orders of magnitude often occurred [21, 22].Table 2
Elements content in the caps and stipes ofBoletus and underlying soil (mg/kg dw, mean, SD).
Species
Ca
Cu
Fe
K
Mg
Mn
Na
P
Zn
Boletus speciosus
Cap
172 ± 36
66 ± 12
1021 ± 216
9017 ± 453
909 ± 158
21 ± 6
130 ± 76
5612 ± 587
148 ± 25
Stipe
141 ± 91
22 ± 5
959 ± 232
6105 ± 829
504 ± 307
30 ± 2
118 ± 13
2218 ± 573
56 ± 26
Soil
449 ± 234
35 ± 21
20081 ± 3426
3169 ± 432
1134 ± 673
140 ± 32
876 ± 27
656 ± 32
63 ± 2
Boletus griseus
Cap
538 ± 56
40 ± 13
1166 ± 133
17310 ± 667
577 ± 54
48 ± 22
324 ± 26
7126 ± 334
205 ± 55
Stipe
512 ± 32
24 ± 6
1194 ± 244
15308 ± 565
407 ± 75
63 ± 22
226 ± 13
4789 ± 454
125 ± 52
Soil
1076 ± 32
39 ± 13
26989 ± 2411
5373 ± 3458
1169 ± 113
459 ± 89
1020 ± 675
1686 ± 242
113 ± 7
Boletus luridus
Cap
475 ± 29
65 ± 13
1600 ± 345
11206 ± 677
556 ± 81
67 ± 23
105 ± 12
6832 ± 565
131 ± 18
Stipe
395 ± 165
20 ± 12
1117 ± 212
7594 ± 434
340 ± 223
85 ± 21
90 ± 27
2742 ± 345
51 ± 23
Soil
2438 ± 341
54 ± 23
28210 ± 788
6665 ± 178
2694 ± 252
773 ± 95
2292 ± 321
1293 ± 132
87 ± 54
Boletus umbriniporus
Cap
166 ± 33
43 ± 11
747 ± 256
10740 ± 234
431 ± 56
21 ± 4
421 ± 67
5325 ± 453
90 ± 23
Stipe
95 ± 12
34 ± 13
357 ± 32
8360 ± 568
279 ± 32
26 ± 5
451 ± 134
2176 ± 234
33 ± 6
Soil
758 ± 54
26 ± 12
19966 ± 4663
5154 ± 126
990 ± 645
315 ± 13
2071 ± 234
1778 ± 543
110 ± 78
Boletus tomentipes
Cap
99 ± 45
48 ± 6
376 ± 32
11488 ± 345
386 ± 234
17 ± 2
170 ± 11
5155 ± 324
115 ± 45
Stipe
113 ± 34
28 ± 5
751 ± 65
10775 ± 454
314 ± 32
38 ± 3
107 ± 76
3089 ± 235
90 ± 6
Soil
1081 ± 38
53 ± 6
38286 ± 479
5761 ± 46
1118 ± 67
281 ± 37
681 ± 89
850 ± 46
108 ± 23
Boletus edulis
Cap
320 ± 26
51 ± 34
931 ± 82
9413 ± 567
429 ± 54
26 ± 11
191 ± 53
6615 ± 343
88 ± 4
Stipe
317 ± 33
32 ± 4
4200 ± 678
4865 ± 245
297 ± 65
70 ± 13
122 ± 23
2429 ± 545
41 ± 33
Soil
1624 ± 45
152 ± 20
52613 ± 656
8533 ± 234
3665 ± 867
945 ± 77
1972 ± 45
1495 ± 22
118 ± 67
Boletus pallidus
Cap
342 ± 234
78 ± 6
1475 ± 56
18968 ± 676
1239 ± 82
36 ± 2
601 ± 4
10611 ± 234
45 ± 76
Stipe
378 ± 56
39 ± 4
1823 ± 341
15325 ± 459
935 ± 240
39 ± 22
500 ± 345
5621 ± 248
37 ± 9
Soil
2624 ± 787
261 ± 55
83294 ± 676
3617 ± 89
1745 ± 456
1092 ± 88
1288 ± 67
1330 ± 234
396 ± 78
Boletus brunneissimus
Cap
669 ± 34
33 ± 23
741 ± 78
11757 ± 346
759 ± 21
29 ± 8
472 ± 44
4942 ± 986
167 ± 50
Stipe
154 ± 78
16 ± 4
702 ± 23
10320 ± 654
513 ± 78
38 ± 2
216 ± 56
2949 ± 873
88 ± 57
Soil
1879 ± 245
50 ± 14
32165 ± 343
6765 ± 652
1307 ± 45
744 ± 22
891 ± 454
2007 ± 13
145 ± 29
Boletus rubellus
Cap
285 ± 67
56 ± 34
1376 ± 46
11606 ± 428
773 ± 65
41 ± 16
203 ± 46
5888 ± 106
223 ± 54
Stipe
632 ± 35
35 ± 21
3488 ± 785
10732 ± 345
631 ± 76
71 ± 13
340 ± 78
4853 ± 906
131 ± 86
Soil
3289 ± 442
159 ± 45
57870 ± 466
5675 ± 545
1802 ± 42
682 ± 24
825 ± 74
2176 ± 346
251 ± 57
Boletus aereus
Cap
140 ± 21
61 ± 41
654 ± 45
11365 ± 343
758 ± 67
26 ± 3
546 ± 50
5467 ± 535
165 ± 24
Stipe
139 ± 6
37 ± 5
2323 ± 210
7905 ± 676
556 ± 35
77 ± 4
291 ± 65
2497 ± 342
75 ± 6
Soil
687 ± 43
60 ± 3
34440 ± 652
5675 ± 874
1535 ± 257
378 ± 35
2393 ± 256
695 ± 57
77 ± 20Among the mushroom species analyzed, the greatest contents of Cu, K, Mg, Na, and P were quantified in the caps and stalks ofBoletus pallidus, and Mn and Zn were found inBoletus luridus andBoletus rubellus. Highest Ca and Fe contents were found in the caps ofBoletus brunneissimus and stipes ofBoletus edulis, namely, 669 and 4200 mg/kg dw, respectively. In the study by Zhou and Yin (2008) [23],Boletus edulis showed higher contents of K, Na, Ca, Mg, and Fe thanBoletus speciosus andBoletus aereus. In our early study, values of 13.6, 121, 248, and 20.3 mg/kg dw for Cu, Fe, Mg, and Zn were determined inBoletus tomentipes, respectively, which are lower than the present results [24]. Similarly, contents of K, Ca, Fe, Mg, and Zn forBoletus speciosus andBoletus griseus collected from Yunnan province in 2009 were lower than the data in Table 2 [25].K contents in caps and stalks ofBoletus edulis (cap: 29000 mg/kg, stalk: 20000 mg/kg dw) andBoletus subtomentosus (cap: 46000 mg/kg, stalk: 43000 mg/kg dw) from Poland were much higher than the values in our study (cap: 9017–18968 mg/kg, stalk: 4865–15325 mg/kg dw) [8, 26]. P contents were found at the ranges of 4942–10611 mg/kg dw and 2176–5621 mg/kg dw for caps and stalks ofBoletus, respectively. Higher values were found to be 8700–16000 mg/kg dw in caps and 4100–7500 mg/kg dw in stalks ofMacrolepiota procera, and lower values of 640–4490 mg/kg dw were for the fruiting body of thirty macrofungi species from Turkey [27, 28].The range of Fe contents in this study was 376–1600 in caps and 357–4200 mg/kg dw in stalks, which are much higher than the values previously reported [8, 29]. Similar values were found to be 150–1741 mg/kg dw, and a particularly higher value was 11460 mg/kg dw forLepista nuda [30, 31]. Reported Ca contents inBoletus edulis,Boletus speciosus, andBoletus tomentipes were 913.9, 1147.6, and 1097.4 mg/kg dw, which are higher than the values observed in this study [32].Mg and Zn concentrations in differentBoletus were in the ranges of 386–1239 and 45–223 mg/kg dw for caps and 279–935 and 33–131 mg/kg dw for stalks, respectively, which coincide with the literature reports [5]. Cu and Mn contents inBoletus badius,Boletus luridus, andBoletus edulis were found to be lower than the results in our study, that is, 33–78 and 17–67 mg/kg dw for caps and 16–39 and 26–85 mg/kg dw for stalks, respectively [5, 33, 34]. Other species such asMacrolepiota procera andLepista nuda contained higher content of Cu (236.5 mg/kg dw) and Mn (480 mg/kg dw) [6, 31]. The range of Na contents in caps was 105–601 mg/kg dw and 90–500 mg/kg dw in stalks, which are lower than values in species such asBoletus subtomentosus (77–1200 mg/kg dw),Pleurotus ostreatus (220–1400 mg/kg dw), andAgaricus bisporus (16000–25000 mg/kg dw) [26, 35, 36].Uneven distribution of elements between caps and stalks is shown in Table2. The caps ofBoletus contained higher contents of K, P, Cu, Mg, and Zn and lower contents of Mn when compared to stalks. Reports also suggested similar results for these elements inBoletus edulis,Boletus subtomentosus, andBoletus scaber [26, 37, 38]. However, the contents of Ca, Fe, and Na between caps and stalks have no certain regularity (Table 2). Contents of Cu, P, and Zn in caps are approximately twice or even thrice higher than in stalks, and similar findings were obtained in the review of Falandysz and Borovička [5]. As can be seen from Table 2, both caps and stalks can be considered as abundant in P, K, Fe, Mg, Zn, and Ca, andBoletus could be considered potential dietary sources of these essential elements to humans.According to the EU Scientific Committee, 60 kg of body weight was used for intake calculations. For intake calculations, usually a 300 g portion of fresh mushrooms per meal is assumed, which contains 30 g of dry matter [39]. The elements intakes by a normal (60 kg) consumer in mgper serving for all studied fruiting bodies are presented in Table 3.Table 3
Daily metal intakes by a normal, 60 kg consumer in mg/serving.
Species
Ca
Cu
Fe
K
Mg
Mn
Na
P
Zn
Boletus speciosus
Cap
5.16 ± 1.08
1.98 ± 0.36
30.6 ± 6.48
271 ± 13.6
27.3 ± 4.74
0.63 ± 0.18
3.9 ± 2.28
168.4 ± 17.6
4.44 ± 0.75
Stipe
4.23 ± 2.73
0.66 ± 0.15
28.8 ± 6.96
183 ± 24.9
15.1 ± 9.21
0.9 ± 0.06
3.54 ± 0.39
66.5 ± 17.3
1.68 ± 0.78
Boletus griseus
Cap
16.1 ± 1.68
1.2 ± 0.39
35.0 ± 3.99
519 ± 20.0
17.3 ± 1.62
1.44 ± 0.66
9.72 ± 0.78
214 ± 10.0
6.15 ± 1.65
Stipe
15.4 ± 0.96
0.72 ± 0.18
35.8 ± 7.32
459 ± 17.0
12.2 ± 2.25
1.89 ± 0.66
6.78 ± 0.39
144 ± 13.6
3.75 ± 1.56
Boletus luridus
Cap
14.3 ± 0.87
1.95 ± 0.39
48 ± 10.4
336 ± 20.3
16.7 ± 21.43
2.01 ± 0.69
3.15 ± 0.36
205 ± 17.0
3.93 ± 0.54
Stipe
11.9 ± 4.95
0.6 ± 0.36
33.5 ± 6.36
228 ± 13.0
10.2 ± 6.69
2.55 ± 0.63
2.7 ± 0.81
82.3 ± 10.4
1.53 ± 0.69
Boletus umbriniporus
Cap
4.98 ± 0.99
1.29 ± 0.33
22.4 ± 7.68
322 ± 7.02
12.9 ± 1.68
0.63 ± 0.12
12.6 ± 2.01
160 ± 13.4
2.7 ± 0.69
Stipe
2.85 ± 0.36
1.02 ± 0.39
10.7 ± 0.96
251 ± 17.0
8.37 ± 0.96
0.78 ± 0.15
13.5 ± 4.02
65.3 ± 7.02
0.99 ± 0.18
Boletus tomentipes
Cap
2.97 ± 1.35
1.44 ± 0.18
11.3 ± 0.96
345 ± 10.4
11.6 ± 7.02
0.51 ± 0.06
5.1 ± 0.33
155 ± 9.72
3.45 ± 1.35
Stipe
3.39 ± 1.02
0.84 ± 0.15
22.5 ± 1.95
323 ± 13.6
9.42 ± 0.96
1.14 ± 0.09
3.21 ± 2.28
92.7 ± 7.05
2.7 ± 0.18
Boletus edulis
Cap
9.6 ± 0.78
1.53 ± 1.02
27.9 ± 2.46
282 ± 17.0
12.9 ± 1.62
0.78 ± 0.33
5.73 ± 1.59
198 ± 10.3
2.64 ± 0.12
Stipe
9.5 ± 0.99
0.96 ± 0.12
126 ± 20.3
146 ± 7.35
8.91 ± 1.95
2.1 ± 0.39
3.66 ± 0.69
72.9 ± 16.4
1.23 ± 0.99
Boletus pallidus
Cap
10.3 ± 7.02
2.34 ± 0.18
44.3 ± 1.68
569 ± 20.3
37.2 ± 2.46
1.08 ± 0.06
18.0 ± 0.12
318 ± 7.02
1.35 ± 2.28
Stipe
11.3 ± 1.68
1.17 ± 0.12
54.7 ± 10.2
460 ± 13.8
28.1 ± 7.2
1.17 ± 0.66
15 ± 10.4
168.6 ± 7.44
1.11 ± 0.27
Boletus brunneissimus
Cap
20.1 ± 1.02
0.99 ± 0.69
22.2 ± 2.34
353 ± 10.4
22.8 ± 0.63
0.87 ± 0.24
14.2 ± 1.32
148 ± 29.6
5.01 ± 1.5
Stipe
4.62 ± 2.34
0.48 ± 0.12
21.1 ± 0.69
310 ± 19.6
15.4 ± 2.34
1.14 ± 0.06
6.48 ± 1.68
88.5 ± 26.2
2.64 ± 1.71
Boletus rubellus
Cap
8.55 ± 2.01
1.68 ± 1.02
41.3 ± 1.38
348 ± 12.8
23.2 ± 1.95
1.23 ± 0.48
6.09 ± 1.38
177 ± 3.18
6.69 ± 1.62
Stipe
19.0 ± 1.05
1.05 ± 0.63
105 ± 23.6
322 ± 10.4
18.9 ± 2.28
2.13 ± 0.39
10.2 ± 2.34
146 ± 27.2
3.93 ± 2.58
Boletus aereus
Cap
4.2 ± 0.63
1.83 ± 1.23
19.6 ± 1.35
341 ± 10.3
22.7 ± 2.01
0.78 ± 0.09
16.4 ± 1.5
164 ± 16.1
4.95 ± 0.72
Stipe
4.17 ± 0.18
1.11 ± 0.15
69.7 ± 6.3
237 ± 20.3
16.7 ± 1.05
2.31 ± 0.12
8.73 ± 1.95
74.9 ± 10.3
2.25 ± 0.18


### 3.2. Bioconcentration Factor (BCF)

Bioconcentration factor (BCF) values in caps and stalks ofBoletus are summarized in Table 4. Among the elements determined, P and K exhibit BCF > 1, except for BCF for stalk ofBoletus edulis (Table 4), while Ca, Fe, Mg, Mn, and Na are bioexcluded (BCF < 1) by theBoletus species studied. Although a certain element in the soil is abundant and could accumulate to relatively high contents in the mushroom, BCF below 1 may be obtained, which was reported for Ca, Fe, Mg, Mn, and Na in a recent study [8].Table 4
Bioconcentration factor (BCF) values of caps and stipes ofBoletus.
Species
Ca
Cu
Fe
K
Mg
Mn
Na
P
Zn
Boletus speciosus
Caps
0.38 ± 0.1
1.89 ± 0.24
0.05 ± 0.01
2.85 ± 0.57
0.80 ± 0.03
0.15 ± 0.02
0.15 ± 0.04
8.55 ± 1.27
2.35 ± 0.78
Stipes
0.31 ± 0.12
0.63 ± 0.29
0.05 ± 0.04
1.93 ± 0.75
0.44 ± 0.18
0.21 ± 0.08
0.13 ± 0.02
3.38 ± 1.69
0.89 ± 0.23
Boletus griseus
Caps
0.5 ± 0.08
1.03 ± 0.3
0.04 ± 0.01
3.22 ± 0.59
0.49 ± 0.07
0.1 ± 0.04
0.32 ± 0.03
4.23 ± 0.88
1.81 ± 0.12
Stipes
0.48 ± 0.05
0.62 ± 0.06
0.04 ± 0.01
2.85 ± 1.32
0.35 ± 0.03
0.14 ± 0.02
0.22 ± 0.05
2.84 ± 0.39
1.11 ± 0.45
Boletus luridus
Caps
0.2 ± 0.04
1.2 ± 0.37
0.06 ± 0.05
1.68 ± 0.67
0.21 ± 0.11
0.1 ± 0.03
0.05 ± 0.02
5.28 ± 1.84
1.51 ± 0.34
Stipes
0.16 ± 0.08
0.37 ± 0.02
0.04 ± 0.01
1.14 ± 0.52
0.13 ± 0.01
0.11 ± 0.05
0.04 ± 0.01
2.12 ± 1.55
0.59 ± 0.33
Boletus umbriniporus
Caps
0.2 ± 0.13
1.7 ± 0.76
0.04 ± 0.03
2.08 ± 1.27
0.44 ± 0.26
0.1 ± 0.08
0.2 ± 0.12
2.99 ± 0.65
0.82 ± 0.37
Stipes
0.13 ± 0.03
1.31 ± 0.54
0.02 ± 0.01
1.62 ± 0.75
0.28 ± 0.02
0.08 ± 0.04
0.22 ± 0.16
1.22 ± 0.48
0.3 ± 0.19
Boletus tomentipes
Caps
0.1 ± 0.05
0.9 ± 0.53
0.01 ± 0.04
1.99 ± 0.45
0.35 ± 0.21
0.1 ± 0.02
0.2 ± 0.08
6.06 ± 2.14
1.06 ± 0.65
Stipes
0.1 ± 0.04
0.53 ± 0.3
0.02 ± 0.03
1.87 ± 0.56
0.28 ± 0.03
0.14 ± 0.01
0.16 ± 0.09
3.63 ± 0.73
0.8 ± 0.21
Boletus edulis
Caps
0.2 ± 0.04
0.3 ± 0.17
0.02 ± 0.01
1.1 ± 0.93
0.12 ± 0.04
0.03 ± 0.01
0.1 ± 0.07
4.42 ± 1.3
0.75 ± 0.23
Stipes
0.2 ± 0.06
0.21 ± 0.03
0.08 ± 0.07
0.57 ± 0.01
0.08 ± 0.02
0.07 ± 0.03
0.06 ± 0.02
1.62 ± 0.43
0.3 ± 0.11
Boletus pallidus
Caps
0.1 ± 0.06
0.3 ± 0.14
0.02 ± 0.01
5.2 ± 1.46
0.71 ± 0.15
0.03 ± 0.02
0.5 ± 0.27
7.98 ± 2.19
0.11 ± 0.04
Stipes
0.1 ± 0.04
0.15 ± 0.02
0.02 ± 0.01
4.24 ± 0.58
0.54 ± 0.09
0.04 ± 0.03
0.39 ± 0.14
4.23 ± 0.88
0.1 ± 0.02
Boletus brunneissimus
Caps
0.36 ± 0.07
0.66 ± 0.28
0.02 ± 0.01
1.74 ± 0.42
0.58 ± 0.01
0.04 ± 0.02
0.53 ± 0.23
2.46 ± 0.67
1.15 ± 0.17
Stipes
0.08 ± 0.04
0.32 ± 0.08
0.02 ± 0.01
1.53 ± 1.2
0.39 ± 0.14
0.05 ± 0.01
0.24 ± 0.16
1.47 ± 0.28
0.61 ± 0.03
Boletus rubellus
Caps
0.09 ± 0.02
0.35 ± 0.16
0.02 ± 0.01
2.05 ± 1.07
0.43 ± 0.29
0.06 ± 0.02
0.25 ± 0.04
2.71 ± 0.78
0.89 ± 0.06
Stipes
0.19 ± 0.07
0.22 ± 0.1
0.06 ± 0.01
1.89 ± 0.76
0.35 ± 0.2
0.1 ± 0.06
0.41 ± 0.27
2.23 ± 0.55
0.52 ± 0.12
Boletus aereus
Caps
0.2 ± 0.09
1.02 ± 0.34
0.02 ± 0.01
2.0 ± 1.07
0.49 ± 0.23
0.07 ± 0.02
0.23 ± 0.01
7.87 ± 2.09
2.14 ± 0.24
Stipes
0.2 ± 0.04
0.62 ± 0.01
0.07 ± 0.03
1.39 ± 0.56
0.36 ± 0.21
0.2 ± 0.17
0.12 ± 0.04
3.59 ± 1.22
0.97 ± 0.43Wild mushrooms such asPholiota nameko,Tricholoma quercicol, andRamaria flava collected from Sichuan province (China) showed lower BCF values for potassium, that is, 0.84, 0.48, and 0.5, respectively [40]. Higher BCF values for K, Na, Zn, Cu, P, and Mg were found inBoletus subtomentosus, namely, 4400, 340, 110, 77, 40, and 21 for caps and 3900, 310, 67, 27, 18, and 11 for stalks, respectively [26].Boletus edulis collected from Poland also showed higher levels of BCF values for Cu and Zn, that is, 3.6–31 for caps and 1.7–16 for stipes [41]. In the study by Ma et al., BCF values of Zn and Cu were less than 0.01 in five kinds of wild edibleBoletus from China [42]. In early studies, the blockage of Ca, Fe, and Mn (BCF < 1) was reported in fruiting body ofMacrolepiota procera,Leccinum griseum, andTricholoma quercicol [27, 29, 40, 43], which agrees with our results.


### 3.3. Correlation Analysis

Matrices of correlation coefficients among elements concentrations of the fruiting body (caps and stalks) and underlying soils are presented in Tables5 and 6. Cu (r = 0.556) and Mn (r = 0.431) had significant correlations in caps, and high correlation were seen between Ca (r = 0.727), Cu (r = 0.6), and Fe (r = 0.569) in stalks. Similar results were obtained for Cu (r = 0.478), Mn (r = 0.389), and Fe (r = 0.417) inVerpa conica,Tricholoma terreum, andBoletus badius, respectively [44]. Meanwhile, significant correlations were also found between Ca-Fe (r = 0.681), Cu-P (r = 0.775), Fe-P (r = 0.728), Mn-P (r = 0.667), Zn-K (r = 0.673), Zn-Mg (r = 0.675), and Zn-P (r = 0.76) for caps. For stalks, significant correlations were found between Cu-Mg (r = 0.721), Cu-P (r = 0.659), Fe-Mg (r = 0.719), Fe-P (r = 0.693), Zn-Mg (r = 0.824), Zn-P (r = 0.684), and Zn-P (r = 0.818).Table 5
Correlation matrix that gives the relationship between element concentrations of caps and underlying soil.
Elements in soils
Elements in mushrooms
Ca
Cu
Fe
K
Mg
Mn
Na
P
Zn
Ca
0.406
0.262
0.681∗
0.299
0.322
0.57
−0.031
0.445
0.065
Cu
0.021
0.556
0.487
0.475
0.58
0.1
0.289
0.775∗
∗
−0.392
Fe
0.01
0.492
0.382
0.509
0.54
0.061
0.322
0.728∗
−0.355
K
0.327
−0.477
−0.162
−0.362
−0.644∗
0.159
−0.233
−0.305
0.067
Mg
0.173
0.242
0.372
−0.217
−0.176
0.345
−0.318
0.257
−0.262
Mn
0.52
0.253
0.563
0.403
0.328
0.431
0.241
0.667∗
−0.336
Na
−0.131
0.214
0.09
−0.217
−0.232
0.22
0.174
0.046
−0.321
P
0.582
−0.5
0.292
0.186
−0.092
0.294
0.111
0.016
0.276
Zn
0.137
0.423
0.483
0.673∗
0.675∗
0.128
0.456
0.760∗
−0.295
∗Correlation is significant at the 0.05 level (2-tailed).
∗
∗Correlation is significant at the 0.01 level (2-tailed).Table 6
Correlation matrix that gives the relationship between element concentrations of stipes and underlying soil.
Elements in soils
Elements in mushrooms
Ca
Cu
Fe
K
Mg
Mn
Na
P
Zn
Ca
0.727∗
0.133
0.423
0.307
0.469
0.374
0.234
0.62
0.204
Cu
0.482
0.6
0.6
0.33
0.721∗
0.112
0.472
0.659∗
−0.156
Fe
0.452
0.601
0.569
0.405
0.719∗
0.113
0.452
0.693∗
−0.057
K
0.094
−0.173
0.445
−0.384
−0.544
0.537
−0.422
−0.307
0.054
Mg
0.336
0.091
0.718∗
−0.439
−0.145
0.628
−0.316
−0.103
−0.318
Mn
0.495
0.181
0.497
0.224
0.435
0.334
0.233
0.474
−0.197
Na
−0.164
0.281
0.175
−0.464
−0.253
0.47
0.089
−0.442
−0.571
P
0.522
−0.056
0.171
0.295
0.027
0.05
0.359
0.378
0.338
Zn
0.466
0.505
0.26
0.626
0.824∗
∗
−0.126
0.684∗
0.818∗
∗
−0.012
∗Correlation is significant at the 0.05 level (2-tailed).
∗
∗Correlation is significant at the 0.01 level (2-tailed).


## 3.1. Element Concentrations

The element contents in fruiting bodies ofBoletus (cap and stalk) and underlying soil samples are presented in Table 2. As previously reported, fruiting bodies ofBoletus can be considered as rich in P, K, Na, Ca, and Mg and also abundant in trace elements such as Cu, Zn, and Mn. Among the minerals determined in this study, K, P, Fe, Mg, and Ca exhibited higher concentrations than Na, Zn, Cu, and Mn, which is in accordance with the literature [7]. WhileBoletus collected from Yunnan contained lower levels of K, Na, Ca, Mg, Fe, and Mn than other reports [20], significant differences were obtained not only among variousBoletus species but also within different part of fruiting body (Table 2). Similarly to previous studies, the ranges of concentrations spread over one to two orders of magnitude often occurred [21, 22].Table 2
Elements content in the caps and stipes ofBoletus and underlying soil (mg/kg dw, mean, SD).
Species
Ca
Cu
Fe
K
Mg
Mn
Na
P
Zn
Boletus speciosus
Cap
172 ± 36
66 ± 12
1021 ± 216
9017 ± 453
909 ± 158
21 ± 6
130 ± 76
5612 ± 587
148 ± 25
Stipe
141 ± 91
22 ± 5
959 ± 232
6105 ± 829
504 ± 307
30 ± 2
118 ± 13
2218 ± 573
56 ± 26
Soil
449 ± 234
35 ± 21
20081 ± 3426
3169 ± 432
1134 ± 673
140 ± 32
876 ± 27
656 ± 32
63 ± 2
Boletus griseus
Cap
538 ± 56
40 ± 13
1166 ± 133
17310 ± 667
577 ± 54
48 ± 22
324 ± 26
7126 ± 334
205 ± 55
Stipe
512 ± 32
24 ± 6
1194 ± 244
15308 ± 565
407 ± 75
63 ± 22
226 ± 13
4789 ± 454
125 ± 52
Soil
1076 ± 32
39 ± 13
26989 ± 2411
5373 ± 3458
1169 ± 113
459 ± 89
1020 ± 675
1686 ± 242
113 ± 7
Boletus luridus
Cap
475 ± 29
65 ± 13
1600 ± 345
11206 ± 677
556 ± 81
67 ± 23
105 ± 12
6832 ± 565
131 ± 18
Stipe
395 ± 165
20 ± 12
1117 ± 212
7594 ± 434
340 ± 223
85 ± 21
90 ± 27
2742 ± 345
51 ± 23
Soil
2438 ± 341
54 ± 23
28210 ± 788
6665 ± 178
2694 ± 252
773 ± 95
2292 ± 321
1293 ± 132
87 ± 54
Boletus umbriniporus
Cap
166 ± 33
43 ± 11
747 ± 256
10740 ± 234
431 ± 56
21 ± 4
421 ± 67
5325 ± 453
90 ± 23
Stipe
95 ± 12
34 ± 13
357 ± 32
8360 ± 568
279 ± 32
26 ± 5
451 ± 134
2176 ± 234
33 ± 6
Soil
758 ± 54
26 ± 12
19966 ± 4663
5154 ± 126
990 ± 645
315 ± 13
2071 ± 234
1778 ± 543
110 ± 78
Boletus tomentipes
Cap
99 ± 45
48 ± 6
376 ± 32
11488 ± 345
386 ± 234
17 ± 2
170 ± 11
5155 ± 324
115 ± 45
Stipe
113 ± 34
28 ± 5
751 ± 65
10775 ± 454
314 ± 32
38 ± 3
107 ± 76
3089 ± 235
90 ± 6
Soil
1081 ± 38
53 ± 6
38286 ± 479
5761 ± 46
1118 ± 67
281 ± 37
681 ± 89
850 ± 46
108 ± 23
Boletus edulis
Cap
320 ± 26
51 ± 34
931 ± 82
9413 ± 567
429 ± 54
26 ± 11
191 ± 53
6615 ± 343
88 ± 4
Stipe
317 ± 33
32 ± 4
4200 ± 678
4865 ± 245
297 ± 65
70 ± 13
122 ± 23
2429 ± 545
41 ± 33
Soil
1624 ± 45
152 ± 20
52613 ± 656
8533 ± 234
3665 ± 867
945 ± 77
1972 ± 45
1495 ± 22
118 ± 67
Boletus pallidus
Cap
342 ± 234
78 ± 6
1475 ± 56
18968 ± 676
1239 ± 82
36 ± 2
601 ± 4
10611 ± 234
45 ± 76
Stipe
378 ± 56
39 ± 4
1823 ± 341
15325 ± 459
935 ± 240
39 ± 22
500 ± 345
5621 ± 248
37 ± 9
Soil
2624 ± 787
261 ± 55
83294 ± 676
3617 ± 89
1745 ± 456
1092 ± 88
1288 ± 67
1330 ± 234
396 ± 78
Boletus brunneissimus
Cap
669 ± 34
33 ± 23
741 ± 78
11757 ± 346
759 ± 21
29 ± 8
472 ± 44
4942 ± 986
167 ± 50
Stipe
154 ± 78
16 ± 4
702 ± 23
10320 ± 654
513 ± 78
38 ± 2
216 ± 56
2949 ± 873
88 ± 57
Soil
1879 ± 245
50 ± 14
32165 ± 343
6765 ± 652
1307 ± 45
744 ± 22
891 ± 454
2007 ± 13
145 ± 29
Boletus rubellus
Cap
285 ± 67
56 ± 34
1376 ± 46
11606 ± 428
773 ± 65
41 ± 16
203 ± 46
5888 ± 106
223 ± 54
Stipe
632 ± 35
35 ± 21
3488 ± 785
10732 ± 345
631 ± 76
71 ± 13
340 ± 78
4853 ± 906
131 ± 86
Soil
3289 ± 442
159 ± 45
57870 ± 466
5675 ± 545
1802 ± 42
682 ± 24
825 ± 74
2176 ± 346
251 ± 57
Boletus aereus
Cap
140 ± 21
61 ± 41
654 ± 45
11365 ± 343
758 ± 67
26 ± 3
546 ± 50
5467 ± 535
165 ± 24
Stipe
139 ± 6
37 ± 5
2323 ± 210
7905 ± 676
556 ± 35
77 ± 4
291 ± 65
2497 ± 342
75 ± 6
Soil
687 ± 43
60 ± 3
34440 ± 652
5675 ± 874
1535 ± 257
378 ± 35
2393 ± 256
695 ± 57
77 ± 20Among the mushroom species analyzed, the greatest contents of Cu, K, Mg, Na, and P were quantified in the caps and stalks ofBoletus pallidus, and Mn and Zn were found inBoletus luridus andBoletus rubellus. Highest Ca and Fe contents were found in the caps ofBoletus brunneissimus and stipes ofBoletus edulis, namely, 669 and 4200 mg/kg dw, respectively. In the study by Zhou and Yin (2008) [23],Boletus edulis showed higher contents of K, Na, Ca, Mg, and Fe thanBoletus speciosus andBoletus aereus. In our early study, values of 13.6, 121, 248, and 20.3 mg/kg dw for Cu, Fe, Mg, and Zn were determined inBoletus tomentipes, respectively, which are lower than the present results [24]. Similarly, contents of K, Ca, Fe, Mg, and Zn forBoletus speciosus andBoletus griseus collected from Yunnan province in 2009 were lower than the data in Table 2 [25].K contents in caps and stalks ofBoletus edulis (cap: 29000 mg/kg, stalk: 20000 mg/kg dw) andBoletus subtomentosus (cap: 46000 mg/kg, stalk: 43000 mg/kg dw) from Poland were much higher than the values in our study (cap: 9017–18968 mg/kg, stalk: 4865–15325 mg/kg dw) [8, 26]. P contents were found at the ranges of 4942–10611 mg/kg dw and 2176–5621 mg/kg dw for caps and stalks ofBoletus, respectively. Higher values were found to be 8700–16000 mg/kg dw in caps and 4100–7500 mg/kg dw in stalks ofMacrolepiota procera, and lower values of 640–4490 mg/kg dw were for the fruiting body of thirty macrofungi species from Turkey [27, 28].The range of Fe contents in this study was 376–1600 in caps and 357–4200 mg/kg dw in stalks, which are much higher than the values previously reported [8, 29]. Similar values were found to be 150–1741 mg/kg dw, and a particularly higher value was 11460 mg/kg dw forLepista nuda [30, 31]. Reported Ca contents inBoletus edulis,Boletus speciosus, andBoletus tomentipes were 913.9, 1147.6, and 1097.4 mg/kg dw, which are higher than the values observed in this study [32].Mg and Zn concentrations in differentBoletus were in the ranges of 386–1239 and 45–223 mg/kg dw for caps and 279–935 and 33–131 mg/kg dw for stalks, respectively, which coincide with the literature reports [5]. Cu and Mn contents inBoletus badius,Boletus luridus, andBoletus edulis were found to be lower than the results in our study, that is, 33–78 and 17–67 mg/kg dw for caps and 16–39 and 26–85 mg/kg dw for stalks, respectively [5, 33, 34]. Other species such asMacrolepiota procera andLepista nuda contained higher content of Cu (236.5 mg/kg dw) and Mn (480 mg/kg dw) [6, 31]. The range of Na contents in caps was 105–601 mg/kg dw and 90–500 mg/kg dw in stalks, which are lower than values in species such asBoletus subtomentosus (77–1200 mg/kg dw),Pleurotus ostreatus (220–1400 mg/kg dw), andAgaricus bisporus (16000–25000 mg/kg dw) [26, 35, 36].Uneven distribution of elements between caps and stalks is shown in Table2. The caps ofBoletus contained higher contents of K, P, Cu, Mg, and Zn and lower contents of Mn when compared to stalks. Reports also suggested similar results for these elements inBoletus edulis,Boletus subtomentosus, andBoletus scaber [26, 37, 38]. However, the contents of Ca, Fe, and Na between caps and stalks have no certain regularity (Table 2). Contents of Cu, P, and Zn in caps are approximately twice or even thrice higher than in stalks, and similar findings were obtained in the review of Falandysz and Borovička [5]. As can be seen from Table 2, both caps and stalks can be considered as abundant in P, K, Fe, Mg, Zn, and Ca, andBoletus could be considered potential dietary sources of these essential elements to humans.According to the EU Scientific Committee, 60 kg of body weight was used for intake calculations. For intake calculations, usually a 300 g portion of fresh mushrooms per meal is assumed, which contains 30 g of dry matter [39]. The elements intakes by a normal (60 kg) consumer in mgper serving for all studied fruiting bodies are presented in Table 3.Table 3
Daily metal intakes by a normal, 60 kg consumer in mg/serving.
Species
Ca
Cu
Fe
K
Mg
Mn
Na
P
Zn
Boletus speciosus
Cap
5.16 ± 1.08
1.98 ± 0.36
30.6 ± 6.48
271 ± 13.6
27.3 ± 4.74
0.63 ± 0.18
3.9 ± 2.28
168.4 ± 17.6
4.44 ± 0.75
Stipe
4.23 ± 2.73
0.66 ± 0.15
28.8 ± 6.96
183 ± 24.9
15.1 ± 9.21
0.9 ± 0.06
3.54 ± 0.39
66.5 ± 17.3
1.68 ± 0.78
Boletus griseus
Cap
16.1 ± 1.68
1.2 ± 0.39
35.0 ± 3.99
519 ± 20.0
17.3 ± 1.62
1.44 ± 0.66
9.72 ± 0.78
214 ± 10.0
6.15 ± 1.65
Stipe
15.4 ± 0.96
0.72 ± 0.18
35.8 ± 7.32
459 ± 17.0
12.2 ± 2.25
1.89 ± 0.66
6.78 ± 0.39
144 ± 13.6
3.75 ± 1.56
Boletus luridus
Cap
14.3 ± 0.87
1.95 ± 0.39
48 ± 10.4
336 ± 20.3
16.7 ± 21.43
2.01 ± 0.69
3.15 ± 0.36
205 ± 17.0
3.93 ± 0.54
Stipe
11.9 ± 4.95
0.6 ± 0.36
33.5 ± 6.36
228 ± 13.0
10.2 ± 6.69
2.55 ± 0.63
2.7 ± 0.81
82.3 ± 10.4
1.53 ± 0.69
Boletus umbriniporus
Cap
4.98 ± 0.99
1.29 ± 0.33
22.4 ± 7.68
322 ± 7.02
12.9 ± 1.68
0.63 ± 0.12
12.6 ± 2.01
160 ± 13.4
2.7 ± 0.69
Stipe
2.85 ± 0.36
1.02 ± 0.39
10.7 ± 0.96
251 ± 17.0
8.37 ± 0.96
0.78 ± 0.15
13.5 ± 4.02
65.3 ± 7.02
0.99 ± 0.18
Boletus tomentipes
Cap
2.97 ± 1.35
1.44 ± 0.18
11.3 ± 0.96
345 ± 10.4
11.6 ± 7.02
0.51 ± 0.06
5.1 ± 0.33
155 ± 9.72
3.45 ± 1.35
Stipe
3.39 ± 1.02
0.84 ± 0.15
22.5 ± 1.95
323 ± 13.6
9.42 ± 0.96
1.14 ± 0.09
3.21 ± 2.28
92.7 ± 7.05
2.7 ± 0.18
Boletus edulis
Cap
9.6 ± 0.78
1.53 ± 1.02
27.9 ± 2.46
282 ± 17.0
12.9 ± 1.62
0.78 ± 0.33
5.73 ± 1.59
198 ± 10.3
2.64 ± 0.12
Stipe
9.5 ± 0.99
0.96 ± 0.12
126 ± 20.3
146 ± 7.35
8.91 ± 1.95
2.1 ± 0.39
3.66 ± 0.69
72.9 ± 16.4
1.23 ± 0.99
Boletus pallidus
Cap
10.3 ± 7.02
2.34 ± 0.18
44.3 ± 1.68
569 ± 20.3
37.2 ± 2.46
1.08 ± 0.06
18.0 ± 0.12
318 ± 7.02
1.35 ± 2.28
Stipe
11.3 ± 1.68
1.17 ± 0.12
54.7 ± 10.2
460 ± 13.8
28.1 ± 7.2
1.17 ± 0.66
15 ± 10.4
168.6 ± 7.44
1.11 ± 0.27
Boletus brunneissimus
Cap
20.1 ± 1.02
0.99 ± 0.69
22.2 ± 2.34
353 ± 10.4
22.8 ± 0.63
0.87 ± 0.24
14.2 ± 1.32
148 ± 29.6
5.01 ± 1.5
Stipe
4.62 ± 2.34
0.48 ± 0.12
21.1 ± 0.69
310 ± 19.6
15.4 ± 2.34
1.14 ± 0.06
6.48 ± 1.68
88.5 ± 26.2
2.64 ± 1.71
Boletus rubellus
Cap
8.55 ± 2.01
1.68 ± 1.02
41.3 ± 1.38
348 ± 12.8
23.2 ± 1.95
1.23 ± 0.48
6.09 ± 1.38
177 ± 3.18
6.69 ± 1.62
Stipe
19.0 ± 1.05
1.05 ± 0.63
105 ± 23.6
322 ± 10.4
18.9 ± 2.28
2.13 ± 0.39
10.2 ± 2.34
146 ± 27.2
3.93 ± 2.58
Boletus aereus
Cap
4.2 ± 0.63
1.83 ± 1.23
19.6 ± 1.35
341 ± 10.3
22.7 ± 2.01
0.78 ± 0.09
16.4 ± 1.5
164 ± 16.1
4.95 ± 0.72
Stipe
4.17 ± 0.18
1.11 ± 0.15
69.7 ± 6.3
237 ± 20.3
16.7 ± 1.05
2.31 ± 0.12
8.73 ± 1.95
74.9 ± 10.3
2.25 ± 0.18


## 3.2. Bioconcentration Factor (BCF)

Bioconcentration factor (BCF) values in caps and stalks ofBoletus are summarized in Table 4. Among the elements determined, P and K exhibit BCF > 1, except for BCF for stalk ofBoletus edulis (Table 4), while Ca, Fe, Mg, Mn, and Na are bioexcluded (BCF < 1) by theBoletus species studied. Although a certain element in the soil is abundant and could accumulate to relatively high contents in the mushroom, BCF below 1 may be obtained, which was reported for Ca, Fe, Mg, Mn, and Na in a recent study [8].Table 4
Bioconcentration factor (BCF) values of caps and stipes ofBoletus.
Species
Ca
Cu
Fe
K
Mg
Mn
Na
P
Zn
Boletus speciosus
Caps
0.38 ± 0.1
1.89 ± 0.24
0.05 ± 0.01
2.85 ± 0.57
0.80 ± 0.03
0.15 ± 0.02
0.15 ± 0.04
8.55 ± 1.27
2.35 ± 0.78
Stipes
0.31 ± 0.12
0.63 ± 0.29
0.05 ± 0.04
1.93 ± 0.75
0.44 ± 0.18
0.21 ± 0.08
0.13 ± 0.02
3.38 ± 1.69
0.89 ± 0.23
Boletus griseus
Caps
0.5 ± 0.08
1.03 ± 0.3
0.04 ± 0.01
3.22 ± 0.59
0.49 ± 0.07
0.1 ± 0.04
0.32 ± 0.03
4.23 ± 0.88
1.81 ± 0.12
Stipes
0.48 ± 0.05
0.62 ± 0.06
0.04 ± 0.01
2.85 ± 1.32
0.35 ± 0.03
0.14 ± 0.02
0.22 ± 0.05
2.84 ± 0.39
1.11 ± 0.45
Boletus luridus
Caps
0.2 ± 0.04
1.2 ± 0.37
0.06 ± 0.05
1.68 ± 0.67
0.21 ± 0.11
0.1 ± 0.03
0.05 ± 0.02
5.28 ± 1.84
1.51 ± 0.34
Stipes
0.16 ± 0.08
0.37 ± 0.02
0.04 ± 0.01
1.14 ± 0.52
0.13 ± 0.01
0.11 ± 0.05
0.04 ± 0.01
2.12 ± 1.55
0.59 ± 0.33
Boletus umbriniporus
Caps
0.2 ± 0.13
1.7 ± 0.76
0.04 ± 0.03
2.08 ± 1.27
0.44 ± 0.26
0.1 ± 0.08
0.2 ± 0.12
2.99 ± 0.65
0.82 ± 0.37
Stipes
0.13 ± 0.03
1.31 ± 0.54
0.02 ± 0.01
1.62 ± 0.75
0.28 ± 0.02
0.08 ± 0.04
0.22 ± 0.16
1.22 ± 0.48
0.3 ± 0.19
Boletus tomentipes
Caps
0.1 ± 0.05
0.9 ± 0.53
0.01 ± 0.04
1.99 ± 0.45
0.35 ± 0.21
0.1 ± 0.02
0.2 ± 0.08
6.06 ± 2.14
1.06 ± 0.65
Stipes
0.1 ± 0.04
0.53 ± 0.3
0.02 ± 0.03
1.87 ± 0.56
0.28 ± 0.03
0.14 ± 0.01
0.16 ± 0.09
3.63 ± 0.73
0.8 ± 0.21
Boletus edulis
Caps
0.2 ± 0.04
0.3 ± 0.17
0.02 ± 0.01
1.1 ± 0.93
0.12 ± 0.04
0.03 ± 0.01
0.1 ± 0.07
4.42 ± 1.3
0.75 ± 0.23
Stipes
0.2 ± 0.06
0.21 ± 0.03
0.08 ± 0.07
0.57 ± 0.01
0.08 ± 0.02
0.07 ± 0.03
0.06 ± 0.02
1.62 ± 0.43
0.3 ± 0.11
Boletus pallidus
Caps
0.1 ± 0.06
0.3 ± 0.14
0.02 ± 0.01
5.2 ± 1.46
0.71 ± 0.15
0.03 ± 0.02
0.5 ± 0.27
7.98 ± 2.19
0.11 ± 0.04
Stipes
0.1 ± 0.04
0.15 ± 0.02
0.02 ± 0.01
4.24 ± 0.58
0.54 ± 0.09
0.04 ± 0.03
0.39 ± 0.14
4.23 ± 0.88
0.1 ± 0.02
Boletus brunneissimus
Caps
0.36 ± 0.07
0.66 ± 0.28
0.02 ± 0.01
1.74 ± 0.42
0.58 ± 0.01
0.04 ± 0.02
0.53 ± 0.23
2.46 ± 0.67
1.15 ± 0.17
Stipes
0.08 ± 0.04
0.32 ± 0.08
0.02 ± 0.01
1.53 ± 1.2
0.39 ± 0.14
0.05 ± 0.01
0.24 ± 0.16
1.47 ± 0.28
0.61 ± 0.03
Boletus rubellus
Caps
0.09 ± 0.02
0.35 ± 0.16
0.02 ± 0.01
2.05 ± 1.07
0.43 ± 0.29
0.06 ± 0.02
0.25 ± 0.04
2.71 ± 0.78
0.89 ± 0.06
Stipes
0.19 ± 0.07
0.22 ± 0.1
0.06 ± 0.01
1.89 ± 0.76
0.35 ± 0.2
0.1 ± 0.06
0.41 ± 0.27
2.23 ± 0.55
0.52 ± 0.12
Boletus aereus
Caps
0.2 ± 0.09
1.02 ± 0.34
0.02 ± 0.01
2.0 ± 1.07
0.49 ± 0.23
0.07 ± 0.02
0.23 ± 0.01
7.87 ± 2.09
2.14 ± 0.24
Stipes
0.2 ± 0.04
0.62 ± 0.01
0.07 ± 0.03
1.39 ± 0.56
0.36 ± 0.21
0.2 ± 0.17
0.12 ± 0.04
3.59 ± 1.22
0.97 ± 0.43Wild mushrooms such asPholiota nameko,Tricholoma quercicol, andRamaria flava collected from Sichuan province (China) showed lower BCF values for potassium, that is, 0.84, 0.48, and 0.5, respectively [40]. Higher BCF values for K, Na, Zn, Cu, P, and Mg were found inBoletus subtomentosus, namely, 4400, 340, 110, 77, 40, and 21 for caps and 3900, 310, 67, 27, 18, and 11 for stalks, respectively [26].Boletus edulis collected from Poland also showed higher levels of BCF values for Cu and Zn, that is, 3.6–31 for caps and 1.7–16 for stipes [41]. In the study by Ma et al., BCF values of Zn and Cu were less than 0.01 in five kinds of wild edibleBoletus from China [42]. In early studies, the blockage of Ca, Fe, and Mn (BCF < 1) was reported in fruiting body ofMacrolepiota procera,Leccinum griseum, andTricholoma quercicol [27, 29, 40, 43], which agrees with our results.


## 3.3. Correlation Analysis

Matrices of correlation coefficients among elements concentrations of the fruiting body (caps and stalks) and underlying soils are presented in Tables5 and 6. Cu (r = 0.556) and Mn (r = 0.431) had significant correlations in caps, and high correlation were seen between Ca (r = 0.727), Cu (r = 0.6), and Fe (r = 0.569) in stalks. Similar results were obtained for Cu (r = 0.478), Mn (r = 0.389), and Fe (r = 0.417) inVerpa conica,Tricholoma terreum, andBoletus badius, respectively [44]. Meanwhile, significant correlations were also found between Ca-Fe (r = 0.681), Cu-P (r = 0.775), Fe-P (r = 0.728), Mn-P (r = 0.667), Zn-K (r = 0.673), Zn-Mg (r = 0.675), and Zn-P (r = 0.76) for caps. For stalks, significant correlations were found between Cu-Mg (r = 0.721), Cu-P (r = 0.659), Fe-Mg (r = 0.719), Fe-P (r = 0.693), Zn-Mg (r = 0.824), Zn-P (r = 0.684), and Zn-P (r = 0.818).Table 5
Correlation matrix that gives the relationship between element concentrations of caps and underlying soil.
Elements in soils
Elements in mushrooms
Ca
Cu
Fe
K
Mg
Mn
Na
P
Zn
Ca
0.406
0.262
0.681∗
0.299
0.322
0.57
−0.031
0.445
0.065
Cu
0.021
0.556
0.487
0.475
0.58
0.1
0.289
0.775∗
∗
−0.392
Fe
0.01
0.492
0.382
0.509
0.54
0.061
0.322
0.728∗
−0.355
K
0.327
−0.477
−0.162
−0.362
−0.644∗
0.159
−0.233
−0.305
0.067
Mg
0.173
0.242
0.372
−0.217
−0.176
0.345
−0.318
0.257
−0.262
Mn
0.52
0.253
0.563
0.403
0.328
0.431
0.241
0.667∗
−0.336
Na
−0.131
0.214
0.09
−0.217
−0.232
0.22
0.174
0.046
−0.321
P
0.582
−0.5
0.292
0.186
−0.092
0.294
0.111
0.016
0.276
Zn
0.137
0.423
0.483
0.673∗
0.675∗
0.128
0.456
0.760∗
−0.295
∗Correlation is significant at the 0.05 level (2-tailed).
∗
∗Correlation is significant at the 0.01 level (2-tailed).Table 6
Correlation matrix that gives the relationship between element concentrations of stipes and underlying soil.
Elements in soils
Elements in mushrooms
Ca
Cu
Fe
K
Mg
Mn
Na
P
Zn
Ca
0.727∗
0.133
0.423
0.307
0.469
0.374
0.234
0.62
0.204
Cu
0.482
0.6
0.6
0.33
0.721∗
0.112
0.472
0.659∗
−0.156
Fe
0.452
0.601
0.569
0.405
0.719∗
0.113
0.452
0.693∗
−0.057
K
0.094
−0.173
0.445
−0.384
−0.544
0.537
−0.422
−0.307
0.054
Mg
0.336
0.091
0.718∗
−0.439
−0.145
0.628
−0.316
−0.103
−0.318
Mn
0.495
0.181
0.497
0.224
0.435
0.334
0.233
0.474
−0.197
Na
−0.164
0.281
0.175
−0.464
−0.253
0.47
0.089
−0.442
−0.571
P
0.522
−0.056
0.171
0.295
0.027
0.05
0.359
0.378
0.338
Zn
0.466
0.505
0.26
0.626
0.824∗
∗
−0.126
0.684∗
0.818∗
∗
−0.012
∗Correlation is significant at the 0.05 level (2-tailed).
∗
∗Correlation is significant at the 0.01 level (2-tailed).


## 4. Conclusion

The present study gives an overview for the levels of elements accumulation, determined in caps and stalks of ten species ofBoletus from Yunnan province, southwest of China. From the nutritional point of view, theseBoletus could be considered as a potential dietary source of essential elements such as P, K, Mg, Cu, Zn, Mn, and Fe. Elements K, P, Cu, Mg, and Zn are preferably accumulated in the cap ofBoletus, while Mn is preferably accumulated in stalk. Depending on the environmental conditions and mushroom species, the values of BCF varied highly depending on chemical element and were >1 for P and K, while they were <1 for Ca, Fe, Mg, Mn, and Na. The correlation analysis showed that Cu, Mn, Ca, and Fe contents were highly correlated in the mushrooms as compared to the corresponding soils. Significant correlations were also obtained between Cu-P (r = 0.775), Fe-P (r = 0.728), and Zn-P (r = 0.76) for caps and Cu-Mg (r = 0.721), Fe-Mg (r = 0.719), Zn-Mg (r = 0.824), and Zn-P (r = 0.818) for stalks.



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*Source: 165412-2015-06-04.xml*