# Aluminium accumulation in loengo (Anisophyllea boehmii Engl.), a fruit from the Miombo ecoregion consumed in Angola

Famoroso João da Costa, Bettencourt Munanga, Adrien Servent, Manuel Dornier

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Famoroso João da Costa, Bettencourt Munanga, Adrien Servent, Manuel Dornier. Aluminium accumulation in loengo (Anisophyllea boehmii Engl.), a fruit from the Miombo ecoregion consumed in Angola. Food and Humanity, 2026, pp.101052. 10.1016/j.foohum.2026.101052. hal-05487469

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# Aluminium accumulation in loengo (*Anisophyllea boehmii* Engl.), a fruit from the Miombo ecoregion consumed in Angola

Famoroso João da Costa<sup>a,b</sup>, Bettencourt Munanga<sup>a,©</sup>, Adrien Servent<sup>b,c</sup>, Manuel Dornier<sup>b,*</sup><sup>©</sup>

## ARTICLE INFO

### Keywords:

- Wild fruit

- Tropical fruit

- Miombo forest

- Angola

- Aluminium accumulation

## ABSTRACT

The fruit of *Anisophyllea boehmii*, known as loengo in Angola, is a wild fruit typically harvested in the Miombo forest. It is widely consumed locally and appreciated for its organoleptic qualities. It also has proven nutritional interests. However, analysis of the mineral profile of the fruit pulp using inductively coupled plasma with mass spectrometry (ICP-MS) on 7 samples collected in 3 geographical areas over 3 consecutive years revealed an uncommon aluminium content of around 8 g·kg⁻¹ of dry matter. Indeed, the concentrations measured in the leaves confirmed that the plant is an aluminium hyperaccumulator. No correlation was found between the aluminium content of the pulp and that in soil. This particularly high value led to the recommendation to limit consumption of the fruit to protect local populations from excessive and repeated exposure to aluminium.

## 1. Introduction

The Miombo forest is an ecological zone characteristic of southern Africa that spans seven countries (Dewees et al., 2010). It is very rich in bioresources and is home to many plant species that produce edible fruits. These wild fruits are traditionally part of the local population's diet but are poorly understood and characterized in terms of composition. Among these forest resources, the fruit of *Anisophyllea boehmii* Engl. is particularly appreciated for its pleasant flavor.

A recent study conducted in Angola, including a field survey and an in-depth compositional work, showed that this fruit is widely consumed throughout most of the year in the form of fresh fruits or processed products like beverages, and that it has interesting nutritional and sensorial potentials (da Costa et al., 2025). The fruit is quite energy-dense. It is rich in sugars, fibers, minerals, polyphenols especially anthocyanins, and carotenoids. It has a distinctive flavor linked to a complex aromatic profile consisting mainly of esters. The composition of the mineral profile in the edible part of the fruit has been addressed. From a nutritional point of view, the pulp of the fruit contains particularly interesting contents of Mg, Mn, Fe, Zn and Cu. Nevertheless, during these first investigations, an abnormally high aluminium content was found in fruits sampled in Angola in 2021. This result was very surprising because aluminium is an element that generally does not

accumulate in plants as it is toxic at the cellular scale (Chauhan et al., 2021; Ofoe et al., 2023).

Given that this element has proven subchronic toxicity to humans, and due to the total lack of data on the subject, the objective of this short communication is to investigate the aluminium content of *A. boehmii* fruit by comparing several samples from various sites in Angola, collected over three consecutive years. The ultimate goal is to make recommendations regarding the consumption of this fruit.

## 2. Materials and methods

### 2.1. Samples

Fruits of unspecified origin were collected from local markets in September 2021. Between July and August 2022, 3 new fruit samples (3 kg·area⁻¹) were collected in different areas of Angola (Fig. 1): Malanje (Guiné-Malanje), Huambo (Luvili) and Hufla (Tchimbungo-Caconda). Fruit samples were prepared as described by da Costa et al. (2025). They were depulped (Auriol PH3 refiner, Marmande, France), freeze-dried at -18°C, and then freeze-dried (Cryonext Benchtop freeze dryer, Montpellier, France) before being analyzed. In November 2023, in the same areas, fruits (3 kg·area⁻¹), leaves, roots (0.5 kg·area⁻¹), and soils (1 kg·area⁻¹) were collected. The leaves and roots were washed

<footnote><sup>a</sup> Instituto de Tecnologia Agro-Alimentar, Rainha Njinga a Mbande University, Malanje, Angola</footnote>

<footnote><sup>b</sup> QualiSud, Université de Montpellier, Avignon Université, CIRAD, Institut Agro Montpellier, IRD, Université de La Réunion, Montpellier, France</footnote>

<footnote><sup>c</sup> CIRAD, UMR QualiSud, Montpellier F-34398, France</footnote>

<footnote>* Corresponding author.
E-mail address: manuel.dornier@institut-agro.fr (M. Dornier).</footnote>
<figure><img src="image_2.png" /><figcaption>**Fig. 1.** Locations where samples of fruits, leaves, roots and soils were collected.</figcaption></figure>

with tap water, dried at room temperature, and packaged in polyethylene bags. The soils were removed from the rhizosphere at approximately 40 cm depth, dried at room temperature, and also packaged in polyethylene bags without pretreatment. All samples were transported to the Institute of Agro-Food Technology in Malanje (Angola) and then to the CIRAD analysis center (France), with intervals between collection and analysis of 1 – 4 months.

## 2.2. Aluminium analysis

Aluminium content was analyzed by inductively coupled plasma with mass spectrometry (ICP-MS). Around 50 mg of the sample was digested with a HNO₃:H₂O₂ solution (65:35, v/v) using a MARS Xpress microwave system (CEM Corporation, Mathews, France). The digestion conditions were as follows: up to 120°C in 15 min and then constant for 10 min, up to 160°C in 20 min and constant for 15 min, final cooling to 22°C for 30 min and diluted with deionized ultrapure water. The ICP-MS device used was a Thermo Elemental, X-Series (Germany). The uncertainty of the measurement was around 10% and the limit of detection was evaluated at 0.2 mg·kg⁻¹.

## 2.3. Statistical evaluation

Statistical data treatment was realized using XLSTAT 2025 software (Addinsoft, Paris, France). For the analysis done in triplicate, comparison between average values were carried out using the Tukey HSD test (p < 0.05). Correlations were evaluated through the linear regression coefficient R².

# 3. Results and discussions

## 3.1. Aluminium contents

Table 1 summarizes the results of aluminium measurements carried out during this exploratory work.

The average aluminium content of the fruit pulp, calculated from all samples collected (n = 18), was 8188 ± 1321 mg·kg⁻¹ dry basis (DB). Considering the pulp fruit moisture varies from 72 and 80% with an average value of 78.4% (da Costa et al., 2025), this corresponded to a content of approximately 1769 mg·kg⁻¹ fresh basis (FB). A comparison of the contents obtained in pulp samples collected in 2021 and 2022 revealed significant differences depending on the origin of the samples.

With regard to leaves, the average aluminium content obtained from the Malanje, Huambo and Huíla samples was 12906 ± 5179 mg·kg⁻¹ DB. This content is particularly elevated but corresponds to those measured in the leaves of a number of aluminium hyperaccumulating

<caption>**Table 1**</caption>

Total aluminium content of fruit pulps, leaves, roots of A. boehmii and of soils by region and year of collection, expressed in dry basis (DB).

<table><thead><tr><th>Samples</th><th>Origin</th><th>Sampling year</th><th>Total Al content (mg·kg<sup>-1</sup> DB)</th></tr></thead><tbody><tr><td rowspan="6">Fruit pulp</td><td>Angola, blend</td><td>2021</td><td>9175 ± 384<sup>a</sup></td></tr><tr><td>Malanje</td><td>2022</td><td>7738 ± 21<sup>a</sup></td></tr><tr><td>Malanje</td><td>2023</td><td>7370 ± 41<sup>**</sup></td></tr><tr><td>Huambo</td><td>2022</td><td>8304 ± 292<sup>c</sup></td></tr><tr><td>Huambo</td><td>2023</td><td>6297 ± 40<sup>**</sup></td></tr><tr><td>Huíla</td><td>2022</td><td>10280 ± 136<sup>a</sup></td></tr><tr><td rowspan="3">Leaves</td><td>Malanje</td><td>2023</td><td>6783 ± 126<sup>**</sup></td></tr><tr><td>Huambo</td><td></td><td>16660</td></tr><tr><td>Huíla</td><td></td><td>6997</td></tr><tr><td rowspan="3">Roots</td><td>Malanje</td><td></td><td>15060</td></tr><tr><td>Huambo</td><td></td><td>423</td></tr><tr><td>Huíla</td><td></td><td>1429</td></tr><tr><td rowspan="3">Soil</td><td>Malanje</td><td></td><td>10533</td></tr><tr><td>Huambo</td><td></td><td>10611</td></tr><tr><td>Huíla</td><td></td><td>15675</td></tr><tr><td></td><td></td><td></td><td>51019</td></tr></tbody></table>

Mean and standard deviation (n = 3* or n = 2**). Same letters in the last column indicate no significant difference at p < 0.05 (only for the samples analyzed in triplicate).

plants found in tropical areas as *Eumachia* or *Miconia* species (Metali et al., 2012; Timpone et al., 2025; Turner et al., 2021). However, it was 1.6 times higher than that measured by Baumgärtel et al. (2022) in the leaves of a closely related species (*Anisophyllea quangensis* Engl. ex Henriq.) collected in a nearby region of Angola (7884 mg·kg⁻¹ DB).

The results obtained for root samples ranged from 400 to over 10000 mg·kg⁻¹ DB. Finally, for soils, the measured levels were high but corresponded to results already obtained for certain soils of the same type in tropical areas (Timpone et al., 2025).

Correlation analysis, based on samples collected in 2023 (Table 2), revealed a potential association between aluminium content in leaves and fruit pulp (R² = 0.832). A strong correlation was obtained between root and soil aluminium contents (R² ≥ 0.999). However, there was no clear correlation between aluminium content in pulp and that in soil or roots. Of course, these first results need to be confirmed by supplementing the data with further measurements in more samples.

## 3.2. Comparison with other fruits

Common edible fruits contain low aluminium amount with most fruits between 3 and 20 mg·kg⁻¹ DB (Table 3). Fruits that are usually grown for large-scale human consumption do not concentrate aluminium. These plant dispersal organs therefore do not accumulate this element, even when the soil contains significant amounts of it. Citrus hydroponic studies showed Al is immobilized primarily in roots and root cell walls by pectin-binding with comparatively low translocation to shoots, indicating limited movement toward aerial tissues under many conditions (Zhang et al., 2022). Experimental studies in other species likewise find the highest Al in roots and root-associated fractions (de Abreu et al., 2021). These plant-level findings support the general expectation that fruit pulp often contains less Al than root tissues.

For a given fruit, Al content can vary according to soil chemistry, agronomic practices (irrigation sources, liming, etc.), genotype and local

<caption>**Table 2**</caption>

Correlation table (R²) between aluminium contents in fruit pulp, leave, root and soil samples taken in 2023.

<table><thead><tr><th></th><th>Fruit pulp</th><th>Leaves</th><th>Roots</th><th>Soil</th></tr></thead><tbody><tr><th>Fruit pulp</th><td>1</td><td>0.832</td><td>0.021</td><td>0.029</td></tr><tr><th>Leaves</th><td></td><td>1</td><td>0.075</td><td>0.063</td></tr><tr><th>Roots</th><td></td><td></td><td>1</td><td>0.999</td></tr><tr><th>Soil</th><td></td><td></td><td></td><td>1</td></tr></tbody></table>
<caption>**Table 3**</caption>

Aluminium content in several cultivated edible fruits, expressed in dry basis (ANSES, 2025a; Bobuș Alkaya et al., 2022; Liang et al., 2019).

<table><thead><tr><th>Fruits</th><th>Al content (mg·kg<sup>-1</sup> DB)</th></tr></thead><tbody><tr><td>Stone fruits: peach, apricot, cherry, plum</td><td>5.0–21.3</td></tr><tr><td>Citrus: orange, lime, lemon, grapefruit</td><td>9.5 – 18.4</td></tr><tr><td>Berries: strawberry, blueberry, raspberry</td><td>5.6 – 13.4</td></tr><tr><td>Grape</td><td>3.4 – 4.5</td></tr><tr><td>Tropical fruits: banana, papaya, pineapple, mango</td><td>2.5 – 8.0</td></tr><tr><td>Pome fruits: apple, pear</td><td>3.6 – 5.1</td></tr><tr><td>Watermelon</td><td>3.3</td></tr></tbody></table>

contamination. Low soil pH (acidic soils) increases Al solubility and so bioavailable Al. Raising soil pH by liming reduces exchangeable/toxic Al and shifts Al into less bioavailable forms. Tomato experiments in tropical soils showed liming lowered exchangeable Al and reduced plant uptake, and genotype responses differed accordingly (Nogueiroli et al., 2015). Plant genotype and root-cell-wall chemistry strongly influence retention versus translocation. For example, in Citrus, pectin in the root cell wall preferentially binds Al and limits Al translocation to shoots; species/genotype differences in root-cell wall affinity control how much Al moves upward (Zhang et al., 2022). Other experimental works emphasize that species, cultivar/rootstock and developmental stage alter accumulation and tolerance. Some rootstocks/cultivars tolerate and sequester more Al in roots without translocating to shoots (de Abreu et al., 2021; Ofoe et al., 2023). Aluminium can also be in competition with calcium and other cations. High calcium content in roots was for instance associated with reduced Al uptake (Frankowski, 2016). Finally, comparisons between polluted and protected sites showed substantially higher plant tissue Al where soils or local emissions due to anthropogenic activities increased available Al, supporting geographic/environmental hotspots for elevated plant Al.

Nevertheless, the aluminium contents measured in loengo pulp were therefore unusual and could not be compared to well-known and well-characterized fruits. Indeed, the aluminium content of loengo pulp is at least 300 times higher in dry basis than that of standard edible fruits. However, there is very little literature available on the detailed mineral profile of endemic African wild fruits. It is therefore difficult to say whether the loengo is an exception, and it would be useful to analyze the mineral composition of other fruits collected in the same ecosystems.

### 3.3. Elements of toxicology and recommendations

After ingestion of foods, acidity in the stomach tends to solubilize the aluminium compounds mainly as Al³⁺. However, the pH increases in the intestine progressively that results in the formation of aluminium insoluble complexes or salts as hydroxides, which cannot be absorbed and so are eliminated in feces. This phenomenon contributes to the weak bioavailability of aluminium that is evaluated between 0.1 % and 0.3 % (ANSES, 2025b). Nevertheless, Al bioavailability does not depend only on water solubility. It can also be modulated by other compounds that are simultaneously present in the bolus and that can increase (organic acids for example) or decrease it (polyphenols for example).

After intestinal absorption, aluminium is mainly carried in blood by transferrin, a metal binding plasmatic protein (Aguilar et al., 2008). Despite being mainly eliminated through urine excretion (> 80 %), a small but significant amount of this circulating metal is able to accumulate in various tissues, especially bones, as shown by various studies on animal models. Clinically demonstrated in cases of high chronic exposure, the toxic effects of aluminium mainly affect the central nervous system (encephalopathies, psychomotor disorders) and bone tissues. However, no study has yet clearly demonstrated such effects in a standard human population exposed to aluminium solely through their regular diet (Aguilar et al., 2008).

Based on various toxicity studies and population exposure (Aguilar et al., 2008; ANSES, 2025b), EFSA set a Provisional Tolerable Weekly

Intake (PTWI) of 1 mg·kg⁻¹ body weight per week in 2008 (a sevenfold reduction from the previous PTWI established in 1990 by FAO-WHO). In 2011, JECFA revised the value established in 2008 upwards, setting the PTWI at 2 mg·kg⁻¹ body weight per week (ANSES, 2025b). This PTWI includes all chemical species of aluminium potentially present in food.

Without considering other potential sources of aluminium in the diet, calculations made for an adult weighing 60–80 kg, assuming that the average weight of a fruit is 14 g and that the mass fraction of pulp in a fruit is 55 %, show that it is not advisable to consume more than 10 loengo fruits per week. This number drops to 5 for a 10-year-old child (30 kg). These results deserve special attention when considering the data on fruit consumption provided by da Costa et al. (2025).

## 4. Conclusion

Based on the analysis of seven different fruit samples collected from three distinct areas over three consecutive years, this study clearly showed that A. boehmii is a species that hyperaccumulates aluminium. While high aluminium levels have already been described in the leaves of various tropical plant species, to our knowledge, such accumulation in edible fruit has never been reported.

As the amount of aluminium present in the edible part of the fruit is very elevated, chronic toxicity problems can be expected for regular consumers of the fruit. For populations accustomed to consuming it, special attention is required, particularly for children. In any case, it is advisable not to consume this fruit in large quantities.

Of course, in order to complete this exploratory work and to be clearer for the fruit consumption recommendation, it would be necessary to conduct further studies by increasing the number of samples and carrying out cross-checks between different laboratories. A better understanding of how the plant accumulates aluminium in its fruits would also be of great interest.

### CRediT authorship contribution statement

**Manuel Dornier:** Conceptualization, Data curation, Formal analysis, Funding acquisition, Methodology, Project administration, Resources, Supervision, Validation, Visualization, Writing – original draft. **Bettencourt Munanga:** Conceptualization, Funding acquisition, Project administration, Resources, Supervision, Writing – review & editing.

**Famoroso João da Costa:** Data curation, Investigation, Software, Validation, Visualization, Writing – review & editing. **Adrien Servent:** Data curation, Formal analysis, Methodology, Supervision, Validation, Visualization, Writing – review & editing.

### Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

### Acknowledgements

The authors would like to thank the French Embassy in Angola (Luanda) for funding the study, CIRAD (Montpellier, France) for financial contribution and Rainha Njinga a Mbande University (Malanje, Angola) for support.

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