# Study of the Phenolic Compound Profile of _Arbutus unedo_ L.
## 3 Results and Discussion
### Analysis of Phenolic Compounds by HPLC-TQ-MS/MS
#### 3.3.2 Profile of Phenolic Compounds at Different Ripening Stages
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Class**} & \multirow{2}{*}{**Analyte ([M-H]\({}^{-1}\)/MS 2:]**} & \multicolumn{3}{c}{**mg 100 g\({}^{-1}\) DW**} \\ \cline{3-5}  & & **Unripe** & **Intermediate** & **Ripe** \\ \hline Hydroxybenzoic acids & 4-hydroxybenzoic acid (163.8/92.9) & 0.50 \(\pm\) 0.03 a & 0.34 \(\pm\) 0.02 b & 0.37 \(\pm\) 0.02 b \\  & Gallic acid (168.9/124.7) & 1.4 \(\pm\) 0.1 a & 2.1 \(\pm\) 0.2 b & 4.7 \(\pm\) 0.4 c \\  & Protocatechuic acid (152.7/108.7) & X & X & X \\  & Syringic acid (197.0/180.7) & ✓ & ✓ & 0.63 \(\pm\) 0.04 \\  & Vanillic acid (167.0/151.7) & X & X & X \\ Hydroxycinnamic acids & P-comamic acid (163.0/118.8) & ✓ & ✓ & ✓ \\  & Chlorogenic acid (353.1/190.7) & ✓ & ✓ & 0.676 \(\pm\) 0.005 \\  & Caffeic acid (178.9/134.7) & X & X & X \\  & Caftaric acid (310.9/148.8) & ✓ & ✓ & ✓ \\ Flavonols & Quercetin (300.9/150.6) & 0.79 \(\pm\) 0.01 a & 0.84 \(\pm\) 0.01 a & 0.84 \(\pm\) 0.01 a \\  & Quercetin 3-\(\beta\)-glucoside (463.1/299.7) & 2.3 \(\pm\) 0.2 a & 1.7 \(\pm\) 0.1 b & 2.6 \(\pm\) 0.2 a \\  & Rutin (609.5/300.1) & 0.43 \(\pm\) 0.03 a & 0.54 \(\pm\) 0.04 b & 0.57 \(\pm\) 0.04 b \\  & Kaempfer (284.9/226.3) & 0.74 \(\pm\) 0.08 a & 0.39 \(\pm\) 0.04 b & 0.73 \(\pm\) 0.09 a \\ Flavanols & (+) Catequin (288.9/108.8) & 149 \(\pm\) 19 a & 29 \(\pm\) 4 b & 28 \(\pm\) 5 b \\  & (-)-Epigallocatechin gallate (457.1/124.4) & 1.83 \(\pm\) 0.04 & ✓ & ✓ \\  & Epigallocatechin (304.9/164.6) & 26 \(\pm\) 2 a & 10 \(\pm\) 1 b & 11 \(\pm\) 1 b \\  & Procyanidin B2 (577.2/288.8) & 49 \(\pm\) 2 a & 41 \(\pm\) 2 b & 36 \(\pm\) 2 c \\ Flavanones & Narringin (579.1/151.0) & ✓ & 0.35 \(\pm\) 0.04 & ✓ \\ Flavones & Vitevan (431.1/311.1) & 0.911 \(\pm\) 0.004 a & 0.980 \(\pm\) 0.004 a & 0.895 \(\pm\) 0.005 a \\ Stilbenes & _trans_-Resveratrol (226.9/142.8) & ✓ & ✓ & ✓ \\  & _trans_-Piceid (390.0/227.4) & ✓ & ✓ & ✓ \\ \hline \hline \end{tabular}  
* _A. unedo_ L. berries harvested in Madrid in 2016.
* Product ions used for quantification; X: not detected; ✓: detected but not quantified; a.b.c mean values within a row followed by different superscript letters are significantly different when subjected to statistical analysis (\(p\leq\) 0.05).  
\end{table} 
Table 4: Content of phenolic compounds in _A. unedo_ L. berries * at different ripening stages analyzed by HPLC-TQ-MS/MS. \(\beta\)-glucoside, rutin, and kaempfer) were identified and quantified in the three ripening stages with similar amounts. Among these flavonoids, quercetin-3-\(\beta\)-glucoside was the analyte that presented the highest concentration values (2.3, 1.7 and 2.6 mg of quercetin-3-\(\beta\)-glucoside/100 g of DW in unripe, intermediate, and ripe berries, respectively) (Figure S3). Flavanols or flavan-3-ols derived from flavans can exist as monomeric forms (catechin being the most representative monomeric flavanol), or as condensed polymers (also so-called proanthocyanidins) [15]. Catechins and proanthocyanidins are common and abundant in a wide range of fruits (e.g., grapes, apples, plums, kiwi, red fruits), cereals, seeds, spices and aromatic plants, and to a lesser extent, in vegetables and foods of plant origin [34; 35]. High amounts of (+)-catechin, procyanidin B2, epigallocatechin and (\(-\))-epigallocatechin gallate were found in the samples analyzed (Figure S3), particularly in the unripe strawberry tree fruits (149, 49, 26, and 1.83 mg/100 g of DW, respectively). In the intermediate and ripe stages, the amount of these compounds decreased, being similar in both ripening stages and finding statistical significance with respect to the unripe strawberry tree berries (Table 4). This trend observed for flavanols during the maturation stage agrees with the results obtained for the TPC and RSA, obtaining the highest values in the unripe fruits (Tables 1 and 2). Naringin, which belongs to the flavanones group, was identified and quantified at a small amount (0.35 \(\pm\) 0.01 mg/100 g of DW) in the fruits with intermediate ripening.