Variation in the composition and antioxidant activity of Vaccinium myrtillus populations collected in Croatia and Montenegro

Vaccinium myrtillus L., Ericaceae, (bilberry) leaves are traditionally used in southeastern Europe for the treatment of diabetes. In the present study, the variation of the phytochemical composition, as well as antiradical and tyrosinase-inhibiting activity of 11 bilberry populations from Croatia (5) and Montenegro (6) was investigated, considering their use for cosmetic purposes. Content of phenols, flavonoids and phenolic acids, as well as antiradical and enzyme inhibiting activity of leaf extracts were determined spectrophotometrically. The content of the most abundant flavonoid, hyperoside, was determined using HPLC with DAD detection. Furthermore, the content of selected metals (K, Ca, Mn, Fe, Cu, Zn, Br, Rb, Sr) was determined using TXRF. A significant quantitative variability of total phenols (386.8–133.9 mg/g), flavonoids (83.1–12.0 mg/g) and phenolic acids 112.4–38.0 mg/g) was recorded. The extracts displayed excellent antiradical activity (IC₅₀ between 120.8–11.1 mg/g) and somewhat weaker anti-tyrosinase activity (IC₅₀ between 400.3–170.9 mg/g). The hyperoside content in the extracts varied between 73.1 and 5.7 mg/g. There was no statistically significant correlation between the content and area of origin. However, the chromatograms of extracts from Montenegro could be easily distinguished from the Croatian ones by the presence of an additional peak in chromatogram, which, according to its UV spectrum, represents a quercetin derivative. The observed activities of bilberry leaf extracts suggest that they might be used in cosmetic products. However, before the development of such products, a detailed analysis of plant material is advisable in order to select the populations with the highest activity.