Geographic Variability of Biologically Active Compounds, Antioxidant Activity and Physico-Chemical Properties in Wild Bilberries (Vaccinium myrtillus L.)

Abstract

The aim of this study was to characterize the variation in biologically active compounds, antioxidant activity and physico-chemical properties in naturally grown bilberries gathered from different sites in Northern Europe. The variability in the biologically active compounds, antioxidant capacity and physico-chemical properties, as well as the development of tools for the authenticity and quality control of wild bilberries (V. myrtillus L.) in different geographical locations was evaluated. The berries of bilberries were handpicked during the summers of 2019 and 2020 during the time periods when they are typically harvested for commercial purposes in Northern Europe (Norway (NOR), Finland (FIN), Latvia (LVA) and Lithuania (LTU)). Berries from locations in NOR were distinguished by their higher mean TPC (791 mg/100 g FW, average), whereas the mean TPC of samples from the most southern country, LTU, was the lowest (587 mg/100 g FW). The TPC of bilberries ranged from 452 to 902 mg/100 g FW. The TAC values of investigated bilberry samples varied from 233 to 476 mg/100 g FW. A high positive correlation was found between TPC and antioxidant activity of the bilberry samples (R = 0.88 and 0.91 (FRAP and ABTS assays, respectively)), whereas the correlation between TAC and antioxidant activity was lower (R = 0.65 and 0.60). There were variations in the TPC and TAC values of investigated berries, suggesting that genotype also affects the TPC and TAC in berries. In 2020, the pH values and TSS contents of berries were significantly lower than in 2019. To the best of our knowledge, this is the first comprehensive reported evaluation of the biologically active compounds in wild bilberries from different Northern European countries using one laboratory-validated method.

Keywords: anthocyanins; antioxidant activity; bilberry; different geographical locations; natural habitats; polyphenol.

Figure 1

pH values of bilberries. Values are presented as means ± standard deviations. Different letters within the same column indicate significant differences between the collection locations (B1–B12) (p < 0.05). Significant differences between 2019 and 2020 are indicated by asterisks (*) (p < 0.05). Locations of bilberry sample collection include Norway (NOR), Finland (FIN), Latvia (LVA) and Lithuania (LTU).

Figure 2

TSS values of bilberries. Values are presented as means ± standard deviations. Different letters within the same column indicate significant differences between the collection locations (B1–B12) (p < 0.05). Significant differences between 2019 and 2020 are indicated by asterisks (*) (p < 0.05). Locations of bilberry sample collection include Norway (NOR), Finland (FIN), Latvia (LVA) and Lithuania (LTU).

Figure 3

Total phenolic content (TPC) of bilberries mg/100 g FW. Values are presented as means ± standard deviations. Different letters within the same column indicate significant differences between the collection locations (B1–B12) (p < 0.05). Significant differences between 2019 and 2020 are indicated by asterisks (*) (p < 0.05). Locations of bilberry sample collection include Norway (NOR), Finland (FIN), Latvia (LVA) and Lithuania (LTU).

Figure 4

Total anthocyanin content (TAC) of bilberries mg/100 g FW. Values are presented as means ± standard deviations. Different letters within the same column indicate significant differences between the collection locations (B1–12) (p < 0.05). Significant differences between 2019 and 2020 are indicated by asterisks (*) (p < 0.05). Locations of bilberry samples collection include Norway (NOR), Finland (FIN), Latvia (LVA) and Lithuania (LTU).

Figure 5

Ferric-reducing antioxidant power (FRAP) of bilberries (μmol TE/g FW). Different letters above the same color bars indicate significant differences between the mean values (p < 0.05). Significant differences between 2019 and 2020 are indicated by asterisks (*) (p < 0.05). Locations of bilberry samples collection include Norway (NOR), Finland (FIN), Latvia (LVA) and Lithuania (LTU).

Figure 6

ABTS radical scavenging activity (RSA) of bilberries (μmol TE/g FW). Different letters above the same color bars indicate significant differences between the mean values (p < 0.05). Significant differences between 2019 and 2020 are indicated by asterisks (*) (p < 0.05). Locations of bilberry samples collection include Norway (NOR), Finland (FIN), Latvia (LVA) and Lithuania (LTU).