Variation in Antioxidant Activity and Flavonoid Aglycones in Eggplant (Solanum melongena L.) Germplasm

Eggplant (Solanum melongena L.) is an excellent source of vitamins A and C and of flavonoid compounds, which are important antioxidant components believed to reduce the risk of various diseases. We investigated the antioxidant activity and flavonoid content in eggplant leaves and fruits to identify genetic resources with high antioxidant capacity for use in food or as feed additives, and also determined the influence of days to flowering, leaf blade colors, and latitudes of origin on the antioxidant activity and flavonoid content in eggplant leaves. The accessions originating from 45°N showed the highest flavonoid contents (AVG. = 15.4 μg mg-1) followed by accessions from 30°～45°N (AVG. = 13.0 μg mg-1), 15°～30°N (AVG. = 11.0 μg mg-1), and 0°～15°N (AVG. = 9.5 μg mg-1). The same pattern was also found in 2,2 -azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and 1,1-diphenyl-2- picryl-hydrazil (DPPH) antioxidant activities. High ABTS and DPPH activity and flavonoid content were found in the early-flowering accessions. All flavonoids of the greenish violet leaves were significantly higher than those of green leaves. The flavonoid concentration in eggplant leaves was 10 to 20 fold greater, at an average of 15.6 μg mg-1, than that of the fruit (AVG. = 0.9 μg mg-1). Taken together, eggplant leaves represent a potential source of natural antioxidants due to their high flavonoid content.