Role of polyphenols in antioxidant capacity of napiergrass from different growing seasons

Napiergrass, used in Taiwan as a new organic nourishment, showed fluctuating antioxidant capacities under different growth conditions. An index for selection of best quality material is therefore needed. Since polyphenols made the highest contribution to their antioxidant capacity, the individual effects of plant parts, growing seasons, and growth periods on both polyphenols and antioxidant activities were studied, using two varieties of napiergrass (purple, NBM and green, TLG2). Results demonstrated that leaves of NBM had a higher antioxidant capacity than their stems and all parts of the green varieties. Classification of napiergrass according to polyphenols revealed the effects of varieties and seasons on the anthocyanins and their close relationship to antioxidant capacity. Discriminant analysis confirmed that anthocyanins are the most effective component in classifying napiergrass. Therefore, red colour of anthocyanin might be used as a good index for the physiological activity of napiergrass.