Evaluation of environment on polyphenols and flavonoids in oxalis corymbosa extracts as a potential source of antioxidants

Oxalis corymbs is an important medicinal and edible perennial herb that distributes widely in the world. To evaluate the effect of the environment on the antioxidant components in Oxalis corymbs, this study was performed to evaluate phenolic compounds contents and antioxidant activities of O. corymbs in different parts and seasons. Total phenolic content (TPC) and total flavonoid content (TFC) of different parts were decreased in four seasons in the following order: shoots > leaves > stems. The highest TPC and TFC were 76.63 ± 4.32 mg GAE/g and 71.22±3.61 mg RE/g in shoots in winter. Notably, the decreased trend of DPPH and FRAP was also in the order of shoots > leaves > stems in four seasons. The supreme antioxidant activities (IC50) of DPPH and FRAP were 0.07±0.00 mg/mL and 0.08±0.00 mg/mL in shoots respectively. A good antioxidant potential of neutralization OH radical was gained in shoots and stems, the averages of IC50 were 2.89 mg/mL and 2.59 mg/mL respectively. The highest protection factor of Ranchman was 1.43±0.01 in leaves, which was first reported in the extracts of Oxalidaceae. Moreover, a strong correlation between TPC, TFC and antioxidant activities indicated that phenolic compounds were the main components responsible for the antioxidant behavior of O. corymbosa. Consequently, the shoots of O. Corymbosa may have good oxidation resistance in winter due to its high contents of TPC and TFC. This study demonstrates that O. corymbosa possessed potent antioxidant properties, and could be a valuable natural source of antioxidants used in both medical and food industries.