Evaluation of Oxalis Corymbosa Extracts from Different Plant Parts and Seasons as a Potential Source of Antioxidants

Abstract

Oxalis corymbosa is an important medicinal and edible perennial herb widely distributed throughout the world. The aim of this study was to evaluate the phenolic contents and antioxidant activities of O. corymbosa in different plant parts and seasons. We found that different parts of the plant could be sorted in the following order, shoots > leaves > stems in terms of total phenolic content (TPC) and total flavonoid content (TFC) in four seasons. The highest TPC and TFC appear in shoots during winter, which were 76.63 ± 4.32 mg GAE/g and 71.22 ± 3.61 mg RE/g, respectively. Notably, 2, 2-diphenyl-1-picryl-hydrazine (DPPH) and ferric reducing antioxidant power (FRAP) were also different among different parts in four seasons, specifically, in the order of shoots > leaves > stems. And the supreme antioxidant activities [(the half maximal inhibitory concentration (IC50)] of DPPH and FRAP were 0.07 ± 0.00 mg/mL and 0.08 ± 0.00 mg/mL in shoots, respectively. We found that a good antioxidant potential of neutralization OH radical was higher in shoots and stems, with IC50 of 2.89 mg/mL and 2.59 mg/mL on average, respectively. In addition, the highest protection factor using the Rancimat method was 1.43 ± 0.01 in leaves. To the best of our knowledge, we are the first to report such finding in the extracts of Oxalidaceae. Moreover, a strong correlation between TPC, TFC and antioxidant activities was found, which indicated that phenolic compounds were the main components responsible for the antioxidant behavior of O. corymbosa. Consequently, we conclude that the shoots of O. corymbosa may have good oxidation resistance during winter due to its high 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 medicinal and food industries.