Comparison of active constituents, antioxidant capacity, and α-glucosidase inhibition in Pluchea indica leaf extracts at different maturity stages

Pluchea indica (L.) Less. or Indian camphorweed leaves have been used as a traditional herbal medicine in addition to being consumed in various vegetable dishes throughout India, Southeast Asia, Australia, and America. The chemical composition and some biological activities have been studied using extracts of these leaves; however, the effects of the maturation stage and geographical origin have not been studied in depth. The concentrations of 6 active compounds, 3-O-caffeoylquinic acid, 4-O-caffeoylquinic acid, 5-O-caffeoylquinic acid, 3,4-O-dicaffeoylquinic acid, 3,5-O-dicaffeoylquinic acid, and 4,5-O-dicaffeoylquinic acid, were determined in the leaf extracts from three different maturity stages of P. indica collected from three locations in Thailand using high-performance liquid chromatography. The total phenolic content and in vitro alpha-glucosidase inhibition of the leaf extracts were also studied in addition to the antioxidant properties, including the 1,1-diphenyl-2-picrylhydrazyl and 2,2'-azinobis (3-ethyl-benzothiazoline-6-sulfonic acid) diammonium salt free radical scavenging capabilities and ferric reducing antioxidant power. Notably, the juvenile leaf shoot extracts contained significantly higher concentrations of the bioactive and phenolic compounds and showed stronger inhibition of alpha-glucosidase activity compared to every stage of the mature leaves. The antioxidant capacities of the juvenile leaves also surpassed those of the mature leaves. Taken together, these data suggest that juvenile P. indica leaves may be a more suitable choice for further development as a functional food and other nutraceutical products.