HPLC-ESI-QTOF-MS analysis of phenolic compounds, antioxidant capacity and alpha-glucosidase inhibitory effect of Bambusa nutans leaves

摘要

Bambusa nutans (BN), an important bamboo species, generates vast quantity of leaves as underutilized biomass residue during harvesting of the poles for various industrial applications. One of the approaches for management of this biomass is the recovery of valuable components for socio-economic and environmental benefits. In the current study, eight different extracts of fresh and shade dried leaves of BN using methanol and methanol: water (4:1, v/v) under Soxhlet and at room temperature have been prepared and evaluated for their yield, total phenolic content, total flavonoid content, total antioxidant capacity employing DPPH free radical scavenging, reducing power, hydroxyl radical scavenging and metal chelating assays. The hot methanol:water (4:1) extract of the fresh leaves, being promising has been further fractionated with petroleum ether, ethyl acetate, butanol and water. Ethyl acetate and butanol fractions display potent antioxidant activity. They however, show weak alpha-glucosidase inhibitory activity. A total of 16 phenolic compounds (7 phenolic acids, 7 flavones and 2 flavonols) with varied distribution in these fractions have been identified using HPLC-ESI-QTOF-MS. A significant correlation is found between phenolics and antioxidant capacity as well as within the various antioxidant assay methods. The findings suggest the use of Bambusa nutans leaves as a potential natural source of antioxidants.