The preventive and therapeutic potency against oxidative stress and
diabetic complications of Nelumbo nucifera were evaluated via the
1,1-diphenyl-2-picrylhydrazyl (DPPH),
Trolox equivalent
antioxidant capacity (TEAC), and total
reactive oxygen species (ROS) assays, as well as the rat lens
aldose reductase (RLAR) and
advanced glycation endproducts (AGE) assays. The leaf extract of N. nucifera exerted potent
antioxidant effects as well as marked inhibitory effects for RLAR and AGE formation, corresponding to high values for total phenolic content (TPC) and total
flavonoid content (TFC). Among several
solvent fractions, the EtOAc and n-BuOH fractions, having prominent TPC and TFC values, showed significant
antioxidant effects in the DPPH and TEAC assays. Moreover, the EtOAc fraction exhibited superior inhibitory effects in the total ROS, RLAR, and AGE assays, with IC(50) values of 9.4, 2.4, and 28.2microg/ml, respectively. Also, the HPLC profiles of the active EtOAc fraction indicated that
quercetin 3-O-beta-d-glucopyranoside (Qc-3-Glc) and Qc 3-O-beta-d-glucuronopyranoside (Qc-3-Gln) were two of its major components, as well as Qc 3-O-beta-d-galactopyranoside (Qc-3-Gal) as a minor compound. Therefore, the results suggest that two key
antioxidant flavonoids, Qc-3-Glc and Qc-3-Gln, may play important roles in the
antioxidant and RLAR inhibitory effects of N. nucifera leaves. Also, the leaves, and the
flavonoids contained within them, would clearly have potential uses in the development of therapeutic or preventive agents for
diabetic complications and oxidative stress-related diseases.