ABSTRACT
Valeriana rigida Ruiz & Pav. (V. rigida) has long been used as a herbal medicine in Peru; however, its phytochemicals and pharmacology need to be scientifically explored. In this study, we combined the offline 2,2-diphenyl-1-picryl-hydrazyl-hydrate (DPPH)-/ultrafiltration-high-performance liquid chromatography (HPLC) and high-speed counter-current chromatography (HSCCC)/pH-zone-refining counter-current chromatography (pH-zone-refining CCC) to screen and separate the antioxidants and aldose reductase (AR) inhibitors from the 70% MeOH extract of V. rigida, which exhibited remarkable antioxidant and AR inhibitory activities. Seven compounds were initially screened as target compounds exhibiting dual antioxidant and AR inhibitory activities using DPPH-/ultrafiltration-HPLC, which guided the subsequent pH-zone-refining CCC and HSCCC separations of these target compounds, namely 3-O-caffeoylquinic acid, 4-O-caffeoylquinic acid, 5-O-caffeoylquinic acid, 3,4-O-di-caffeoylquinic acid, 3,5-O-di-caffeoylquinic acid, 4,5-O-di-caffeoylquinic acid, and 3,4,5-O-tri-caffeoylquinic acid. These compounds are identified for the first time in V. rigida and exhibited remarkable antioxidant and AR inhibitory activities. The results demonstrate that the method established in this study can be used to efficiently screen and separate the antioxidants and AR inhibitors from natural products and, particularly, the root extract of V. rigida is a new source of caffeoylquinic acids with antioxidant and AR inhibitory activities, and it can be used as a potential functional food ingredient for diabetes.
ABSTRACT
In the present study, the antioxidant and aldose reductase inhibitory activities of 24 Peruvian infusion tea plants were investigated by 2,2'-diphenyl-1-picrylhydrazyl (DPPH), 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), and aldose reductase assays. Phoradendron sp. showed the highest inhibition of aldose reductase (IC50, 1.09±0.06µg/mL) and considerable antioxidant (IC50 of DPPH, 58.36±1.65µg/mL; IC50 of ABTS, 9.91±0.43µg/mL) effects. In order to identify the antioxidants and aldose reductase inhibitors of Phoradendron sp., DPPH-high performance liquid chromatography (HPLC) and ultrafiltration-HPLC assays were performed. Chlorogenic acid, 3,5-di-O-caffeoylquinic acid, and 1,3,5-tri-O-caffeoylquinic acid were identified as the antioxidants and aldose reductase inhibitors; apigenin was identified as the antioxidant. Finally, Phoradendron sp. and its aldose reductase inhibitors also showed a dose-dependent anti-inflammatory effect without cellular toxicity. These results suggested that Phoradendron sp. can be a potent functional food ingredient as an antioxidant, aldose reductase inhibitor and anti-inflammatory agent.
