Screening In Vitro Targets Related to Diabetes in Herbal Extracts from Peru: Identification of Active Compounds in Hypericum laricifolium Juss. by Offline High-Performance Liquid Chromatography.

This study investigates in vitro targets related to diabetes in 30 herbal extracts from Peru, for the first time, using α-glucosidase, aldose reductase (AR) inhibitory assays and 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) scavenging assays. Among the 30 herbal extracts, Hypericum laricifolium Juss. (HL) was the herb which showed more than 50% inhibition in all assays, presenting 97.2 ± 2.0%, 56.9 ± 5.6%, 81.9 ± 2.5%, and 58.8 ± 4.6% inhibition for the α-glucosidase, AR, DPPH, and ABTS assays, respectively. Finally, six bioactive compounds, namely, protocatechuic acid, chlorogenic acid, caffeic acid, kaempferol 3-O-glucuronide, quercetin, and kaempferol were identified in HL by offline high-performance liquid chromatography (HPLC). Quercetin exhibited the strongest inhibition in all enzyme assays and the strongest antioxidant activity. The results suggest that HL shows great potential for the complementary treatment of diabetes and its complications.

Investigation of the antioxidant and aldose reductase inhibitory activities of extracts from Peruvian tea plant infusions.

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.

Screening of Peruvian Medicinal Plants for Tyrosinase Inhibitory Properties: Identification of Tyrosinase Inhibitors in Hypericum laricifolium Juss.

Tyrosinase inhibitors are of far-ranging importance in cosmetics, medicinal products, and food industries. Peru is a diverse country with a wide variety of plants that may contain excellent anti-tyrosinase inhibitors. In the present study, the tyrosinase inhibitory properties of 50 medicinal plant extracts from Peru were investigated using tyrosinase assay. Among plant extracts, those that showed an inhibition rate >50% were Hypericum laricifolium Juss., Taraxacum officinaleF.H.Wigg., and Muehlenbeckia vulcanicaMeisn., with H. laricifolium Juss. showing the greatest anti-tyrosinase activity. Although H. laricifolium Juss. has been widely used as a medicinal plant by Peruvians, little is known regarding its bioactive components and effects on tyrosinase activity. For this reason, we attempted to discover tyrosinase inhibitors in H. laricifolium Juss. for the first time. The bioactive components were separated by Sephadex LH-20 chromatography and eluted with 100% methanol. Eight compounds were discovered and characterized by high-performance liquid chromatography coupled with diode array detection (HPLC-DAD): protocatechuic acid, p-hydroxybenzoic acid, chlorogenic acid, vanilic acid, caffeic acid, kaempferol 3-O-glucuronide, quercetin, and kaempferol. In addition, the concentration of these compounds required for 50% inhibition (IC50) of tyrosinase activity were evaluated. Quercetin exhibited the strongest tyrosinase inhibition (IC50 14.29 ± 0.3 µM). Therefore, the Peruvian plant H. laricifolium Juss. could be a novel source for anti-tyrosinase activity.