Inhibitory effects of Nelumbo nucifera leaves on rat lens aldose reductase, advanced glycation endproducts formation, and oxidative stress.

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.

Re-evaluation of the antioxidant prenylated flavonoids from the roots of Sophora flavescens.

The objective of this research was to re-evaluate the antioxidant effects of the prenylated flavonoids from Sophora flavescens via in vitro 1,1-diphenyl-2-picrylhydrazyl (DPPH), 2,2'-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS), peroxynitrite (ONOO(-)), and total reactive oxygen species (ROS) assays. In addition, a further examination of kuraridinol, kurarinol, and kurarinone, also isolated from S. flavescens, was carried out by the inhibition of tert-butylhydroperoxide (t-BHP)-induced intracellular ROS generation and t-BHP-induced activation of nuclear factor-kappaB (NF-kappaB). Upon re-examination of the ethyl acetate (EtOAc) soluble fraction of S. flavescens, two major prenylated chalcones, including kuraridin and kuraridinol, along with a minor prenylated flavonol, kushenol C, were isolated as good DPPH scavengers. This was in contrast to the prenylated flavanones, sophoraflavanone G and kurarinone, which were isolated from the methylene chloride (CH(2)Cl(2)) fraction of the same source. Five flavanones consisting of kushenol E, leachianone G, kurarinol, sophoraflavanone G, and kurarinone exhibited significant antioxidant potentials in the ABTS, ONOO(-), and total ROS assays; however, the prenylated chalcones and prenylated flavonol showed more potent scavenging/inhibitory activities than the prenylated flavanones. Therefore, the prenylated chalcones and prenylated flavonol, rather than the prenylated flavanones, may make important contributions toward the marked antioxidant capacities of S. flavescens. Furthermore, kuraridinol, kurarinol, and kurarinone showed significant inhibitory activities against intracellular ROS levels as well as NF-kappaB activation by t-BHP. Overall, the results indicate that S. flavescens and its prenylated flavonoids may possess good anti-inflammatory activity, which is implicated in their significant antioxidant activity.

Comparative antioxidant activity and HPLC profiles of some selected Korean thistles.

As yet, no comparative analyses have been conducted regarding the comparative antioxidant activities and HPLC profiles of thistles distributed in Korea. Thus, this study was performed in order to evaluate the antioxidant potentials of seven Korean thistles: Cirsium lineare, Cirsium chanroenicum, Cirsium setidens, Cirsium japonicum var. ussuriense, Cirsium nipponicum, Cirslum pendulum and Carduus crispus, via peroxynitrite and DPPH free radical assays. Among seven Korean thistles, Carduus crispus exhibited the most significant antioxidant activity in both DPPH assay and peroxynitrite. In order to characterize the compounds contained in Korean thistles, we conducted HPLC analyses on the following ten flavonoids: luteolin-5-glucoside (1), luteolin-7-glucoside (2), apigenin-7-glucoside (3), hispidulin-7-neohesperidoside (4), apigenin-7-glucuronide (5), cirsimarin (6), pectolinarin (7), luteolin (8), apigenin (9) and acacetin (10). The results of our HPLC analyses indicated the presence of pectolinarin in the whole plants of C. setidens, C. lineare, C. nipponicum, C. pendulum, the aerial and underground parts of C. japonicum var. ussuriense, and the aerial parts of C. chanroenicum. Moreover, we were able to identify hispidulin-7-neohesperidoside and luteolin-7-glucoside in the whole plants of Carduus crispus, acacetin in the aerial parts of C. chanroenicum, cirsimarin in C. lineare.

Hypolipidemic effects of Sophora flavescens and its constituents in poloxamer 407-induced hyperlipidemic and cholesterol-fed rats.

In this study, we investigated the hypolipidemic effects of Sophora flavescens in poloxamer 407-induced hyperlipidemic and cholesterol-fed rats. The MeOH extract and 4 fractions of S. flavescens were administered at doses of 250 and 100 mg/kg body weight, respectively, once a day for 3 d to the poloxamer 407-induced hyperlipidemic rats. Serum lipid levels such as total cholesterol (TC), triglycerides (TG), and low-density lipoprotein-cholesterol (LDL-C) were markedly elevated in the poloxamer 407-induced hyperlipidemic control rats, while lipid levels were significantly decreased in the rats administered the MeOH extract or 4 fractions of S. flavescens. In addition, serum high-density lipoprotein-cholesterol (HDL-C) was reduced in the poloxamer 407-induced hyperlipidemic control rats. However, oral administration of both the MeOH extract and 4 fractions significantly increased HDL-C levels. Of the tested fractions, the EtOAc fraction showed the strongest lipid-lowering effect, as well as a high antiatherogenic potential with atherogenic index (A.I.) values of less than 1.92. We also investigated the hypolipidemic effects of the main compounds of the EtOAc fraction, kurarinol and kuraridinol, using the hyperlipidemic and hypercholesterolemic animal models. Here, elevated TC, TG, and LDL-C levels in the poloxamer 407-induced hyperlipidemic and cholesterol-fed rats were significantly reduced after oral administration of the compounds, and HDL-C levels had a significant increase. Furthermore, A.I. values were lowered by administering kurarinol and kuraridinol. In particular, kuraridinol exhibited stronger protective activities against hyperlipidemia than kurarinol. These results suggest that S. flavescens and its constituents may be effective cholesterol-lowering agents and useful for preventing hypercholesterolemic atherosclerosis.

Inhibitory effects of kurarinol, kuraridinol, and trifolirhizin from Sophora flavescens on tyrosinase and melanin synthesis.

Previously, it was reported that some prenylated flavonoids contained in the dichloromethane fraction of the ethanolic extract of Sophora flavescens, such as kuraridin, sophoraflavanone G, kurarinone, and kushenol F, are tyrosinase inhibitors; however, based on the level of these inhibitors in the extract, its inhibitory effect on tyrosinase activity was higher than expected. This has led us to further investigate other possible constituents that may contribute to the extract's strong inhibitory activity. The results of this study indicate that kurarinol (1), kuraridinol (2), and trifolirhizin (3), from the ethyl acetate fraction of Sophora extract, can inhibit tyrosinase activity. Compared with kojic acid (16.22+/-1.71 microM), compounds 1-3 possessed potent tyrosinase inhibitory activity with IC(50) values of 8.60+/-0.51, 0.88+/-0.06, and 506.77+/-4.94 microM, respectively. These three compounds were further tested for their inhibitory effects on melanogenesis. In cultured B16 melanoma cells, 1-3 markedly inhibited (>50%) melanin synthesis at 50 microM. This is the first study indicating that 1-3 exert varying degrees of inhibition on tyrosinase-dependent melanin biosynthesis, and therefore, are candidates as skin-whitening agents.