Uric acid metabolic disorder is considered to be the main pathogenesis of uric acid nephropathy (UN). Smilax glabra Roxb. is a traditional Chinese herb which has been used in the treatment of gout, but the mechanism was unclear. In this study, we investigated the protective effects of the flavonoid-rich fraction from rhizomes of Smilax glabra Roxb. (SGF) on uric acid nephropathy rats and its underlying mechanisms of promoting uric acid excretion. Sprague Dawley (SD) rats were induced by high purine diet (yeast pellets + adenine) for 5 weeks. Rats were orally treated with SGF or allopurinol daily. The biochemical parameters and enzymes in different treated rats were determined by commercial kits. Kidney pathology was visualized using optical microscopy and electron microscopy. Renal inflammatory factors were detected by ELISA. Renal fibrosis factors and uric acid transporters were analyzed by real time RT-PCR and western blot. The results showed that SGF significantly improved kidney function. Histopathologic examination revealed that urate-induced renal damage was markedly reversed by SGF. Meanwhile, SGF treatment was also found to significantly inhibit renal oxidative stress. SGF treatment obviously suppressed the inflammatory factors of interleukin-6 (IL-6), tumor necrosis factor alpha (TNF-α), interleukin-1β (IL-1β), cyclooxygenase-2 (COX-2) and the profibrotic factors of basic fibroblast growth factor (bFGF), transforming growth factor-β1 (TGF-β1) expression in UN rats. Moreover, SGF either significantly inhibited uric acid production or promoted uric acid excretion in UN rats. The mechanism of SGF promoting uric acid excretion was related to its increase of ATP-binding cassette transporter G2 (ABCG2), organic anion transporter 1 (OAT1), organic anion transporters 2 (OCT2) and organic cation/carnitine transporters 2 (OCTN2) expression. In conclusion, SGF could ameliorate renal oxidative stress and inflammation in UN rats through promoting uric acid excretion.

The total phenolic and flavonoid, antioxidant and antibacterial activities of six Sonchus wild vegetables (Sonchus oleraceus L., Sonchus arvensis L., Sonchus asper (L.) Hill., Sonchus uliginosus M.B., Sonchus brachyotus DC. and Sonchus lingianus Shih) in China were investigated. The results revealed that S. arvensis extract and S. oleraceus extract contained the highest amount of phenolic and flavonoid, respectively. Among the methanol extracts of six Sonchus species, S. arvensis extract exhibited the highest radical (DPPH and ABTS⁺) scavenging power and lipid peroxidation inhibitory power. It also exhibited the highest reducing power at 500 µg mL⁻¹ by A ₇₀₀ = 0.80. The results of antibacterial test indicated that the S. oleraceus extract showed higher activity than the other five Sonchus wild vegetables extracts, both in Gram-negative bacteria (Escherichia coli, Salmonella enterica and Vibrio parahaemolyticus) and in a Gram-positive bacterium (Staphylococcus aureus). These results indicate that Sonchus wild food plants might be applicable in natural medicine and healthy food.

This study aimed to isolate, prepare and identify the main flavonoids from a standardized Smilax glabra flavonoids extract (SGF) using preparative HPLC, MS, ¹H NMR and ¹³C NMR, determine the contents of these flavonoids using UPLC, then compare their pharmacological activities in vitro. We obtained six flavonoids from SGF: astilbin (18.10%), neoastilbin (11.04%), isoastilbin (5.03%), neoisoastilbin (4.09%), engeletin (2.58%) and (−)-epicatechin (1.77%). The antioxidant activity of six flavonoids were evaluated by determining the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical and 2,2′-Azinobis (3-ethylbenzothiazoline-6-sulphonic acid) diammonium salt (ABTS⁺) radical scavenging activity and ferric reducing antioxidant power (FRAP). In addition, the anti-inflammatory activity of six flavonoids were evaluated by determining the production of cytokines (IL-1β, IL-6), nitric oxide (NO) using enzyme linked immunosorbent assay and the NF-κB p65 expression using Western blotting in lipopolysaccharide (LPS)-stimulated RAW264.7 cells. The results showed that (−)-epicatechin, astilbin, neoastilbin, isoastilbin and neoisoastilbin had strong antioxidant activities, not only in DPPH and ABTS⁺ radicals scavenging capacities, but in FRAP system. Furthermore, all the six flavonoids could significantly inhibit the secretion of IL-1β, IL-6, NO (p < 0.01) and the protein expression of NF-κB p-p65 (p < 0.01) in LPS-stimulated RAW264.7 cells. This study preliminarily verified the antioxidant and anti-inflammatory activities of six flavonoids in S. glabra.