Comparative effects of quercetin, luteolin, apigenin and their related polyphenols on uric acid production in cultured hepatocytes and suppression of purine bodies-induced hyperuricemia by rutin in mice

Abstract

Hyperuricemia, the high uric acid (UA) state in blood, has been accepted as an important risk factor for gout. The liver is a main factory of UA production. In the present study, we have examined the effects of three kinds of flavonol and flavones as typical aglycons, i.e., quercetin, luteolin, apigenin, their glycosides and related compounds, on UA productivity in cultured hepatocytes, adopting allopurinol as the positive control drug. Quercetin, luteolin, diosmetin (4'-O-methylluteolin) and apigenin at 10, 30 and 100 μM as well as allopurinol at 0.1, 0.3 and 1 μM dose-dependently and significantly decreased UA production in the hepatocytes, when compared with 0 μM (control). Both rutin (quercetin-3-O-rutinoside) and quercitrin (quercetin-3-O-ramnoside) significantly reduced UA production in the hepatocytes at 100 μM. Luteolin glycosides such as orientin (luteolin-8-C-glucoside) and isoorientin (luteolin-6-C-glucoside) exerted no influences on it even at 100 μM. Likewise, apigenin glycosides such as vitexin (apigenin-8-C-glucoside) and isovitexin (apigenin-6-C-glucoside) showed no inhibitory effect on it, while apigetrin (apigenin-7-O-glucoside) significantly reduced it at 100 μM. In model mice with purine bodies-induced hyperuricemia, allopurinol completely suppressed the hyperuricemia at a dose of 10 mg/kg body weight. Rutin suppressed significantly the hyperuricemia at a dose of 300 mg/kg body weight, while vitexin showed no significant effect up to 300 mg/kg body weight. Thus, rutin (O-glycoside) is demonstrated to be hypouricemic in both cultured hepatocytes and model mice with recently contrived purine bodies-induced hyperuricemia.

Keywords: AML12 hepatocytes; Hyperuricemia; Purine body; Quercetin; Rutin; Uric acid.

Fig. 1

Effects of allopurinol, quercetin and its glycosides on UA production in cultured AML12 hepatocytes. The hepatocytes were treated with allopurinol at 0 (control), 0.1, 0.3 and 1 µM as a positive control drug (a) or quercetin (b), rutin (c), quercitrin (d) and isoquercitrin (e) at 0 (control), 10, 30 and 100 µM for 2 h in BSS containing guanosine and inosine (100 µM each) in combination (GI mixture) as UA precursors. Each value represents mean ± SEM for 6 wells (duplicate measurement per well). Values not sharing a common letter are significantly different at P < 0.05 (Tukey’s test)

Fig. 2

Effects of luteolin, its glycosides and related compound on UA production in cultured AML12 hepatocytes. The hepatocytes were treated with luteolin (a), orientin (b), isoorientin (c) and diosmetin (d) at 0 (control), 10, 30 and 100 µM for 2 h in BSS containing guanosine and inosine (100 µM each) in combination (GI mixture) as UA precursors. Each value represents mean ± SEM for 6 wells (duplicate measurement per well). Values not sharing a common letter are significantly different at P < 0.05 (Tukey’s test)

Fig. 3

Effects of apigenin and its glycosides on UA production in cultured AML12 hepatocytes. The hepatocytes were treated with apigenin (a), vitexin (b), isovitexin (c), apigetrin (d) and rhoifolin (e) at 0 (control), 10, 30 and 100 µM for 2 h in BSS containing guanosine and inosine (100 µM each) in combination (GI mixture) as UA precursors. Each value represents mean ± SEM for 6 wells (duplicate measurement per well). Values not sharing a common letter are significantly different at P < 0.05 (Tukey’s test)

Fig. 4

Direct inhibitory effects of aglycons and their glycosides on xanthine oxidase activity in vitro. Data on direct XO inhibitions in vitro are expressed as means from two individual experiments. IC50 values were calculated by curve fitting of at least six different concentrations of test samples as described in Materials and methods. Allopurinol was adopted as a positive control drug. IC50 values are shown in Fig. a (allopurinol, quercetin, rutin), b (luteolin, orientin, isoorientin) and c (apigenin, vitexin, isovitexin), respectively

Fig. 5

Effects of rutin and vitexin on purine bodies-induced hyperuricemia in mice. Allopurinol was adopted as positive control drug. Each value represents mean ± SEM for 10 (model control group) or 8 (other groups) mice. *P < 0.05 vs. hyperuricemic mice (model control group) by Dunnett's multiple-comparisons test