Objective:To assess anti-psoriatic activity of the methanol extract and the isolated flavonoid quercetin from the rhizome of Smilax china(S.china) Linn.Methods:Mouse tail test was used for the evaluation of anti-psoriatic activity.Methanol extract(100 and 200 mg/kg b.w.) and isolated flavonoid quercetin(25 and 50 mg/kg b.w.) were tested in Swiss albino mice.Parameters studied in the mouse tail test were changes in epidermal thickness and percentage orthokeratotic values.The anti-inflammatory role of the methanol extract and isolated flavonoid quercetin was evaluated using carrageenan-induced pleurisy in rats.In vitro antiproliferant assay on HaCaT cell lines was also carried out.Results:The isolated flavonoid quercetin from the rhizome of S.china produced significant orthokeratosis(P<0.01) in the mouse tail test.In epidermal thickness,a significant reduction with respect to control was observed in groups treated with retinoic acid and isolated flavonoid quercetin.The methanol extract(200 mg/kg) and isolated flavonoid quercetin(50 mg/kg) showed anti-inflammatory effect in terms of significant inhibition(P<0.001) in leukocyte migration.Maximum antiproliferant activity was shown by isolated flavonoid quercetin(IC_(50),62.42± 10.20 μg/mL).Conclusions:From the above data,the flavonoid quercetin shows significant orthokeratosis,anti-inflammatory and maximum antiproliferant activities.To our knowledge,this is the first report on the anti-psoriatic effect of the flavonoid quercetin which is promising for further investigations to prove its anti-psoriatic activity. Objective: To assess anti-psoriatic activity of the methanol extract and the isolated flavonoid quercetin from the rhizome of Smilax china (S. china) Linn. Methods: Mouse tail test was used for the evaluation of anti-psoriatic activity. Methanol extract (100 and 200 mg / kg bw) and isolated flavonoid quercetin (25 and 50 mg / kg bw) were tested in Swiss albino mice. Parametrics studied in the mouse tail test were changes in epidermal thickness and percentage orthokeratotic values. The anti-inflammatory role of the methanol extract and isolated flavonoid quercetin was evaluated using carrageenan-induced pleurisy in rats. In vitro antiproliferant assay on HaCaT cell lines was also carried out. Results: The isolated flavonoid quercetin from the rhizome of S. chine produced significant orthokeratosis (P <0.01 ) in the mouse tail test. In epidermal thickness, a significant reduction with respect to control was observed in groups treated with retinoic acid and isolated flavonoid quercetin. The methanol extract (2 (50 mg / kg) showed anti-inflammatory effects in terms of significant inhibition (P <0.001) in leukocyte migration. Maximum antiproliferant activity was shown by isolated flavonoid quercetin (IC 50 (50), 62.42 ± 10.20 μg / mL) .Conclusions: From the above data, the flavonoid quercetin shows significant orthokeratosis, anti-inflammatory and maximum antiproliferant activities.To our knowledge, this is the first report on the anti-psoriatic effect of the flavonoid quercetin which is promising for further investigations to prove its anti-psoriatic activity.