Xanthine Oxidase Inhibitors from the Leaves ofAlsophila Spinulosa(HOOK) Tryon

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Abstract
Diploptene(1), β-sitosterol(2), a mixture of 6′-O-(E-P-coumaroyl)-α-glucopyranose and 6′-O-(E-P-coumaroyl)-β-glucopyranose(3), a mixture of 6′-O-(E-P-caffeoyl)-α-glucopyranose and 6′-O-(E-P-caffeoyl)-β-gIucopyranose(4), caffeic acid(5) and astragalin(6) were isolated from an ethanolic extract of the leaves of Alsophila spinulosa Hook Tryon (Cyatheaceae). The plant has been used in folk medicine for hepatitis, gout, rheumatism and tumor and these compounds were tested for their inhibitory effect on xanthine oxidase. Caffeic acid was the most potent constituent (IC50 = 39.21 μM; Ki = 28.2 μM) and was an uncompetitive inhibitor of the enzyme with respect to the substrate xanthine.