The enzyme xanthine oxidase catalyses the oxidation of hypoxanthine to xant
hine and then to uric acid, which plays a crucial role in gout. A total of
122 traditional Chinese medicinal plants, selected according to the clinica
l efficacy and prescription frequency for the treatment of gout and other h
yperuricemia-related disorders, have been evaluated for the enzyme inhibito
ry activity. Among the 122 methanol extracts derived from these species, 69
were shown to be inhibitory at 100 mug/ml, with 29 having greater than 50%
inhibition. As to the equal-amount of water extracts, 40 were disclosed to
be active at 100 mug/ml, with 13 possessing more than 50% inhibition. At 5
0 mug/ml, 58 methanol and 24 water extracts exhibited inhibitory activity,
with 15 of the former and two of the latter showing greater than 50% inhibi
tion. The most active was the methanol extract of the twig of Cinnamomum ca
ssia (Lauraceae) (IC50, 18 mug/ml), which was followed immediately by those
of the flower of Chrysanthemum indicum (Asteraceae) (IC50, 22 mug/ml) and
the leaves of Lycopus euiopaeus (Lamiatae) (IC50, 26 mug/ml). Among the wat
er extracts, the strongest inhibition of the enzyme was observed with that
of the rhizome of Polygonum cuspidatum (Polygonaceae) (IC50, 38 mug/ml). Th
e IC50 value of allopurinol used as a positive control was 1.06 mug/ml. The
study demonstrated that the effects for these medicinal plants used for th
e gout treatment were based, at least in part, on the xanthine oxidase inhi
bitory action. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.