EFFECTS OF TISSUE-CULTURED ANOECTOCHILUS-FORMOSANUS HAY - EXTRACTS ON THE ARACHIDONATE METABOLISM

Tissue-cultured Anoectochilus formosanus Hay., a precious Chinese herb used for the treatment of cardiovascular diseases, was examined for its physiological activity on arachidonic acid (AA) metabolism. Extracts of the herb were found to inhibit thromboxane A2 (TXA2) production in platelets and to activate prostacyclin (PGI2) production in aortic endothelial tissues. All the inhibitions and activations found were concentration-dependent. These effects were similar to those obtained previously when wildtype A. formosanus plants were used. In addition, the substances inhibiting TXA2 production in platelets were found to occur in the stems plus roots whereas substances activating PGI2 production in endothelial tissues were found to occur in the leaves of the tissue-cultured A. formosanus plants. By using different precursors, AA and prostaglandin H2 (PGH2), it was found that lower production of TXA2 in platelets and higher production of PGI2 in endothelial tissues were caused by the inhibition of thromboxane synthase and activation of cyclooxygenase, respectively. These results suggest that the tissue-cultured A. formosanus contains at least two different bioactive components affecting TXA2 and PGI2 production, which could play important physiological and pharmacological roles in the treatment of cardiovascular diseases.