Confomational analysis and antiallergic activity of triterpenes

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Cell suspension cultures of Luffa cylindrica accumulate large quantities of bryonolic acid (BA,D : C-friedoolean-8-en-3beta-ol-29-oic acid) , an acidic, pentacyclic tritepene found exclusively in the roots of the intact plant. Pharmacological tests using mice demonstrated that BA or its derivative is active against at least three types of allergies and that its activity could be increased significantly by preparing synthetic derivatives, in particular a potassium salt of its succinate ester (BS) . To study the relationship between conformation and antiallergic activity of triterpenes, synthetic BS derivatives that differ in the conformation of D/E rings (Fold type, Stretch type, and Equilibrium type) were subjected to an antiallergic test (passive cutaneous anaphylaxis) . The results of experiments suggested that not only Fold type conformation but also a functional group containing oxygen at C-29 is needed for the potentiation of antiallergic activity. A succinate ester (K salt) of D : C-friedoolean-7,9 (11) -dien-3beta-ol-29-oic acid was less effective than BS,suggesting that the conformation between B and C rings is also of importance in modulating the biological activity.