BIOLOGICAL-ACTIVITIES OF BENZOQUINONES FROM BADULA-BARTHESIA AND EMBELIA-ANGUSTIFOLIA

In our screening; program for antihypertensive plant constituents extr acts of the leaves and bark of Badula barthesia showed strong in vitro inhibition of angiotensin converting enzyme (ACE). Rapanone (1), 2,5- dihydroxy-3-tridecyl-1,4-benzoquinone, was isolated as an active const ituent of the leaves. The IC,, values of rapanone and three 3-alkyl-2, 5-dihydroxybenzoquinones, (2)-(4), ,5-dihydroxy-3-(pentadec-8-enyl)-1, 4-benzoquinone, hydroxy-3-(heptadeca-8,11-dienyl)-1,4-benzoquinone and 2,5-dihydroxy-3-(heptadec-8-enyl)-1,4-benzoquinone recently isolated from Embelia angustifolia were determined. The following IC50 +/- S.D. values have been obtained (1) 36 +/- 4.6 mu M, (2) 19 +/- 6.2 mu M, ( 3) 19 +/- 8.7 mu M and (4) 16 +/- 3.0 mu M. The IC50 value for the ref erence compound captopril was determined to 12 +/- 2.6 nM. The antimic robial activity of the four compounds was determined by thin layer chr omatography agar overlay technique as minimum growth inhibitory amount in mu g One yeast, Candida albicans, and four bacteria, Bacillus subt ilis, Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aure us were used as test organisms.