Screening of Zulu medicinal plants for angiotensin converting enzyme (ACE)inhibitors

Twenty plants used by traditional healers in South Africa for the treatment of high blood pressure were investigated for their anti-hypertensive prope rties, utilizing the angiotensin converting enzyme assay. A hit rate of 65% was achieved, with the highest inhibition (97%) obtained by Adenopodia spi cata leaves. A further seven plants exhibited an inhibition greater than 70 % and five more over 50%. The leaves of the plants showed the greatest leve ls of inhibition. There was little difference in the overall hit rate betwe en ethanolic and aqueous extracts, although in most cases there was a marke d difference in activity between aqueous and ethanolic extracts from the sa me species. Plants exhibiting inhibition levels greater than 50% were furth er tested for the presence of tannins in order to eliminate possible false positives. Active plants that did not contain tannins were Agapanthus afric anus, Agave americana, Clausena anisata, Dietes iridioides, Mesembruanthemu m spp., Stangeria eriopus and Tulbaghia violacea. (C) 1999 Published by Els evier Science Ireland Ltd. All rights reserved.