ACE inhibitor activity of nutritive plants in Kwa‐Zulu Natal

Abstract

Traditional herbal remedies form an integral part of South African culture thus much research is directed toward providing scientific rationale for the use of these herbal remedies. Organic and aqueous extracts from sixteen nutritive plants found in KwaZulu Natal, South Africa were screened for angiotensin I-converting enzyme (ACE) inhibitor activity using a flourometric enzyme assay. A plant was considered to have potential antihypertensive properties if it inhibited the ACE enzyme and thus the conversion of angiotensin I (Ang I) to angiotensin II (Ang II) by greater than 50%. Nine of the sixteen plants screened demonstrated potent ACE inhibition activity. These nine plants were then subjected to a gelatin salt block test for tannins to eliminate any false positive results. Tulbaghia violacea showed 71% ACE inhibition in the methanolic extract and 68% ACE inhibition in the aqueous extract. This mechanism of ACE inhibition was further demonstrated in vivo by co-administering exogenous Ang I with organic crude leaf extracts of T. violacea (50 mg/kg) intravenously followed by continuous invasive blood pressure monitoring. Furthermore, acute in vivo blood pressure screening involving a two week treatment with organic crude leaf extracts of T. violacea (50 mg/kg, i.p., daily) demonstrated hypotensive activity by reducing the mean systolic and diastolic blood pressure (BP) in the Dahl salt-sensitive rat. Tulbaghia violacea lowers blood by acting as an ACE inhibitor.