Dilatory effects and safety of a polyphenol-rich Extract of Steganotaenia araliacea Hochst (Apiaceae) on Rat Aortic Rings

Newton Simfukwe¹Lavina Prashar¹James Nyirenda^1*Fastone Mathew Goma¹Christian C Ezeala²

• ¹University of Zambia, Lusaka, Zambia
• ²Africa University College, Mutare, Zimbabwe

Background: Hypertension is a major global public health concern. Many communities in developing countries still rely on medicinal plants as a source of primary health care for treatment of hypertension than conventional antihypertensive drugs. Steganotaenia araliacea is used traditionally to treat hypertension, but no scientific study has been done to prove this, hence this study sought to undertake this work.Aims of the study: The study evaluated the vasorelaxant effect of a phenolic-rich extract from the roots of S. araliacea on isolated rat aortic rings. Methods: Fresh roots of S. araliacea collected from Chongwe District, Zambia were dried and ground to fine powder and polyphenols were extracted by maceration. An in vitro experiment was carried out to test S. araliacea polyphenol-rich extract (SAPE) on isolated rat aortic rings. Isometric tension measurements on the aortic rings were evaluated to study the vasodilatory effects using the tissue/organ bath and the Powerlab data acquisition system. Phenylepherine (PE) was used for pre-contraction of aortic rings whereas cumulative concentrations (0.2 mg/ml to 16.91mg/ml) of SAPE were tested to antagonize the aortic contraction. Acetylcholine (ACh) and sodium nitroprusside (SNP) served as standard drugs for inducing dilatory effects against PE. L-Nitro-arginine-methyl-ester (L-NAME) was applied to block endothelial nitric oxide synthase (eNOS) activity for establishing the possible involvement of NO/cGMP mechanism of action. Results: Total polyphenol content ranged from 952 ± 3.40 mg gallic acid equivalent (GAE/100 g) to 97.8 ± 1.20 mg GAE/100g of dry extract. The methanolic extract induced significant dilatory effects on endothelium intact and denuded aortic rings with maximum percentage relaxation of 98.9 ± 0.714 % and 97.29 ± 3.34 %, respectively. Median IC-50 values were 5.07 ± 1.05 mg/ml and 5.56 ± 1.08 mg/ml. Vasodilatory effects reduced significantly in the presence of L-NAME, p value < 0.05. The aqueous root extract was found to be practically nontoxic at a concentration of 10,000 mg/kg on mice .The study demonstrated that the polyphenol-rich extract of S. araliacea produces significant vasodilatory effects providing potential to act as an antihypertensive agent. Further studies are needed to validate these findings.