A comparative study of the antioxidant and ACE inhibitory activities of selected herbal extracts

Abstract

Some herbal bioactives possess high antioxidant and angiotensin converting enzymes (ACE) inhibition activity, which affects blood pressure levels. Herbal bioactives promote health benefits via different molecular mechanisms and most of these mechanisms are yet to be fully elucidated. In the present study, health promoting potential of aqueous extracts of six herbs viz. Allium sativum L., Withania somnifera (L.) Dunal, Ocimum sanctum L., Hibiscus sabdriffa L., Ginkgo biloba L. and Emblica officinalis at different concentrations (50 to 10,000 μg/mL) were assessed through their antioxidant and ACE inhibitory potential. Results showed that the DPPH (2, 2-diphenyl-1-picrylhydrazyl) activity of the six different herbs ranged from 1.58 ± 0.63 to 11.39 ± 0.15 mM/mL trolox equivalent and was in the order of Emblica officinalis >Withania somnifera >Hibiscus sabdriffa >Ginkgo biloba >Ocimum sanctum =Allium sativum at 1000 μg/mL concentration. Emblica officinalis had IC50 value 180.35 ± 1.17 μg/mL. The corresponding observation for the herb with 2, 2'-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) was 167.19 ± 1.04 μg/mL. Ferric reducing antioxidant power (FRAP) values were significantly higher for Emblica officinalis than the other herbs, and varied from 1.78 ± 0.08 to 251.62 ± 6.31 mM/mL ascorbic acid equivalent at different concentrations (50 to 10000 μg/mL). Emblica officinalis had the strongest ACE inhibition potential (82.08 ± 5.18 %), followed by Withania somnifera, Hibiscus sabdriffa, Ginkgo biloba, Ocimum sanctum and Allium sativum. ACE inhibitory activity of herbs studied was lower (31.64 ± 5.05 %) than that of Captopril (0.002173 μg/mL), a standard medicine used for hypertension. The study compared and elucidated the antioxidant and ACE inhibitory potential of aqueous extracts of herbs at different concentrations. The study results may be useful in the selection of herbal bioactives for functional foods and aqueous nutraceutical formulations.