Antihypertensive Effects of Osteospermum Imbricatum in Two Hypertensive Rat Models

Introduction: Osteospermum imbricatum is used traditionally in Eastern Cape, South Africa for the management of hypertension, chest and stomach complaints. This study was aimed at investigating the antioxidant and antihypertensive effects of this plant. Methods: Antioxidant capacity was determined by radical scavenging assays and ferric reducing antioxidant power. Antihypertensive effects after once off treatment with the leaf/root extracts (500 mg/kg) were evaluated in spontaneously hypertensive rats (SHR). The effect of the extracts on established hypertension was determined in Wistar rats treated with Nω-Nitro-L-arginine methyl ester (L-NAME) (40 mg/kg/day) for 4 weeks followed by co-treatment with L-NAME and extracts (200 mg/kg and 400 mg/kg) or amlodipine (5 mg/kg) or normal saline for 4 more weeks. Results: The concentration at which there was 50 % inhibition (IC₅₀) of DPPH radical by the extracts was lower for the leaf extract (0.79 mg/mL) compared to the root extract (1.15 mg/mL). The leaf extract significantly (p<0.01) decreased systolic and diastolic blood pressures in both rat models. Conclusion: The extracts of Omsteospermum imbricatu have moderate antioxidants and antihypertensive properties.