Objective The pathophysiology of several diseases, including hypertension, is linked to oxidative stress. Natural antioxidants play a crucial role in maintaining the balance between pro- and antioxidant levels. Angiotensin-converting enzyme inhibitors (ACEIs) are a class of drugs that treat high blood pressure, also known as hypertension. The limitations of orthodox antihypertensive medications, including side effects and high costs, emphasize the need for alternative therapies. This study investigates the ethnobotanical relevance, antioxidant properties, and antihypertensive potential of selected medicinal plants. Methods Seven plants, including Picralima nitida, Securidaca longipedunculata, Tetracera alnifolia, Senna fistula, Peperomia pellucida, Kigelia africana , and Mangifera indica, were selected for the study from an ethnobotanical survey conducted in Ibadan, Nigeria. The plant samples were collected, authenticated, air-dried, and pulverized. 200 g of the powdered samples were extracted using 70% ethanol at room temperature for 72 h. The extracts were concentrated using a rotary evaporator at 40 °C. Phytochemical screenings were conducted to detect the presence and absence of secondary metabolites. The antioxidant activities were evaluated using 2,2-Diphenyl-1-Picrylhydrazyl (DPPH), Ferric Reducing Antioxidant Power (FRAP), and Nitric Oxide (NO) assays. Ascorbic acid, Trolox, and sodium nitrite were used as standards. Four plants with the highest antioxidant activity were selected for in vitro antihypertensive activity, which was assessed through an angiotensin-converting enzyme (ACE) inhibition assay using hippuryl-L-histidyl-L-leucine (HHL) as the substrate. Captopril was used as the standard. Absorbance was read at 208 nm. Experiments were conducted in triplicate, and the values were expressed as percentage inhibition, using version 5.01 for Windows, GraphPad Software, San Diego, California, USA. P -values that were less than 0.05 were deemed significant. Results Phytochemical screening revealed the presence of saponin, flavonoid, tannin, cardiac glycosides, anthraquinones, and alkaloids in Picralima nitida , Senna fistula, and Kigelia africana . Alkaloids were absent in Securidaca longipenduculata and Mangifera indica . Kigelia africana (94.55% ± 0.11%) and Mangifera indica (95.20% ± 0.03%) showed the strongest DPPH scavenging ability, while Picralima nitida (82.88% ± 0.57%) and Securidaca longipedunculata (72.59% ± 1.61%) had moderate activity. Kigelia africana and Securidaca longipedunculata had ferric reducing antioxidant capacities of 5.50 ± 0.41 μg TE/mg and 5.39 ± 0.20 μg TE/mg, respectively. Securidaca longipedunculata (82.13% ± 2.82%) and Tetracera alnifolia (80.72% ± 4.45%) excelled as NO scavenging agents, while Picralima nitida had the strongest inhibitory effect on ACE (64.24% ± 0.56%). Conclusion Picralima nitida possesses significant angiotensin-converting enzyme inhibitory activity, while Kigelia africana and Mangifera indica exhibit notable antioxidant properties. These results support the traditional use of these plants as alternative therapies for hypertension and oxidative stress, validating their ethnobotanical use as potential antihypertensive agents. These findings underscore the therapeutic potential of the tested plants.
Ordia et al. (Mon,) studied this question.