Antioxidant Properties and Effects on Nitric Oxide Release of Ethanolic Extracts of Some Selected Cameroonian Medicinal Plants

In the Southern region of Cameroon, some medicinal plants are used for the treatment of the male reproductive system disorders; including Palisota ambigua, Rauvolfia macrophylla, Terminalia superba, Pycnanthus angolensis, Pausynistalia yohimbe and Schumanniophyton magnificum. The aim of our study was to investigate the antioxidant properties of the ethanolic extracts of these plants, as well as their phytochemical constituents and their effects on nitric oxide release. Rat peritoneal macrophages were isolated and used to assess in vitro effects of plant extracts on nitric oxide release. Then, antioxidant properties of alcoholic extracts of the plants were screened through 2,2-diphenyl-1-picrylhydrazyle test, total antioxidant capacity test and ferric reducing power test and lipid peroxidation inhibition test. Phytochemical constituents, total phenol and flavonoid contents were also investigated. Results showed that only the extracts of T. superba and P. yohimbe were found to be strong 2,2-diphenyl-1-picrylhydrazyle free radical scavengers with low EC50 (8.40 [8.31, 8.53]; 17.73 [17.67, 17.74] µg of plant extract/mol 2,2-diphenyl-1-picrylhydrazyle). The plants extracts exhibited better inhibitions of the lipid peroxidation in concentration-dependent manner; especially R. macrophylla with an IC50 of 2.38 (2.13, 4.92) µg/mL. No significance difference was observed neither among the total phenolic nor flavonoids contents of the plant extracts. Extract of T. superba exhibited strong antioxidant properties. Though, the extracts of R. macrophylla and P. angolensis and S. magnificum were also able to protect against lipid peroxidation and free radicals. The phytochemical screening revealed the presence of alkaloids, flavonoids, phenols, tannins, coumarins, glycosids in most of the plants extracts. These properties sustain their use for treatment of male infertility and erectile dysfunction.