Abstract

The prevalent disease conditions globally, the detrimental effects, and the resistance of microorganisms to synthetic drugs are really worrisome. Measures to checkmate these situations include researches on the role of medicinal plants in health care delivery. This study is aimed at assessing the antioxidant activities of some medicinal plants normally used for the treatment of various ailments in southern Nigeria and searching for new sources of environmentally benign antioxidants. Thirty-eight medicinal plant extracts were screened for phytochemicals and in vitro antioxidant properties by the diphenyl-1-picrylhydrazyl, nitric oxide, and ferric-reducing power assays. The leaf extract of Chrysophyllum albidum exhibited the highest total phenolics of 348.98±0.941 mgGAE/g, while the lowest concentration was obtained in the fruit exocarp extract of Persea Americana (19.00±1.191 mgGAE/g). The highest and the lowest total flavonoids were observed in the leaf extract of Icacina trichanta (109.59±0.481 mgCE/g) and the seed extract of Persea Americana (1.46±0.000 mgCE/g). Total flavonols were highest in the whole-plant extract of Cleome ciliata (933.90±0.186 mgQUE/g) and lowest in the root extract of Combretum racemosum (63.97±0.121 mgQUE/g). Nine extracts gave the best antioxidant scavenging activity with a percentage DPPH ?70.00% and an IC50 ?0.5000 mg/ml. These results suggest that some medicinal plants in southern Nigeria have strong antioxidant scavenging abilities. Further investigation to determine the antioxidant activity of the nine active extracts by in vivo methods, as well as isolation and characterization of these active antioxidant compounds, may enhance the development of new drugs for the treatment of oxidative-stress-related illnesses.

Key words: Thirty-eight plant extracts; total phenolics, flavonoids, flavonols, and antioxidant activity.