Phytochemical Investigation, GC‒MS Analysis, and Antioxidant Activity of Acokanthera schimperi Stem Bark Crude Extracts

Introduction Oxidative stress, resulting from excessive production of reactive oxygen species and thereby playing a critical role in the development of chronic diseases, derives a growing interest in medicinal plants as a source of natural antioxidant phytochemicals. Acokanthera schimperi (A. DC.) Schweinf., is a traditionally important medicinal plant that has been poorly studied for the phytochemical composition and antioxidant potential of its stem bark. Objectives The aim of the present study was to evaluate the phytochemical constituents using gas chromatography‒mass spectrometry (GC‒MS) analysis and determine the antioxidant activity of the stem bark of A. schimperi crude extracts. Methods The powdered stem bark was sequentially extracted with ethyl acetate and methanol using a Soxhlet apparatus. Phytochemical screening tests were employed by standard protocols to qualitatively identify phytochemicals. The crude extract was analyzed by GC‒MS, and its antioxidant activity was assessed using the DPPH assay. Results Phytochemical screening of stem bark extracts of A. schimperi showed the presence of phenols, alkaloids, steroids, terpenoids, and glycosides in the methanolic extract, while the ethyl acetate extract contained terpenoids, glycosides, and steroids. From GC‒MS analysis of ethyl acetate extracts identified trans-2-methyl-4-n-pentylthiane, S,S-dioxide (31.06%), trans-2-Methyl-4-n-butylthiane, S,S-dioxide (30.57%) and N-(5-azidopentyl)-4-methyl-4-vinylazetidin-2-one (6.82%); and n-hexadecanoic acid (5.01%) as a major components. The methanolic extract was dominated by Myo-Inositol, 4-C-methyl (49.40%); 2-Azido-2,4,4,6,6-pentamethylheptane (8.96%); and Catechol (4.041%). The methanol extract exhibited strong antioxidant activity, achieving 96.57±0.01% inhibition at a concentration of 100 μg/mL, comparable to the control ascorbic acid (97.10±0.01%), whereas the ethyl acetate extract showed moderate antioxidant activity with 48.14±0.10% inhibition. Conclusions This finding provides the scientific evidence on the natural antioxidant phytochemical constituents of A. schimperi stem bark extracts.