Chemical Composition and Evaluation of the Antioxidant Activity of Essential Oils from the Leaves and Bark of Alstonia boonei De Wild

Abstract

Alstonia boonei De Wild is used in traditional medicine to treat several diseases according to the literature. This study aimed to characterise the chemical composition of essential oils obtained from the leaves and bark of Alstonia boonei De Wild acclimatised in Congo and to evaluate their antioxidant potential. In this study, the essential oils of the leaves and bark of Alstonia boonei were analysed by GC-MS and GC/FID, and their antioxidant activity was tested by TLC. Fifty and sixty-one chemical compounds were identified, including alkanes (24.60%), fatty acids (17.59%), aldehydes (12.01%), sesquiterpenes (4.10%), oxygenated sesquiterpenes (6.16%) as major families in the essential oil of the leaves, and fatty acids (32.32%), oxygenated monoterpenes (12.96%) in that of the bark. n-heptane (15.25%), palmitic acid (13.72%), pentadecanal (8.68%), n-nonacosane (5.79%), hexahydrofarnesyl acetone (2.94%) and phytol (2.15%) are the most abundant compounds in the essential oil of the leaves, and hexadecanoic acid (32.32%), α-terpineol (7.66%) and eugenol (6.28%) in that of the bark. Thin-layer chromatography (TLC) analysis of the essential oils from Alstonia boonei. revealed spots with retention factors (Rf) of 0.44 for the leaves and 0.83 for the bark, confirming the presence of antioxidant compounds.