Variation in chemical composition, insecticidal and antioxidant activities of essential oils from the leaves, stem barks, and roots of Blighia unijugata (Baker) and B. sapida (K. D. Koenig).

Blighia unijugata (Baker) and B. sapida (K.D. Koenig) (Sapindaceae) are forest trees widespread in Tropical Africa. They are used in folk medicine for the treatment of rheumatism, cardiovascular diseases, yellow fever, dysentery, and epilepsy. The essential oils of the air-dried leaves, stem bark, and roots of the plants were extracted using the hydrodistillation method and were analyzed by Gas Chromatography-Mass Spectrometry (GC-MS). The antioxidant activity was determined using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical method using a-tocopherol and ascorbic acid as standards. The insecticidal activity of the oils was investigated by determining the percentage mortality of the grain insects (Sitophilus zeamaise). Results showed that the yield of the colorless oils (% w/w) from the leaves, stem bark, and roots of the plants were 0.91%, 0.42%, and 0.34% for B. unijugata and 0.67%, 0.32%, and 0.48% for B. sapida, respectively. The most abundant compounds in B. unijugata leaves were pentadecanoic acid (14-methyl-, methyl ester) (38.34%), carbonic acid, propyl-en-2-yl undecylpropyl ester (36.79%), and 9-octadecanoic acid (Z)-methyl ester (24.86%). The stem bark was rich in 1,3-dimethoxybenzene (79.01%) while the root contained limonene (20.51%), trans-13-octadecanoic acid (16.74 %), and cis-vaccenic acid (9.50%). The leaf essential oil of B. sapida had hexahydrofarnesyl acetone (21.43%), phytol (20.45%), geosmin (16.258%), and a-ionone (8.271%) as the major constituents. The stem bark had cholesterol (38.66%) as the major constituent while the root contained nonanal (18.09%) and 4-cyclopropyl carbonyl tetradecane (11.6%). The antioxidant analysis revealed that B. unijugata root had 83.96% inhibition at 100 mg/ml, while B. sapida stem had 79.73% inhibition, better than a-tocopherol. No significant insecticidal activity was observed in the essential oils of the plants against S. zeamaise except for B. sapida stem which showed 50% toxicity to the maize weevils. However, the two plants can be the source of antioxidant agents against oxidative stress and related diseases. [ABSTRACT FROM AUTHOR]