ANTIMICROBIAL, ANTIOXIDANT AND CYTOTOXIC ACTIVITIES OF PURIFIED EXTRACTS AND ESSENTIAL OILS FROM SOME MELIACEOUS PLANTS

Abstract

Investigations were conducted to determine the antimicrobial, antioxidant and cytotoxic activities of extracts and essential oils from Khaya senegalensis, K. ivoriensis, K. grandifoliola, Trichilia heudelotti and Lovoa trichiliodes using standard methods. The essential oils and extracts (ethanol, acetone and water) of the leaves and stem bark of the test plants were assayed for antimicrobial activity against clinical isolates and typed cultures of some human pathogenic bacteria and fungi. The acetone stem bark extracts of L. trichiliodes at 50mg/ml recorded highest activity against Bacillus subtilis ATCC6633 (22.33±0.33mm) followed by B. subtilis (22.00±1.00mm), Klebsiella pneumoniae (21.33±0.58mm), Pseudomonas aeruginosa (20.33±0.58mm) and Salmonella typhi ATCC6539 (19.33±0.33mm). The essential oils of L. trichiliodes stem bark at 50mg/ml induced the highest activity against Escherichia coli ATCC25922 (20.33±0.88mm) followed by Staphylococcuss aureus ATCC25923 (19.67±0.33mm) at the same concentration. The effective concentration of the test plant extracts ranged from 2.5 to 100mg/ml for bacteria and 2.5 to 200mg/ml for fungi while that of essential oils varied from 3 to 20μg/ml and 7.5 to 40μg/ml for bacteria and fungi respectively. The antimicrobial efficacy of the plant extracts and essential oils decreased with increase in pH value and storage period, but temperature and ultra violet light had no effect on the potency of the plant extracts. Mild cytotoxic effect was recorded for the plants’ essential oils while the extracts of all the plant materials indicated that they are virtually non-toxic. The following phytochemicals were present in the plant materials: alkaloids (0.23±0.01 -0.48±0.01%), saponins (1.34±0.01 – 1.56±0.01%), tannins (0.02±0.01 – 0.05±0.01%) and phenols (0.06±0.00 – 0.11±0.01%). Others like flavonoids, steroids, terpenes, glycosides and phlobatannins were present in smaller quantities. The free radical scavenging activity of the samples increased with increase in oil concentration. The major chemical components of the most potent extracts and essential oils of the test plant materials include ivorenolide, khivorine, 3-diacetylkhivorine, +-catechin, 4-Terpeneol, Transpinocarveol, α-thujone, Limonene, Naphthalene, Terpene, Benzene-1-ethyl-2-methyl, α-Phellandrene, 7-diacetyl-7-oxogedunine, Khayasine, Methyl-angolensate, α-terpeneol, β-pinene, Menthone, β-thujone, terpinen-4-ol, Terpeninolene and β-Bisabolene. Haematological and histopathological parameters assessed using albino rats revealed an improved growth performance without any detrimental impact on the physiological status as related to the blood and vital organs. However, the essential oils induced minor hemorrhage of the heart section. The demonstration of broad antimicrobial spectrum, high free radical scavenging activity and the non-cytotoxic effect exhibited by the plants explained the basis for the scientific use of these plants in the traditional treatment of diseases, and provide for probable use of the extracts as alternative antibiotics and the use of the mild toxic essential oils as antitumor agents against human cancerous cells