Abstract
Interest in plants’ essential oils has grown recently due to increased use of natural products in medicine and cosmetics. In spite of its long use, there has been little prior study on the bioactivity and toxicity of the essential oils of Crassocephalum crepidioides (Benth S. More). Thus in this work, the anti-bacterial and brine shrimps’ lethality of the essential oils obtained through hydro-distillation were evaluated. The oils were analyzed by gas chromatography and gas chromatography/mass spectrometric techniques. The toxicity of the oils was considered using the brine shrimps’ lethality assay at concentrations of 10, 100 and 1000 ppm. The antimicrobial assay was carried out using the agar diffusion method. The bacteria were three strains of Gram-positive bacteria (Staphylococcus aureus, Bacillus subtilis and Salmonella Typhi) and two strains of Gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa). The main constituents of the leaves essential oil of C. crepidioides were α-caryophyllene (10.29%) and β-cubebene (13.77%), while the stem essential oil were mainly thymol (43.93%) and 4-cyclohexybutyramide (20.94%). The results of the brine shrimps’ lethality assay suggest that the essential oil of the stem (LC50 = 9.10 µg/mL) was just as toxic as the essential oil of the leaves (LC50 = 9.2 µg/mL). The essential oils were active against all the bacterial strains but low when compared with the standard antibiotic, Gentamicin. Key words: Essential oils, toxicity, antibacterial activity, Crassocephalum crepidioides, Nigeria.
Highlights
Medicinal plants are very useful for human health
The LC50 calculated for the essential oils of the leaf and stem of C. crepidioides were quite close, 9.1 and 9.2 μg/mL (Table 1)
According to Ghisalberti (1993) and McLaughin et al (1993), it appears that brine shrimps lethality (BSL) is predictive of cytotoxicity and pesticidal activity
Summary
Medicinal plants are very useful for human health. A number of studies have shown that medicinal plants could be ethical phyto-medicine for recovering from illnesses. Essential oil from an Ocimum genus, Ocimum micranthum showed a dose-dependent antifungal activity against pathogenic and food spoiling yeasts (Morris et al, 1979) In another investigation, essential oil of another genius of Ocimum, Ocimum gratissimum inhibited the growth of four candida species (Nakamura et al, 2004). Persistent research into local plants to verify their usefulness especially in the maintenance of human health remains a necessity This is due to the fact that anti-malarial plants used by the Kenyah Dyale people of Borneo in Indonesia were better antibiotics than control plants without such use in tradition (Leaman et al, 1995).
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