Abstract

Aframomum melegueta (Roscoe) K. Schum, family of Zingiberaceae, is a tropical tree with spicy edible fruit. This plant has both medicinal and nutritive values. There is paucity of literature on the toxicity and bioactivity of the essential oils from this plant from Nigeria. Essential oils were extracted from the leaves, stems, roots (rhizomes) and seeds of the plant through hydro-distillation using the Clevenger-type apparatus. The toxicity of the volatile oils was determined using the brine shrimp toxicity assay at concentrations of 10.0, 100.0 and 1000.0 ppm and the median lethal concentration (LC₅₀) was calculated using Finney’s probit analysis. The antimicrobial assay was carried out using the cup plate agar diffusion method. Five bacteria consisting of three strains of Gram-positive bacteria (Staphylococcus aureus, Bacillus subtilis and Salmonella typhi) and Gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa) were screened.  The stems’ essential oil displayed the highest toxicity (LC₅₀ = 0.2 µg/mL) followed by the seeds’ essential oil (LC₅₀ = 0.3 µg/mL), while LC₅₀ of the essential oil from the leaves offered the least toxicity (LC₅₀ = 17.5 µg/mL) in brine shrimp toxicity assay. All essential oils showed moderate inhibition of the tested bacteria at 1mg/mL but showed no inhibition below 125 µg/mL concentration. The high brine shrimps’ toxicity and bactericidal activity of the essential oils is indicative of their potentials as sources of pharmaceuticals or natural pesticides.

Key words: Essential oils, brine shrimps toxicity, bactericidal activity, A. melegueta