Effects of derivitization on antimicrobial activity of Embelin isolated from Embelia schimperi berries

Abstract

Chromatographic separation of ethyl acetate extract from Embelia schimperi berries led to isolation of embelin 2,5-dihydroxy-3-undecyl- 1,4-benzoquinone(1). Embelin was identified on the basis of physical and spectroscopic data. Three quantities of compound 1 weighing 0.02g each were used to synthesize three derivatives by addition of sulphonyl, acetyl and alkyl imino groups to the parent compound’s structure. The synthesized compounds were identified as 2,5- dihydroxy-5-sulpho-3-undecyl-1,4-benzoquinone (2), 1,2,4,5 tetra acetoxy-3-undecyl benzene (3) and 2,5-dihydroxy-1-di-ethyl imino-3-undecyl-4- benzoquinone (4) on the basis of MS and FTIR spectroscopic data. Embelin and its synthetic derivatives were tested against clinical strains of Pseudomonas aeruginosa, Escherichia coli, Staphylococcus aureus and Candida albicans. Plate titration technique was used; and presence or absence of microbial growth after respective incubation periods used to determine antimicrobial activity. The incubation period for antibacterial test was 24 hours and 48 hours for antifungal test respectively. Compound 1 and 4 were found to be active against S. aureus (gram positive bacteria) at dilutions of 100 ppm and 200 ppm respectively while compounds 2 and 3 were inactive. Compounds 1, 2, 3 and 4 were inactive against P. aeruginosa, E. coli (gram negative bacteria) and C. albicans (fungi) at all dilutions. The inactivity of embelin and its synthetic derivatives could possibly be attributed to inability of compounds to penetrate through the cell walls of P.aeruginosa, E.coli (gram negative bacteria) and C. albicans (a fungus). Retention of activity against S. aureus in compound 4 is an indication that effect of functional groups on properties of parent compound should be considered prior to derivatization. Addition of certain functional groups may affect compounds properties such as solubility, polarity and stability which determine the uptake and metabolism of a drug in the target organism.