In-vitro Anti-Bacterial Activity of Extracts of Euphorbia abyssinica (Desert Candle) Stem-Bark and Latex

Abstract

Aim: This study was aimed at evaluating Euphorbia abyssinica (Desert Candle), a medicinal plant extensively used in folklore medicine among the Kendem people of South-west Cameroon for antibacterial activity and extracts analyzed for phytochemical composition. Study Design: The completely randomized block design was used and data analyzed using of two way analysis of variance. Significant means were separated using Duncan’s New Multiple Range Test. Place and Duration of Study: This study was carried out in the Department of Microbiology, University of Nigeria Nsukka, Enugu State, Nigeria, between April 2011 and August 2012. Methodology: Extraction was done using absolute methanol, 50% methanol (in water) and water as solvents. Qualitative analysis methods were used to assay the phytochemical constituents. Agar-well diffusion, macro broth dilution and agar dilution and time-kill assay were the susceptibility test methods adapted. Results: The phytochemical constituents detected were alkaloids, flavonoids, tannins, cardiac glycosides, carbohydrates and steroids, and saponins. The 50% methanol extract of the stem-bark was highly active against Staphyloccocus aureus, Escherichia coli, Salmonella typhi and Pseudomonas aeruginosa and compared favorably with the Gentamycin control drug. The inhibition zone diameters (IZDs) obtained with 50% methanol extract measured 23 mm for S. aureus and 19 mm for P. aeruginosa compared to 18 mm achieved with the absolute methanol extract for both              S. aureus and P. aeniginosa. For the aqueous extract the overall IZD range of 10±1.60-13±2.16 mm. The susceptibility patterns obtained using both dilutions (agar and macro-broth) methods were similar to that obtained with the agar diffusion method above. S. aureus (with MIC, 10.93±1.00-; MBC, 25-mg/mL, agar dilution or MIC, 3.9±1.60 -, MBC, 12.5-mg/mL, macro broth dilution methods, respectively). It was considered to be the most significantly susceptible bacteria strain tested (significant mean value 3.933), while E. coli was the least susceptible (with MIC, 50±0.00-, MBC, 100-mg/mL, in the agar dilution; MIC, 25±0.00-, MBC, 50-mg/mL in the broth dilution and a significant mean value of 14.70).  The stem-bark extracts was also significantly more active than the latex extracts P= .05 with significant mean values of 13.48 and 19.53 respectively. In the time-kill assay, all (100%) the organisms tested were killed by 50% methanol extract of E. abyssinica at concentrations equivalent to 1MIC- 4MIC. Conclusion: E. abyssinica extracts showed considerable antibacterial activity against the bacterial species tested. These findings authenticate the folklore use of Euphorbia abyssinica for broad spectrum treatment of bacterial infections.