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

Introduction: Plants are a limitless gift of nature to humans and they possess very appreciative
values and roles. They have stood the test of time in the life of man since creation. All over the world,
they are hugely exploited for food, fuel, timber, medicine etc. The natural endowment of plants with
numerous metabolites and bioactive compounds makes them good sources of therapeutic agents
capable of replacing synthetic antibiotics; For example, Salversan and Penicillin are synthetic drugs
formerly used for the treatment of Syphilis and Staphylococcus aureus infections, respectively, but
which became less preferred because these pathogens developed resistance to the drugs.
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. The determination of the antimicrobial activity of Euphorbia abyssinica stem (bark and Latex extracts) extract included the 50% methanol, absolute methanol and
aqueous extracts of these plant parts. The antimicrobial activity variously exhibited by the 50%
methanol extracts of all the two plant parts tested, is significant. This is because it validates the
popular traditional uses of dilute alcohol concoctions of medicinal plant preparations in ethno
medicinal practice in south-West region of Cameroon. Secondly, the results indicated that these herbs
used in traditional medicine have selective antimicrobial activities. Thus, the microorganisms which
were susceptible to these extracts are those often associated with wound and ear infections, urinary
and gastrointestinal tract infections as well as pyrexia of unknown origin. This explains the
discriminate uses of these plants in the treatment of particular ailments. These findings provide
evidence that E. abyssinica is a strong candidate in microgram concentrations while the plant extracts
were effective in milligram concentrations. Therefore actual comparison between the control drugs
and the extracts would await isolation, purification and determination of molar concentrations of the
pure active ingredients of these plants extracts.