Abstract:
Background: Coastal Sri Lankan Volkameria inermis belongs to the family Lamiaceae, is a plant
with traditional ayurvedic uses. Its antibacterial properties and phytochemical composition is not
scientifically explored adequately.
Objectives: To evaluate the antibacterial activities of hexane, dichloromethane and ethyl acetate
extracts of V. inermis against common human pathogens i.e., Staphylococcus aureus, Methicillin
resistant Staphylococcus aureus (MRSA), Escherichia coli and Diphtheroids along with
phytochemical screening
Methods: Fresh leaves (750g) of V. inermis were extracted with hexane, dichloromethane and
ethyl acetate sequentially for three times, extraction yielded 102mg, 163mg and 41mg
respectively. Crude extracts were separately dissolved in DMSO (100mg/mL). Ciprofloxacin
(3mg/mL) and DMSO used as the positive and negative controls. Antibacterial sensitivity was
tested using agar disc diffusion assay (10µL per disc) in triplicates, and mean diameter was
calculated.
Results: Hexane extract showed the highest inhibition against S. aureus, MRSA, and
Diphtheroids with mean(±SD) inhibition zone diameters of 10.4(±0.3)mm, 11.3(±0.6)mm and
12.1(±0.6)mm, respectively. Dichloromethane extract, and ethyl acetate extract inhibited the
growth of MRSA and S. aureus with inhibition zone diameters in the range of 8mm to 11mm,
while the positive control exhibited inhibition zone diameters more than 24mm for all the tested
organisms. However, none of the extracts showed inhibition of E. coli. Negative control did not
show inhibition zones for the tested organisms. Phytochemical screening tests revealed the
presence of terpenoid compounds in all of the extracts. Dragendorff’s test for alkaloids and FeCl3
test for phenolic compounds were positive only for the ethyl acetate extract.
Conclusions: Hexane and dichloromethane extracts were effective against most tested organisms.
It can be concluded that relatively non-polar metabolites within the plant exhibit strong
antibacterial effects. Additionally, the ethyl acetate extract shows evidence of antibacterial
phenolic compounds and alkaloids
