Abstract:
Solanum trilobatum which is known as Toothuvilai in Tamil has
been widely used to treat respiratory disorders, especially bronchial asthma.
Therefore this study was designed to test the antibacterial activity and
phytochemical property of sequential solvent extracts of leaves of Solanum
trilobatum. Leaf powder was successively extracted with solvent of
dichloromethane (DCM), then by ethylacetate (EA) and finally by ethanol
(EtOH). 10 mg/100 µL, 30 mg/100 µL and 50 mg/100 µL doses of the crude
extracts were used for this study. The crude extracts were dissolved in the
solvent mixture of 30% of acetone and 70% of the mother solvent. The crude
extracts were tested for antibacterial activity by in vitro agar well diffusion
method and screening test was done against five bacterial pathogens. Two of
them were Gram positive bacteria Bacillus subtilis, Staphylococcus aureus and
three of them were Gram negative bacteria Escherichia coli, Pseudomonas
aeruginosa and Klebsiella. Streptomycin and solvents used to dissolve extracts
were used as standard and control respectively. Among the extracts, EA and
EtOH were more effective for the in vitro control of bacteria. These two
extracts had inhibition on all test bacteria at all test concentrations. S.aureus,
B.subtilis, P.aeruginosa and Klebsiella were highly inhibited by EA extract at 50
mg/100µL but E.coli was highly inhibited by EtOH extract at the same
concentration. However, at 10 mg/100µL EA extract revealed higher
inhibition on all test bacteria compared to EtOH extract, ranged from
11.8±0.3 mm to 18.8±0.8 mm. Statistical analysis revealed that there were
significant (p<0.05) difference in the inhibitory effect of the extracts with
tested bacteria. Among the test bacteria the Klebsiella was found to be the
most sensitive to EA extract. Time course analysis revealed that there was no
considerable change in the inhibitory effect of the test samples until 72h
incubation. Standard antibiotic streptomycin failed to inhibit the growth of
P.aeruginosa and E.coli at the test concentration and the diameter of inhibition
zone produced by the streptomycin on S.aureus was found to be less than that
of the EA extract on same bacteria
