Aim: To examine the antimicrobial activity and evaluate the anti-mycobacterial potency of Pulicaria crispa and Scoparia dulcis whole plant extracts in solvents of different polarities (n-hexane, ethyl acetate and methanol.
Study Design: Assessing the anti-microbial and anti-Mycobacterium tuberculosis activity of two Nigerian medicinal plants which have been reported according to folklore for treatment of various ailments including respiratory tract infections.
Place and Duration of Study: The experiment was conducted at the Chemistry Department of Ahmadu Bello University, Zaria, Nigeria and at the National Institute for Pharmaceutical Research and Development, Abuja, Nigeria between November 2014 and September 2015.
Methodology: The standard pan sensitive tuberculosis reference strain (H37Rv), eleven bacterial and four fungal clinical isolates were used. Methanol, Ethyl Acetate and Hexane extracts of Scoparia dulcis and Pulicaria crispa (whole plants) were tested at 0, 20 and 40 µg/ml using the Microplate Alamar Blue Assay. The minimum inhibitory, minimum bactericidal and minimum fungicidal concentrations of each solvent extract were assessed. Phytochemical analysis was also performed.
Results: Phytochemical compounds obtained in the methanol extract fractions where alkaloids, balsams, cardiac glycosides, glycosides, phenols, steroids and tannins in Scoparia dulcis (Linn), while extracts of Pulicaria crispa showed the presence of alkaloids, balsams, cardiac glycosides, flavonoids, glycosides, phenols, tannins and terpenoids. Saponins were detected in the n-hexane fractions for both plants but only appeared in the semi-polar fractions of Scoparia dulcis (Linn). Microplate Alamar Blue Assay (MABA) used for sensitivity study of Mycobacterium tuberculosis with 10 µg/ml rifampicin revealed that the n-hexane extract of Puliaria crispa and Scoparia dulcis gave 48.44±0.75, 12.14±0.02 mm zones of inhibition respectively, whereas the methanol and ethyl acetate extracts gave a 24.10±1.35 mm and 17.00±0.91 zones of inhibition for Puliaria crispa and Scoparia dulcis respectively in comparison to 33.70±0.64 mm obtained from the control. The minimal inhibitory content (MIC) of the methanol and n-hexane extracts for Pulicaria crispa were recorded at 8.01±1.70 and 10.03±1.33, while the MIC values for the ethyl acetate and n-hexane extracts of Scoparia dulcis was 12.03±0.86 and 20.40±0.24. The MIC value recorded for rifampicin was 0.38±1.40.
Conclusion: The results obtained suggested that the studied plants possess anti-tuberculosis and selective antimicrobial activities with the major activity tailored to the phyto-constituents.