Antibacterial Activity of Pennisetum glaucum Crude Extracts and Pre-purified Fractions against Selected Pathogenic Microorganisms

Background: Penisetum glaucum is one of the earliest indigenous food crops in East Africa. Pearl millet contains numerous phytocompounds. Isolation and characterization of secondary metabolites from pearl millet and evaluation of their bioactivity is necessary. These will act as “markers” for pharmacological quality, increasing the acceptability of pearl millet. The current study was therefore undertaken to provide thin layer chromatography (TLC) profile using different solvent systems and pre-purified fractions.

Methods: Maceration and sequential extraction methods were used. Thin layer chromatography and column chromatography techniques were used in extracts purification. The antibacterial activity of the crude extracts and pre-purified fractions was determined using well diffusion method.

Results: Pearl milletethyl acetate and petroleum ether extracts gave good activity as compared to other tested crude extracts. Petroleum ether inhibited Serratia liquefaciens the most with an average inhibition zone of 10.66±0.882 while ethyl acetate inhibited Bacillus cereus (12.333±0.577). Methanol extract inhibited the growth of only E. coli. Fraction 10 which was obtained from the petroleum ether extract inhibited the growth of all the microorganisms tested. Gentamicin which was used as the positive control had significantly higher inhibition zones against all the selected microorganisms as compared to the plant test samples (p<0.001). DMSO which was used as the negative control did not inhibit the growth of any of the selected microorganisms.

Conclusion: The results obtained in the current investigation of P. glaucum show that the cereal contains secondary metabolites with useful pharmacological activities. The antibacterial activity observed in this study could be a scientific justification of the plants potency in prevention and management of gastrointestinal infections due to its ability to inhibit the growth of E. coli. A lot has been done on the primary metabolites of pearl millet ascertaining its richness in minerals, vitamins and primary nutritional molecules. It is therefore necessary to give attention to the secondary metabolites concentration and their pharmacological importance. Further purification, isolation, identification and characterization of pearl millet bioactive compounds remain to be our priority in future.