Antimicrobial Activity of Tannins and Extracts of Different Parts of Conocarpus Erectus L

In this study, the antimicrobial activity of crude extracts of flower, fruit, stem and leaf of Conocarpus erectus and purified tannins were evaluated against three fungi and seven Gram-positive, Gram-negative and acid-fast bacteria. While, by disc diffusion method, extracts of different parts of C.erectus were active only against Saccharomyces cerevisiae, purified tannins were active against Sac. cerevisiae, Aspergillus niger and Penicillium chrysogenum. Disc diffusion method was also used to evaluate the antibacterial activity of the crude methanolic extracts. The extracts had broad spectrum activity and their descending order of activity was flower, fruit, stem and root. Gram-positive bacteria were more sensitive to extracts than other bacteria. Methanol extracts of different parts of C. erectus were fractionated by chloroform, ethyl acetate, and n-butanol and their MICs and MBCs were determined against the tested bacteria. Generally speaking ethyl acetate extracts were more active than other fractionated extracts. The two tested Gram-positive bacteria, Staphylococcus aureus and Bacillus subtilis were the most sensitive, Mycobacterium phlei and Pseudomonas aeruginosa were intermediate, and Escherichia coli, Salmonella typhimurium and Klebsiella pneumonia were the least sensitive to the extracted fractions. Compared to crude methanol extract, tannins of C. erectus were significantly (p ≤ 0.01) more active than alcohol extracts against the tested bacteria and had 6 to 12 times lower MICs and MBCs. Therefore, it may be concluded that C. erectus extracts have broad spectrum antimicrobial activity and their activity could be attributed, to a great extent, to their contents of tannins.