Abstract:
The antibacterial activity of the leaves and bark of mangrove plants, Avicennia marina, A. offi cinalis, Bruguiera
sexangula, Exoecaria agallocha, Lumnitzera racemosa, and Rhizophora apiculata was evaluated against antibiotic
resistant pathogenic bacteria, Staphylococcus aureus and Proteus sp. Soxhlet extracts of petroleum ether, ethyl acetate,
ethanol and water were prepared and evaluated the antibacterial activity using agar diffusion method. Most of the
plant extracts showed promising antibacterial activity against both bacterial species. However, higher antibacterial
activity was observed for Staphylococcus aureus than Proteus sp. The highest antibacterial activity was shown by
ethyl acetate of mature leaf extracts of E. agallocha for Staphylococcus aureus. All ethyl acetate extracts showed
higher inhibition against S. aureus while some extracts of chloroform, ethyl acetate and ethanol gave inhibition
against Proteus sp. None of the petroleum ether and aqueous extracts showed inhibition against Proteus sp. All
fresh plant materials did also show more antibacterial activity against both bacterial strains than did dried plant
extracts. Antibacterial activity of fresh and dried plant materials reduced for both bacterial strains with time after
extraction. Since L. racemosa and A. marina gave the best inhibition for bacterial species, they were used for further
investigations. Charcoal treated plant extracts of L. racemosa and A. marina were able to inhibit both bacterial
strains more than those of untreated plant extracts. Phytochemical screening of mature leaf, bark of L. racemosa
and leaf extracts of A. marina has been carried out and revealed that leaf and bark contained alkaloids, steroids,
triterpenoids and fl avonoids. None of the above extracts indicate the presence of saponins and cardiac glycosides.
Separated bands of extracts by TLC analysis showed antibacterial activity against S. aureus.
