Antimicrobial activity of aqueous, ethanolic and methanolic leaf extracts from ACACIA spp. And Eucalyptus nicholii

Abstract

Background: In Europe, Acacia and Eucalyptus, originate large amounts of biomass, due to their need by industries and other biological control, that can be used to extract antimicrobial substances. Materials and Methods: Foliar aqueous, ethanolic and methanolic extracts of Acacia baileyana (Cootamundra wattle), Acacia dealbata (silver wattle), Acacia melanoxylon (black wattle) and Eucalyptus nicholii (narrow-leaved black peppermint) were assessed for antimicrobial activity against Escherichia coli, Bacillus cereus, Candida albicans and Candida parapsilosis, using the disc diffusion method. Results: Ethanolic extracts from A. baileyana and A. dealbata showed significant (P< 0.05) antimicrobial activity. Concerning the microbial species tested, differences were found in A. baileyana (P< 0.01) and E. nicholii (P< 0.0001) extracts. These two extracts were effective mostly against B. cereus, followed by C. parapsilosis. According to the antimicrobial activity classification, eucalypt and Cootamundra and silver wattles extracts (both water and ethanol) presented good efficacy against B. cereus, a food poisoning agent, and moderate efficacy against the remaining microorganisms. E. coli, a Gram negative, exhibited low sensibility to all foliar extracts. Conclusion: A. baileyana, E. nicholii and A. dealbata foliar biomass could be used to develop alternative substances in microbial control.