Anti-adhesion potential of non-polar compounds and extracts from Ficus natalensis

Abstract Four triterpenoids, ergosta-4,6,8(14),22-tetraene-3-one 1, stigma-4-ene-3-one 2, 3β-hydroxy-21β-H-hop-22(29)-ene 3, sitosterol and a quinone, tectoquinone 4, were isolated from the leaf, stem bark and fruit extracts of Ficus natalensis subsp. natalensis, Moraceae, a medicinal fig found in Africa. The pure compounds 1-4 and crude extracts were tested for their antibacterial activity against five Gram-negative and seven Gram-positive strains and for their potential anti-biofilm activity. Antimicrobial susceptibility was observed with all pure compounds tested at 250 µg against the majority of Gram-negative and Gram-positive strains. The dichloromethane-soluble fruit extract was active against sensitive and resistant Staphylococcus aureus strains, Enterococcus faecalis and Staphylococcus xylosus. Compounds 2, 3 and 4 demonstrated broad-spectrum antibiotic effects against eight of the twelve bacterial strains tested. In the anti-biofilm assay, exposure to ethyl acetate, methanol and aqueous methanol leaf, stem bark and fruit extracts decreased adhesion with a biofilm reduction of ≥100% for all three tested organisms: Escherichia coli, Pseudomonas aeruginosa and S. aureus. The methanol leaf extract demonstrated the most potent anti-adhesion potential against E. coli (218% biofilm reduction). The greatest ability to decrease adhesion was observed with compounds 2, 3 and 5 against P. aeruginosa at the lowest concentration tested (100 µg ml−1).