Antibacterial and anti-biofilm activity of flavonoids and triterpenes isolated from the extracts of Ficus sansibarica Warb. subsp. sansibarica (Moraceae) extracts

Abstract

Background: Ficus species are used in African traditional medicine in the treatment of a wide variety of ailments and diseases such as convulsive disorder, wound healing, gonorrhea, tuberculosis, diabetes, diarrhoeal infections, dysentery, malaria and HIV. The aim of this study was to isolate the phytochemical constituents in the plant and test them for their antibacterial activity.

Materials and methods: The fruits, leaves and stem bark were extracted with organic solvents and the compounds in the extracts separated and purified by column chromatography before being identified by NMR spectroscopy and by comparison of the NMR data against values reported in the literature. The antibacterial activity of the pure compounds and extracts were tested using the disk diffusion method.

Results: Three triterpenes and three flavonoids: lupeol acetate (1); cycloart-23-ene-3,25-diol (2); β-sitosterol (3); 5,7,4'-trihydroxyflavan-3-ol (4); epicatechin (5); and isovitexin (6) were isolated in this study. Antimicrobial activity was observed at 8 mg mL(-1) for Staphylococcus aureus ATCC 29213 with four of the six isolated compounds, with no activity being observed at 1 - 4 mg mL(-1) against Escherichia coli ATCC 25922, E. coli ATCC 35218 and S. aureus ATCC 43300. Epicatechin (5) was found to decrease adhesion of E. coli ATCC 25922 and S. aureus ATCC 29213. Decreased adhesion of S. aureus ATCC 29213 was also observed with 5,7,4'-trihydroxyflavan-3-ol (4) and isovitexin (6).

Conclusions: The results of this study provide baseline information on F. sansibarica's potential validity in the treatment of infections associated with Gram-positive microorganisms.

Keywords: Ficus sansibarica; Moraceae; anti-adhesion properties; antimicrobial; flavonoids; triterpenoids.

Figure 1

Chemical structures of compounds isolated from Ficus sansibarica. Lupeol acetate (1), cycloart-23-ene-3,25-diol (2), sitosterol (3), 5,7,4′-trihydroxyflavan-3-ol, R = H, (4), epicatechin, R = OH (5), isovitexin (6).

Figure 2

Anti-adhesion activity of 1 – 15 mg mL⁻¹ of compounds 1 and 4–6 on biofilm formation by E. coli and S. aureus strains: (a) lupeol acetate (1); (b) epicatechin (5); (c) 5,7,4′-trihydroxyflavan-3-ol (4); (d) isovitexin (6).