Antibacterial and Anti-Biofilm Activity of Flavonoids and Triterpenes Isolated from The Extracts of <i>Ficus Sansibarica</i> Warb. <i>Subsp. Sansibarica</i> (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.

Antibacterial Activity of Some Flavonoids and Organic Acids Widely Distributed in Plants

“…Particularly, works on the antibacterial activity of individual pure compounds are relatively few. There is a small number of microbiological investigations describing the effects of some common flavonoid glycosides such as vitexin [55][56][57][58], isovitexin [59,60], vitexin 2"-O-rhamnoside [61], orientin [62,63], and isoorientin [56,60,62].…”

“…In addition, literature data are difficult to compare due to the use of various methods for assessing antibacterial activity, different solvents, and the origin and purity of test compounds, often isolated from various plant extracts [55,57,59,60,[62][63][64][65]. Antimicrobial properties of natural chemicals were described not only by the minimum inhibitory concentration (MIC) [33,54,57,62,64,[66][67][68][69][70][71][72] and by the minimum bactericidal concentration (MBC) [72], but also by the agar well or disc-diffusion methods [59,60,63,65]. Some authors expressed results as the IC 50 or MIC 80 values [33,67,73].…”

“…Although most authors utilized dimethyl sulfoxide, sometimes they did not give its concentration [59,62,63,65] or it is 100% DMSO [54], which may affect the level of antimicrobial activity of the tested solutions. The other solvents used were, for example, acetone [67], chloroform [59], Mueller Hinton II broth [68], and water [71]. In several cases, there was no information about dissolving procedures [57,58,60].…”

Efficacy and Mechanism of Traditional Medicinal Plants and Bioactive Compounds against Clinically Important Pathogens

“…Plant antimicrobial secondary metabolites are generally categorized into three broad classes, namely phenolic compounds, terpenes, and alkaloids. Numerous studies have shown that the antimicrobial activity of the plant extracts and their active compounds have the following potential: to promote cell wall disruption and lysis, induce reactive oxygen species production, inhibit biofilm formation, inhibit cell wall construction, inhibit microbial DNA replication, inhibit energy synthesis, and inhibit bacterial toxins to the host [75,85,[105][106][107][108][109]. In addition, these compounds may prevent antibacterial resistance as well as synergetics to antibiotics, which can ultimately kill pathogenic organisms (Figure 1).…”

“…Interestingly, numerous researchers have described how flavonoids cause the aggregation of multicellular composites of bacteria and inhibit bacterial growth after aggregation, which indicates that flavonoids are potent antibiofilm compounds. The bioactive flavonoids such as galangin (18), isovitexin (19), EGCG (20) and 3-O-octanoyl-epicatechin (21), as well as 5, 7, and 40-trihydroxyflavanol (22) induce pseudo multicellular aggregation of S. aureus and S. mutans [106][107][108][109]. Quorum sensing involves cell signaling molecules called autoinducers present in E. coli, Vibrio cholerae, and S. typhi, which is a notable regulatory factor for biofilm formation [126].…”