Antibacterial and antifungal activities of the crude extract and compounds from Dorstenia turbinata (Moraceae)

The aim of this study was to evaluate the antimicrobial activity of the crude extract of the twigs of Dorstenia turbinata (DTT) as well as that of five of the nine compounds isolated from this extract, namely 5-methoxy-3-[3-(ß-glucopyranosyloxy)-2-hydroxy-3-methylbutyl]psoralen (1), 5-methoxy-3-(3-methyl-2,3-dihydroxybutyl)psoralen (2), (2′S, 3′R)-3′-hydroxymarmesin (3), 4-hydroxy-3-methoxybenzaldehyde (4) and 4-methoxyphenol (5). Gram-positive, Gram-negative bacterial species as well as fungi were used. The agar disc diffusion test was used to determine the sensitivity of the tested samples while the well micro-dilution was used to determine the minimal inhibition concentrations (MIC) and the minimal microbicidal concentration (MMC) of the active samples. The results of the disc diffusion assay showed that the crude extract (DTT), compounds 1 to 3 were able to prevent the growth of all the tested pathogens at the tested concentrations. Compounds 4 and 5 showed moderate and selective activities. The results of MIC determinations indicated values ranging from 19.53 to 78.12 µg/ml for the DTT and from 9.76 to 78.12 µg/ml for compound 2. The MIC values recorded on 91% of the tested organisms for compounds 1 and 3. The lowest MIC value for the crude extract of D. turbinata (19.53 µg/ml) was noted on Trichophyton rubrum and Escherichia coli. The corresponding value for the tested compounds (9.76 µg/ml) was obtained with 2 and 3 on T. rubrum. The antimicrobial activity of this plant as well as that of compounds 1-2 is being reported for the first time. The overall results provide promising baseline information for the potential use of the crude extracts from DTT as well as some of the isolated compounds in the treatment of bacterial and fungal infections.