ABSTRACT
Endophytic fungi serve as a reservoir for important secondary metabolites. The current study focused on the antibacterial properties of endophytic fungi isolated from Artemisia sieberi. Initially, six endophytic fungi were isolated and purified from the stem of A. sieberi. Endophytic fungi were identified by morphological characteristics, as well as by molecular identification using 18S rRNA gene sequencing method. All the six isolates were subjected to the preliminary screening for their antibacterial activity against nine important pathogenic bacteria using the disk-diffusion method. Crude extracts of the most active isolate were obtained using ethyl acetate. Antibacterial activity of the ethyl acetate extract was evaluated using well diffusion method on the selected isolate. The antibacterial efficiency of the selected isolate was evaluated by determining the Minimum Inhibitory Concentration (MIC). MIC values were in appreciable quantity against both Gram-positive and Gram-negative bacteria ranging from 3.125 to 6.25 µg/mL and 12.5 to 50 µg/mL, respectively. This result indicated that Gram-positive bacteria were more susceptible to the endophytic fungi extract. Moreover, the molecular identification results revealed that all the isolates belong to Ascomycota and represented Aspergillus and Penicillium genera and three species: A. oryzae (three isolates), A. niger (one isolate), and P. chrysogenum (two isolates). All six endophytic fungi were able to inhibit the growth of at least two of the tested bacteria. Among the isolated strains, isolate AS2, which identified as P. chrysogenum, exhibited the highest antibacterial activity against all nine tested bacteria and was higher than or equal to the positive control against most of the tested bacteria. Future studies are required to isolate and identify these bioactive substances, which can be considered as a potential source for the synthesis of new antibacterial drugs to treat infectious diseases.
ABSTRACT
BACKGROUND: Candida infections are becoming more drug resistant; it is necessary to search for alternative medications to treat them. Therefore, the present study estimates the anticandidal activity of Vitex agnus-castus (VA-C) leaf extracts. METHODS: We used the agar well diffusion method to assess the anticandidal activity of three different VA-C leaf extracts (ethanol, methanol, and water) against three Candida species (Candida tropicalis, Candida albicans, and Candida ciferrii). The minimum inhibitory concentration (MIC) was estimated using the two-fold dilution method and the minimum fungicidal concentration (MFC) was determined using the classic pour plate technique. The MFC/MIC ratio was calculated to estimate the microbicidal or microbiostatic activity. A gas chromatography mass spectrometer was used to screen the phytochemicals of the VA-C leaf extracts (ethanol, methanol, and water). RESULTS: All VA-C extracts ethanol, methanol, and water were significantly inhibited the growth of the test Candida species and the inhibition activity depended on the solvent used and the Candida species. The results showed that C. tropicalis was the most highly inhibited by all extracts followed by C. albicans and C. ciferrii. The MIC values were 12.5-25 µg/ml, and MFC values were 25-100 µg/ml. The ratios of MFC/MIC were two-fold to four-fold which was considered candidacidal activity. Ninety-five phytochemical compounds were identified by the GC-MS assay for the VA-C leaf extracts. The total number of compounds per extract differed. Methanol had 43 compounds, ethanol had 47 compounds, and water had 52 compounds. The highest compound concentrations were: 4,5-Dichloro-1,3-dioxolan-2-one in ethanol and methanol, 1H-Indene, 2,3-dihydro-1,1,2,3,3-pentamethyl in ethanol, Isobutyl 4-hydroxybenzoate in methanol, and Benzoic acid and 4-hydroxy- in water. These phytochemical compounds belong to different bioactive chemical group such as polyphenols, fatty acids, terpenes, terpenoids, steroids, aldehydes, alcohols, and esters, and most of which have anticandidal activity. CONCLUSIONS: VA-C leaf extracts may be useful alternatives to anticandidal drugs, based on their effectiveness against all test Candida species at low concentrations. However, appropriate toxicology screening should be conducted before use.
ABSTRACT
BACKGROUND AND OBJECTIVE: Searching for a new antimicrobial agent is a significant challenge because of increasing resistance of microbes to antibiotics. Because plants are an inexpensive source of rich metabolic substances that are highly efficient, this study was designed to evaluate the antimicrobial activity of Sarcocolla gum resin extracted from Astragalus sarcocolla root and its phytochemicals. To the best of the author's knowledge, the antimicrobial activity of Sarcocolla gum resin has not previously been reported. MATERIALS AND METHODS: The antimicrobial activity of Sarcocolla gum resin was evaluated using a well diffusion assay. The effect of water and ethanol extracts in various concentrations (20, 40 and 60%) against the growth of pathogenic bacteria and yeast were tested. RESULTS: The results showed that the lower concentration (20%) of water and ethanol extracts had no inhibitory effect on any of the tested microbes except Staphylococcus aureus (S. aureus) ATCC 29213. However, an antimicrobial effect of water and ethanol extracts was observed on most tested microbes at higher concentrations (40 and 60%). The S. aureus ATCC 29213 was resistant to all ethanol extract concentrations. In contrast, S. aureus ATCC 29213 was inhibited by water extracts at all concentrations tested. Minimum inhibitory concentrations (MIC) were estimated using a 2-fold dilution method and MIC values were between 12.5-25 µg mL-1. Phytochemical screening was performed using standard procedures that showed the presence of sterols, terpenoids, flavonoids, alkaloids, saponins and tannins. CONCLUSION: This study showed that Sarcocolla gum resin extract possesses high antimicrobial activity that depends on the solvent type, the concentration of plant extract and the microbe type. These results provide a new source of antimicrobial that may be useful in the manufacture of antibiotics.
