Proma Khondkar

Optimal Conditions for Antimicrobial Metabolites Production from a New Streptomyces sp. RUPA-08PR Isolated from Bangladeshi Soil

Abstract An actinomycete strain was isolated from northern part of Bangladesh and identified as a new Streptomyces species on the basis of its morphological, biochemical, cultural characteristics and 16S rRNA data. Attempts were made to optimize the culture conditions for the production of antimicrobial metabolites by this strain. Antimicrobial metabolites production was started after 7 days of incubation of culture broth and reached its maximum levels after 10 days and thereafter gradually decreased. The maximum production of antimicrobial metabolites was obtained when the culture medium pH was adjusted to 8. The optimum temperature for antimicrobial metabolites production was 39°C, indicated the new strain as mesophilic organism. Basel medium supplemented with glucose and yeast extract as carbon and nitrogen sources, respectively, was proved to be the best for the production of bioactive metabolites. Maximum production of bioactive metabolites was when NaCl concentration was 1% and among different minerals tested, K2HPO4 and NaCl showed positive influence on antibiotic production by the strain.

Antimicrobial and cytotoxic constituents of Loranthus globosus.

(+)-Catechin, 3,4-dimethoxycinnamyl alcohol and 3,4,5-trimethoxycinnamyl alcohol were isolated from the barks of Loranthus globosus. All compounds showed significant antimicrobial and cytotoxic activities.

Antibacterial and Antifungal Activities of the Constituents of Flemingia paniculata

Abstract A salicylic acid derivative (1), a cinnamaldehyde (2), and six isoflavones (3–8) from the stem bark of Flemingia paniculata. Wall. (Leguminosae) were tested for antibacterial (both Gram-positive and Gram-negative) and antifungal activities. All the compounds showed significant activities against the test organisms having MIC values in the range of 1.57–200 μ g/mL. The highest potency (MIC = 1.57 μ g/mL) was exhibited by 3 against Staphylococcus aureus..

Mosquitocidal triterpenes from the stem of Duranta repens

Two triterpenes, β-amyrin and 12-oleanene 3β, 21β-diol, were isolated as a mixture from the chloroform soluble fraction of an ethanol extract of Duranta repens Linn (Verbenaceae) stem. The structures of the two compounds were confirmed by analysis of their IR, 1H-NMR, 13C-NMR and LC-MS spectral data. The mixture of β-amyrin and 12-oleanene 3β, 21β-diol (compound 1) was highly effective against the larvae of the mosquito, Culex quinquefasciatus Say (Diptera: Culicidae), as a mosquitocide.

Analogues of Disulfides from Allium stipitatum demonstrate potent anti-tubercular activities through drug efflux pump and Biofilm inhibition

Disulfides from Allium stipitatum, commonly known as Persian shallot, were previously reported to possess antibacterial properties. Analogues of these compounds, produced by S-methylthiolation of appropriate thiols using S-methyl methanethiosulfonate, exhibited antimicrobial activity, with one compound inhibiting the growth of Mycobacterium tuberculosis at 17 µM (4 mg L−1) and other compounds inhibiting Escherichia coli and multi-drug-resistant (MDR) Staphylococcus aureus at concentrations ranging between 32–138 µM (8–32 mg L−1). These compounds also displayed moderate inhibitory effects on Klebsiella and Proteus species. Whole-cell phenotypic bioassays such as the spot-culture growth inhibition assay (SPOTi), drug efflux inhibition, biofilm inhibition and cytotoxicity assays were used to evaluate these compounds. Of particular note was their ability to inhibit mycobacterial drug efflux and biofilm formation, while maintaining a high selectivity towards M. tuberculosis H37Rv. These results suggest that methyl disulfides are novel scaffolds which could lead to the development of new drugs against tuberculosis (TB).