CHEMICAL PROFILE OF THE ANTIBACTERIAL COMPONENT FROM LEPTOLYNGBYA SP. HNBGU 002 ISOLATED FROM A HOT SPRING OF GARHWAL HIMALAYA

Cyanobacteria are a well-established source of antibacterial compounds. However, the hot spring cyanobacterial strains are not properly explored for the purpose. The study investigates the antibacterial potential of the thermophilic oscillatoriales isolated from a hot spring of Garhwal Himalaya. Out of 48 endo-metabolite pools, extracted from 16 thermophilic cyanobacterial strains, tested for antibacterial activity against the bacterial pathogens, the DEEL (diethyl-ether extract of Leptolyngbya sp. HNBGU 002) was found to be active against Staphylococcus aureus ATCC 25923 with the minimum inhibitory concentration of 2.0 mg ml^-1 and was able to disrupt the cell membrane function of bacteria as evidenced by an increase in membrane conductivity. In addition, DEEL was also found to be active against MRSA (methicillin-resistant Staphylococcus aureus) and VRE (vancomycin-resistant Enterococcus faecium) strains. Gas chromatography-mass spectrometry analysis revealed the hydrocarbons and phenolics as the major compounds present in the DEEL. Besides, a triazolo-pyrimidine (TP) derivative, 1; 7-methyl-6-nitro[1,2,4] triazolo[1,5-a] pyrimidin-5-ol, was also detected in the active fraction. The findings suggest that the antibacterial activity of DEEL may be attributed to the hydrocarbons, phenolics, the TP derivative (1), and their synergistic effects. To the best of our knowledge, being the first report on the occurrence of a TP derivative (1) from cyanobacterial sources, this is an interesting finding in view of pharmaceutical industries. The study suggests that the DEEL is a potential source of antibacterial metabolites and must be fractionated to characterize these compounds.