Phytochemicals Profiling of Blue-Green Alga Nostoc sp. HANL07: Antioxidant, Antibacterial Activity and GC-MS Analysis

Abstract

In recent years, studies on phytochemicals, antioxidants, and antibiotics using blue green algae from harsh environments has become increasingly prevalent. The search for novel bioactive molecules exhibiting diverse biological activity is one of the most important strategies for addressing the issue of rising concerns regarding bacterial antibiotic resistance. In present study, the phytochemicals, antioxidant potentiality and antibacterial assessment of organic solvent extracts of blue-green alga isolated from Naini lake water were characterized. From the mass culture of alga, extracts were prepared in MeOH, EtOH, acetone, AcOEt, hexane and DCM and antioxidant potential and antibacterial properties were studied against multiple antibiotic-resistant E. coli, P. aeruginosa, P. fluorescence, S. enteric, S. typhimurium and Sh. dysenteriae. The 16S rRNA gene sequence analysis and phylogenetic tree revealed that blue-green algal isolate belongs to Nostoc sp. A higher extraction yield (5.3%) was recorded for MeOH extract as compared to other solvent extracts. Alkaloids, flavonoids and phenols were present in all extracts. DPPH free radical scavenging activity was determined using various concentrations of extracts (1 to 2048 µg mL-1). Maximum % inhibition (free radical scavenging activity) was observed in MeOH extract (35.23 ± 0.12). The methanolic extract was found to be inhibitory against P. aeruginosa and P. fluorescence. 2048 µg mL-1 MIC value was recorded against P. aeruginosa. In GC-MS profiling, a total of 8 significant peaks showing various compounds were identified among the 21 peaks. Oxirane hexadecyl was reported as the main components in this compound. The results showed that Nostoc sp. HANL07 is a good source of antioxidant and antibacterial compounds and could be used for further study in the field of drug discovery.