In vitro antioxidant and antibacterial activity of Scenedesmus obliquus collected from Similipal biosphere reserve, Odisha, India

Abstract

Microalgae have the ability to produce natural bioactive chemicals that are difficult to synthesize chemically. Natural antioxidants derived from microalgal sources may be effective substitutes for manufactured antioxidants due to their antibacterial action and low side effects. The influence of several solvents on phytochemical screening, antioxidant, and antibacterial properties of Scenedesmus obliquus, collected from Similipal Biosphere Reserve, was investigated in this study. The results revealed the presence of various phytoconstituents such as phenols, tannins, flavonoids, saponins, terpenoids, sterols, glycosides, and alkaloids, which were extracted using organic solvents of various polarities. For qualitative identification of phytochemicals, chloroform extract performed better than petroleum ether, acetone, methanol, and aqueous. Owing to their free radical scavenging and total antioxidant activity, total phenolic, total flavonoid, and total antioxidant activity of different solvent extracts of S. obliquus were examined. The highest phenolic content was found in chloroform and the lowest in aqueous extract. Flavonoid concentration was highest in chloroform extract and lowest in petroleum ether and acetone. Similarly, methanol extract displayed higher DPPH radical scavenging activity and lower total antioxidant activity than aqueous. Furthermore, agar cup diffusion testing of antibacterial activity against eight pathogenic bacteria revealed that all solvent extracts have the ability to block at least two of the test pathogens, with the exception of aqueous, which showed no action. The highest zone of inhibition (12 mm) was observed with chloroform and acetone extracts against Shigella dysenteriae, moderate (10 mm) with petroleum ether, chloroform, and acetone extracts against Bacillus brevis, and Bacillus licheniformis with petroleum ether and methanol extracts. The results showed that extracts of the green microalga S. obliquus in chloroform, acetone, and methanol have regained antioxidant and antibacterial activity, which could be useful for medicinal applications.