Bioactive Analysis of Antibacterial Efficacy and Antioxidant Potential of Aloe barbadensis Miller Leaf Extracts and Exploration of Secondary Metabolites Using GC-MS Profiling

Aloe barbadensis Miller (ABM) is a traditional medicinal plant all over the world. Numerous studies were conducted to exhibit its medicinal properties and most of them were concentrated on its metabolites against human pathogens. The current research work evaluates the attributes of different polar-based extracts (ethanol, methanol, ethyl acetate, acetone, hexane, and petroleum ether) of dried Aloe barbadensis leaf (ABL) to investigate its phytochemical constituents, antioxidant potential (DPPH, ABTS), phenolic, tannin, flavonoid contents, identification of bioactive compounds, and functional groups by gas chromatography-mass spectrometry (GC-MS) and fourier transform infrared spectroscopy (FT-IR) respectively, and comparing antibacterial efficacy against human pathogens, aquatic bacterial pathogens, and zoonotic bacteria associated with fish and human. The present results showed that the methanolic extract of ABL showed higher antioxidant activity (DPPH-59.73 +/- 2.01%; ABTS-74.1 +/- 1.29%), total phenolic (10.660 +/- 1.242 mg GAE/g), tannin (7.158 +/- 0.668 mg TAE/g), and flavonoid content (49.545 +/- 1.928 mu g QE/g) than that of other solvent extracts. Non-polar solvents hexane and petroleum ether exhibited lesser activity among the extracts. In the case of antibacterial activity, higher inhibition zone was recorded in methanol extract of ABL (25.00 +/- 0.70 mm) against Aeromonas salmonicida. Variations in antibacterial activity were observed depending on solvents and extracts. In the current study, polar solvents revealed higher antibacterial activity when compared to the non-polar and the mid-polar solvents. Diverse crucial bioactive compounds were detected in GC-MS analysis. The vital compounds were hexadecanoic acid (30.69%) and 2-pentanone, 4-hydroxy-4-methyl (23.77%) which are responsible for higher antioxidant and antibacterial activity. Similar functional groups were identified in all the solvent extracts of ABL with slight variations in the FT-IR analysis. Polar-based solvent extraction influenced the elution of phytocompounds more than that of the other solvents used in this study. The obtained results suggested that the ABM could be an excellent source for antioxidant and antibacterial activities and can also serve as a potential source of effective bioactive compounds to combat human as well as aquatic pathogens.