Phytochemical analysis and in vitro antioxidant and antimicrobial activities of hydroalcoholic extracts of the leaves of Salacia kraussii

Abstract

Abstract The present work was aimed at identifying the bioactive compounds and determine the in vitro antioxidant and antimicrobial activities of the hydroethanolic extract of S. kraussii leaves. Phytochemical analysis was performed using gas chromatography-mass spectrometry (GC-MS) and classical colorimetric methods. Folin-Ciocalteu method, aluminum chloride precipitation, and casein precipitation were employed for quantification of total phenols, flavonoids, and tannins, respectively. The antioxidant activity was estimated by DPPH scavenging, phosphomolybdate (TAC), ABTS radical scavenging, and reducing power assays (FRAP-1 and FRAP-2). Antimicrobial activity was determined by the disk diffusion method against Escherichia coli, Staphylococcus aureus, Proteus mirabilis, Klebsiella pneumoniae, and Candida albicans. Phytochemical tests revealed the presence of flavonoids, quinones, alkaloids, steroids, tannins, and saponins. GC-MS analysis identified 17 biologically important compounds belonging to different classes, including fatty acids, carbohydrates, and terpenoids. The extract showed relatively low content of total phenols, tannins, and flavonoids of 5.00 mgEAG g−1, 0.08 mgEAT g−1, and 0.67 ± 0.29 mgEQ g−1, respectively. Its antioxidant potential was considerably stronger than that of the other Salacia sp. with EC50 values of 64.28 ± 0.01, 36.44 ± 0.67, 35.78 ± 0.09, 33.91 ± 0.12, and 2.22 ± 0.25 μg mL−1 as measured by FRAP-1, TAC, DPPH, FRAP-2, and ABTS radical scavenging assays, respectively. Regarding the antimicrobial activity, the extract inhibited the growth of all the test organisms with minimum inhibitory concentrations of 125 μg mL−1 and 250 μg mL−1 for the bacteria and fungus, respectively. This insightful study is a significant step towards the exploitation of S. kraussii leaves as a cheap source of broad-spectrum antimicrobial agents.