Antioxidants, anti-proliferative, anti-inflammatory, anti-diabetic and anti-microbial effects of isolated compounds from Swertia corymbosa (Grieb.) Wight ex C.B. Clark – An in vitro approach

The present study, antioxidant, enzyme inhibitory, anti-inflammatory and antimicrobial activity of isolated compounds such as Decussatin (1), Gentiacaulein (2), Swertianin (3), 1,8-dihydroxy-2,6-dimethoxy xanthone (methylswertianin) (4) 8-hydroxy-1,2,4,6-tetramethoxyxanthone (5) and 1,2-dihydroxy-6-methoxyxanthone-8-O-β-D-xylopyranosyl (6) were investigated using an in vitro model. Results of antioxidant studies revealed that the compound 6 possessed an efficient 2,2-diphenyl-1-picryl-hydrazyl (DPPH^•) (IC₅₀ 07.19 ± 4.56 μmol/mL), 2,2-azinobis (3-ethylbenzothiozoline-6-sulfonic acid)(ABTS^•+) (42.62 ± 0.25 mmol/L TE/g), superoxide (57.89 ± 3.45 μmol/mL), nitric oxide (18.45 ± 1.23 μmol/mL) and hydroxyl (12.13 ± 2.76 μmol/mL) radical scavenging activities, ferric reducing antioxidant power (14.76 ± 0.10 molar Fe (Ⅱ)/g), metal chelating (213.85 ± 27.18 mg EDTA/g) ability. Compounds 6 and 3 exhibited significant anti-proliferative activity. Compound 6 displayed strongest antibacterial activity against Streptococcus pneumoniae and Escherichia coli with MIC value of 3.90 μg/mL and 21.21 ± 0.25 and 20.27 ± 0.11 mm zone of inhibition at 25 μg/mL concentration respectively. In the membrane stabilization and protein denaturation test 3 was the most potent with an IC₅₀ value of 12.57, 18.75 μmol/mL respectively.