Abstract Angiotensin I-converting enzyme inhibitors are used as therapeutic agents for the treatment of hypertension. Regular consumption of black tea (Camellia sinensis (L.) Kuntze, Theaceae) has been reported to lower blood pressure. The aims of the present work were to compare chemical composition and angiotensin I-converting enzyme inhibitory properties of infusion and decoction of four samples of black tea. GC/MS based metabolomics approach helped in identification of fifty-one metabolites including ten organic acids, one inorganic acid, sixteen amino acids, two sugars, five sugar alcohols, fifteen phenols and flavonoids, two fatty acids from infusions and decoctions of four black tea samples. Partial least squares discriminant analysis and orthogonal partial least squares discriminant analysis models showed good classification among the two groups, diffusion and infusion, based on metabolites. Both infusion and decoction inhibited the enzyme. However, the activity differed with samples. Multivariate analysis also segregated extracts on the basis of activity. Thearubigin, theaflavin, catechin inhibited the enzyme. Epicatechin, epigallocatechin gallate, gallic acid, caffeine showed lower activity.

ABSTRACT β-Glucuronidase inhibitors are suggested as potential hepatoprotective agents. Swertia chirayita (Roxb.) Buch.-Ham. ex C.B. Clarke, Gentianaceae, is known for its hepatoprotective and anti-hepatotoxic activity in Ayurvedic system of medicine for ages. This plant is substituted by other species like S. decussata Nimmo ex C.B. Clarke and S. bimaculata (Siebold & Zucc.) Hook. f. & Thomson ex C.B. Clarke. The aim of the study was to compare metabolite profile and β-glucuronidase inhibitory activity of these three important species of Swertia and to identify the active constituents. S. chirayita (IC50 210.97 µg/ml) and S. decussata (IC50 269.7 µg/ml) showed β-glucuronidase inhibitory activity significantly higher than that of silymarin, the known inhibitor of the enzyme. The activity of S. bimaculata was low. The metabolites present in the three species were analyzed by HPLC and GC-MS based metabolomics approach. Five amino acids, twenty one organic acids, one inorganic acid, eight fatty acids, twenty one phenols including xanthones, eight sugars, seven sugar alcohols, five terpenoids and amarogentin were identified. Activities of the xanthones mangiferin (IC50 16.06 µg/ml), swerchirin (IC50 162.84 µg/ml), decussatin (IC50 195.11 µg/ml), 1-hydroxy-3,5,8-trimethoxy xanthone (IC50 245.97 µg/ml), bellidifolin (IC50 390.26 µg/ml) were significantly higher than that of silymarin (IC50 794.62 µg/ml). Quinic acid (IC50 2.91 mg/ml), O-acetylsalicylic acid (IC50 48.4 mg/ml), citric acid (IC50 1.77 mg/ml), D-malic acid (IC50 14.82 mg/ml) and succinic acid (IC50 38.86 mg/ml) also inhibited the enzyme β-glucuronidase. The findings suggest that constituents, in addition to the xanthones, probably also contribute to the bioactivity of different Swertia species by synergistic effect. Further in vivo study is required to support the claim.