Polyphenolic profile and biological activity of Salvia splendens leaves

Abstract

The aim of this study was to investigate a new flavone triglycoside, together with eleven phenolic metabolites from 80% aqueous methanol extract of S. splendens leaves (AME) and assessment of its hypoglycemic and antiinflammatory activities along with in vitro antioxidant effect. The phenolic composition of S. splendens leaves was analyzed using UV, 1D and 2D NMR and negative ESI-MS spectroscopy. Hypoglycemic activity of AME was assessed by measuring blood glucose in streptozotocin induced-diabetic rats. Antiinflammatory activity was evaluated using the carrageenan-induced paw oedema test. Antioxidant activity was evaluated in vitro using DPPH test. Twelve phenolic metabolites including three phenolic acids, namely caffeic acid 1, rosmarinic acid 2 and methyl rosmarinate 3; four flavone glycosides viz the new compound luteolin 7-O-(4″,6″-di-O-α-L-rhamnopyranosyl)-β-D-glucopyranoside 4, apigenin 7-O-β-D-rutinoside 5, cosmosiin 6 and cinaroside 7, together with four flavones aglycone, luteolin 8, apigenin 9, pedalitin 10 and crisiliol 11 in addition to one coumarin, 6,7-dihydroxycoumarin 12 were isolated from the leaves of S. splendens Sellow ex Roem & Schult. The AME of S. splendens was non toxic to mice up to 5 g/kg b.wt. it exhibited a significant hypoglycemic activity at 250 and 500 mg/kg as compared with control pre-drug (zero time) for each group as well as the diabetic control. Moreover, AME exhibited a significant antiinflammatory activity only at 1000 mg/kg in comparison to indomethacin. Finally, AME exhibited a marked significant scavenging activity against DPPH; the maximum reactive reaction rate after 5 min was 62.9, 82.5, 83.7, 84.3 and 85.1% for the concentrations 10, 20, 30, 40 and 50 mg/ml, respectively in comparison to L-ascorbic acid (86.8%). This is the first study reporting the identification of a new flavone triglycoside, along with eleven known phenolic metabolites from AME of S. splendens. It showed significant hypoglycemic and antiinflammatory effects in dose dependant manner. Moreover it showed an in vitro antioxidant activity.