Bioactivity-Guided Isolation of Potential Antidiabetic and Antihyperlipidemic Compounds from<i>Trigonella stellata</i>

Abstract

The in vitro antidiabetic and antihyperlipidemic activities of an alcoholic extract of Trigonella stellata were evaluated in terms of the activation of PPAR_α and PPAR_γ in human hepatoma (HepG2) cells. The extract was investigated phytochemically, aiming at the isolation of the most active compounds to be used as a platform for drug discovery. Three new isoflavans, (3 S,4 R)-4,2',4'-trihydroxy)-7-methoxyisoflavan (1), (3 R,4 S)-4,2',4'-trihydroxy-7-methoxy-4'- O-β-d-glucopyranosylisoflavan (2), and (2 S,3 R,4 R)-4,2',4'-trihydroxy-2,7-dimethoxyisoflavan (3), were isolated and characterized along with the five known compounds p-hydroxybenzoic acid (4), 7,4'-dihydroxyflavone (5), dihydromelilotoside (6), quercetin-3,7- O-α-l-dirhamnoside (7), and soyasaponin I (8). The structures of 1-3 were elucidated using various spectroscopic techniques including HRESIMS and 1D and 2D NMR. The absolute stereochemistry of the new isoflavans (1-3) was determined using both experimental and calculated electronic circular dichroism as well as DP4 calculations. The isolated compounds were tested for their PPAR_α and PPAR_γ activation effects in HepG2 cells.