New protein glycation inhibitory free radical scavenging compound from Duranta repens L.

Abstract

BackgroundHyperglycemia induced oxidative stress, increased generation of free radicals and free radicals mediated glycation of protein molecules are important events aggravating development of a number of diabetic complications. AimsTo identify antiglycation principles with free radicals scavenging activities from traditional oriental medicinal plants. MethodsBiological activity ABTS+ radical scavenging in particular, guided isolation of active compounds was performed from methanolic extract of traditional oriental medicinal plants Duranta repense. Isolated compounds were further studied for their DPPH radical scavenging activity and advanced glycation end-products inhibitory potentials in vitro. ResultsActivity guided isolation from methanolic extract of D. repens led to the identification of five iridoids namely Caryoptoside (1), Duraterectoside A (2), Durantoside III (3), Durantoside I (4), Lamiide (7) and two lignans namely (+) 5′Methoxyisolariciresinol (5), (−)5′Methoxyisolariciresinol (6). All the compounds scavenged ABTS+ radical, Caryoptoside (1) and (+) 5′Methoxyisolariciresinol (5) being most potent ABTS+ scavenger (IC50 = 6.0 and 3.1 μg/mL respectively). Only (+) 5′Methoxyisolariciresinol (5) displayed DPPH scavenging activity (IC50 = 70.5 μg/mL). Despite being potent ABTS+ scavenges, iridoid compounds rather augmented glucose induced formation of advanced glycation end-products in bovine serum albumin protein. (+) 5′Methoxyisolariciresinol (5) displayed both, the potent ABTS+ and DPPH scavenging activity however, showed mild (10%) antiglycation activity. On the other hand, (−) isomer of lignin 5′Methoxyisolariciresinol (6) that displayed moderate ABTS+ scavenging activity (IC50 = 42.6 μg/mL) potently inhibited (45%) glucose induced glycation of bovine serum albumin (BSA) protein. ConclusionMethanol extract of D. repense possess potent antioxidant compounds. Iridoids augmented glucose induced glycation of BSA. Lignans displayed antiglycation activity. The (−) isomer of lignan 5′Methoxyisolariciresinol (6) was five times more potent in inhibiting glucose induced generation of AGEs in BSA.