[Antidepressant activity of flavonoid ethanol extract of Abelmoschus manihot corolla with BDNF up-regulation in the hippocampus].

Abelmoschus manihot (L.) Medic., a folk herbal medicine in China, is a flowering plant belonging to Abelmoschus L. genus and Malvaceae family, which has been reported with an antidepressant activity. The study was designed to isolate flavonoids from Abelmoschus manihot corolla and explore the action mechanism of antidepressant activities. The flavonoids were isolated and purified by D101 macroporous resin column, polyamide column and Sephadex LH-20 sequentially and identified as myricetin-3-O-β-D-glucoside (1), gossypetin-8-O-β-D-glucuronide (2, G-8-G), gossypetin-3'-O-β-D-glucoside (3), quercetin-3'-glucoside (4, Q-3-G), isoquercitrin (5, IQT), hyperoside (6, HY), myricetin (7), quercetin (8, QT). Compounds 2, 4, 5, 6 and 8 (15, 30 and 60 mg·kg−1) were orally administered to mice and the reaction was observed in tail suspension test (TST) and forced swimming test (FST). Western blot analysis was used in determination of the protein expressions of brain-derived neurotrophic factor (BDNF), tyrosine receptor kinase B (TrkB) and phosphorylation eukaryotic elongation factor 2 (p-eEF2). The results revealed that only Q-3-G and G-8-G (15, 30, 60 mg ·kg−1) significantly reduced the immobility time in FST and TST. Furthermore, Q-3-G and G-8-G remarkably increased the expression of BDNF and TrkB, and decreased the expression of p-eEF2. These results suggest that Q-3-G and G-8-G had an obvious antidepressant activity via up-regulation of BDNF expression. The new observation will provide a new direction in the development of antidepressant in the treatment of major depressive disorder (MDD).