Pharmacological Exploration of the Sedative Mechanism of Hesperidin Identified as the Active Principle of Citrus sinensis Flowers

The infusion of flowers of several species of Citrus genera is used as a sedative to treat insomnia in Mexican traditional medicine. The aims of this study were to investigate the sedative effect of different extracts of flowers of Citrus sinensis (L.) Osbeck (Rutaceae) and describe the pharmacological action mechanism of the sedative active compounds of this plant. The methanol and dichloromethane extracts, obtained from the flowers of Citrus sinensis (L.) Osbeck (Rutaceae), showed a dose-dependent sedative effect in the exploratory cylinder model in mice, with ED50 (i.p) values of 47.04 +/- 12.03 mg/kg and 129.15 +/- 21.25 mg/kg, respectively. Hesperidin (ED50 = 11.34 +/- 2.48 mg/kg) was identified in the methanol extract as the sedative active principle of this plant. The pretreatment with atropine (1 mg/kg i.p.), flumazenil (2 mg/kg i.p.), clonidine (0.01 mg/kg i.p.), isoproterenol (0.3 mg/kg i.p.), haloperidol (0.3 mg/kg i.p.), WAY 100635 (3 mg/kg i.p.), p-chlorophenylalanine (250 mg/kg i.p., twice per day for 2 days), forskolin (3 mg/kg i.p.) and rolipram (0.173 mg/kg i.p.) did not modify the sedative effect of 30 mg/kg hesperidin. However, the sedative effect of this compound was potentiated by yohimbine (1.25 mg/kg i.p.) and buspirone (1 mg/kg i.p.), and reverted by pretreatment with aminophylline (30 mg/kg i.p.), caffeine (30 mg/kg i.p.) and several doses of 1,3-dimethyl-8-phenylxanthine (10, 30 and 54.7 mg/kg i.p.). These results suggest that adenosine receptors might be involved in the sedative action of hesperidin, identified as the active principle of the flowers of Citrus sinensis.