Investigation of the interaction for three Citrus flavonoids and α-amylase by surface plasmon resonance.

Flavonoids, a class of natural drugs with broad biological activity, exhibit inhibitory effect on α-amylase. Citrus peel is a good source of flavonoids. The real-time interactions between three Citrus flavonoids (naringin, neohesperidin, hesperidin) and α-amylase were investigated by surface plasmon resonance biosensor, and were compared with the α-amylase inhibitors, acarbose. These results showed the binding affinities of naringin, neohesperidin and hesperidin with α-amylase reach the highest at pH6 with KD values of 2.27±0.18mM, 3.09±0.20mM and 3.51±0.09mM, and can be reinforced with 0.2M NaCl and 0.1M CaCl2, respectively. The results of 1, 1-diphenyl-2-picryl hydrazyl radical assay indicate that the antioxidant activities of naringin, neohesperidin and hesperidin are significantly inhibited by interacting with α-amylase, and the inhibition percentage are 47.61±0.034%, 22.81±0.037% and 21.01±0.051%, respectively. Additionally, it is found that both the number and the position of hydroxyl group play an important role in the interaction of three Citrus flavonoids and α-amylase. These results provide useful information for rapid screening inhibitors of α-amylase from plant-based food.

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 (ip) 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 pre-treatment 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 100 635 (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.