Pharmaceutical study of 3-O-methylquercetin as a promising antirhinoviral and anti-inflammatory drug.

摘要

3-O-methylquercetin (3-MQ) has been synthesised by an original method, based on current organic reactions using rutin as the starting material. Rutin was successfully alkylated by benzylbromide and the sugar moiety, rutinose, was cleaved in hot acidic medium. The new intermediary was firstly methylated by dimethylsulfate and secondarly debenzylated in hot acidic medium, yielding 3-O-methylquercetin. 3-MQ was found in vitro active against picornaviruses (poliovirus I, Coxsackie B2 and B4 and Rhinovirus 81) up to the concentration of 1 mug/ml, against Varicella zoster (EC50 = 0.23 mug/ml, for TK+ and 0.8mug/ml, for TK-) and against SARS coronavirus (EC50 = 3.482 mug/ml, 100% maximal protection). The aqueous solubility of 3MQ (21.67 mug/ml) was maximally increased by nonionic surfactants such as polysorbate 80 and highly hydrosoluble cyclodextrins, such as hydroxypropyl-beta-cyclodextrin (HP-beta-CD). The degree of complexation between 3-MQ and HP-beta-CD was found higher than 80% (in water) and about 30% (in supercritical CO2). By using lysine, we proved that 3-MQ was complexed by HP-beta-CD by involving its hydrogen atoms, H-6 and H-8. HP-beta-CD and polysorbate 80 did not modify the antipicornaviral activity of 3-MQ, however, the surfactant increased its cytotoxicity (up to 6.25 mug/ml). In in vitro study, using monolayers of cultured epithelial cells, HP-beta-CD at 1 and 3% (w/v) did not affect the ciliary beat frequency (CBF), but polysorbate 80 1% (w/v) caused a reversible cilio-inhibitory effect of 40, 53, and 49% at 0.1, 0.3, and 1%, respectively. At 2 and 10 mug/ml, 3-MQ showed a reversible cilio-stimulatory effect of 18 and 14%, respectively. However, at 20 mug/ml, the compound was found cilio-safe. The results were similar for 3-MQ alone and combined to HP-beta-CD 3% (w/v). The combination of 3-MQ and polysorbate 80 1% (w/v) irreversibly decreased the CBF. The aqueous solution of 3-MQ and HP-beta-CD 3% (w/v) was stable at 6°C during 158 days only. Thus, a freeze-dried formulation of 3-MQ would be preferred to aqueous solutions. In vitro anti-complement showed that 3-MQ could not prevent cells from hemolysis. In the same order of study, in vivo anti-inflammatory study did not prove that 3-MQ was active after oral administration. For the future, we recommend the following investigations: the improvement of the rate of debenzylation, more tests on the new discovered activities of 3-MQ (anti- Varicella Zoster and SARS coronavirus activity), and improving the model of anti-inflammatory test, after oral administration of 3-MQ.