Evaluation of the use of different solvents to extract the four main components of Yinqiaosan and their in vitro inhibitory effects on influenza-A virus.

High-performance liquid chromatography coupled with an ultraviolet detector was used to quantitatively determine the amount of caffeoylquinic acid, arctium lappa glycoside, aurantiamarin and forsythin present in five solvent extracts (water, 30% ethanol, 50% ethanol, 70% ethanol and 95% ethanol) of Yinqiaosan (YQS). The calibration curves of the four components were linear (r(2) > 0.998) over the concentration range of 0.9-151.5 microg/mL. This method showed good repeatability with relative standard deviations of less than 2.9% and mean recoveries of 91.3-100.5%. We established the relative amounts of each of the four main ingredients in YQS for all five solvent extracts. The direct inhibitory effects of the five YQS extracts on influenza-A virus in vitro and the therapeutic effects on infected embryonated hen eggs were evaluated. YQS extracted in 50% ethanol and used at concentrations of 500 mg/mL and 250 mg/mL exerted the greatest therapeutic effect in infected embryonated hen eggs and was significantly superior to ribavirin (p < 0.05). Therefore, the 50% ethanol extract of YQS seems to be the most effective for the inhibition of influenza-A virus. Based on these results, further studies are warranted to evaluate the use of YQS extracts as a possible therapy for influenza. Copyright 2010 Elsevier. Published by Elsevier B.V. All rights reserved.