Studies on standardization of folium strobilanthis, radix strobilanthis and their preparations.

Determination of 4(3H)-quinazolinone, a newly found antiviral and immunopatentiating constituent was proposed as a method of evaluating the quality of two antiviral Chinese herbal drugs Daqingye (Folium Strobilanthis) and Banlangen(Radix Strobilanthis) and their preparations ('Antipyretic and common cold granules', 'Banlangen granules'). An HPLC method for determining the content of 4(3H)-quinazolinone was established with satisfactory results. The method showed good linearity (r = 0.9998, n = 5) in the range of 0.25-50 micrograms/mL of 4(3H)-quinazolinone, the average recovery was above 99% with RSD < 0.78% (n = 3).