Abstract: Amethod of RP -HPLCquantitative determination of lovastatin in monascu s at its open ring formwas introduced.The sample of monascus was dissolved in 0.2mol /L NaOH.For extraction and transformation of lovastatin in to its open ring form,u ltrasonic treatment was used at 50℃f or 60min.Use silica adsorption chromatography for removing pigmen t and part of the impurities in the sam ple.After pretreatment the crude sample was purified by reverse phase-HPLC(phosphate buffer -acetonitril system V /V =65∶35as mo-tive phase,elute rate 1ml /min).The ultraviolet detector at 238nma ssayed the open ring formof lovastatin.By this method it revealed a good linear relationship within 0.2～6μg /ml andγ=0.9991.The lower limit of detection was 0.2μg /ml.The assay of 6repeated samples with standard showed the recovery as96%±3%.The variation coefficient was 3%.Fi ve lovastatin samples of Monascus fe rmentation products were determined by the above method and successful re sults were obtained.It revealed that this method was reliable for use.

Key words: monascus, lovastatin of open circul ar form, high performance liquid chr omatography