Mumefural is a component of Japanese apricot fruit juice concentrate, which has been used as a traditional nonofficial medicine in Japan, and was reported to have an activity to improve the blood fluidity. For quantitative analysis of mumefural, water extract of the fruit-juice concentrate was loaded on a cartridge column for solid-phase extraction (Oasis(R) HLB, Waters) and eluted with 20% acetonitrile. Following HPLC analysis on a XTerra(TM) MS C-18 column (Waters) by linear gradient elution with acetonitrile-20 mM sodium phosphate buffer (pH 2.3) gave a peak of mumefural at 280 nm, from which area quantity of the compound could be elucidated based on the calibration curve obtained in this work. Mumefural content of 4 Japanese apricot fruit-juice concentrates was determined as 1.41 mg/g, 0.361 mg/g, 11.5 mg/g, and 3.82 mg/g, respectively, by this method. Accurate molar absorption coefficient (e) of mumefural was determined as 1.78X10(4) (lambda(max) 282 nm, water). Since mumefural is highly hygroscopic amorphous solid, it is difficult to weigh out an accurate quantity for preparation of a standard solution. Molar absorption coefficient of mumefural is, therefore, useful to calibrate the concentration of the standard solution for HPLC analysis.