Identification of aminotadalafil and its stereoisomers contained in health foods using chiral liquid chromatography-mass spectrometry

Using chiral liquid chromatography-mass spectrometry (LC/MS), a simple and rapid identification test was developed for aminotadalafil [(6R,12aR)-2-amino-6-(1,3-benzodioxol-5-yl)-2,3,6,7,12,12a-hexahydropyrazino[1',2' : 1,6]pyrido[3,4-b]indole-1,4-dione; RR-ATDF] and its stereoisomers contained in health foods, e.g. herbal products. A sample solution was prepared using methanol extraction. Analysis was performed on a chiral column with the mixture of 0.1% formic acid/acetonitrile (7: 3) as mobile phase at 30 degrees C. Each resolution value of four stereoisomers of ATDF was greater than 1.3. A mass spectrometer was used as a detector to enhance specificity by excluding the effects of general components derived from the sample. The four individual stereoisomers of ATDF in the health foods were identified based on their respective retention times. Results showed that structural conversions of RR-ATDF into (6R,12aS)-2-amino-6-(1,3-benzodioxol-5-yl)-2,3,6,7,12,12a-hexahydropyrazino[1',2' : 1,6]pyrido[3,4-b]indole-1,4-dione (RS-ATDF) and (6S, 12aS)-2-amino-6-(1,3benzodioxol-5-yl)-2,3,6,7,12,12a-hexahydropyrazino[1',2': 1,6]pyrido[3,4-b]indole-1,4-dione (SS-ATDF) into (6S, 12aR)-2-amino-6-(1,3-benzodioxol-5-yl)-2,3 6,7 12, 12a-hexahydropyrazi no[1', 2' : 1,6]pyrido[,3,4-b]indole-1,4-dione (SR-ATDF) occurred under strongly basic conditions, which indicates that such conditions must be avoided during sample preparation. Using this method, RR-ATDF and SR-ATDF were detected in a health food; this is the first report describing that ATDF diastereomers are present in health foods.