The identification of dipalmityl zeaxanthin as the major carotenoid in GouQi Zi by high pressure liquid chromatography and mass spectrometry

The carotenoid in Gou Qi Zi was extracted by hexane, followed by repeated c hromatography on a silica column. The major carotenoid recovered from the c hromatographic step was subjected to hydrolysis in potassium hydroxide (KOH ). The hydrolytic products were separated on a silica column followed by an alysis for their molecular sizes by a Micromass Platform LCZ. The retention time of the carotenoid in Gou Qi Zi is 2.3 min. Upon hydrolysis, new carot enoid peaks appeared. The molecular ions detected by APCI(-) of the caroten oid at 2.3, 6.8 and 28 min are 1044, 806 and 568, respectively. The molecul ar sizes matched to that of dipalmityl zeaxanthin, monopalmityl zeaxanthin and zeaxanthin, respectively. The monopalmityl zeaxanthin peak appeared fir st and faded away as the free zeaxanthin peak reached the maximal size.