Quality control of Lycium barbarum fruits: a valuable source of carotenoids

Lycium barbarum L. fruits (Solanaceae), commonly known as Goji berries, are a traditional food and medicine in East Asia which nowdays is becoming widely popular in Europe and North America [1]. In view of its popularity robust quality control studies are necessary to assure its safety. In the framework of the preparation of TCM herbal drug monographs suitable for the European Pharmacopoea the analytical method for the quality of Goji berries was undertaken. A method based on HPLC-UV-DAD coupled to an ESI-MS interface was developed for the determination of the carotenoids in L. barbarum fruits. The method was simple and effective, taking into consideration most of the problematics regarding carotenoid analysis and is suitable for the routine control of L. barbarum. The method was further validated in terms of linearity and intermediate precision (different days and at three different concentration levels). All validation criteria were fulfilled. A reversed phase column was applied with isocratic eluent system consisting of acetone and methanol. Detection of carotenoids was at 450nm. Carotenoids were expressed as beta carotene. Furthermore, an extraction protocol was developed and optimized in order to have a more accurate determination of the carotenoid content in L. barbarum fruits which is considerably higher than the one reported in the literature [2, 3]. Zeaxanthine palmitate was the main constituent in all tested commercial samples, varying from 56 – 84 mg 10 g-1 of edible portion.