Development and validation of a HPLC method for the direct separation of carnosine enantiomers and analogues in dietary supplements.

The chiral purity of some molecules such as nutraceuticals is fundamental to ensure their beneficial activities and it must be checked during quality control analysis. Carnosine is a natural histidine dipeptide used as ingredient for food supplements, but only his L-enantiomer is absorbed and active. Despite of this feature, a method for the separation of carnosine enantiomers without derivatization has only recently been published. Herein, we validated a method based on a Chirobiotic T column and an UV detector for the direct quantification of carnosine enantiomers, following ICH guideline. Moreover, we demonstrated that elution with water containing 0.1% formic acid and 20-40% ensures stereo-, chemo- and regio-selectivity for the separation and the identification of carnosine enantiomers and natural analogues. Moreover, the method allows a direct hyphenation with electrospray mass spectrometry to increase detection selectivity and sensitivity. As far as we know, this is the first method allowing the simultaneous identification and quantification of natural analogues of carnosine, which can be important for application such as the identification of enantiomeric impurities or adulteration that can occur during the storage or the preparation of foods or food supplements containing histidine dipeptides.