Determination of the pungent principles of chillies and ginger by reversed‐phase high‐performance liquid chromatography with use of a single standard substance

Abstract

AbstractQuantitative determination of the capsaicinoids and the gingerols, pungent constituents of chillies and ginger respectively, is important for objective assessment of the pungency of these spices and their oleoresins. High‐performance liquid chromatography (HPLC) procedures applicable to these groups of compounds have been reported from several laboratories. The principal difficulty with gingerol determinations hitherto has been the lack of a stable and easily purified analytical standard, since the gingerols (and their dehydration products, the shogaols) are labile, oily liquids which are difficult to purify. Since the capsaicinoids and the gingerols and their analogues have closely related chemical structures, the possibility of selecting from among them one easily purified crystalline compound to serve as an external standard for determination of both groups of compounds by HPLC was investigated. It was found that caprylic acid vanillyl amide (CVA), one of the minor naturally occurring capsaicinoids but an easily synthesized crystalline compound, was very suitable for this purpose, and that a commercially available mixture of capsaicin and dihydrocapsaicin could be used as a slightly less convenient alternative. Reversed‐phase HPLC methods based on this principle are described, and shown to be suitable for the analysis (without clean‐up) of chillies and ginger or their oleoresins. An acceptable level of precision (relative standard deviation less than 2% and 5% respectively) is demonstrated for the summed major pungent principles in dried chillies and dried ginger, and it is shown that fair agreement between the HPLC and spectrophotometric difference methods can be obtained for chillies of varying pungency levels.