Flow Injection Analysis–Mass Spectrometry for the fast detection of frauds in Coleus forskohlii food supplements

Coleus forskohlii supplements (FKSs) are widely consumed for their obesity-preventing effects, mainly related to forskolin, its main bioactive compound. However, these supplements are susceptible to adulteration and various types of frauds have been described. Therefore, the development of rapid and sensitive methodologies is of great interest in order to determine the quality of these products. In this work, a new method by Flow Injection Analysis-Mass Spectrometry (FIA-MS) has been developed and validated for the detection of potential frauds in FKSs. A Box-Behnken experimental design was used for the optimization of MS parameters under both positive and negative polarity modes of the electrospray ionization source. The best results were obtained for positive polarity mode at 3000 V of capillary voltage, a flow rate of 12 L min^-1 of drying gas, 300 °C of nebulization gas temperature, a pressure of 30 psi and a fragmentor voltage of 149 V, using 1 % of 1 mM sodium acetate in the carrier. When 22 FKSs were analysed by the optimised FIA-MS method, 45 % of the samples were found to be free of forskolin. There was also a high percentage (69%) of mismatches between the quantified forskolin content and that declared on the FSK labels. In general, results were comparable with those obtained by LC-MS. Thus, it has been proved that FIA-MS is a fast, cost-effective and simple tool to evaluate the authenticity of FKSs.