A NEW ANALYTICAL METHOD FOR THE QUANTIFICATION OF THREE LIGNANS IN ESPRESSO COFFEE BY USING HPLC-MS/MS TRIPLE QUADRUPOLE

Introduction: Lignans, phenolic compounds that are present in a number of foodstuffs, possess some biological activities i.e., antioxidant and antiestrogenic [1,2]. The aim of our work was to develop a new analytical method to quantify three lignans, i.e., secoisolariciresinol (SECO), lariciresinol (LARI), matairesinol (MAT) from espresso coffee (EC) by using HPLC-MS/MS Triple Quadrupole. Methods: Different sample preparation methods, including dilutions, acidic hydrolysis and enzymatic digestions were evaluated and, once validated, the most performing was applied for the quantification of target compounds in coffee samples. The HPLC-MS/MS Triple Quadrupole, equipped with elettrospray ionization (ESI) source, operating in negative ionization mode, was used for the analysis. Detection was performed in multiple reaction monitoring (MRM) mode. Results: Each lignan showed different transitions with different intensities of MS/MS acquisition parameters in MRM mode; the highest product ion abundances for all three compounds were found at 350° C as temperature of the drying gas of ionization source. At this temperature the precursor ions for lignans were the deprotonated molecules [M-H]- in negative polarity; therefore, those conditions were chosen for lignan monitoring. About the sample preparation process, the most performing was the enzymatic digestion with the Clara-Diastase (mixture of enzymes), because it showed the highest recovery values (93.55 – 97.62 %). The analytical method was characterized by short chromatography run time (the separation of target compounds was obtained within 4 minutes) and high sensitivity (LOD ranging from 2 to 3 µg l-1 and LOQ ranging from 5 to 10 µg l-1). SECO and LARI were found in all nine EC samples from 27.9 to 52.0 µg l-1 and from 5.3 to 27.8 µg l-1, respectively, contrary to MAT that it was not possible to detect it in each type of coffee. Conclusions: A new analytical method for the quantification of three lignans that avoided long clean up and enrichment sample procedures has been developed and validated. The application of our method to EC samples showed that SECO was the lignan present at the highest concentration (27.9 – 52.0 µg l-1) followed by LARI (5.3 – 27.8 µg l-1). Therefore, regular consumption of EC can contribute to the dietary intake of lignans. Novel Aspect: The developing of a new analytical method for the quantification of three lignans in espresso coffee by using HPLC-MS/MS and their determination in different coffee samples. References: [1] Landete J. M., Food Research International, 46, 410 (2012). [2] Adlercreutz H., Mazur W., Annals of medicine, 29, 95 (1997).