Coffee Silverskin and Spent Coffee Ground investigation: A new analytical method for 30 bioactive compounds quantitation

Nowadays, there is great political and social pressure to reduce the pollution arising from industrial activities, including coffee sector[1]. Coffee is one of the largest traded commodity worldwide since the consumption of coffee beverages is overtaken only by that of water and tea[2][3]. Hence, to satisfy the immense demand for coffee, coffee industry produces a huge quantity of byproducts which cannot be considered just as waste materials but should be considered as starting raw materials for other projects. The main coffee byproducts, produced during roasting process and both soluble coffee industry and coffee brewing, are Coffee Silverskin (CS) and Spent Coffee Ground (SCG), respectively[4]. The purpose of this project was to deepen the knowledge about CS and SCG in the perspective of their reuse as nutraceutical. A new analytical method for quantitation of 30 phenolic compounds by using UHPLCMS/ MS has been developed. Then, various extractions, i.e. magnetic stirrer and ultrasoundassisted extraction, using different solvents viz., hydroalcoholics, alcoholics and aqueous, were evaluated for their ability to take out target molecules from those matrices. From an analytical point of view, UHPLCMS/ MS studies were performed using an Agilent 1290 Infinity series and a Triple Quadrupole 6420 (Agilent Technology) equipped with an ESI source operating in negative and positive ionization mode. The separation was achieved using a Kinetex PFP analytical column (50 × 2.10 mm i.d., 2.6 μm) using a binary gradient of water (A) and methanol (B) both with 0.1% formic acid. The method was sensitive (LOQs for all compounds were from 1 to 100 μg kg1), linear (R2 for all analytes was higher than 0.9907), accurate and robust. Results demonstrated that highest content of total phenolic compounds were found in ultrasound extraction with a mixture of EtOH:H2O 70:30 v/v. In this case, the highest amount of total bioactive compounds concentration was found, followed by aqueous extraction with magnetic stirrer and methanolic ultrasound extraction. In the future, several biological activities, i.e., antioxidant, prebiotic and antimicrobial, will further be studied in the most promising extracts. Acknowledgments: The authors are grateful to the University of Camerino for funding the FAR project (year 2018).