Unveiling the chemical profile of Sicilian Coffea arabica L. leaves

Coffee leaves have been recently approved in the EU as a traditional food, and they show potential as an innovative ingredient for the preparation of hot and cold brew beverages as well as a source of bioactive-rich extracts. This study aims to explore the chemical composition of Coffea arabica leaves (cv. Caturra) from plants grown in Sicily, and to identify intra-age and inter-age differences, using non-targeted metabolomics, lipidomics analysis and volatilomics. Overall, the analysis of the polar and apolar fractions allowed the tentative annotation of 44 compounds in the polar fraction and 114 in the non-polar fraction. The polar fraction was dominated by phenylpropanoids such as chlorogenic acids, flavonoids, and xanthones (mangiferin), alongside alkaloids (caffeine, trigonelline, theobromine). The non-polar fraction included prenol lipids (terpenoids) and phytosterols, with terpenoids peaking in adult leaves. Phytochemical profiles revealed that caffeine, mangiferin, and chlorogenic acids accumulated most in adult leaves, while epicatechin gallate increased with maturation. Regarding the volatile fraction, 76 unique compounds across 14 classes were identified, with aldehydes, ketones, terpenes, and alcohols prevailing. Key odorants, such as benzaldehyde, hexanal, linalool, and alpha-/beta-ionone, were consistently detected, showing clear age-dependent shifts from green and fermented notes in young leaves to citric and floral notes in adult and mature samples. Our findings can be used for the upcycling of coffee leaves in the production of infusions and in the extraction of bioactive compounds, thus fostering a circular economy.