Determination of phenolic compounds in human saliva after oral administration of red wine by high performance liquid chromatography

Red wine is a relevant source of bioactive compounds, which contribute to its antioxidant activity and other beneficial advantages for human health. However, the bioavailability of phenols in humans is not well understood, and the inter-individual variability in the production of phenolic compounds has not been comprehensively assessed to date. The present work describes a new method for the extraction and analysis of phenolic compounds including gallic acid (Gal), vanillic acid (Van), caffeic acid (Caf), syringic acid (Sir); (–)-epicatechin (Epi); p-coumaric acid (Cum) and resveratrol (Rsv) in human saliva samples. The target analytes were extracted using Fabric Phase Sorptive Extraction (FPSE), and subsequently analysed by high-performance liquid chromatography (HPLC) coupled with photodiode array detector (PDA). Chromatographic separation was achieved using a Symmetry C18 RP column in gradient elution mode, with methanol and phosphate buffer as the mobile phases. The linearity (intercept, slope, and determination coefficient) was evaluated in the range from 1 to 50 µg/mL. The limit of quantification (LOQ) was 1 µg/mL (LLOQ ≥0.8 µg/mL), whereas limit of detection was 0.25 µg/mL. The intra and inter–day RSD% and BIAS% values were less than ±15%. The analytical performances were further tested on human saliva collected from healthy volunteers after administering red wine. To the best of our knowledge, this is the first FPSE procedure for the analysis of phenols in saliva, using a non-invasive and easy to perform sample collection protocol. The proposed fast and inexpensive approach can be deployed as a reliable tool to study other biological matrices to proliferate understanding of these compounds distribution in human body.