Determination of phenolic compounds in residual brewing yeast using matrix solid-phase dispersion extraction assisted by titanium dioxide nanoparticles.

A simple and efficient low-cost matrix solid-phase dispersion (MSPD) extraction based on TiO2 nanoparticles (NPs) and diatomaceous earth has been developed for the recovery of phenolic compounds from residual brewing yeast. Experimental conditions for MSPD extraction were optimized by an experimental design approach. A screening factorial design plus replicates at the center point, followed by surface response analysis were used. The simultaneous identification and quantification of eleven main natural polyphenols: caffeic, chlorogenic, p-coumaric, 3,4-dihydroxibenzoic, trans-ferulic and gallic acids, kaempferol, myricetin, naringin, quercetin and rutin, was possible by combining MSPD and capillary liquid chromatography couple to a diode array detection system (cLC-DAD) and liquid chromatography couple to a triple quadrupole analyzer (LC-MS/MS). Moreover, residual brewing yeast extracts were evaluated in terms of DPPH (1,1-diphenyl-2 picrylhydrazyl) free radical scavenging activity. Polyphenol-nanoparticle interaction was studied by UV-vis spectroscopy and electron transmission microscopy (TEM), pointing out a stable interplay that assists phenolic isolation. The extracted polyphenol quantities were within the 3.2-1,500 µg g-1 range, and the high antioxidant activity estimated suggested that developed MSPD is a successful, simple, efficient and rapid method for the extraction and recovery of bioactive phenolic compounds, which promotes the reuse and re-evaluation of brewing yeast agri-food by-products.