Selective Separation of Quercetin from Grape Pomace Based on Experimental Solubility in Organic Monosolvents

Polyphenols are bioactive molecules with strong antioxidant properties, associated with antitumor, anti-aging, antimicrobial, and anti-inflammatory effects. Their potential applications in food, pharmaceutics, and cosmetics have sparked growing interest in recent years. As these compounds are abundant in a wide range of plant species, their extraction from natural sources—particularly from agro-industrial waste—has been extensively studied, contributing significantly to circular economy initiatives. However, research focused on the selective extraction of polyphenols still remains limited, mainly due to the complexity of plant matrices, which hinders achieving high purities. Within this framework, this work addresses the selective separation of target polyphenols from grape pomace, an unvalorized waste from the winemaking industry.

After drying and grinding the raw grape pomace, a first extraction was performed with ethanol, and the extract was submitted to HPLC-MS/MS analysis to characterize the material. The polyphenolic profile of the grape pomace extract revealed that, among many compounds, quercetin turned out to be the predominant one. Thus, in order to achieve a highly purified quercetin extract, the experimental solubility of quercetin was measured in several organic solvents, which were selected for their green character and variety of functional groups: methanol, ethanol, methyl ethyl ketone (MEK), methyl isobutyl ketone (MiBK), ethyl acetate, n-propyl acetate, and butyl acetate.

According to the solubility differences obtained, the most selective solvents were chosen to elaborate a selective separation sequence of quercetin from grape pomace.