Valorization of avocado peels by conventional extraction and hydrothermal carbonization for cosmeceutical applications

Abstract

Avocado peels (APs) are an agro-industrial non-edible residue from avocado processing industries that lack commercially valuable applications despite their content of bioactive molecules. This work investigates for the first time the combined use of conventional extraction with hydrothermal carbonization (HTC) as a new strategy to maximize the bioactive fractions obtained from APs for potential cosmeceutical applications. APs were extracted by maceration, while the extracted biomass was subjected to HTC at 200, 250, and 300 °C. The ethanolic extract (EEPA), liquid phases (LBOs), and heavy bio-oils (HBOs) were characterized by FTIR, and their content of total phenol, hydroxycinnamic acids, flavonoids, and proanthocyanidins were further determined. The antioxidant properties of all fractions and their effects on tyrosinase and elastase activities were spectrophotometrically analyzed, whereas the most promising fractions were examined by GC-MS. LBOs were rich in total phenols, hydroxycinnamic acids, and flavonoids, whereas EEPA showed the highest content of proanthocyanidins. EEPA and LBOs exhibited the highest antioxidant ability. In contrast, HBOs had significant inhibitory effects on tyrosinase and elastase activities, higher than those of kojic acid and epigallocatechin gallate, used in the cosmeceutical industry to counteract hyperpigmentation and skin flaccidity, respectively. Esters (42 %) were the dominant molecules identified in EEPA, while phenols prevailed in LBO 250 °C (45 %) and HBO 250 °C (22%). These results open the way to apply conventional extraction and HTC as a new strategy for recycling avocado waste to develop sustainable cosmeceutical products.