Bioactive Phenolic Compounds From Agri-Food Wastes: An Update on Green and Sustainable Extraction Methodologies

Abstract

Phenolic compounds are broadly represented in plant kingdom, and their occurrence in easily accessible low-cost sources like wastes from agri-food processing have led in the last decade to an increase of interest in their recovery and further exploitation. Indeed, most of these compounds are endowed with beneficial properties to human health (e.g., in the prevention of cancer and cardiovascular diseases), that may be largely ascribed to their potent antioxidant and scavenging activity against reactive oxygen species generated in settings of oxidative stress and responsible for the onset of several inflammatory and degenerative diseases. Apart from their use as food supplements or as additives in functional foods, natural phenolic compounds have become increasingly attractive also from a technological point of view, due to their possible exploitation in materials science. Several extraction methodologies have been reported for the recovery of phenolic compounds from agri-food wastes mostly based on the use of organic solvents such as methanol, ethanol, or acetone. However, there is an increasing need for green and sustainable approaches leading to phenolic-rich extracts with low environmental impact. This review addresses the most promising and innovative methodologies for the recovery of functional phenolic compounds from waste materials that have appeared in the recent literature. In particular, extraction procedures based on the use of green technologies (supercritical fluid, microwaves, ultrasounds) as well as of green solvents such as deep eutectic solvents (DES) are surveyed.

Keywords: Naviglio extractor; agri-food wastes; deep eutectic solvents; microwave assisted extraction; phenolic compounds; supercritical fluid extraction; sustainability; ultrasound assisted extraction.

Figure 1

Main fruit byproducts and their most prominent phenolic constituents with reported bioactivities.

Figure 2

Main vegetable and lignocellulosic byproducts. Shown are the most abundant phenolic components and the reported bioactivities.

Figure 3

Schematic representation of MAE equipment and characteristics.

Figure 4

Schematic representation of UAE equipment and characteristics.

Figure 5

Schematic representation of SFE equipment and characteristics.

Figure 6

Schematic representation of extraction of phenolic compounds with DES.

Figure 7

Representative examples of phenolic compounds recovered from grape byproducts.

Figure 8

Representative examples of phenolic compounds recovered from olive byproducts.

Figure 9

Representative examples of phenolic compounds recovered from orange byproducts.

Figure 10

Representative examples of phenolic compounds recovered from lignocellulosic byproducts.

Figure 11

Schematic representation and examples of extraction of bioactive compounds with (A) Naviglio Extractor®, (B) PEF, and (C) steam explosion.