Procyanidins are an important group of bioactive molecules known for their benefits to human health. These compounds are promising in the treatment of chronic metabolic diseases such as cancer, diabetes, and cardiovascular disease, as they prevent cell damage related to oxidative stress. It is necessary to study effective extraction methods for the recovery of these components. In this review, advances in the recovery of procyanidins from agro-industrial wastes are presented, which are obtained through ultrasound-assisted extraction, microwave-assisted extraction, supercritical fluid extraction, pressurized fluid extraction and subcritical water extraction. Current trends focus on the extraction of procyanidins from seeds, peels, pomaces, leaves and bark in agro-industrial wastes, which are extracted by ultrasound. Some techniques have been coupled with environmentally friendly techniques. There are few studies focused on the extraction and evaluation of biological activities of procyanidins. The identification and quantification of these compounds are the result of the study of the polyphenolic profile of plant sources. Antioxidant, antibiotic, and anti-inflammatory activity are presented as the biological properties of greatest interest. Agro-industrial wastes can be an economical and easily accessible source for the extraction of procyanidins.

Procyanidins are bioactive molecules with industrial and pharmaceutical relevance, they are present in recalcitrant agro-industrial wastes that are difficult to degrade. In this study, we evaluated the potential consumption of procyanidins from Aspergillus niger and Trichoderma harzianum strains in submerged fermentations. For this purpose, a culture medium containing salts, glucose, and procyanidins was formulated, where procyanidins were added to the medium after the near-total consumption of glucose. The submerged cultures were carried out in amber flasks at 30 °C and 120 rpm. The addition of procyanidins to the culture medium increased the formation of micellar biomass for all the strains used. The use of glucose affected the growth of A. niger GH1 and A. niger HS1, however, in these assays, a total consumption of procyanidins was obtained. These results show that the consumption of procyanidins by fungal strains in submerged fermentations was influenced by the pH, the use of glucose as the first source of carbon, and the delayed addition of procyanidins to the medium. The study showed that A. niger and T. harzianum strains can be used as a natural strategy for the consumption or removal of procyanidins present in recalcitrant residues of risk to the environment and human health.

The coffee industry generates a large amount of waste that is difficult to treat due to its chemical composition, namely, the presence of caffeine and its derivatives, as well as recalcitrant molecules such as tannins (mainly condensed tannins or polymeric procyanidins), which make it an undervalued waste product. Procyanidins are compounds beneficial to human health and can be found in nature in fruit, grain, seeds, and beverages, among other foods. The zero-waste approach has allowed for the valorization of by-products from the food industry. Currently, coffee pulp is the target of research on extraction, purification, and alternative use. Research on the fungal degradation of procyanidins has emerged as an avenue for the efficient use of these by-products. In this study, the degradation and biotransformation of procyanidin is evaluated and comprises three steps: first, the extraction and partial purification of procyanidins from coffee pulp; second, the production of the potential procyanidin-degrading enzyme by submerged fermentation with Aspergillus niger GH1; third, enzymatic extracellular extract evaluation using a model system with commercial procyanidin C1. The biodegradation/biotransformation results reveal the formation of new compounds, including a final compound with an m/z of 289, possibly a monomeric molecule such as catechin or epicatechin. Identification of the compounds by HPLC-MS confirmed procyanidin C1 depletion under the described assay conditions, which could be used to understand biodegradation pathways proposed for future study. Furthermore, these results confirm that A. niger GH1 is able to degrade and biotransform procyanidin C1.