Bioactive compounds from natural sources, due to their widely-recognized benefits, have been exploited as cosmeceutical ingredients. Among them, phenolic acids emerge with a very interesting potential. In this context, this review analyzes hydroxycinnamic acids and their derivatives as multifunctional ingredients for topical application, as well as the limitations associated with their use in cosmetic formulations. Hydroxycinnamic acids and their derivatives display antioxidant, anti-collagenase, anti-inflammatory, antimicrobial and anti-tyrosinase activities, as well as ultraviolet (UV) protective effects, suggesting that they can be exploited as anti-aging and anti-inflammatory agents, preservatives and hyperpigmentation-correcting ingredients. Due to their poor stability, easy degradation and oxidation, microencapsulation techniques have been employed for topical application, preventing them from degradation and enabling a sustained release. Based on the above findings, hydroxycinnamic acids present high cosmetic potential, but studies addressing the validation of their benefits in cosmetic formulations are still scarce. Furthermore, studies dealing with skin permeation are scarcely available and need to be conducted in order to predict the topical bioavailability of these compounds after application.

In the present study, the ethanolic extracts of fourteen edible mushrooms were investigated for their anti-inflammatory potential in LPS (lipopolysaccharide) activated RAW 264.7 macrophages. Furthermore the extracts were chemically characterized in terms of phenolic acids and related compounds. The identified molecules (p-hydroxybenzoic, p-coumaric and cinnamic acids) and their glucuronated and methylated derivatives obtained by chemical synthesis were also evaluated for the same bioactivity, in order to establish structure-activity relationships and to comprehend the effects of in vivo metabolism reactions in the activity of the compounds. The extracts of Pleurotus ostreatus, Macrolepiota procera, Boletus impolitus and Agaricus bisporus revealed the strongest anti-inflammatory potential (EC50 values 96±1 to 190±6μg/mL), and also the highest concentration of cinnamic acid (656 to 156μg/g), which was also the individual compound with the highest anti-inflammatory activity. The derivatives of p-coumaric acid revealed the strongest properties, specially the derivative methylated in the carboxylic group (CoA-M1) that exhibited similar activity to the one showed by dexamethasone used as anti-inflammatory standard; by contrast, the derivatives of p-hydroxybenzoic revealed the lowest inhibition of NO production. All in all, whereas the conjugation reactions change the chemical structure of phenolic acids and may increase or decrease their activity, the glucuronated and methylated derivatives of the studied compounds are still displaying anti-inflammatory activity.

Nowadays, the food sector is highly concerned with environmental issues and foreseen to develop strategies to reduce waste and losses resulting from activities developed in the food system. An approach is to increment added value to the agro-industrial wastes, which might provide economic growth and environmental protection, contributing to a circular economy. Mushroom by-products represent a disposal problem, but they are also promising sources of important compounds, which may be used due to their functional and nutritional properties. Research has been developed in different fields to obtain value added solutions for the by-products generated during mushroom production and processing. Bioactive compounds have been obtained and applied in the development of nutraceutical and pharmaceutical formulations. Additionally, other applications have been explored and include animal feed, fertilizer, bioremediation, energy production, bio-based materials, cosmetics and cosmeceuticals. The main purpose of this review is to highlight the relevant composition of mushroom by-products and discuss their potential as a source of functional compounds and other applications. Future research needs to explore pilot and industrial scale extraction methods to understand the technological feasibility and the economic sustainability of the bioactive compounds extraction and valorization towards different applications.