Fig (Ficus carica L.) bioresidues as sources of bioactive compounds and natural pigments for the food industry

The 17 goals of sustainable development address several topics, such as: (2) Zero hunger and sustainable agriculture; (9) Industry, Innovation, and Infrastructure; (12) Responsible consumption and production; that are essential for the promotion of the circular economy, product development and conscious production [1]. Fig is a food matrix, cultivated in Portugal and valued by the Portuguese people for consumption in natura, being also used in wines, liqueurs, and jams. As this fruit is very appreciated and consumed, it´s cultivation leads to the production of tons of leaves, usually discarded [2]. Therefore, in the present work, the leaves of five fig varieties (Figure 1), namely Dauphine (Da), Longue d'Aout (La), Pasteliere (Pa), Marseille (Ma) and Bourjassote Noire (Bn), were nutritionally and chemically characterized to detect possible bioactive molecules. The antioxidant and antimicrobial, activities were also analyzed, to provide the food industry with natural additives in alternative to the artificial ones; and at the same time, promote the circular economy. Regarding the nutritional profile of the five leaves, La sample exhibited the highest amount in proteins (18.0±0.6 g/100g dw), while Pa revealed the highest content in fats (2.2±0.1 g/100g dw). The highest moisture content was presented by Da leaves (17.3±0.1 g/100g fw), and for the ashes, La sample was the one that presented the highest value (14.18±0.06 g/100g fw). Concerning the organic acids, these molecules were most abundant in Ma leaves, where it was possible to identify oxalic, malic and citric acids with a total of 139.6±0.4 mg/g dw. For the soluble sugars profiling, in all samples it was possible to identify five sugars, namely, fructose, glucose, sucrose, trehalose, and raffinose in different concentrations; however, Da leaves revealed the higher amount (17±1 g/100g dw). Tocopherols where also analyzed, and in all samples, three of the four isoforms where detected, being Pa sample standing for the predominance of these compounds (4.14±0.05 mg/100 g dw). For the bioactive analysis, different assays were performed, and Pa sample showed the strongest antioxidant potential for the TBARS assay, with an EC50 value of 105±5 mg/mL. For the antimicrobial activity assay, Da leaf extract was the one displaying the best results, by presenting Minimum Inhibitory Concentrations (MIC) ranging from 1.25 to 10 mg/mL against the tested bacterial strains. On the other hand, for the antifungal activity, the samples present very similar profiles, with the exception of the Pa sample, that present the lowest MIC of 5 mg/mL for Aspergillus fumigatus. In general, these leaf extracts can be used in the food industry namely in pastry and bakery products as promising sources of bioactive compounds, and at the same time, this reuse of biowaste promotes circular economy, and reduces the impact of biowaste resulting from the fig industry, thus meeting some of the goals of sustainable development. The authors are grateful to the Foundation for Science and Technology (FCT, Portugal) for financial support through national funds FCT/MCTES to the CIMO (UIDB/00690/2020). S.Heleno and M. Carocho thank FCT for their individual employment program–contract (CEEC-IND/00831/2018, CEECIND/03040/2017), and L. Barros also thanks to the national funding by FCT through the institutional scientific employment program–contract for her contract. the European Regional Development Fund (ERDF) through the Competitiveness and Internationalization Operational Program for financial support to the project 100% Figo (POCI-01-0247-FEDER-064977) and for C. Shirashi PhD grant. info:eu-repo/semantics/publishedVersion