From by-products to new application opportunities: the enhancement of the leaves deriving from the agricultural sector for new potential healthy products Provisionally Accepted

Lucia Regolo¹ Francesca Giampieri^{2, 3} Maurizio Battino^{2, 4, 5} Yasmany Armas Diaz⁴ Bruno Mezzetti^{1, 2} Maria Elexpuru-Zabaleta² Cristina Mazas^{2, 6} Kilian Tutusaus^{2, 7} Luca Mazzoni^1*

• ¹Department of Agricultural, Food and Environmental Sciences, Marche Polytechnic University, Italy
• ²Research Group on Foods, Nutritional Biochemistry and Health, Universidad Europea del Atlántico, Spain
• ³Department of Biochemistry, Faculty of Sciences, King Abdulaziz University, Saudi Arabia
• ⁴Dipartimento di Scienze Cliniche e Odontostomatologia, Facoltà di Medicina e Chirurgia, Università Politecnica delle Marche, Italy
• ⁵International Joint Research Laboratory of Intelligent Agriculture and Agri-Product Processing, Jiangsu University, China
• ⁶Universidad Internacional Iberoamericana, Mexico
• ⁷Research Center for Foods, Nutritional Biochemistry and Health, Universidade Internacional do Cuanza, Angola

In the last decades, the world population has grown exponentially, as well as the demand for any kind of productand demand for any kind of product has grown exponentially. The rhythm of production to satisfy the request of the population has become unsustainable and the concept of the linear economy, introduced after the industrial revolutionIndustrial Revolution, has been replaced by a new economic approach, the circular economy. In this new economic model, the concept of "the end of life" is substituted by the concept of restoration, providing a new life to many industrial wastes. Leaves are a by-product of several agricultural cultivations. In recent years, the scientific interest regarding leaf biochemical composition grew, recording that plant leaves may be considered an alternative source of bioactive substances. Plant leaves' main bioactive compounds are similar to those in fruits, i.e., phenolic acids and esters, flavonols, anthocyanins, and procyanidins. Bioactive compounds can positively influence human health; in fact, it is no coincidence that the leaves were used by our ancestors as a natural remedy for various pathological conditions. Therefore, leaves can be exploited to manufacture many products in the food (e.g., being incorporated in food formulations as natural antioxidants, or used to create edible coatings or films for food packaging), cosmetic and pharmaceutical industries (e.g. promising ingredients in anti-aging cosmetics such as oils, serums, dermatological creams, bath gels, and other products). This review focuses on the leaves' main bioactive compounds and their beneficial health effects, indicating their applications until today to enhance them leaves as a harvesting by-product and highlight their potential possible beneficial effectsreuse for new potential healthy products.