Innovative nutraceutical and antibacterial proprieties of Humic extracts from composted vegetable wastes.

Compost is commonly used as an organic fertilizer to recover and preserve the chemical and physical properties of agricultural soils. Effectively, the use of recycled biomasses, residues and by-products, such as compost, is an effective way to improve the environmental and economic sustainability of agroecosystems and agri-food value chains. The use of green compost is increasingly acknowledged in the EU policies as one of the most sustainable approaches to implement the circular economy in agricultural sector due to an economic and environmental re-evaluation of agricultural biomass. Following the raising attention on compost as valuable organic resource for crop productivity, in the recent years the research activity was addressed on the innovative utilization of specific compost fractions such as humic substances and compost teas for crop biostimulation, acting as bio-effectors on biochemical activities, physiological processes and plant microbial interactions The research described in this thesis, is focused on the application of compost as renewable resource for the production of these potential bioactive materials such as humic substances (HS) and compost teas (CTs) as biostimulant to promote the biosynthesis of nutraceutical products in aromatic crop represented by common basil plant. These organic materials were obtained from different composted agricultural biomasses: artichoke, coffee and pepper. Compost teas and humic substances isolated from the different on-farm composts were characterized in details for their chemical properties and molecular composition. Experiments using HS and CTs obtained from artichoke, coffee and pepper composted biomasses highlighted a relationship with the capacity to increase the development of Basil plants with positive effects on phenological parameters such as fresh and dry biomasses and chlorophyll content. Moreover, the plant treatments with compost extracts promoted the synthesis of metabolites with antioxidant proprieties and antibacterial activity against some common human pathogens. In line with the most advanced research approaches, the results indicated the occurrence of structural-activity relationships based on a combination of physical and chemical features of applied organic fractions as triggering factors for biostimulant properties. The data of molecular characterization suggested the prevalent role of hydrophobic conformation and aromatic components, lignin derivatives and peptidic cluster in the modulation of analysed metabolic pathways. The application of metabolomics and lipidomic approaches have shown an increase in the biosynthesis of secondary metabolites with nutraceutical properties such as hydroxycinnamic acids (caffeic, ferulic, trans-cinnamic and p-cumaric) naringenin, resveratrol and coenzyme Q-10, thus confirming the effect of compost derivatives on plant metabolism. The organic materials influenced the production of primary metabolic intermediates such as erythrosis-4-phosphate and phosphoenolpyruvate that activate the production of metabolites involved in the biochemical pathway of schikimic acid. Moreover, the treatment of Basil plants with humic materials such as HS-artichoke improved the yield, antimicrobial and antioxidant properties of Essential oils (EOs) extracted from Basil leaves by steam distillation with a clear dose-response effect on the production of most bioactive chemical components like eucalyptol, methyl-chavicol, eugenol, methyl-Eugenol, trans-α-Bergamotene, geranyl acetate. Finally, medical applications of the HS and CTs extracted from different composted biomasses were carried out using in vitro assays on epithelial adenocarcinoma epithelial colon cancer cells (CaCo-2) and immortalized cells of cervical tumor (HeLa). The results of the determination of cytotoxic activity showed the significant inhibition in the proliferation of these tumorigenic cell lines, thus further supporting the reliable utilization and exploitation of natural compost extracts in pharmaceutical, nutraceutical and cosmetic field