Titolo della tesi: Food Waste and Officinal Plants as a Valuable Sources of Bioactive Compounds Helpful for Human Health and Biopolymer to Formulate Nanoparticles
Part A. Agro-food waste valorisation
The fruit and vegetable supply chain generates thousands of tons of food waste annually. The volume of trash from the entire food chain until domestic consumption became a global issue for governments and institutions to face, encouraging and supporting innovative solutions towards a zero-waste future. Therefore, this research line aims to characterise food byproducts to valorise and consider them as a valuable source of bioactive compounds and biopolymers beneficial in promoting human health.
The studied food wastes were valorised by producing biostimulants, identifying healthful compounds, and extracting a polymer to formulate nanoparticles.
The protein hydrolysate of cauliflower and artichoke by-products was developed in water using the Flavour enzyme as protease and applied as plant biostimulants to enhance the overall plant performance and quality of vegetables. Its germination and growth-promoting effects were investigated on soil-grown barley, wheat, eggplant, and pepper plants or as a foliar spray in the nutrient solution of greenhouse tomatoes and lettuce.
The chemical-biological profile of Sulmona red garlic aerial bulbils suggested the potential use of this byproduct in phytotherapeutic remedies to manage colon inflammatory diseases. In particular, NMR analyses allowed sugars, organic acids, amino acids, and the organosulphur compounds alliin and allicin to be determined. In contrast, the HPLC-DAD analyses revealed the presence of phenolic compounds (catechin, chlorogenic acid, and gallic acid). Accounted to this phytochemical profile, a chemopreventive effect was observed on HCT116 colon cancer cells, reducing gene expression of TRPM8 receptor (possibly involved in the inflammatory pathway; alliin may directly interact with it), TNF-α (tumour necrosis factor), HIF1-α (hypoxia-inducible factor) and VEGFA (vascular endothelial growth factor).
The polymer lignin was isolated from the woody, non-edible part of dried fruit (exocarp of almonds, walnuts, hazelnuts, and peanuts). After extraction, the lignin structure was investigated by FT-IR and NMR spectroscopies (1H, 1H-13C HSQC), revealing an SG-type lignin due to the presence of Syringyl and Guaiacyl units. In each one, the sugar xylose was a contaminant. By the nanoprecipitation method, the extracted biopolymer allowed the formulation of time-stable nanoparticles loaded with curcumin (LNPs-CUR). The lignin nanoparticles, morphologically spherical, showed an excellent encapsulation efficiency (EE %) and good curcumin release profile after 24 h.
The recovery and reuse of chemically and biologically characterised food byproducts valorise them and allow the production of high-quality products, aligning with the circular economy approach.
Part B. Officinal plants, a valuable source of beneficial phytochemicals
Officinal plants are a source of secondary metabolites with biologically relevant properties. Due to the variability in phytochemical profile caused by various factors, including pedoclimatic conditions, assessing the difference between ecotypes of the same species could be necessary.
The primary objective of this study was to investigate the impact of different altitudes and agronomical practices (Land, Mountain Spontaneous, and Organically grown Ecotypes, namely LSE, MSE, and OE, respectively) on the metabolite profile of three officinal plants: burdock root (Arctium lappa), dandelion root and aerial part (Taraxacum officinale), and lemon balm aerial part (Melissa officinalis).
Different compounds, such as sugars, amino acids, organic acids, polyphenols, fatty acids, and other metabolites from NMR untargeted analysis, were identified and quantified in all samples. Some metabolites were tissue-specific markers: arginine was found in roots, whereas myo-inositol, galactose, glyceroyldigalactose moiety, pheophytin, and chlorophyll were identified in aerial parts. Caftaric and chicoric acids, 3,5 di-caffeoylquinic acid, and chlorogenic and rosmarinic acids were detected in dandelion, burdock and lemon balm, respectively. The metabolite amount changed significantly according to crop, tissue type and ecotype, providing insights into the chemistry of officinal plants, thus supporting nutraceutical-phytopharmaceutical research.
The second objective was focused on Taraxacum officinale, for which the hydroalcoholic extract’s chemical composition and neuroprotective properties were investigated. HPLC-DAD targeted analysis was carried out on dandelion under the three above-mentioned agronomical practices. The MSE ecotype had the wealthiest phytochemical profile because of specific polyphenols, such as caftaric acid and chicoric acid, confirming the NMR outcomes.
For that reason, MSE hydroalcoholic extracts were tested on the HypoE22 cell line employing MTT assays to evaluate biocompatibility and antioxidant activity. The extracts protected cells from the pro-oxidant stimulus (H2O2), showing good biocompatibility.
Moreover, the same extracts were tested on mice C57/BL6 brain specimens (prefrontal cortex and hypothalamus) treated with lipopolysaccharide, showing a reduced gene expression of TNF-α (tumour necrosis factor) and NOS-2 (nitric oxide synthase-2) and an increased expression for BDNF (brain-derived neurotrophic factor). These results demonstrated the effects of dandelion extracts on ameliorating neuroinflammation due to their phytochemical profile.
These results have enabled us to consider the Taraxacum officinale MSE as a valuable source of bioactive compounds, thus supporting nutraceutical-phytopharmaceutical research.