Keivani, Niloufar (2024) Identification and characterization of product and byproduct with high content of oligomeric procyanidins to develop new nutraceuticals. [Tesi di dottorato]

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Abstract

Natural-source nutraceuticals, including foods, food substances, and dietary supplements, play a crucial role in global public health. These bioactive compounds, such as alkaloids, terpenoids, polyphenols, and carotenoids, exhibit potent antioxidant properties that have been extensively studied in vitro and in vivo. By neutralizing harmful reactive oxygen species (ROS), these phytochemicals offer a promising approach to preventing and mitigating a wide range of degenerative and chronic diseases, including arthritis, heart disease, cancer, osteoporosis, diabetes, and hypercholesterolemia. Bioactive compounds, naturally occurring extra-nutritional substances, are ubiquitously present in diverse food sources of plant, animal, and aquatic origin. While these compounds are often found in minute quantities, they confer significant health benefits beyond basic nutritional sustenance. By modulating and regulating essential metabolic processes and functions, bioactive compounds contribute to the promotion of overall well-being. The biosynthesis of these bioactive compounds is a common secondary metabolic process in plants and microorganisms. The research presented in this thesis was primarily focused on the extraction and chemical characterization of polyphenolic compounds, procyanidins, and glycoalkaloids derived from plant sources. The initial chapter commences with an introduction to the botanical characteristics, background chemical profiles, biosynthetic pathways, and a description of the target compounds in selected matrices. In the project several medicinal herbal plants are extensively analyzed in order to be considered as sources of bioactive compounds with beneficial effects on human health. The study assessed the procyanidin and polyphenol profiles together with the antioxidant potential of seven herbal medical matrices. To achieve this aim, procyanidin extraction from grape pomace was used as a test matrix to be optimized and validated by monitoring monomeric-trimeric procyanidins. The proposed quantification method was then applied to the seven medical herbs (Sambucus nigra L. flower, Sambucus nigra L. leaves, Crataegus monogyna Jacq. flowers and leaves, Peumus boldus Molina leaves, Eleutherococcus senticosus Maxim. Root, Paullinia cupana Kunth. Seed, and Hamamelis virginiana L. leaves) and it proved to be a very efficient protocol for procyanidin-rich extracts analysis. In addition, the Paullinia cupana Kunth. seed was identified as a very rich source of procyanidins (about 5 mg/g dry matrix of each dimeric and about 3 mg/g dry matrix trimeric) with very high antioxidant properties. The polyphenolic profile was assessed by HPLC-HESI-MS/MS analysis. The in vitro antioxidant activity was evaluated to explore the antioxidant properties of the extracts, which were substantially higher in Peumus boldus Molina leaves extracts concerning the other matrices. Moreover, a high Pearson coefficient value was observed between the total flavonoid content (TFC) and DPPH in comparison with the total polyphenol content (TPC) and DPPH, indicating flavonoids as the principal bioactive with antioxidant activity in the extracts. The digestion effect on antioxidant activity of the optimized extract was investigated. Additionally, the effect of the optimized extract on myoblast mitochondrial activity was assessed using the MTT and mitochondrial activity assays. Besides, unripe tomatoes which are among the main waste produced during tomato cultivation and processing, from seven different Italian cultivars have been investigated to evaluate their nutraceutical potential. Phytochemical investigation allowed shedding light on the identification of seventy-five bioactive compounds. The Datterini tomato variety demonstrated the highest concentrations of polyphenolic compounds, glycoalkaloids, and exhibited the most pronounced antioxidant activity. The Datterini tomato variety possesses a unique characteristic in the form of its exceptionally high chlorogenic acid content, which is tenfold greater than that of other cultivars. Moreover, the total α-tomatine content of this variety has been found to be substantially higher, reaching 34.699 ± 1.101 mg/g dry weight, in comparison to other tomato varieties analyzed. Furthermore, the metabolomic profiles of different cultivars were investigated with the PCA approach. Based on Datterini cultivar’s metabolomic profile, its waste-recovery could represent a good option for further added value products in pharmaceutical and nutraceutical areas with a high α-tomatine content.

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