Kinetic and mechanistic studies on unconventional antioxidant activities of natural compounds

Guo, Yafang (2021) Kinetic and mechanistic studies on unconventional antioxidant activities of natural compounds, [Dissertation thesis], Alma Mater Studiorum Università di Bologna. Dottorato di ricerca in Chimica, 33 Ciclo. DOI 10.48676/unibo/amsdottorato/9950.
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In chapter one, the autoxidation kinetics of natural oil substrates, including, triglyceric sunflower oil, olive oil, terpenic squalene, and p-cymene were calibrated through differential oximetry methods. Calibration allows their use as reference oxidizable substrates for further studies, e.g. for quantitative testing of antioxidants under biomimetic settings. Several essential oils samples, of different botanical species or different productions of same species were studied for their antioxidant activity in inhibited autoxidation kinetics. Their antioxidant activities were matched with their composition analyzed by GC-MS. In chapter two, the molecular mechanism of the synergy between the common phenolic antioxidants such as tocopherol and catechols with widespread essential component gamma-terpinene was studied through lipid oxidation kinetics. Wherein, gamma-terpinene was able to disclose the key intermediacy HOO·, which acted as a reducing agent regenerating the phenolic antioxidant. This counterintuitive role of HOO· radicals was further investigated in detail and allowed to rationalize for the first time the purported antioxidant behavior of PDA melanin nanoparticles. It will also open to a deeper understanding of the redox biology of quinones. Regarding melanin, its role is broadly important in living organisms and its control, including its inhibition, is of great importance with several relevant applications ranging from food preservation to control of human skin pigmentation. In chapter three, an oximetry method combined with the traditional UV-Vis spectroscopy was developed to study the tyrosinase inhibition kinetics, which allowed identifying Glabridin (from G. glabra, L.), as one of the most effective natural tyrosinase inhibitors.

Tipologia del documento
Tesi di dottorato
Guo, Yafang
Dottorato di ricerca
Settore disciplinare
Settore concorsuale
Parole chiave
autoxidation kinetics, antioxidant activity, peroxyl radicals, natural oil substrates, essential oils; γ-Terpinene, Synergy of antioxidants, Quinones’ regeneration, melanins, polydopamine, tyrosinase inhibition, glabridin, oximetry
Data di discussione
19 Ottobre 2021

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