C9543 - ATTIVITA' ANTIOSSIDANTE DI METABOLITI SECONDARI

Learning outcomes

At the end of the course, the student has acquired knowledge of the chemical characteristics of antioxidants and of the main families of secondary metabolites that may display antioxidant activity in different contexts.

Course contents

1. Oxidative processes in bio-based and biological systems

Oxidation reactions in food, cosmetics, bio-based materials and biological systems. Chemical principles of autoxidation and lipid peroxidation.

• Reactive oxygen and nitrogen species.
• Initiation, propagation and termination of radical chain reactions.
• Lipid peroxidation of saturated, monounsaturated and polyunsaturated fatty acids.
• Primary and secondary lipid oxidation products: hydroperoxides, aldehydes, ketones, epoxides and volatile compounds.
• Consequences of lipid oxidation: rancidity, loss of quality, toxicity, cellular damage and ferroptosis.

2. Chemical mechanisms of antioxidants

Classification of antioxidants according to their mechanism of action and application context.

• Preventive antioxidants: metal chelation, hydroperoxide decomposition and singlet oxygen quenching.
• Chain-breaking or radical-trapping antioxidants.
• Radical-exporting antioxidants and antioxidant regeneration systems.
• Synergistic effects between antioxidants.
• Structure–activity relationships: O–H bond dissociation enthalpy, radical stabilization, electronic and steric effects, lipophilicity and hydrophilicity.
• Possible pro-oxidant effects.

3. Secondary metabolites with antioxidant activity

Main classes of natural compounds with antioxidant properties and their mechanisms of action.

• Simple phenols and phenolic acids.
• Polyphenols: flavonoids, stilbenes, lignans and tannins.
• Tocopherols and tocotrienols.
• Terpenes, carotenoids and essential oil components.
• Sulfur-containing compounds and other bioactive metabolites.
• Influence of chemical structure, polarity and localization in heterogeneous systems on antioxidant effectiveness.

4. Experimental evaluation of antioxidant activity

Chemical, physicochemical and biological methods for studying antioxidant activity.

• Chemical assays: DPPH, ABTS, FRAP, ORAC and related methods.
• Methods for studying lipid oxidation in oils, emulsions and model membranes.
• Analysis of primary and secondary oxidation products.
• Cell-based assays of oxidative stress.
• Interpretative limitations of antioxidant assays and relevance to real systems.

5. Biological effects of antioxidant secondary metabolites

Biological fate and cellular mechanisms of secondary metabolites with antioxidant activity.

• Bioavailability, absorption, metabolism and chemical transformations.
• Direct and indirect antioxidant activity.
• Modulation of cellular redox pathways.
• Activation of the NRF2–Keap1 system.
• Interactions with lipid peroxidation and inhibition of ferroptosis.
• Differences between in vitro antioxidant activity, biological effects and potential nutraceutical activity.

Readings/Bibliography

Lecture notes and material uploaded to Virtuale.

Teaching methods

The lectures will involve the use power-point presentations. 

Assessment methods

The exam is oral and consists of questions that students can find listed in the file available on Virtuale.

The exam consists of a discussion of two topics chosen from the list available on Virtuale. It has two parts:
The student presents a topic chosen only from those highlighted in bold in the list;
The professor selects and asks about a topic from any on the list.
Further information on exam questions is available in the file on Virtuale.

For both parts, the oral discussion is aimed at assessing the student's acquired knowledge and skills. Exercises will be solved on the board, discussing structures and mechanisms related to organic chemistry. Theoretical aspects will also be explored in depth.

Failing grade: significant gaps in content knowledge; insufficient foundational knowledge in chemistry, inappropriate language use, and lack of orientation within the course topics.

Passing grade: barely appropriate language, weak argumentative ability, and minimal knowledge of the exam topics.

Good evaluation: good memorised knowledge of the subject, decent ability to summarize and analyze content, with correct technical language.

Excellent evaluation: in addition to content knowledge, the student must demonstrate the ability to elaborate and critically interpret; a clear and broad understanding of the topics is required, along with strong argumentative skills, mastery of a wide range of competencies, use of specific technical language, and the ability to solve complex exercises.

Note: A solid understanding of basic organic chemistry and introductory biochemistry is required to properly contextualize the topics.

The average duration of the exam is about 40 minutes for both parts combined

Teaching tools

Multimedia material will be presented, such as slides, movies, animations and three-dimensional visualization of atoms, molecules and materials.

The multimedial material utilized during the lectures will be made available for download from the teacher's web site.

Students with learning disorders and\or temporary or permanent disabilities: please, contact the office responsible (https://site.unibo.it/studenti-con-disabilita-e-dsa/en/for-students) as soon as possible so that they can propose acceptable adjustments. The request for adaptation must be submitted in advance (15 days before the exam date) to the lecturer, who will assess the appropriateness of the adjustments, taking into account the teaching objectives.

Office hours

See the website of Riccardo Amorati