Natural products as potential inhibitors of Advanced Glycation Endproducts (AGEs) and modulators of autophagy

Date: 25 September 2020

Venue: ONLINE DEFENCE - - - - -

Time: 4:00 PM - 6:00 PM

PhD candidate: Stefaniya Velichkova

Principal investigator: Luc Pieters - Kenn Foubert

Short description: Phd defence Stefaniya Velichkova - Department of Pharmaceutical Sciences


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Since centuries, medicinal plants have been providing human civilisation with remedies for health maintenance and disease control. Nowadays, natural sources are still a starting point for drug discovery investigations. They attract attention for their potential application as novel therapeutic agents in the treatment of current diseases with big social and economic impact (e.g. type 2 diabetes, cardiovascular diseases). Various mechanisms have been proposed to explain the causes of chronic conditions, and on biochemical level, protein glycation (formation of advanced glycation endproducts (AGEs)) correlates with many pathological complications. Similar to AGEs, autophagy has been associated with a plethora of different pathologies including heart diseases, cancer, neurodegeneration, infectious diseases, diabetes and autoimmune diseases. Therefore, AGEs and autophagy represent novel therapeutic targets in natural product research. The purpose of this PhD project was to isolate and identify several selected classes of natural products (polymethoxy­flavonoids (PMFs), biflavonoids, quinazoline alkaloids) from four different plant species: Citrus sinensis, Citrus depressa, Ginkgo biloba and Adhatoda vasica; and to evaluate their properties as AGEs inhibitors and autophagy modulators through a set of experimental procedures.

The phytochemical investigation was performed through various chromatographic techniques: open column, flash and semi-preparative liquid chromatography. The structure of the compounds was elucidated by 1D- and 2D- NMR spectroscopy and mass spectrometry. The preliminary testing for AGEs inhibitory properties of the obtained pure compounds was achieved by means of the bovine serum albumin (BSA) / glucose, fructosamine adducts formation and alfa-dicarbonyl compounds formation assays. Due to certain limitations of the standard approaches, a method was developed to evolve from non-selective colorimetric / fluorimetric techniques to a more reliable chromatography-based method. An HILIC UPLC/MS method was aimed to be developed and validated, and consequently, used to investigate the AGEs inhibiting properties of pure compounds and selected commercial standards. To evaluate the autophagy modulation by some isolated pure compounds and commercial standards, different assays were applied: LC3 detection and quantification by western blot analysis, and the Cyto-ID autophagy detection kit. As part of the analytical work, a method for quantifying vasicine – the main quinazoline alkaloid in Adhatoda vasica leaves, was developed and validated. Additionally, the established method was applied for quality control of commercially available herbal products containing Adhatoda powder or extract. Overall, advanced glycation and modulation of autophagy are leading causes for the progression and pathogenesis of many chronic diseases, therefore, the use of validated methods and proved techniques can contribute to the unambiguous discovery of new potent anti-AGEs and autophagy modulating agents.