Advanced glycation end-products (AGEs) are formed during non-enzymatic reactions involving proteins and sugars, i.e. the Maillard or browning reaction. The early glycation is reversible and involves the production of a Schiff base from the carbonyl group of a reducing sugar and the primary amino groups of a protein (lysine, arginine). The imine adduct undergoes a rearrangement yielding Amadori products. During the late stage, complex irreversible oxidation, condensation and cyclisation reactions lead to AGEs via intra- and intermolecular protein crosslinkage.1

In diabetes, when the organism can no longer synthesise or properly metabolize insulin, chronic hyperglycaemia induces increased AGE formation and consequently vascular complications. Therefore insulin or oral antidiabetics are used to lower blood sugar levels and to limit the formation of AGEs.1 However, antioxidants acting by radical scavenging or metal chelation as well as compounds capable of trapping dicarbonyl species or breaking AGEs may also reduce the amount of AGEs and diabetic complications.2 As AGEs are also responsible for the aging of many tissues and accumulate in organisms over time, such substances could also be useful for limiting age-related diseases. With this in mind our research focused on the investigation of new AGE inhibitors.

In the process we have developed a simple, cheap and high-throughput screening (HTS) assay based on AGE fluorescence, which is highly suitable for the analysis of NPs and extracts. The development of this assay will be presented, and in particular its applicability for the systematic quantification of both vesperlysines and pentosidine-like AGEs will be discussed.1,3

By now the main focus of our ongoing project is to identify promising products and plants for future applications as cosmetics and therapeutic agents. Therefore this assay was adapted and patented for the identification of active anti-AGE compounds designated for cosmetic purposes. On the other hand, as anti-AGE compounds are often able to prevent endothelial dysfunction in blood vessels, this HTS assay is also used to select promising NPs and vegetal extracts for further biological applications focusing on the prevention of cardiovascular events4 and graft rejections.

References

1.    L. Séro et al. Tuning a 96-well microtiter plate fluorescence-based assay to identify AGE inhibitors in crude plant extracts. Molecules 2013, 18, 14320-14339 and references therein.

2.    S. Boisard et al. Chemical composition, antioxidant and anti-AGEs activities of a French poplar type propolis. J. Agric. Food Chem. 2014, 62, 1344-1351 and references therein.

3.    S. Derbré et al. Automating a 96-well microtiter plate assay for identification of AGEs inhibitors or inducers: application to the screening of a small natural compounds library. Anal. Bioanal. Chem. 2010, 398, 1747-1758.

4.    B. T. Dang et al. Advanced glycation inhibition and protection against endothelial dysfunction induced by coumarins and procyanidins from Mammea neurophylla. Fitoterapia 2014, 96, 65-75.