Anti-Glycation, Anti- β -Amyloid Aggregation, and Antioxidant Effect of Cassia Seed-Derived Secondary Metabolites

Aggregation and non-enzymatic glycation of amyloidogenic peptides, amyloid-beta (Aβ), and insulin are key features of neuropathology. In this study, we evaluate the anti-glycation effect of Cassia seed-derived secondary metabolites on human insulin and bovine serum albumin, as well as their anti-Aβ aggregation and antioxidant effects using in vitro spectrofluorometric method, thioflavin T fluorescence, and peroxynitrite (ONOO) scavenging assay. Furthermore, molecular docking simulation was performed to investigate the binding characteristics of test compounds and Aβ42 peptide. Among 38 compounds, anthraquinones 9-12 and 14-18; naphthopyrones 24, 25, 27, and 33-36; and 38 from the naphthalenes and naphthalenic lactone groups showed moderate-to-good inhibition of AGE formation with IC50 values ranging from 7.52 ± 1.19 to 155.86 ± 0.79 μM. Likewise, compounds 5, 24, 15, 16, 27, and 20 showed good inhibition of D-ribose-mediated glycation of human insulin, with an IC50 value range of 46.37 ± 4.06 to 97.69 ± 7.88 μM. In the thioflavin-T assay, compounds 8 and 12 showed promising inhibition of Aβ aggregation, comparable to that of the reference compound morin. Molecular docking simulations confirmed that these active compounds have strong potential to interact with Aβ42 peptides and interrupt their self-assembly and conformational transformation, thereby inhibiting Aβ42 aggregation. In addition, compounds 5, 8, 10, 14, and 35 scavenged ONOO- at low concentrations. Overall, Cassia compounds' anti-glycation, anti-Aβ aggregation, and antioxidant effects warrant further in vivo studies to evaluate their potential neuroprotective effects against comorbid AD and diabetes.