Impaired autophagic clearance contributes to proteostasis failure and the accumulation of amyloid-β (Aβ) and pathological Tau in Alzheimer's disease (AD), yet pharmacologically tractable activators of productive autophagy remain limited. Here, we screened an in-house library of 64 natural products, semisynthetic derivatives, and synthetic analogues and identified compound 51 (C51), a synthetic trifluoromethylated 4-hydroxy-3-methoxy chalcone derivative, as an activator of autophagy. C51 enhanced autophagic flux, lysosomal activity, and SQSTM1/p62 turnover in mammalian cells and Caenorhabditis elegans, indicating productive autophagic clearance rather than autophagosome accumulation. C51 reduced APP-, Tau-, and TauP301L-associated proteotoxicity in neuronal cells and ameliorated Aβ- and Tau-related behavioral deficits, protein aggregation, Tau phosphorylation, and oxidative stress in transgenic C. elegans. In 3×Tg-AD mice, C51 improved learning and memory, preserved hippocampal neurons and synaptic proteins, and reduced gliosis, Aβ oligomer accumulation, and phosphorylated Tau burden without overt systemic toxicity. Mechanistically, C51 activated AMP-activated protein kinase (AMPK) and suppressed mechanistic target of rapamycin (mTOR) signaling. Molecular docking and molecular dynamics simulations, together with drug affinity-responsive target stability and cellular thermal shift assays, supported C51-AMPK interaction. AMPK knockdown, Compound C, and aak-2 RNA interference markedly attenuated C51-induced autophagy and protection against Aβ/Tau toxicity, demonstrating a conserved requirement for AMPK signaling. Quantitative proteomics further showed that C51 rebalanced TauP301L-disrupted proteostasis networks. Collectively, C51 represents a potent natural product-inspired autophagy activator with therapeutic potential for AD by restoring AMPK-dependent autophagic clearance and Aβ/Tau proteostasis across complementary AD models.
