G1899, an American ginseng extract, alleviates neuroinflammation and cognitive impairment in models of Alzheimer's disease
Background: Alzheimer's disease (AD) is characterized by amyloid {beta} (A{beta}) accumulation, tau pathology, and chronic neuroinflammation, yet current therapeutic strategies provide only limited efficacy. Natural compounds with pleiotropic actions have emerged as potential adjunctive interventions. This study evaluated G1899, a standardized American ginseng (Panax quinquefolius) extract, for its effects on neuroinflammation, A{beta} clearance, and cognitive function. Methods: Neuronal cultures were exposed to glutamate or A{beta} oligomers (A{beta}o) and pre-treated with G1899 to assess cell viability and excitotoxicity. Primary murine microglia were analyzed for validating expression levels of TMEM119, CD68, NLRP3 inflammasome, IL-1{beta}, Caspase-1, and STAT3 phosphorylation. Behavioral testing was performed in scopolamine-injected mice with short term G1899 treatment and in 5xFAD transgenic mice following long-term G1899 administration at multiple doses. Amyloid burden, microglial recruitment, and plaque morphology were quantified by immunohistochemistry and high-resolution imaging. Human induced microglia (iMG) were examined for neuroinflammatory responses following A{beta}o exposure with or without G1899 treatment. Results: G1899 significantly improved neuronal viability and reduced glutamate- and A{beta}o-induced toxicity. In microglia, G1899 upregulated TMEM119 and CD68, while suppressing NLRP3 inflammasome formation, proinflammatory cytokine expression, and STAT3 phosphorylation. G1899 rescued scopolamine-induced memory deficits and, in 5xFAD mice, reduced hippocampal and cortical A{beta} burden, alleviated neuroinflammatory markers, and improved both spatial/fear learning and memory, with the most consistent efficacy observed at 300 mg/kg. Imaging revealed enhanced microglial recruitment to plaques and facilitated fragmentation of A{beta} deposits. In iMG, G1899 elevated homeostatic and phagocytic markers while attenuating A{beta}o-induced NLRP3/STAT3-mediated neuroinflammatory signaling pathway. Conclusions: G1899 confers multimodal neuroprotection by preserving neuronal survival, modulating microglial activity, and facilitating A{beta} clearance. These findings highlight its potential as a safe and clinically translatable botanical intervention for AD.