Alzheimer's disease (AD) accounts for 60–80 % of dementia cases (Organization, 2022), and is defined biologically as the deposition of amyloid β (Aβ) plaques and tau neurofibrillary tangles (Knopman et al., 2021). These pathological hallmarks cause synaptic and neuronal loss, which ultimately impairs memory and cognition. Reduced acetylcholine (ACh) activity, in particular, is a major feature of AD pathology, and strategies to restore cholinergic function remain central therapeutic targets (Hampel et al., 2019). Increased Aβ burden is associated with decreased choline acetyltransferase (ChAT) levels, which results in diminished ACh synthesis in neurons (Hampel et al., 2019). Reduced ACh levels in synapses result in learning impairments in AD models (Hampel et al., 2019) and lead to decreased brain-derived neurotrophic factor (BDNF) levels (Orciani et al., 2022). Aβ disrupts cAMP-response element-binding protein (CREB) phosphorylation, which leads to impaired CREB-mediated gene expression, reduced BDNF levels, and inhibition of long-term potentiation (LTP), which is a key mechanism of memory formation (Amidfar et al., 2020). Therefore, restoration of CREB–BDNF signaling has been highlighted as a potential therapeutic strategy, with exogenous BDNF shown to rescue memory in animal models (Amidfar et al., 2020).

Cholinesterase inhibitors (ChEIs)—including donepezil, rivastigmine, and galantamine—are frequently prescribed, providing symptomatic relief and, in some cases, slowed disease progression (Hampel et al., 2019). A notable example is donepezil, which has demonstrated efficacy in restoring BDNF levels in both AD patients (Leyhe et al., 2008) and animal models (Jian et al., 2020). However, the efficacy of ChEIs is primarily observed in mild to moderate AD, and their long-term benefits remain uncertain (Marucci et al., 2021), highlighting the necessity for novel therapeutic interventions.

Paeonia lactiflora, a medicinal herb, has been traditionally utilized in some Asian countries (Kim et al., 2009). P. lactiflora has been documented to possess therapeutic effects, including anti-inflammatory and anti-oxidant properties, as well as neuroprotective effects (Kim et al., 2002, 2021; Lee et al., 2016; Shi et al., 2017). To further investigate P. lactiflora, the single compounds were isolated and reported for their neuroprotective effects (Chen et al., 2024; Wu et al., 2024). In the seeds of P. lactiflora, the presence of several compounds, including gnetin H, was confirmed through isolation procedures. This compound is an oligostilbenoid, a resveratrol derivative. While resveratrol possesses diverse pharmacological properties, its pharmacokinetic profile presents notable limitations (Pannu and Bhatnagar, 2019). Given these considerations, we investigated the neuroprotective potential of gnetin H, a structurally related compound. This molecule has been reported to exhibit enhanced bioactivity in comparison with resveratrol with regard to its anti-tumor proliferation properties (Gao et al., 2015). In addition, the substance has been reported to possess a number of therapeutic effects, including antioxidative activity (Kim et al., 2002; Degfie et al., 2022), anti-metastatic activity in cancer cells (Gao and He, 2017), and anti-bacterial effects (Degfie et al., 2022). Furthermore, the prior observations of neuroprotective effects of a singular oligostilbenoid from P. lactiflora seeds (Kim et al., 2023), with the support of these reports, suggest that gnetin H may exert protective effects on neuronal function.

To investigate this potential, a scopolamine-induced memory deficit model was employed, as it is a widely used method for the discovery of drugs for AD. Scopolamine, a non-selective muscarinic acetylcholine receptor (mAChR) antagonist, has been demonstrated to suppress cholinergic signaling and disrupt short-term memory (Klinkenberg and Blokland, 2010). This model replicates the AD-associated dysregulation of CREB–BDNF signaling (Tang, 2019). Given the evidence that adult hippocampal neurogenesis is reduced in early AD (Salta et al., 2023), the recovery of doublecortin (DCX)-positive cells in the dentate gyrus is also an important endpoint (Couillard-Despres et al., 2005).

In accordance with this hypothesis, the neuroprotective effects of gnetin H were investigated across a range of models, including cellular, slice, and animal studies. In the initial evaluation, cell survival in SH-SY5Y neuroblastoma cells was examined under scopolamine challenge. TrkB antagonist ANA-12 was assessed for its effects on BDNF expression. We then proceeded to assess the impact of acutely bath-applied Gnetin H on hippocampal LTP. Finally, in a mouse scopolamine model, we investigated short- and long-term memory behaviors, cholinergic markers, CREB –BDNF signaling and hippocampal neurogenesis (DCX), along with astrocytic (GFAP) and microglial (Iba1) reactivity.