Phytochemical and Fungal Bioactive Compounds in the "Brain Health Triad": A Narrative Review on Neurostimulating, Neurotrophic, and Neuroprotective Synergy.

This narrative review proposes the 'Brain Health Triad' as a novel integrative framework for neurorehabilitation and cognitive enhancement, built upon three interdependent biological pillars: neurostimulation, neurotrophy, and neuroprotection. We illustrate how the synergistic interplay between a 'core triad' composed of Hericium erinaceus, Bacopa monnieri, and L-Theanine targets these pillars with high specificity. Hericium erinaceus fosters neurotrophy by inducing Nerve Growth Factor (NGF) and Brain-derived neurotrophic factor (BDNF) synthesis through erinacines and hericenones; Bacopa monnieri complements this by enhancing neurostimulation and synaptic plasticity via bacosides; and L-Theanine regulates neurotransmitter balance and alpha-wave activity to stabilize the neural signaling environment. This core architecture is further reinforced by adjunctive nootropic clusters-including withanolides, ginkgolides, citicoline, cordycepin, macamides, and fulvic acid-which provide essential support for mitochondrial resilience and the mitigation of amyloid-β and tau toxicities. By synthesizing molecular evidence from the BDNF/TrkB/CREB signaling axis and the Nrf2/NF-κB homeostatic switch, we demonstrate that this multi-target strategy offers a more robust path to neuronal resilience than traditional single-target approaches. We conclude that this integrated model provides a solid framework for future clinical applications in the management of age-related cognitive decline and neurodegenerative diseases.