Cashew-Derived Flavonoids Modulate the Th1/Th2 Balance at Peyer's Patches via a C-Ring Oxidation-Dependent Molecular Switch.

Intestinal mucosal homeostasis is fundamentally governed by the T-helper 1/T-helper 2 (Th1/Th2) cytokine equilibrium within immune induction sites such as Peyer's patches (PPs). While cashew nuts (Anacardium occidentale L.) are globally consumed for their nutritional value, the immunomodulatory potential of their polar constituents remains under-characterized. In this study, an activity-guided fractionation strategy led to the isolation of nine phenolic compounds. Their effects on T-helper polarization were evaluated ex vivo using murine PP cells following oral administration. We identified a structural "molecular switch" that dictates the direction of immune modulation: dihydroflavonols, specifically aromadendrin (1) and naringenin (2), significantly upregulated Th1 cytokines, interferon-gamma (IFN-γ), and interleukin-2 (IL-2), whereas flavan-3-ols, such as afzelechin (3) and epiafzelechin (4), promoted a Th2-biased response, interleukin-4 (IL-4). Structure-activity relationship (SAR) analysis revealed that the C-ring oxidation state (C4-carbonyl group) is the primary determinant of the immunomodulatory direction, while the C2-C3 stereochemical configuration specifically modulates the inhibitory potency against Th1-type cytokines. Integrated network pharmacology and molecular docking simulations further mapped these divergent activities to distinct molecular targets: the Th1-promoting effects of aromadendrin were associated with the SRC/phosphoinositide 3-kinase (PI3K)-protein kinase B (Akt) axis, while the Th2-bias of afzelechin was linked to the epidermal growth factor receptor (EGFR)/mitogen-activated protein kinase (MAPK) signaling cascade. These findings provide a structural and mechanistic framework for utilizing specific cashew-derived flavonoids as targeted functional ingredients to calibrate Th1/Th2 imbalances in intestinal immune disorders.