Beyond Antioxidant Neuroprotection: Palm-Derived Tocotrienols, Microglial Immunometabolism, and NLRP3 Inflammasome Signalling in Alzheimer's Disease—A Critical Review

Alzheimer's disease (AD) involves amyloid and tau pathology alongside dysregulated innate immunity, bioenergetic stress, and altered lipid processing. Palm-derived tocotrienols have been investigated for antioxidant and anti-inflammatory effects, yet it remains uncertain whether their actions extend to disease-relevant microglial immunometabolism and NLRP3 inflammasome signalling. This critical qualitative literature review interprets studies published principally during 2020–2026 across tocotrienol pharmacology, experimental neuroinflammation, AD microglial biology, inflammasome mechanisms, and translational research. Evidence indicates that microglial responses depend on disease stage, metabolic flexibility, APOE/TREM2-associated lipid handling, and selective inflammatory signaling. Tocotrienol-rich preparations reduce selected inflammatory readouts in non-AD experimental models; a structurally related vitamin E derivative suppresses NLRP3-associated pyroptosis in macrophages. These observations do not establish direct suppression of microglial NLRP3 by defined palm tocotrienol congeners in humans with AD. Divergent preparations, uncertain brain exposure, incomplete inflammasome assays, and limited clinical outcomes impede causal inference. The review proposes a congener-to-exposure-to-target-engagement framework that integrates compound identity, pharmacokinetics, inflammasome priming and activation, mitochondrial function, phagocytosis, and AD-specific biomarkers. Future investigations should prioritize patient-derived microglia, causal perturbation experiments, disease-stage stratification, and pharmacokinetic confirmation before clinical efficacy claims. The available evidence supports a mechanistically testable research program, not the clinical use of tocotrienols as an established Alzheimer's treatment.