Harnessing Plant-Derived Tryptophan: Bridging the Gap Between Neurobiology and Psychiatry in Depression Management

Major depressive disorder (MDD) remains a leading cause of disability worldwide, with conventional antidepressants offering incomplete and often transient relief. Mounting ev-idence highlights disturbances in tryptophan (Trp) metabolism as a key biological axis linking inflammation, neuroplasticity, and mood regulation. Plant-derived compounds that modulate this pathway, including 5-hydroxytryptophan, isoflavones, berberine, and polyphenols, have emerged as promising candidates for integrative treatment strategies. Yet, despite encouraging preclinical and clinical findings, knowledge gaps persist re-garding long-term efficacy, mechanistic specificity, and standardized therapeutic proto-cols. This narrative review explores how plant-derived Trp modulators influence central and peripheral mechanisms relevant to depression, from serotonergic synthesis and kynurenine shunting to gut–brain–immune interactions. Evidence from animal models and randomized clinical trials is critically synthesized, with particular attention to out-comes on mood stabilization, anxiety reduction, cognitive function, and sleep regulation. Special emphasis is placed on translational potential, methodological limitations, and the need for harmonized research frameworks. Here we highlight that phytochemical inter-ventions represent a mechanistically informed and biocompatible strategy for advancing depression management. By bridging neurobiology and clinical psychiatry, these insights may pave the way for next-generation therapeutics that integrate dietary, microbio-ta-targeted, and anti-inflammatory approaches. Broader application of this research could ultimately refine personalized psychiatry, expand therapeutic horizons, and contribute to global mental health resilience.