A Review on Theanine: Neural Benefits and the Biosynthesis in Tea Plant

Abstract Background Theanine, which specifically accumulates in Camellia sinensis (L.) O. Kuntze, has demonstrated remarkable pharmaceutical and clinical benefits. Continuous investigations and related documents regarding theanine have been disclosed, and they are abundant and complex. Methodology Literatures disclosed in the most recent 5 years were indexed, and those focusing on the neuro-related functions of theanine and biosynthesis in the tea plant were selected and reviewed. Results and Key Findings Neuro-related pharmaceutical activities of theanine were present in treating with neural disorders, including sleep disorders, stress management, cognitive enhancement, reversal of neurol injury, and organ protection. Furthermore, the combination of theanine with other phytochemicals exerts a synergistic effect, which expands the applications of theanine. Meanwhile, the metabolism of theanine in tea plant was proposed. Genetic factors participating in the biosynthesis, transportation and distribution of theanine were combed and illustrated. In addition, advantages of enzyme engineering and microbial engineering for the production of theanine were also summarized. Conclusion A concise summary of the neuro-related benefits of theanine, as well as a systematic understanding of the accumulation of theanine in tea plant would be anticipated. Furthermore, clarification of the pharmacological mechanism, exploration of more novel pharmaceutical effects, and strategies to improve accumulation in tea products are awaiting elucidation. All with the desire for resource development and utilization of theanine.