PLANT PIGMENTS IN PSYCHIATRY AND NEUROLOGY: HISTORICAL AND MODERN USES. PART I (LITERATURE REVIEW)
Authors: Bekker Roman A. , Bykov Yuriy V. 
Published: March 2024

Purpose. To provide the reader with a detailed historical overview of the human use of plant pigments for medical purposes, starting from ancient times. To show how modern chemical theory of color and evolutionary biology of plants explain, from their very different points of view — some commonly observed properties of many plant pigments, such as their antioxidant and anti-free radical activity. To present modern data on pharmacological properties and potential therapeutic utility in psychiatry and neurology of some selected plant pigments.

Methodology. To get an idea of what originally were the rationales for human use of plant pigments for medical purposes, we turned to books on the history of medicine and on the history of pharmacology. To get an idea of what is the relationship between the absorption spectrum of a molecule and its chemical properties (in particular, properties of a reducing agent, an electron donor, an antioxidant and a free radical scavenger) — we turned to the book on the chemistry of pigments. And to get an idea of the evolutionary role of pigments in plant tissues — to the book on evolutionary biology. We then selected, based on the lists of plant pigments provided in two of the most authoritative manuals for DIY fabric dyeing with natural dyes — some of the plants that looked most interesting for our purposes. We then searched for information about the use of these plants in psychiatry and neurology and about their neuropharmacological properties, with the use of search engines such as PubMed, Google Scholar, Science Direct, Web of Science. The data we have collected were summarized and presented to the reader in this review.

Results. The data that we have obtained in the process of compiling this review, in our opinion, do indicate a significant therapeutic potential for the use of certain plant pigments in psychiatry and neurology. The evidence base for the use of various plant pigments in psychiatry and neurology — significantly varies in quality. For some plant pigments (for example, for curcumin from turmeric, or for crocetin and crocin from saffron, or for roburin from common oak bark, epigallocatechin gallate from green tea leaves, chlorogenic acid and caffeic acid from coffee beans), there is positive data from small randomized clinical trials. For others, so far there is only data from population studies (for example, on the correlation between consumption of walnuts and olives with the lowered incidence of depression), combined with some open-label studies on dietary supplements that contain those pigments.

Practical implications. Our results, in our opinion, provide theoretical and practical grounds for the use of some plant pigments (curcumin, crocin and crocetin, epigallocatechin gallate, chlorogenic and caffeic acids, roburin, oleuropein, juglone) in the combination treatment of chronic fatigue syndrome, mild forms of anxiety and depressive disorders, mild cognitive impairment, early stages of Alzheimer disease and other neurodegenerative diseases, especially in patients who refuse pharmacotherapy or who do not tolerate it well.