Nootropic Herbs, Shrubs, and Trees as Potential Cognitive Enhancers

Abstract

Plant-based nootropics are a diverse group of natural drugs that can improve cognitive abilities through various physiological mechanisms, especially in cases where these functions are weakened or impaired. In many cases, the nootropics enhance erythrocyte plasticity and inhibit aggregation, which improves the blood’s rheological properties and increases its flow to the brain. Many of these formulations possess antioxidant activity that protects brain tissue from neurotoxicity and improves the brain’s oxygen supply. They can induce the synthesis of neuronal proteins, nucleic acids, and phospholipids for constructing and repairing neurohormonal membranes. These natural compounds can potentially be present in a great variety of herbs, shrubs, and even some trees and vines. The plant species reviewed here were selected based on the availability of verifiable experimental data and clinical trials investigating potential nootropic effects. Original research articles, relevant animal studies, meta-analyses, systematic reviews, and clinical trials were included in this review. Selected representatives of this heterogeneous group included Bacopa monnieri (L.) Wettst., Centella asiatica (L.) Urban, Eleutherococcus senticosus (Rupr. & Maxim.) Maxim., Ginkgo biloba L., Lepidium meyenii Walp., Panax ginseng C.A. Meyer, Paullinia cupana Kunth, Rhodiola rosea L., Schisandra chinensis (Turcz.) Baill., and Withania somnifera (L.) Dunal. The species are depicted and described, together with their active components and nootropic effects, and evidence of their efficacy is presented. The study provides brief descriptions of the representative species, their occurrence, history, and the chemical composition of the principle medicinal compounds, with uses, indications, experimental treatments, dosages, possible side effects, and contraindications. Most plant nootropics must be taken at optimal doses for extended periods before measurable improvement occurs, but they are generally very well tolerated. Their psychoactive properties are not produced by a single molecule but by a synergistic combination of several compounds. The available data suggest that including extracts from these plants in medicinal products to treat cognitive disorders can have substantial potential therapeutic benefits.

Chlorogenic Acids, Acting via Calcineurin, Are the Main Compounds in Centella asiatica Extracts That Mediate Resilience to Chronic Stress in Drosophila melanogaster

“…CA has been an important medicinal herb in traditional medicine used to improve cognition and memory but also to reduce anxiety and stress [ 12 , 45 ]. Although clinical trials that studied its effect on anxiety and depression have been very limited [ 17 ], antidepressant properties have been suggested by some studies in rodents that showed improvement in stress-induced behavior in rats and mice [ 46 , 47 ].…”

Emerging evidence that ginseng components improve cognition in subjective memory impairment, mild cognitive impairment, and early Alzheimer's disease dementia

“…One of the physiological and pharmacological actions of ginseng is nootropic [ 19 ]. There are two types of memory or cognition studies that have explored the effect of ginseng use on humans.…”

Phytochemicals: A Promising Alternative for the Prevention of Alzheimer’s Disease

“…In preclinical studies, Centella asiatica was also discovered to have antidepressant, anxiolytic, antistress, and seizure-prevention properties [182,183]. It has been shown to affect metabolic pathways connected to AD when administered to 5xFAD mice [184]. In rats overexpressed with β-amyloid, Centella asiatica extract has been demonstrated to enhance memory and decision-making, while it lowers hippocampus mitochondrial dysfunctioning.…”

“…In rats overexpressed with β-amyloid, Centella asiatica extract has been demonstrated to enhance memory and decision-making, while it lowers hippocampus mitochondrial dysfunctioning. In a clinical investigation, a 70% water-ethanol extract of C. asiatica demonstrated promising anxiolytic properties by reducing anxiety and stress in patients [184].…”