Phytochemical and Pharmacological Screening of Herbal Drugs for the Treatment of Dementia: A Comprehensive Review

Abstract

Dementia is a progressive neurodegenerative syndrome characterized by deterioration in memory, cognition, behavior, and the ability to perform daily activities. Dementia is one of the major causes of disability and loss of independence among older adults across the world. Among the different types of dementia, Alzheimer's disease is the most common, accounting for nearly 60–70% of all reported cases. Despite considerable advances in modern medicine, currently available pharmacological therapies, including acetylcholinesterase inhibitors and N-methyl-D-aspartate receptor antagonists, primarily provide symptomatic relief and are often associated with limited efficacy and adverse effects. Consequently, increasing attention has been directed toward medicinal plants and phytochemicals as promising alternatives for the prevention and management of dementia.

Herbal medicines contain diverse bioactive constituents such as alkaloids, flavonoids, polyphenols, terpenoids, saponins, glycosides, lignans, and tannins, which exhibit multiple neuroprotective mechanisms. These compounds have demonstrated antioxidant, anti-inflammatory, anti-amyloidogenic, anti-apoptotic, cholinesterase inhibitory, and neurogenesis-promoting activities in various experimental models. Phytochemical screening techniques including qualitative phytochemical tests, thin-layer chromatography (TLC), high-performance thin-layer chromatography (HPTLC), high-performance liquid chromatography (HPLC), gas chromatography–mass spectrometry (GC–MS), liquid chromatography–mass spectrometry (LC–MS), Fourier-transform infrared (FTIR) spectroscopy and nuclear magnetic resonance (NMR) spectroscopy are widely used to identify, characterize, and standardize the bioactive compounds present in herbal medicines. These analytical techniques help confirm the chemical composition, assess the purity of herbal extracts, and ensure the consistency and quality of herbal formulations. Pharmacological evaluation encompasses both in vitro assays such as acetylcholinesterase inhibition, antioxidant assays, neuronal cell culture models, and in vivo animal models including scopolamine-induced amnesia, β-amyloid-induced neurotoxicity, streptozotocin-induced cognitive impairment, and transgenic mouse models of Alzheimer's disease.

This review comprehensively summarizes the phytochemical composition, pharmacological screening methods, molecular mechanisms, experimental evidence, and clinical potential of important medicinal plants including Bacopamonnieri, Withaniasomnifera, Ginkgo biloba, Curcuma longa, Centellaasiatica, Convolvulus pluricaulis, Celastruspaniculatus, Panax ginseng, and several other neuroprotective herbs. Furthermore, current challenges in herbal drug standardization, quality control, safety evaluation, and clinical translation are critically discussed. Collectively, herbal drugs represent promising multi-target therapeutic candidates for dementia management; however, well-designed clinical trials and standardized phytopharmaceutical formulations remain essential before their widespread clinical application.