Therapeutic potential of purpurin, a natural anthraquinone dye, in neuroprotection and neurological disorders.

Purpurin (1,2,4-trihydroxy-9,10-anthraquinone) is a naturally occurring anthraquinone pigment derived primarily from Rubia species. Beyond its traditional use as a natural dye, purpurin has recently gained attention for its multifaceted pharmacological activities, particularly in neuroprotection. This review outlines the biosynthetic pathways leading to anthraquinone formation via the shikimate, mevalonate, and methylerythritol phosphate routes, culminating in the generation of purpurin. Structure-activity relationship analyses highlight the critical role of hydroxyl substitutions in modulating antioxidant, anticancer, antibacterial, and neuroprotective properties through radical stabilization, DNA intercalation, and metal chelation. Evidence from preclinical studies indicates that purpurin exerts beneficial effects in Alzheimer's disease, depression, ischemic stroke, and age-related cognitive decline, primarily through anti-tau aggregation, cholinesterase inhibition, serotonergic modulation, antioxidant activity, and anti-inflammatory mechanisms. While purpurin exhibits low acute toxicity and promising pharmacodynamics, its therapeutic translation remains limited by poor solubility, rapid metabolism, and low brain bioavailability. Nanotechnology-based formulations and molecular modifications are being explored to overcome these challenges. Collectively, purpurin represents a versatile bioactive scaffold with considerable potential for the development of multifunctional neuroprotective agents.