Molecular orchestration and health implications of fruit pigmentation: from metabolic pathways to nutritional quality

The color of fruits is determined by the metabolic balance of chlorophyll, carotenoids and anthocyanins. This process is regulated in multiple ways and is closely related to human health, providing a theoretical basis for quality breeding and nutritional development. The external appearance of fruit serves as a direct visual manifestation of internally accumulated secondary metabolites, including anthocyanins, carotenoids, and chlorophylls, effectively acting as a "visual carrier" for these compounds. These pigments confer distinctive morphological characteristics to fruits, with their composition and concentration not only providing consumers with immediate cues regarding freshness and edibility but also closely correlating with fruit maturity and flavor quality. In recent years, the physiological activities associated with these pigments-such as antioxidant and anti-inflammatory effects-and their implications for human health have garnered significant attention within the fields of plant physiology, food science, and nutrition. This paper systematically elucidates the molecular mechanisms underlying fruit coloration, the regulatory networks involved, and the associated health benefits. Fruit color is primarily determined by the metabolic balance of pigments, including flavonoids (notably anthocyanins), carotenoids, and chlorophylls. Anthocyanin biosynthesis is precisely regulated by transcription factors such as the MYB-bHLH-WD40 (MBW) complex; carotenoid accumulation depends on the coordinated action of key enzymes like PSY and PDS alongside transcription factors including AP2/ERF and WRKY; meanwhile, chlorophyll degradation is modulated by factors such as ethylene and NAC proteins. Environmental stimuli and phytohormones influence pigment synthesis by modulating enzyme activities and gene expression, thereby participating in a complex network of genetic and environmental interactions that govern color regulation. The diversity of fruit coloration arises not only from variations in pigment types and concentrations-for example, red fruits are rich in anthocyanins, whereas orange-yellow fruits accumulate carotenoids-but also from the significant bioactive potential of these compounds in antioxidant, anti-inflammatory functions and in the prevention of metabolic diseases such as diabetes. This review seeks to identify molecular targets pertinent to the targeted breeding of fruit quality through an analysis of the genetic regulatory hierarchy governing pigment metabolism, environmental response mechanisms, and the correlation patterns between coloration and nutritional attributes. Furthermore, it aims to establish a theoretical framework to support the development and application of plant-derived bioactive compounds within the health industry.