Huajuhong (Citri grandis Exocarpium): Phytochemistry, bioactivities, functional food development, and artificial intelligence-driven strategies

Background: Huajuhong, recorded in the Chinese Pharmacopoeia as Citri Grandis Exocarpium (CGE), is the dried exocarp of immature or nearly mature fruits of Citrus grandis ‘Tomentosa’ or C. grandis (L.) Osbeck and has long been used in China as a medicinal and edible resource, particularly for respiratory care. Growing interest in natural functional ingredients and precision health has increased attention to Huajuhong as a multifunctional raw material. Scope and approach: This review summarizes the botanical characteristics, phytochemical composition, processing and extraction technologies, health-related effects, safety, and current applications of Huajuhong. Particular attention is also given to the emerging role of artificial intelligence (AI) in raw-material standardization, quality control, bioactive screening, mechanism prediction, and process optimization. Key findings and conclusions: Huajuhong contains diverse bioactive compounds, mainly flavonoids, volatile oils, polysaccharides, coumarins, and limonoids, and its composition is strongly affected by germplasm source, geographical origin, developmental stage, processing, and storage. Available in vitro and in vivo studies indicate that Huajuhong exhibits respiratory-protective, antioxidant, anti-inflammatory, immunomodulatory, antimicrobial, and metabolic regulatory activities, largely through the regulation of oxidative stress, inflammatory signaling, and host metabolism. These properties support its application in teas, functional beverages, lozenges, oral formulations, and other health-oriented products. However, its utilization is still limited by raw-material heterogeneity, insufficient standardization, limited human evidence, unclear dose–effect relationships, and inadequate validation in real food matrices. Future studies should prioritize standardized grading, deeper composition–function analysis, and clinical validation, while integrating AI and Food Industry 4.0 technologies to support the evidence-based and application-oriented development of Huajuhong as a high-value functional food and health resource.