Plant-derived antioxidants: Biosynthesis, refining and applications

With increasing awareness of health-oriented antioxidant diets, plant-derived antioxidants (PDAs) such as polyphenolics, terpenoids, vitamins, alkaloids and saponins, are promising alternatives to synthetic antioxidants (SAs). PDAs boost human immunity and health by scavenging reactive oxygen species, activating endogenous antioxidant defenses, and reducing oxidative cell damage. As a result, they are widely used in preventing and treating oxidative stress-related chronic diseases, including neurodegenerative diseases (NDDs), viral diseases, cardiovascular diseases (CVDs), and diabetes, as well as certain cancers. Moreover, due to their antioxidant, coloring and preservative effects, PDAs are utilized in food industry to extend shelf-life, improve food quality and inhibit pathogenic microorganisms. However, obtaining high-quality PDAs remains challenging because of their low natural abundance, complex impurities, poor stability, and prone to contamination and deterioration during isolation. This review highlights recent advances in the classification, sources, antioxidation, biosynthesis and regulation, as well as extraction and refining of PDAs. Their functional applications are summarized in two aspects: (i) as food additives (e.g. antioxidants, colorants and preservatives) to reduce potential risk of SAs and enhance food value-added; and (ii) as biomedicines (with anti-inflammatory, anti-NDDs, antiviral, anticancer, anti-CVDs and anti-diabetic effects), providing new strategies for chronic-disease prevention through multi-target regulation of oxidative-stress pathways. Integration of synthetic biology, green purification and nano-delivery is envisioned to overcome industrial challenges of PDAs, offering new insights for their precise design and versatile application in the healthcare and food industries.