Abstract
Fine particulate matter (PM2.5) exposure worsens chronic respiratory diseases through oxidative stress and inflammation. Perilla frutescens (L.) has potential respiratory protective properties, but the impact of growth stages on its beneficial metabolites is unclear. We aimed to evaluate how different growth stages affect phenolic acids, flavonoids, and polycosanols in perilla seeds and flowers and their efficacy in countering PM2.5-induced damage. Perilla seeds and flowers from five varieties at 10, 20, 30, and 40 days post-flowering were analyzed for metabolite content. Their antioxidant, anti-inflammatory, and respiratory protective effects were tested in RPMI 2650 cells. Our findings indicated that perilla flowers contained higher levels of functional components than seeds and exhibited significant variation with maturation. Phenolic acids of perilla flowers were highest at the early stages of maturation after flowering. However, individual flavones of perilla flowers were the highest at the late maturation stages after flowering. Extracts from perilla flowers harvested 20 days after flowering exhibited significant respiratory protection, effectively inhibiting inflammatory cytokines, mucus secretion, and oxidative stress markers. In conclusion, the flower parts of perilla, particularly those harvested 20 days after flowering, are useful materials for obtaining phenolic compounds, including rosmarinic acid, with high antioxidant and respiratory enhancement effects.