Valorisation of marigold floral waste for essential oil extraction and its application in stabilisation of PUFA rich perilla seed oil

Marigold, a culturally important ornamental flower in India, substantial quantities of floral waste that are often improperly discarded, causing environmental burden. Rich in carotenoids, flavonoids, and antioxidants, this waste represents an underutilized bioresource with preservative potential. This study valorized marigold waste by extracting essential oil via hydro-distillation (HD) combined with green pretreatments, namely ultrasound (US), freeze-thaw (FT), and solvent-free microwave extraction (SFME). HD + US and HD + FT increased oil yield by 25% and 17%, respectively, whereas SFME gave 85.3% lower yield than HD. Chromatographic profiling showed high levels of bioactives such as β-caryophyllene, piperitone, tagetone, ocimene, nootkatone, limonene, and isoeugenol, especially in HD-based oils. Antioxidant efficacy of marigold essential oil (MEO) was assessed for stabilizing PUFA-rich perilla seed oil (500, 1000 and 1500 ppm MEO). Across all oxidation indices and antioxidant assays, MEO showed strong protective effects, with 1500 ppm MEO achieving oxidative stability close to that of 200 ppm TBHQ. Hierarchical Cluster Analysis grouped control and 500 ppm samples as low stability while TBHQ and 1500 ppm as high stability. These findings establish marigold waste as a promising source of natural antioxidants for edible oil preservation, supporting sustainable waste management and safer food systems.