Alkamides profile by HP-TLC and GC-EIMS in different structural parts from Heliopsis longipes flower-head and in vitro antioxidant activity

The alkamides profile in different structural parts of Heliopsis longipes flower-head by HP-TLC/GC-EIMS analysis, the free radical scavenging activity assessment (FRSAA), and total antioxidant capacity (TAC) were studied. HP-TLC and GC-EIMS detected two olefinic alkamides, the affinin, and N-2-methylbutyl-2E,6Z,8E-decatrienamide, in specific flower-head structures, mainly in the palea. Quantitative analysis showed affinin as the predominant alkamide, reaching 1.60 mg/g in fresh tissue, followed by N-2-methylbutyl-2E,6Z,8E-decatrienamide (0.16 mg/g). In laboratory tests assessing antioxidant capacity, affinin demonstrated 1.16 times greater FRSSA and 1.48 times higher total antioxidant capacity compared to flower-head extracts. This study is the first to identify alkamides, particularly affinin, in the flower-heads of H. longipes, and to demonstrate their antioxidant properties. These results suggest that H. longipes is a valuable source of natural antioxidants with significant phytopharmaceutical potential.