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

The alkamides profile in different structural parts of <i>Heliopsis longipes</i> 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 <i>N-</i>2-methylbutyl-2<i>E</i>,6<i>Z</i>,8<i>E</i>-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 <i>N-</i>2-methylbutyl-2<i>E</i>,6<i>Z</i>,8<i>E</i>-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 <i>H. longipes</i>, and to demonstrate their antioxidant properties. These results suggest that <i>H. longipes</i> is a valuable source of natural antioxidants with significant phytopharmaceutical potential.