RESUMO
The essential oil (EO) of clove bud dried fruits from Eugenia caryophyllus was obtained by a conventional hydrodistillation process in an excellent yield (11.7 %). Its chemical composition was analyzed by GC-MS, identifying eugenol as a main constituent (60.5%). Four eugenol-like molecules, γ-diisoeugenol, hydroxymethyleugenol, dihydroeugenol and 1,3-dioxanylphenol, were synthesized using eugenol or isoeugenol as initial precursors under green chemistry protocols. To evaluate the possible antioxidant capacity of eugenol compounds including the clove bud EO, the Trolox® Equivalent Antioxidant Capacity value, obtained by the ABTS(+â¢) radical-cation discoloration method, was employed. The methodology was performed in a UV-Vis reader of 96-well microplates (dilution methodology), using well-known antioxidant agents (BHA, BHT and vitamin E) as reference compounds. It was found that the prepared eugenol derivatives had a more potent free radical scavenger activity than the reference compounds. In particular, the most active molecules, γ-diisoeugenol and 1,3-dioxanylphenol, were ca. 3-fold more potent than vitamin E.
RESUMO
Efficient synthesis of new structurally different 2-(het)aryl-4-amidyl-substituted tetrahydroquinolines 8-29 is reported. The synthesis based on BiCl(3)-catalyzed three-component Povarov reaction between anilines, (het)aryl aldehydes and enamides offers a fast, safe, and cheap way for efficient tetrahydroquinoline libraries construction. Using N-vinylamides (N-vinylpyrrolidin-2-one and N-vinylacetamide) in this reaction, it was possible to obtain two series of different cis tetrahydroquinolines with antioxidant properties. Among 14 tested compounds, 7 tetrahydroquinolines revealed a prominent anti-radical capacity, equal or higher than that of the commercial antioxidants. Being the most active molecule, the N-[2-(α-furanyl)-6-methoxy-1,2,3,4-tetrahydroquinolin-4-yl] acetamide 21 was ca. 2.2-fold more potent than the well-known antioxidant, vitamin E (α-tocopherol).
