Investigation of Helichrysum paronychioides afforded a total of nine compounds: 4 phloroglucinol derivatives, 2 of which are novel natural products, and 5 flavone derivatives. Structures were established by various spectroscopic techniques (NMR, MS, UV, IR, CD) and by comparison with literature data for the known compounds. The four phloroglucinols, trans-(2R,3R)-5,7-dihydroxy-2,3-dimethyl-4-chromanone (1), 2-butanoyl-4-prenyl-1-methoxy phloroglucinol (2), 2-(2-methylpropanoyl)-4-prenylphloroglucinol (3) and 2-(2-methyl- butanoyl)-4-prenylphloroglucinol (4) were screened for antioxidant activity against Cu-induced LDL oxidation. Compound 4 was found to be the most active inhibiting LDL oxidation at all concentrations (0.5-10 μM) while the other three showed moderate to no activity.
KEY WORDS: Helichrysum paronychioides, Asteraceae, Phloroglucinol derivatives, CD spectroscopy, Synthesis
Bull. Chem. Soc. Ethiop. 2006, 20(1), 61-68.