Two New Antioxidant Phenylpropanoids from Lindelofia stylosa

Two new phenylpropanoids were isolated from Lindelofia stylosa ( Kar . and Kir .) and characterized as 4‐hydroxy‐ N ‐{4‐[( E )‐3‐(4‐hydroxy‐3‐methoxyphenyl)prop‐2‐enamido]butyl}benzamide ( 1 ) and 2‐[3‐hydroxy‐4‐(4‐hydroxyphenoxy)phenyl]‐1‐(methoxycarbonyl)ethyl ( E )‐3‐(3,4‐dihydroxyphenyl)prop‐2‐enoate ( 2 ). Four known compounds, i.e. two phenylpropanoids, p ‐coumaric acid (=( E )‐3‐(4‐hydroxyphenyl)prop‐2‐enoic acid; 3 ) and ferulic acid (=( E )‐3‐(4‐hydroxy‐3‐methoxyphenyl)prop‐2‐enoic acid; 4 ), and two naphthalene glycosides, 8‐ O ‐ β ‐ D ‐glucopyranosyltorachrysone ( 5 ) and 8‐ O ‐ β ‐ D ‐glucopyranosyl‐6‐demethoxytorachrysone ( 6 ), were also isolated for the first time from the plant. Compounds 1 – 6 were subjected to various antioxidant assays, including DPPH radical‐ and superoxide anion‐scavenging, and Fe 2+ ‐chelation assays. Compound 2 was found to be most active in all assays with potency nearly similar to that of propyl gallate. Besides 2 , compounds 1 and 5 were also found to be active in DPPH radical‐scavenging standard assay.