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-beta-D-glucopyranosyltorachrysone (5) and 8-O-beta-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.