Ferulic acid dehydrodimers from wheat bran: isolation, purification and antioxidant properties of 8-O-4-diferulic acid.
Wheat bran contains several ester-linked dehydrodimers of ferulic acid, which were detected and quantified after sequential alkaline hydrolysis. The major dimers released were: trans-5-[(E)-2-carboxyvinyl]-2-(4-hydroxy-3-methoxy-phenyl)-7-methoxy-2, 3- dihydrobenzofuran-3-carboxylic acid (5-8-BendiFA), (Z)-beta-[4-[(E)-2-carboxyvinyl]-2-methoxyphenoxy]-4-hydroxy-3-methox ycinnamic acid (8-O-4-diFA) and (E,E)-4,4'-dihydroxy-5,5'-dimethoxy-3,3'-bicinnamic acid (5-5-diFA). trans-7-hydroxy-1-(4-hydroxy-3methoxyphenyl)-6-methoxy-1,2-dihydro - naphthalene-2,3-dicarboxylic acid (8-8-diFA cyclic form) and 4,4'-dihydroxy-3,3'-dimethoxy-beta,beta'-bicinnamic acid (8-8-diFA non cyclic form) were not detected. One of the most abundant dimers, 8-O-4-diFA, was purified from de-starched wheat bran after alkaline hydrolysis and preparative HPLC. The resultant product was identical to the chemically synthesised 8-O-4-dimer by TLC and HPLC as confirmed by 1H-NMR and mass spectrometry. The absorption maxima and absorption coefficients for the synthetic compound in ethanol were: lambda max: 323 nm, lambda min: 258 nm, epsilon lambda max (M-1 cm-1): 24,800 +/- 2100 and epsilon 280 (M-1 cm-1): 19,700 +/- 1100. The antioxidant properties of 8-O-4-diFA were assessed using: (a) inhibition of ascorbate/iron-induced peroxidation of phosphatidylcholine liposomes and; (b) scavenging of the radical cation of 2,2'-azinobis (3-ethyl-benzothiazoline-6-sulphonate) (ABTS) relative to the water-soluble vitamin E analogue, Trolox C. The 8-O-4-diFA was a better antioxidant than ferulic acid in both lipid and aqueous phases. This is the first report of the antioxidant activity of a natural diferulate obtained from a plant.
Garcia-Conesa
M T
MT
Biochemistry Department, Institute of Food Research, Norwich, UK.
Plumb
G W
GW
Waldron
K W
KW
Ralph
J
J
Williamson
G
G
D000975:Antioxidants / Q000302:isolation & purification* / Q000494:pharmacology; D001547:Benzaldehydes / Q000302:isolation & purification / Q000494:pharmacology; D002851:Chromatography, High Pressure Liquid; D002934:Cinnamates / Q000737:chemistry / Q000302:isolation & purification* / Q000494:pharmacology*; D003373:Coumaric Acids / Q000302:isolation & purification / Q000494:pharmacology; D004043:Dietary Fiber / Q000032:analysis*; D019281:Dimerization; D016166:Free Radical Scavengers / Q000737:chemistry / Q000302:isolation & purification* / Q000494:pharmacology; D015227:Lipid Peroxidation / Q000187:drug effects*; D008081:Liposomes; D013058:Mass Spectrometry; D019906:Nuclear Magnetic Resonance, Biomolecular
C114889:8-O-4-diferulic acid; D000975:Antioxidants; D001547:Benzaldehydes; D002934:Cinnamates; D003373:Coumaric Acids; D004043:Dietary Fiber; D016166:Free Radical Scavengers; D008081:Liposomes; C004999:ferulic acid; C100058:vanillin