Antioxidative compounds were isolated from the methanol extract of dry outer scales of onion (Allium
cepa L.). Nine phenolic compounds (1
−
9) were finally obtained by reversed-phase high-performance
liquid chromatography, and their structures were elucidated by NMR and mass spectrometry analyses.
They were the six known compounds, protocatechuic acid (1), 2-(3,4-dihydroxybenzoyl)-2,4,6-trihydroxy-3(2H)-benzofuranone (2), quercetin 4‘-O-β-d-glucopyranoside (3), quercetin (5), 4‘-O-β-d-glucopyranoside of quercetin dimer (7), and quercetin dimer (8), and three novel compounds,
condensation products of quercetin with protocatechuic acid (4), adduct of quercetin with quercetin
4‘-O-β-d-glucopyranoside (6), and quercetin trimer (9). These phenolic compounds were tested for
their antioxidant properties using autoxidation of methyl linoleate in bulk phase or free radical initiated
peroxidation of soybean phosphatidylcholine in liposomes. The flavonoid compounds having
o-dihydroxy substituent in the B-ring were shown to be effective antioxidants against nonenzymic
lipid peroxidation.
Keywords: antioxidant; flavonoid; quercetin; lipid peroxidation; onion; Allium cepa
Pronase-treated ovomucin was applied on a Sephacryl S-400 column
chromatography and separated
into five fractions. The SDS−polyacrylamide gel electrophoretic
pattern, and amino acid and
carbohydrate compositions, of each of the obtained fractions were
compared to those of ovomucin
and its α- and β-subunits. Subsequently, bindings of each
fraction to hen newcastle disease virus
(NDV) and anti-ovomucin antibodies were estimated. It was found
that the P1, P2, and P3 fractions
from the β-subunit which were composed of O-glycoproteins, containing
more or less clustered sialic
acid moieties, had higher binding activity to NDV, while the
peptide-rich P4 and P5 fractions mainly
derived from the α-subunit had higher binding activity to the
anti-ovomucin antibodies.
Keywords: Ovomucin; newcastle disease virus; Pronase treatment
Glycosidically bound compounds were isolated from the methanol extract of fresh rhizomes of smaller galanga (Alpinia officinarum Hance). Nine glycosides (1-9) were finally obtained by reversed-phase HPLC and their structures were elucidated by MS and NMR analyses. They were the three known glycosides, (1R,3S,4S)-trans-3-hydroxy-1,8-cineole beta-D-glucopyranoside (1), benzyl beta-D-glucopyranoside (3), and 1-O-beta-D-glucopyranosyl-4-allylbenzene (chavicol beta-D-glucopyranoside, 4); and the six novel glycosides, 3-methyl-but-2-en-1-yl beta-D-glucopyranoside (2), 1-hydroxy-2-O-beta-D-glucopyranosyl-4-allylbenzene (5), 1-O-beta-D-glucopyranosyl-2-hydroxy-4-allylbenzene (demethyleugenol beta-D-glucopyranoside, 6), 1-O-(6-O-alpha-L-rhamnopyranosyl-beta-D-glucopyranosyl)-2-hydroxy-4-allylbenzene (demethyleugenol beta-rutinoside, 7), 1-O-(6-O-alpha-L-rhamnopyranosyl-beta-D-glucopyranosyl)-4-allylbenzene (chavicol beta-rutinoside, 8), and 1,2-di-O-beta-D-glucopyranosyl-4-allylbenzene (9). Compounds 2-9 were detected for the first time as constituents of galanga rhizomes.
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