L. Saulnier et al., ISOLATION AND PARTIAL CHARACTERIZATION OF FERULOYLATED OLIGOSACCHARIDES FROM MAIZE BRAN, Carbohydrate research, 272(2), 1995, pp. 241-253
Maize bran contains phenolic acids [similar to 4% dry matter; mainly f
erulic acid (Fe) and also diferulic acid], heteroxylans (similar to 50
%), and cellulose (similar to 20%), but is devoid of lignin. Treatment
of maize pericarp with 0.05 M trifluoroacetic acid at 100 degrees C f
or 2 h released similar to 90% of the heteroxylans and similar to 90%
of the ferulic acid and its esters. After fractionation of the product
s with Amberlite XAD-2 and Sephadex LH-20 three main feruloylated olig
osaccharides (F-3-F-7) were isolated. They represented similar to 30%
of the ferulic acid, and similar to 2% of the neutral sugars contained
in the hydrolysis supernatant. The compositions of F-7, F-6, and F-3
were Fe-Ara (1:1), Fe-Ara-Xyl (1:1:1), and Fe-Ara-Xyl-Gal (1:1:1:1), r
espectively. The structures of the three oligomers were determined usi
ng chemical methods (methylation, acetalation, reduction) and C-13 NMR
spectroscopy: F-7 was 5-O-(trans-feruloyl)-L-Araf; F-6 was O-beta-D-X
ylp-(1 --> 2)-[5-O-(trans-feruloyl)L-Araf]; and F-3 was O-L-Galp-(1 --
> 4)-O-D-Xylp-(1 --> 2)-[5-O-(trans-feruloyl)-L-Araf]. F-7 has been pr
eviously isolated from other monocots especially from wheat bran and s
oluble arabinoxylans from wheat flour; this is the first report of fer
uloylated oligosaccharides F-6 and F-3. Our results suggest that these
oligomers are side-chain constituents of heteroxylans in maize bran.
Ferulic acid is probably partly responsible for the insolubility of he
teroxylans by coupling polysaccharide chains through ferulic acid dime
rs.