| Résumé | Phenolic compounds in Commander, Majak and Valley sunflowers varied between 3.0 and 3.5g of chlorogenic acid per 100 g of flour. Under neutral and alkaline conditions, sunflower protein solutions develop dark green and brown colors because of bonding with oxidation products of polyphenolic compounds, especially chlorogenic acid. Therefore, a reducing agent was utilized in the present study to inhibit the formation of covalent bonds but 30% of the chlorogenic acid was non-dialyzable and remained bound to the flour constituents. About one-half of the phenolic constituents were extracted with the soluble sunflower proteins by neutral salt solutions and about one-third of this fraction was also nondialyzable.
Fractionation of the neutral salt extracts revealed that all of the soluble chlorogenic acid was associated with the low molecular weight components (mol wt ≤5000) in the third fraction on Sephadex G-25 and fraction V in sephadex G-200 chromatography. the elution behavior on Sephadex gels, the low nitrogen contents, and the low amino acid recoveries demonstrated that these fractions were polypeptides and oligonucleotides. Rechromatography of fraction V on Sephadex G-200 in the presence of a strong hydrogen bonding agent, 7 M urea, revealed that 68% of the salt-soluble polypeptides were hydrogen bonded and about 32% were apparently covalent bonded to chlorogenic acid in Commander sunflower. |
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