Protein‐precipitating capacity of crude condensed tannins of canola and rapeseed hulls

Abstract

The protein-precipitating potentials (PPP) of soluble condensed tannins (SCT) were determined in hulls from several samples of canola and rapeseed varieties. The PPP were expressed as slopes of lines (titration curves) reflecting the amount of SCT-protein precipitated vs. the amount of SCT added to the reaction mixture. The slopes (S p ) of titration curves obtained using the protein-precipitation assay ranged from 2.96 to 10.91 (absorbance units at 510 nm per mg SCT), and those of titration curves, obtained using the dye-labeled bovine serum albumin (BSA) assay (S d ), ranged from 28.1 to 267 (% precipitated BSA per mg SCT). For both assays, a statistically significant (P ≤ 0.001) semilogarithmic linear correlation existed between the slopes and the SCT contents in the canola and rapeseed hulls. Higher amounts of SCT-protein complexes were precipitated at 40°C than at room temperature. Determination of titration curves under standardized conditions (type and concentration of protein, pH and temperature) afforded meaningful differences in the slopes among the range of SCT extracts from canola and rapeseed hulls used in this study. FIG. 3. Effect of protein concentrations on the slope values (S p and S d ) of titration curves obtained by using (A) PPA and (B) DLPA. SCT were extracted from Cyclone canola hulls, sample 5. For symbols and abbreviations see Figures 1 and 2.

Protein-precipitating capacity of bearberry-leaf (Arctostaphylos uva-ursi L. Sprengel) polyphenolics

“…This suggests that the polyphenol-protein interactions can be affected by the nature of proteins involved. The relative affinities of the PP in both the bearberry-leaf crude extract and fraction I are somewhat lower than those reported by Asquith and Butler (1985) for sorghum and quebracho CTs, by Naczk et al (2001aNaczk et al ( , 2001b for CTs from canola hulls, beach pea, evening primrose, and faba beans, as well as by Naczk et al (2006) for PP extracts from blueberry leaves. This may be affected by the chemical structures and molecular weights of the PP present in the investigated samples.…”

“…A series of methanolic solutions of PP extract/fractions (0.1-2.0 mg/ mL) were prepared. The protein-precipitating potential of phenolic extracts was expressed as the slope of the line reflecting the amount of PP-protein complex precipitated vs. the amount of total phenolics added (Naczk, Amarowicz, Zadernowski, & Shahidi, 2001a, 2001b. The amount of precipitated PP-protein complex, measured by the protein precipitation method of Hagerman and Butler (1978), was expressed as absorbance units at 510 nm, A 510 , per assay.…”

Radical scavenging activity of canola hull phenolics

“…Dye-labeled protein assay. The effect of phenolic extract concentrations on the formation of insoluble phenolic-protein complexes was determined by the dye-labeled BSA assay as described by Naczk et al (9). A series of methanolic solutions of extracts (0.1 to 2.0 mg/mL) were prepared.…”

Antioxidant Capacity of Phenolics from Canola Hulls as Affected by Different Solvents

“…The protein precipitating capacity of phenolic extracts was determined as described by Naczk et al (17). The protein precipitating potential of phenolics in the extracts was estimated using the protein precipitation assay of Hagerman and Butler (18) and the dye-labeled bovine serum albumine (BSA) assay of Asquith and Butler (19) as modified by Naczk et al (20).…”

“…The protein precipitation potential of phenolic extracts from canola hulls was expressed as the slopes of lines (titration curves) depicting the amount of phenolic-protein complex precipitated as a function of the amount of extract added to the reaction mixture. According to Naczk et al (20) the slope of the titration curve is a more meaningful measure of protein-precipitating potential of plant phenolics extracts than the measurement carried out at one nonstandardized phenolic/protein ratio (18,19). The numerical values of the slope of titration curves are shown in Table V.…”