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Open access

Magdalena Karamać, Anna Kulczyk and Katarzyna Sulewska

Abstract

Proteins were isolated from defatted flaxseed cake and hydrolysed with pancreatin. The hydrolysis process was conducted at a stable temperature of 50°C and pH 7.5, and monitored with the pH-stat method. The obtained hydrolysates with a degree of hydrolysis (DH) of 5, 10, 15, 20, 25% were investigated in terms of antioxidant properties. The radical scavenging activity was assayed against DPPH· and ABTS·+, the reducing ability - with FRAP assay, and the capability to bind Fe(II) - by reaction with ferrozine. SE-HPLC analysis was used to determine molecular weight distribution of hydrolysis products.

The antiradical activity of pancreatin hydrolysates of flaxseed proteins was increasing along with an increasing DH and for the hydrolysate with DH 25% the EC50 value determined with the DPPH assay accounted for 0.083 mg/assay, and the ABTS·+ scavenging activity - for 0.218 mmol Trolox/g. This hydrolysate was constituted mainly by peptides with low molecular weights (MW) of 0.238-0.556 kDa. In turn, the Fe(II) binding capability increased from 44.5% to 64.9% in the case of hydrolysates with DH 5-20% and decreased in the case of the hydrolysate with DH 25%. A similar de-pendency was observed in the ability of pancreatin hydrolysates of flaxseed proteins to reduce Fe(III). The maximum value of reducing ability reached 0.25 mmol Fe(II)/g for the hydrolysate with DH 20% that was predominated by polypeptides and peptides with MW of 0.238-1.046 Da.

Open access

Magdalena Karamać, Izabela Biskup and Anna Kulczyk

Abstract

Five fractions of phenolic compounds were obtained from the extract of common buckwheat seed (Fagopyrum esculentum Moench) using Sephadex LH-20 column chromatography with methanol as a mobile phase. The total phenolics content ranged from 19.8±1.5 (fraction I) to 164±2.2 mg (+)-catechin eq/g (fraction IV). The profiles of phenolic acids and flavonoids in the fractions were analysed using RP-HPLC-DAD. The antioxidant activity was tested as ABTS⋅+ and DPPH scavenging activity and capability to reduce the Fe(III)/2,4,6-Tris(2-pyridyl)-s-triazine complex to the ferrous form. Results were expressed as Trolox equivalent antioxidant capacity (TEAC), IC50 and ferric reducing antioxidant power (FRAP) values, respectively. The highest antioxidant activity was noted for fraction IV that was predominated by flavones. TEAC, IC50 and FRAP values were: 1.47±0.01 mmol Trolox eq/g, 0.058±0.003 mg/assay and 2.18±0.05 mmol Fe(II)/g, respectively. Rutin constituted 77.7% of the compounds identified in fraction III. The antiradical activity and reducing capability of this fraction were lower compared to fraction IV, but significantly higher than in fractions I and II. The main phenolic compounds of fractions I and II were phenolic acids (caffeic, 5-O-caffeoylquinic and p-coumaric). The antioxidant activity of fraction V was similar to that of fraction III.

Open access

Agnieszka Kosińska, Anna Urbalewicz, Kamila Penkacik, Magdalena Karamać and Ryszard Amarowicz

SE-HPLC-DAD Analysis of Flaxseed Lignan Macromolecule and its Hydrolysates

A lignan macromolecule (LM) was extracted from defatted flaxseeds using an ethanol-dioxan system (1:1, v/v) and purified using Amberlite column chromatography with water and methanol as mobile phases. The LM was subjected to chemical hydrolysis (base, acid, base & acid), as well as to enzymatic processing using pepsin, pancreatin, cellulase, and β-glucuronidase.

The study revealed that lignan macromolecule in flaxseed was not homogenous. The chemical hydrolysis as well as enzymatic treatment using β-glucuronidase and cellulase released low molecular phenolic compounds from the lignan macromolecule. The liberation of secoisolariciresinol (SECO) and free phenolic acids (p-coumaric and ferulic acids) from flaxseed lignan macromolecule as a result of the base and acid hydrolyses was noted. The application of pepsin and pancreatin did not change the composition of the lignan macromolecule.

Open access

Hakime Hülya Orak, Magdalena Karamać, Adnan Orak and Ryszard Amarowicz

Abstract

The antioxidant potential and phenolic compounds content were investigated in ten white bean varieties widely consumed in Turkey. Total phenolic contents of seeds varied between 0.33 and 0.63 mg GAE/g. The Trolox Equivalent Antioxidant Capacity (TEAC) determined by the ABTS assay and the Ferric-Reducing Antioxidant Power (FRAP) of bean varieties ranged from 3.50 to 5.17 μmol Trolox/g seed and from 7.99 to 11.20 μmol Fe2+/g seed, respectively. Strong correlations were found between total phenolic content and FRAP (r=0.850) and between TEAC and FRAP (r=0.734). The antioxidant activity was investigated in a β-carotene-linoleic acid model system, as well. Differences in the inhibition of emulsion oxidation by extracts of white bean varieties were slight. The RP-HPLC fingerprint analysis of extracts showed the presence of five dominant phenolic compounds which were described as ferulic or caffeic acids derivatives. Four of them significantly contributed to reducing power and antiradical activity against ABTS•+ of extracts.

Open access

Michał A. Janiak, Adriana Slavova-Kazakova, Vessela D. Kancheva, Milena Ivanova, Tsvetelin Tsrunchev and Magdalena Karamać

Abstract

The presented study revealed that there were changes in the phenolic compounds profile of extract of wild thyme (Thymus serpyllum L.) after γ-irradiation at the dose of 5 kGy. Ethanolic extracts of irradiated and non-irradiated herb were prepared and their compounds were analyzed by RP-HPLC-DAD technique. Between thirty two detected constituents, twelve phenolic compounds classified as hydroxybenzoic and hydroxycinnamic acids derivatives, flavones and flavanones were identified. Among them, caffeic acid derivatives and flavones predominated with the highest content of rosmarinic acid and luteolin-7-O-glucoside, respectively. Additionally, thymol was recognized in the analyzed extracts. γ-Irradiation slightly affected the quantitative profile of phenolic compounds of a wild thyme ethanolic extract. Only four constituents differed significantly (P<0.05) in terms of their content in the irradiated and non-irradiated samples. The content of phenolic acids (p-coumaric and caffeic acids) decreased and that of flavonoid aglycons (luteolin and eriodictyol) increased after the γ-ray treatment.