Mahinda Wettasinghe

Antioxidant and free radical-scavenging properties of ethanolic extracts of defatted borage (Borago officinalis L.) seeds

Borage meal exerted a concentration-dependent antioxidant activity in a meat model system. At 2% (w/w), it inhibited (p≤0.05) 2-thiobarbituric acid-reactive substances (TBARS), hexanal and total volatile formation in meat by 26.5, 30.5 and 18.6%, respectively. Antioxidant compounds in the meal were concentrated at optimum extraction conditions (in 52% ethanol at 74°C for 62 min) predicted by response surface methodology (RSM). The resulting extract inhibited (p⩽0.05) the coupled oxidation of β-carotene and linoleate in a β-carotene-linoleate system. The system containing extract at a level providing 200 ppm phenolics retained 81% of the initial β-carotene after 2 h of assay whereas the control retained only 11%. Inhibition (p⩽0.05) of TBARS, hexanal and total volatile formation in a meat system containing 200 ppm extract ranged from 18.9 to 88.3%, depending upon the concentration being tested. The extract inhibited (p⩽0.05) conjugated diene, hexanal and total volatile formation in bulk corn oil (8.3–49.6% inhibition) and corn-oil-in water emulsion (5.2–32.2% inhibition). Hydrogen peroxide, hydroxyl radical and superoxide radical-scavenging properties of the extract were somewhat less than, but comparable to, those observed for trans-sinapic acid at similar concentrations of phenolics. At 200 ppm, a 100% quenching of the hydroxyl radical and superoxide radical was evident. The extract scavenged 29–75% of the hydrogen peroxide in assay media after 10 min of assay as compared to 3% reduction in the control.

Scavenging of reactive-oxygen species and DPPH free radicals by extracts of borage and evening primrose meals.

Crude extracts of meals of borage and evening primrose were prepared under optimum extraction conditions and were subjected to Sephadex LH-20 column chromatography. Six fractions from each of the crude extracts were obtained and their content of total, hydrophilic and hydrophobic phenolics determined. The crude extracts and their fractions [at 100 and 200 ppm as sinapic acid (for borage) or catechin (for evening primrose) equivalents] were investigated for their reactive-oxygen species- (ROS; H2O2, O2•-, •OH) and 2,2-diphenyl-1-picrylhydrazyl- (DPPH•) scavenging efficacies. Both types of crude extracts and their fractions exerted a concentration-dependent scavenging of ROS and DPPH•. At 200 ppm, borage crude extract and its fractions III, IV and V exhibited a 100% scavenging of H2O2 whereas evening primrose crude extract and its fraction III, at the same concentration, scavenged H2O2 completely. A complete quenching of O2•- was evident for assay media containing 200 ppm borage and evening primrose crude extracts/fractions with the exception of borage fraction V and evening primrose fraction I which showed about 75% quenching. At 200 ppm, borage and evening primrose crude extracts/fractions (except borage fractions I and III) exerted a complete quenching of •OH. Among the borage and evening primrose crude extracts/fractions investigated, only fraction VI of evening primrose, at 200 ppm, was able to completely quench DPPH•.

Phenolic acids in defatted seeds of borage (Borago officinalis L.)

Abstract An ethanolic extract of borage meal was fractionated (fractions I–VI) on a Sephadex LH-20 column. All fractions tested positive for phenolics, but were negative for condensed tannins. Silica gel thin-layer chromatography (TLC) of fractions allowed the location of one and two strong antioxidative spots in fractions I and IV, respectively. Other fractions produced spots containing either weak antioxidative compounds or compounds with low concentrations. High performance liquid chromatography of the three major TLC spots in fractions I and IV showed the presence of one phenolic compound in each spot. Ultraviolet, proton nuclear magnetic resonance and proton-proton correlation spectroscopies, as well as electron impact-mass spectrometry, allowed the identification of three phenolic acids, namely rosmarinic acid in fraction I, and syringic and sinapic acids in fraction IV. These three compounds contributed to 3.9% of the dry mass of the crude extract whereas their total contribution in the meal was 0.6% (w/w).

Iron (II) chelation activity of extracts of borage and evening primrose meals

Crude extracts of borage and evening primrose meals were prepared and fractionated using a Sephadex LH-20 column. Each extract yielded six major fractions (I–VI). Content of total phenolics in borage and evening primrose fractions ranged from 129 to 366 and 158 to 445 mg/g, respectively. All fractions contained both hydrophilic and hydrophobic phenolics. They possessed excellent iron (II) chelating capacities, which ranged from 33 to 100% for borage and 36 to 100% for evening primrose.

Antioxidant activity of preformed cooked cured-meat pigment in a β-carotene/linoleate model system

Abstract Antioxidative efficacy of preformed cooked cured-meat pigment (CCMP, at concentrations of 2.2, 6.2 and 10.0 μM) was investigated in a β-carotene/linoleate model system. Results were compared to those for butylated hydroxyanisole (BHA), metmyoglobin (MMb) and nitrosylmyoglobin (NOMb) at the same concentrations of 2.2, 6.2 and 10.0 μM. CCMP at a concentration of 2.2 μM exhibited a pro-oxidant effect, but at 6.2 and 10 μM it exhibited a significant ( P