Antioxidants from a heated histidine‐glucose model system. I: Investigation of the antioxidant role of histidine and isolation of antioxidants by high‐performance liquid chromatography

Abstract

The radical-combining activity of Maillard reaction products [MRP (aq) ], produced by heating D-glucose and Lhistidine (3:1) in a 0.1 M phosphate buffer for 10 h at 105°C (final pH 6.53), was estimated directly by means of a diphenylpicrylhydrazyl radical (DPPH • ) method. Additionally, the indirect methods of peroxide values changes (oven test), hexanal formation, and protection factors (Rancimat method) were determined on a lipid model system that consisted of sunflower seed oil/water (1:2), emulsified with 3% (w/w) Tween 40. Results from the DPPH • method showed a potential antioxidant activity of MRP (aq) , which was confirmed by the indirect methods. Surprisingly, histidine in solution alone (heated or not) exhibited an antioxidant activity greater than or similar to the MRP (aq) activity in the indirect methods with the lipid model system, in contrast to the results from the DPPH • method. The suitability of various solvents for extraction of potential antioxidant compounds from freeze-dried MRP (aq) was examined, and ethanol extracts showed the greatest activity by the DPPH • method. Consequently, the ethanol extract of freeze-dried MRP (aq) was separated by means of preparative reverse-phase high-performance liquid chromatography (HPLC) with a 0.05 M phosphate buffer (pH 4.4)/water/acetonitrile gradient system. The antioxidant activity of the eluate was measured through the DPPH • method, and a fraction (Fraction A) with antiradical activity was further purified by preparative HPLC. Fraction B was collected, and its freeze-dried residue exhibited potent antiradical activity, significantly greater than that of the same level of n-propyl gallate.

Water-soluble polysaccharides from Opuntia stricta Haw. fruit peels: recovery, identification and evaluation of their antioxidant activities

“…The ability of WSP to scavenge free radicals was determined using the synthetic free radical compound DPPH, according to (Bersuder et al, 1998) with slight modifications. Different amounts of WSP (3 mg to 50 mg) were prepared in 500 ml of distilled water, and then mixed with 125 ml of DPPH solution (0.02 % in ethanol) and 375 ml of absolute ethanol.…”

Production and Characterization of Melanin from Streptomyces Cavourensis Strain RD8 Using Response Surface Optimization

“…The antioxidant activity of the purified melanin was assessed by measuring the ability of melanin to scavenge 2, 2-diphenyl-1-picrylhydrazyl (DPPH) and hydrogen peroxide (H 2 O 2 ) radicals spectrophotometrically at 517 and 230 nm (Bersuder et al, 1998;Keser et al, 2014). Fe 2+ chelating activity of melanin was determined by measuring the percentage inhibition of ferrozine-Fe 2+ complex formation at 562 nm (Dinis et al, 1994).…”

Composition, functional properties and in vitro antioxidant activity of protein hydrolysates prepared from sardinelle (Sardinella aurita) muscle

“…The DPPH radical-scavenging activity of the hydrolysates was determined as described by Bersuder et al (1998). A volume of 500 μl of each sample at different concentrations (1 to 6 mg/ml) was mixed with 375 μl of 99.5% ethanol and 125 μl of 0.02% DPPH in 99.5% ethanol.…”