Antioxidative properties of ascorbigen in using multiple antioxidant assays

Figures & data

Fig. 1. Chemical structures of indole-derived compounds, ascorbic acid, and AA-2G.

Fig. 2. Time courses of DPPH radical (A)-, galvinoxyl radical (B)-, and ABTS^•+ (C)-scavenging reactions of ascorbigen, ascorbic acid, and AA-2G.

Notes: Ascorbigen (

), ascorbic acid (○), and AA-2G (

) (each 20 μM) or control (∆) and DPPH radical (100 μM) were incubated at room temperature in 60% ethanol/40% citrate buffer (10 mM, pH 6). Ascorbigen, ascorbic acid, and AA-2G (each 2 μM) or control and galvinoxyl radical (10 μM) were incubated at room temperature in 60% ethanol/40% citrate buffer. A sample (20 μM) or control and ABTS^•+ (100 μM) were incubated at room temperature in citrate buffer (50 mM, pH 6). Changes in the remaining radicals were measured at the indicated times. Each value is the mean ±SD of three separate experiments. Absence of the SD bar means that the SD bar is within the symbol.

Fig. 3. HPLC chromatograms of the reaction product of ascorbigen with ABTS^•+.

Notes: Ascorbigen (200 μM) and ABTS^•+ (1.0 mM) were incubated in citrate buffer (50 mM, pH 6). At 30, 60, and 120 min, aliquots of the reaction mixture were withdrawn and analyzed by HPLC.

Fig. 4. Time courses of ABTS^•+-scavenging reactions of ascorbigen, 3-methylindole, indole-3-aldehyde, and ascorbic acid.

Notes: Ascorbigen (

), ascorbic acid (○), 3-methylindole (

), and indole-3-aldehyde (□) (each 20 μM) or control (∆) and ABTS^•+ (100 μM) were incubated at room temperature in 0.2% ethanol/citrate buffer (50 mM, pH 6). Changes in the remaining radicals were measured at the indicated times. Each value is the mean ±SD of three separate experiments. Absence of the SD bar means that the SD bar is within the symbol.

Fig. 5. ORAC assay (A) and OxHLIA (B) for ascorbigen, ascorbic acid, AA-2G, and Trolox.

Notes: ORAC assay (A) reaction mixtures containing ascorbigen (

), ascorbic acid (○), AA-2G (

), and Trolox (●) (each 10 μM) or control (∆), fluorescein (60 nM) and AAPH (18.75 mM) in 200 μL of phosphate buffer (75 mM, pH 7.4) were incubated at 37 °C for 90 min. Changes in fluorescence intensity of fluorescein were monitored. Each value is the mean ±SD of three separate experiments. Absence of the SD bar means that the SD bar is within the symbol. OxHLIA (B) reaction mixtures containing ascorbigen (

), ascorbic acid (○), AA-2G (

), and Trolox (●) (each 50 μM) or control (∆), sheep erythrocytes (0.7%, v/v) and AAPH (40 mM) in 200 μL of PBS were incubated at 37 °C for 280 min. Changes in remaining rate of erythrocytes were monitored. Each value is the mean ±SD of three separate experiments. Absence of the SD bar means that the SD bar is within the symbol.

Fig. 6. HPLC chromatograms of the reaction products of ascorbigen with AAPH-derived radicals.

Notes: Ascorbigen (200 μM) and AAPH (40 mM) were incubated in PBS at 37 °C with shaking. At 30, 60, and 120 min, aliquots of the reaction mixture were withdrawn and analyzed by HPLC.