Antioxidant Flavonoids from the Twigs of Stewartia koreana

Abstract

-In the course of screening for antioxidant compounds by measuring the radical scavenging effect on 1,1-diphenyl-2-picrylhydrazyl (DPPH), a total extract of the twigs of Stewartia koreana (Theaceae) was found to show potent antioxidant activity. Subsequent activity-guided fractionation of the methanolic extract led to the isolation of six phenolic compounds, ampelopsin (1), catechin (2), proanthocyanidin-A2 (3), fraxin (4), (2R, 3R)-taxifolin-3-β-D-glucopyranoside (5), and (2S, 3S)-taxifolin-3-β-D-glucopyranoside (6), as active principles. Their structures were elucidated by spectroscopic studies. Compounds 1-6 were isolated for the first time from this plant. Among them, three compounds 1-3 showed the significant antioxidative effects on DPPH, and riboflavin originated superoxide quenching activity. In riboflavin-nitrobluetetrazolium (NBT)-light system, compound 1 showed better superoxide quenching activity than vitamin C.

Antioxidative phenolic compounds from the whole plant of Juncus diastrophanthus

“…In the course of screening for antioxidant components from Korean natural plants Kim, 2009;Lee et al, 2009;Lee et al, 2010], the EtOAc-and n-BuOH-soluble fractions of methanolic extract of the whole plant of J. diastrophanthus were found to show scavenging activity on the DPPH radical (Fig. 1).…”

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“…·O 2 − can catalytically reduce NBT to form formazan with maximum absorption at 560 nm. Therefore, the ·O 2 − scavenging activity of inhibitors was determined by assessing the inhibition on formazan formation [ 64 , 65 , 66 ]. As demonstrated in Figure 5 b, the absorbance of the control group increased with the duration of illumination, implying the production of ·O 2 − .…”

“…Superoxide radical (·O 2 − ) was produced by reoxidation of photo-reduced riboflavin under aerobic conditions [ 64 , 65 ]. ·O 2 − can react with nitrobluetetrazolium (NBT) to generate blue formazan with maximum absorption at 560 nm.…”

The Occurrence of Flavonoids and Related Compounds in Cedrus brevifolia A. Henry ex Elwes & A. Henry Needles. Inhibitory Potencies on Lipoxygenase, Linoleic Acid Lipid Peroxidation and Antioxidant Activity

“…The methanol extract (6.5 g) yielded taxifolin ( 1 ) [ 8 ], astragalin ( 2 ) [ 9 ], isorhamnetin 3- O -β- d -glucoside ( 3 ) [ 10 ], (−)-catechin ( 4 ) [ 11 ], benzoate glucoside ( 5 ) [ 12 ], benzyl-β- d -glucoside ( 6 ) [ 13 ], benzyl-β- d -rutinoside ( 7 ) [ 14 ], 2-methoxy-phenyl-β- d -glucoside ( 8 ) [ 15 ], 3,4-dimethoxyphenyl-β- d -glucoside ( 9 ) [ 16 ], raspberry ketone ( 10 ) [ 17 ], p-anisic acid ( 11 ) [ 18 ], 4-hydroxybenzoic acid 4- O -β- d -glucoside ( 12 ) [ 19 ], p-coumaric acid ( 13 , 6.0 mg) and its glucoside ( 14 ) [ 20 , 21 ], trans -vaginoside ( 15 ) [ 22 ] and abscisic alcohol glucoside ( 16 ) [ 23 ]. The methanol:water (5:1) extract afforded kaempferol-3- O -β-rutinoside ( 17 ) [ 24 ], kaempferide-3- O -β-rutinoside ( 18 ) [ 25 ], tiliroside ( 19 ) [ 26 ], and syringetin 3- O -β- d -glucoside ( 20 ) [ 27 ] ( Figure 1 ).…”