Mee Jung

Inhibitory activity of flavonoids fromPrunus davidiana and other flavonoids on total ROS and hydroxyl radical generation

Since reactive oxygen species (ROS) and hydroxyl radicals (OH) play an important role in the pathogenesis of many human degenerative diseases, much attention has focused on the development of safe and effective antioxidants. Preliminary experiments have revealed that the methanol (MeOH) extract of the stem ofPrunus davidiana exerts inhibitory/scavenging activities on 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals, total ROS and peroxynitrites (ONOO-). In the present study, the antioxidant activities of this MeOH extract and the organic solvent-soluble fractions, dichloromethane (CH2CI2), ethyl acetate (EtOAc), and n-butanol (n-BuOH), and the water layer ofP. davidiana stem were evaluated for the potential to inhibit OH and total ROS generation in kidney homogenates using 2′,7′-dichlorodihydrofluorescein diacetate (DCHF-DA), and for the potential to scavenge authentic ONOO-. We also evaluated the inhibitory activity of seven flavonoids isolated fromP. davidiana stem, kaempferol, kaempferol 7-O-β-D-glucoside, (+)-catechin, dihydrokaempferol, hesperetin 5-O-β-D-glucoside, naringenin and its 7-O-β-D-glucoside, on the total ROS, OH and ONOO- systems. For the further elucidation of the structure-inhibitory activity relationship of flavonoids on total ROS and OH generation, we measured the antioxidant activity of sixteen flavonoids available, including three active flavonoids isolated fromP. davidiana, on the total ROS and OH systems. We found that the inhibitory activity on total ROS generation increases in strength with more numerous hydroxyl groups on their structures. Also, the presence of anortho-hydroxyl group, whether on the A-ring or B-ring, and a 3-hydroxyl group on the C-ring increased the inhibitory activity on both total ROS and OH generation.

Isolation of flavonoids and a cerebroside from the stem bark ofAlbizzia julibrissin

From the EtOAc fraction of the MeOH extract ofAlbizzia julibrissin (Leguminosae), a rare 5-deoxyflavone (geraldone,1), isookanin (2), luteolin (3), an isoflavone (daidzein,4), five preny-lated flavonoids [sophbflavescenol (5), kurarinone (6), kurarinol (7), kuraridin (8) and kuraridinol (9)], a cerebroside (soya-cerebroside I,10), and (-)-syringaresinol-4-O-β-D-glucopyranoside (11) were isolated and characterized on the basis of spectral data. Compounds2, 3, and11, showed 1,1-diphenyl-2-picrylhydrazyl radical scavenging activity.

Antioxidant activity from the stem bark ofAlbizzia julibrissin

The antioxidant activity of the stem bark fromAlbizzia julibrissin was evaluated for its potential to scavenge 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals, to inhibit the generation of the hydroxyl radical (OH), total reactive oxygen species (ROS) and to scavenge authentic peroxynitrites (ONOO). The methanol extract ofA. julibrissin exhibited strong antioxidant activity in the tested model systems. Therefore, it was further fractionated using several solvents. The antioxidant activity of the individual fractions were in the order of ethyl acetate (EtOAc) <n-butanol (n-BuOH) < dichloromethane (CH2CI2) < and water (H2O). The ethyl acetate soluble fraction, which exhibited strong antioxidant activity, was further purified by repeated silicagel, Sephadex LH-20 and RP-18 gel column chromatography. Sulfuretin (1) and 3′,4′,7-trihydroxy-flavone (2) were isolated as the active principles. Compounds1 and2 exhibited good activity in all tested model systems. Compound1 exhibited five times more inhibitory activity on the total ROS than Trolox. Compound2 showed six times stronger DPPH radical scavenging activity than L-ascorbic acid. These results show the possible antioxidant activity of theA. julibrissin crude extract and its major constituents

Kaempferol glycosides with antioxidant activity from Brassica juncea

From the leaves of Brassica juncea, three kaempferol glycosides, kaempferol-3-O-(2-O-sinapoyl)-β-d-glucopyranosyl-(1→2)-β-d-glucopyranoside-7-O-β-d-glucopyranoside (1), kaempferol-3-O-β-d-glucopyranosyl-(1→2)-β-d-glucopyranoside-7-O-β-d-glucopyranosyl-(1→6)-β-d-glucopyranoside (2), and kaempferol-3-O-(2-O-sinapoyl)-β-d-glucopyranosyl-(1→2)-β-d-glucopyranoside-7-O-β-d-glucopyranosyl-(1→6)-β-d-glucopyranoside (3) were isolated and the structures elucidated on the basis of spectral and chemical evidences. Antioxidant activities were determined by measuring the scavenging activities on 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical and peroxynitrite (ONOO−). Compounds 1 and 3 showed good antioxidant activities with respective IC50 values of 28.61 and 36.93 µM toward DPPH; respective IC50 values of 9.79 and 11.40 µM toward ONOO−. However, compound 2 showed no DPPH scavenging activity and weak ONOO− scavenging activity with an IC50 value of 32.00 µM.

A new kaempferol 7-O-triglucoside from the leaves ofBrassica juncea L

From the leaves ofBrassica juncea, a new rare kaempferol 7-O-triglucoside isolated and characterized as kaempferol 7-0-β-D-glucopyranosyl-(1→3)-[β-D-glucopyranosyl-(1→6)]-glucopy-ranoside (1) based on the spectroscopic evidences. This compound was found to be a scavenger of 1,1-diphenyl-2-picrylhydrazyl radical.

A new abietic acid-type diterpene glucoside from the needles of Pinus densiflora

From the ethyl acetate fraction of the methanol extract of the needles of Pinus densiflora (Pinaceae), a new diterpenoid glucoside [9α,13α-epoxy-8β,14β-dihydroxy-abietic acid-18-O-β-d-glucopyranoside] (1), two flavonoid glucosides [kaempferol 3-O-β-d-glucoside (2) and 6-C-methyl kaempferol 3-O-β-d-glucoside (3)], and two monoterpenoid glucosides [bornyl 6-O-α-Larabinofuranosyl (1→6)-β-d-glucopyranoside (4) and bornyl 6-O-β-d-apiofuranosyl (1→6)-β-d-glucopyranoside (5)] were isolated and characterized on the basis of spectral analysis. Of all the compounds, 2 and 3 showed peroxynitrite scavenging activity.

Further isolation of peroxynitrite and 1,1-diphenyl-2-picrylhy-drazyl radical scavenging isorhamnetin 7-O-glucoside from the leaves ofBrassica juncea L

From the leaves ofBrassica juncea, an radical scavenging isorhamnetin 7-O-glucoside on peroxynitrite and 1, 1 -diphenyl-2-picrylhydrazyl (DPPH) was isolated and characterized based on the spectroscopic evidence. The compound showed the peroxynitrite and DPPH scavenging activities with IC50 values of 2.07 ±0.17 and 13.3 μM, respectively. Penicillamine and L-ascor-bic acid as positive control exhibited radical scavenging activities with IC50 values of 3.17 ± 0.39 and 12.78 μM, respectively.

A new (E)-4-hydroxy-dodec-2-enedioic acid from the stem bark ofalbizzia julibrissin

A new unsaturated hydroxy acid was isolated from the stem bark extract ofAlbizzia julibrissin through repeated silica gel and Sephadex LH-20 column chromatography. The chemical struc-ture of the new acid was determined as (E)-4-hydroxy-dodec-2-enedioic acid on the basis of several spectral data including 2D-NMR. The stereochemical feature of the double bond was determined to beE on the basis of the coupling pattern of related proton signals in the1H-NMR and COSY experiments.