Isolation of 4,5- O

There is a continual need to develop novel and effective melanogenesis inhibitors for the prevention of hyperpigmentation disorders. The plant Artemisia capillaris Thunberg (Oriental Wormwood) was screened for antipigmentation activity using murine cultured cells (B16-F10 malignant melanocytes). Activity-based fractionation using HPLC and NMR analyses identified the compound 4,5-O-dicaffeoylquinic acid as an active component in this plant. 4,5-O-Dicaffeoylquinic acid significantly reduced melanin synthesis and tyrosinase activity in a dose-dependent manner in the melanocytes. In addition, 4,5-O-dicaffeoylquinic acid treatment reduced the expression of tyrosinase-related protein-1. Significantly, we could validate the antipigmentation activity of this compound in vivo, using a zebrafish model. Moreover, 4,5-O-dicaffeoylquinic acid did not show toxicity in this animal model. Our discovery of 4,5-O-dicaffeoylquinic acid as an inhibitor of pigmentation that is active in vivo shows that this compound can be developed as an active component for formulations to treat pigmentation disorders

Flavone Tetraglycosides and Benzyl Alcohol Glycosides from the Mongolian Medicinal Plant <i>Dracocephalum ruyschiana</i>

From an extract of the aerial parts of <i>Dracocephalum ruyschiana</i>, five new flavone tetraglycosides, five new benzyl alcohol glycosides, and 19 known compounds were isolated. The tetraglycosides contain a 7-<i>O</i>-β-d-glucopyranosyl-(1→2)-β-d-glucopyranosyl-(1→2)-[α-l-rhamnopyranosyl-(1→6)]-β-d-glucopyranosyl moiety. The benzyl alcohol glycosides had acyl groups on their glycosyl or aglycone moieties. The compounds were tested for antioxidant activity using DPPH. Although the new compounds were not active, phenylpropanoylquinic acid derivatives were revealed as radical scavengers in <i>D</i>. <i>ruyschiana</i>

Antioxidant Constituents of Cotoneaster melanocarpus Lodd.

The aim of this study was the evaluation of the antioxidant capacity of Cotoneaster melanocarpus Lodd. and the identification of antioxidant active constituents of this plant. C. melanocarpus Lodd. is a shrub indigenous to Mongolia and used in Traditional Mongolian Medicine as a styptic. Before extraction, the plant material was separated into three parts: young sterile shoots, older stems and leaves. All these parts were extracted with water, methanol, ethyl acetate, dichloromethane and hexane, successively. The methanolic extract of the sterile shoots showed the highest antioxidant activity in the DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging assay (IC50 30.91 ± 2.97 µg/mL). This active extract was further analyzed with chromatographic methods. TLC fingerprinting and HPLC indicated the presence of the flavonol glycosides quercetin-3-O-rutinoside (rutin), quercetin-3-O-galactoside (hyperoside) and quercetin-3-O-glucoside (isoquercetin), ursolic acid as well as chlorogenic acid, neochlorogenic acid and cryptochlorogenic acid. The findings were substantiated with LC-MS. All identified compounds have antioxidant properties and therefore contribute to the radical scavenging activity of the whole plant

Antioxidant Flavonols and Phenolic Compounds from <i>Atraphaxis frutescens</i> and Their Inhibitory Activities against Insect Phenoloxidase and Mushroom Tyrosinase

Chemical investigation of the aerial parts of <i>Atraphaxis frutescens</i> resulted in the isolation of five 7-methoxyflavonols with pyrogallol B-ring moieties (<b>1</b>–<b>5</b>), a fisetinidol glucoside (<b>13</b>), and a benzyl glycoside (<b>18</b>), together with 26 known compounds including flavonoids, phenylpropanoid amides, anthraquinone glycosides, lignans, and a benzyl derivative. The principal chemical structural feature of the isolated compounds was either a pyrogallol or catechol B-ring moiety, and they showed potent 1,1-diphenyl-2-picrylhydrazyl radical scavenging activities. To assess the effects of these antioxidants on biological enzymes, their inhibitory effects against an insect phenoloxidase and a mushroom tyrosinase were evaluated. This study indicated that insect phenoloxidase was inhibited by phenylpropanoid amides and that mushroom tyrosinase was inhibited by the characteristic 7-methoxyflavonol 3-<i>O</i>-rhamnopyranosides

Trypanocidal Activity of 2,5-Diphenyloxazoles Isolated from the Roots of <i>Oxytropis lanata</i>

Eleven 2,5-diphenyloxazole derivatives (<b>1</b>–<b>11</b>), together with six known isoflavonoid derivatives, were isolated from the roots of <i>Oxytropis lanata</i>. The 2,5-diphenyloxazole (<b>1</b>) obtained proved to be identical to a standard sample used as a scintillator and liquid laser dye. The other oxazole derivatives isolated were found to have one to four hydroxy and/or <i>O</i>-methyl groups in their phenyl rings. Seven of the oxazole derivatives obtained are new (<b>3</b>–<b>9</b>). The inhibitory activity of the isolated compounds was evaluated against <i>Trypanosoma congolense</i>, the causative agent of African trypanosomosis in animals. Oxazoles with di- and trihydroxy groups showed trypanocidal activity, and 2-(2′,3′-dihydroxyphenyl)-5-(2″-hydroxyphenyl)­oxazole (<b>4</b>) exhibited the most potent inhibitory activity (IC₅₀ 1.0 μM)