Benzofuran lignans

The naturally occurring benzofuran lignan schizotenuin A (164) was isolated from Schizonepeta temifolia Briq. Compound 164 and the synthesized benzofuran lignans 165 and 166 inhibited lipid peroxidation in rat brain homogenate and in rat... 

S Maeda, H Masuda, T Tokoroyama. Studies on preparation of bioactive lignans by oxidative conpUng reaction. 1. Preparatiom and lipid peroxidation inhibitory effect of benzofuran lignans related to schizotenuins. Chem Pharm Bull 42 2500-2505, 1994. 

The phenolics include anthocyanins, anthraquinones, benzofurans, chromones, chromenes, coumarins, flavonoids, isoflavonoids, lignans, phenolic acids, phenylpropanoids, quinones, stilbenes and xanthones. Some phenolics can be very complex in structure through additional substitution or polymerization of simpler entities. Thus xanthones can be prenylated and flavonoids, lignans and other phenolics can be glycosylated. Condensed tannins involve the polymerization of procyaninidin or prodelphinidin monomers and hydrolysable tannins involve gallic acid residues esterified with monosaccharides. As detailed in this review, representatives of some major classes of plant-derived phenolics are potent protein kinase inhibitors. 

Acetylenes, beta-carboline alkaloids, furocoumarins and lignans occur widely among the families listed in Table 1. Acetophenones (benzofurans and benzopyrans) and extended quinones have a much more limited distribution while furochromones, furoquinoline alkaloids and thiophenes are apparently restricted to single families. It should be mentioned that although acetylenic polylnes are phytochemical components of plants from numerous families (4), only those derivatives produced by members of the Asteraceae have been shown to be phototoxic Q). 

Figure 1. Structures of representative phototoxic plant products from various phytochemical classes. (I) 1-phenylhepta-1,2,3-triyne (acetylenic polyine) (II) 6-methoxyeuparin (benzofuran) (III) harmane (beta-carboline alkaloid) (IV) khellin (furo-chromone) (V) 8-methoxypsoralen (furocoumarin) (VI) dictamnine (furoqulnoline alkaloid) (VII) nordihydroguaiaretic acid (lignan) and (VIII) alpha-terthienyl (thiophene).

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