FAD-dependent enzyme-catalysed intermolecular [4+2] cycloaddition in natural product biosynthesis.

The Diels-Alder reaction is one of the most powerful and widely used methods in synthetic chemistry for the stereospecific construction of carbon-carbon bonds. Despite the importance of Diels-Alder reactions in the biosynthesis of numerous secondary metabolites, no naturally occurring stand-alone Diels-Alderase has been demonstrated to catalyse intermolecular Diels-Alder transformations. Here we report a flavin adenine dinucleotide-dependent enzyme, Morus alba Diels-Alderase (MaDA), from Morus cell cultures, that catalyses an intermolecular [4+2] cycloaddition to produce the natural isoprenylated flavonoid chalcomoracin with a high efficiency and enantioselectivity.

Chemistry and biosynthesis of isoprenylated flavonoids from Japanese mulberry tree.

Many isoprenylated flavonoids have been isolated from Japanese mulberry tree (Moraceae). Among them, kuwanons G (1) and H (2) were the first isolated active substances exhibiting a hypotensive effect. These compounds are considered to be formed through an enzymatic Diels-Alder type reaction between an isoprenyl portion of an isoprenylphenol as the diene and an alpha, beta-double bond of chalcone as the dienophile.

Triterpenoids from Peganum nigellastrum.

Two triterpenoids were isolated from the roots of Peganum nigellastrum Bunge. Their structures were elucidated as 3alpha-acetoxy-27-trans-caffeoyloxyolean-12-en-28-oic acid methyl ester (1) and 3-oxotirucalla-7, 24-dien-21-oic acid (2) on the basis of spectroscopic evidence. 1 is a new triterpene ester and 2 is a known compound isolated for the first time from genus Peganum.

Antimicrobial activities of hydrophobic 2-arylbenzofurans and an isoflavone against vancomycin-resistant enterococci and methicillin-resistant Staphylococcus aureus.

Eight 2-arylbenzofurans and an isoflavone isolated from medicinal plants were tested for their antimicrobial activities against vancomycin-resistant enterococci (VRE) and methicillin-resistant Staphylococcus aureus (MRSA). Among these compounds, six hydrophobic 2-arylbenzofurans (log P = 4.4-8.

Novel quinazoline-quinoline alkaloids with cytotoxic and DNA topoisomerase II inhibitory activities.

Two new synthetic analogues of luotonins A and F, 7-acetylaminoluotonin A (6) and 3-[3H(quinazolino-4-one)]quinoline (7) were synthesized. The new analogues, along with four natural quinazoline-quinoline alkaloids, luotonins A (1), B (2), E (3), F (4) and a synthetic deoxoluotonin F (5), showed cytotoxic activity (IC(50) 1.8-40.

Protein kinase C activation by iridal type triterpenoids.

Eleven iridal type triterpenoids from Iris tectorum and Belamcanda chinensis were examined for protein kinase C (PKC) activation and binding activity to PKC. Among the tested compounds, nine iridals showed dose-dependent activities, and a mutual relation between the two activities was also observed. 28-Deacetylbelamcandal, which has been found to be a new class 12-O-tetradecanoylphorbol 13-acetate type tumor promoter, showed the most potent activity in both tests.