C(2)-symmetric bisamidines 8 have been tested as chiral Brønsted bases in the Diels-Alder reaction of anthrones and N-substituted maleimides. High yields of cycloadducts and significant asymmetric inductions up to 76% ee are accessible. The proposed mechanism involves proton transfer between anthrone and bisamidine, association of the resulting ions and finally a cycloaddition step stereoselect...

Rhubarb is one of the most ancient, commonly used and important herbs in Chinese medicine. The modern researches of rhubarb clarified the efficacies, ingredients and mechanisms in a more scientific and rigorous way. The main chemical compositions of rhubarb include anthraquinones, anthrones, stilbenes, tannins, polysaccharides etc. These compositions show extensive pharmacological activities in...

Eggs of leaf beetles of the tribe Galerucini, subfamily Galerucinae, contain polyketides that are unusual in insects: 1,8-dihydroxylated anthraquinones (chrysazin, chrysophanol) and anthrones (dithranol, chrysarobin) deterring predators. The host plants do not contain these compounds. In the present study, we tested the hypothesis that the beetles, but not bacterial or fungal microorganisms liv...

treatment of 10-bromoanthralin (1) with several thiophenols (2) gave the corresponding 10-arylthioanthralins (3) in high yields. oxidation of thioanthralins (3a-c) and (3k-m) using an excess of m-chloroperbenzoic acid gave the corresponding sulfones (4a-c) and (4k-m) in good yields. oxidation of thioanthralins (3d-f) gave a mixture of the corresponding sulfones (4d-f) and anthralin-10,10'-dehyd...

A chemotaxonomic survey of 380 species of Aloe indicated the presence of the anthrone isomers aloin A and B together with the aloinoside isomers and microdontin A and B in 36 (10%) species of Aloe. This group, referred to as the microdontin chemotype, is thus characterised by a combination of exudate compounds and not merely a single phytochemical marker, implying taxonomic significance of leaf...

Hypericin and pseudohypericin were found in 27 of the 36 evaluated species from Hypericum L., belonging to 17 sections of the genus. Pseudohypericin is reported by us in 15 taxa for the first time. Most of the species contained both components and the amount of pseudohypericin usually exceeded that of hypericin. In H. hirsutum and H. empetrifolium only hypericin was found, whereas H. formosissi...

The phytochemical profile of Aloe barbadensis Mill. and Aloe arborescens Mill. was investigated using colorimetric assays, triple quadrupole and time-of-flight mass spectrometry, focusing on phenolic secondary metabolites in the different leaf portions. Hydroxycinnamic acids, several characteristic anthrones and chromones, the phenolic dimer feralolide and flavonoids such as flavones and isofla...

The ethanolic extract of Aloe barbadensis Miller leaf skin showed inhibitory activity against phosphodiesterase-4D (PDE4D), which is a therapeutic target of inflammatory disease. Subsequent bioassay-guided fractionation led to the isolation of two new anthrones, 6'-O-acetyl-aloin B (9) and 6'-O-acetyl-aloin A (11), one new chromone, aloeresin K (8), together with thirteen known compounds. Their...