Cytotoxic xanthones from Psorospermum molluscum from the Madagascar rain forest

Naturally Occurring Organohalogen Compounds-A Comprehensive Review

The present volume is the third in a trilogy that documents naturally occurring organohalogen compounds, bringing the total number-from fewer than 25 in 1968-to approximately 8000 compounds to date. Nearly all of these natural products contain chlorine or bromine, with a few containing iodine and, fewer still, fluorine. Produced by ubiquitous marine (algae, sponges, corals, bryozoa, nudibranchs, fungi, bacteria) and terrestrial organisms (plants, fungi, bacteria, insects, higher animals) and universal abiotic processes (volcanos, forest fires, geothermal events), organohalogens pervade the global ecosystem. Newly identified extraterrestrial sources are also documented. In addition to chemical structures, biological activity, biohalogenation, biodegradation, natural function, and future outlook are presented.

Chemical and Biological Research on Herbal Medicines Rich in Xanthones

Xanthones, as some of the most active components and widely distributed in various herb medicines, have drawn more and more attention in recent years. So far, 168 species of herbal plants belong to 58 genera, 24 families have been reported to contain xanthones. Among them, Calophyllum, Cratoxylum, Cudrania, Garcinia, Gentiana, Hypericum and Swertia genera are plant resources with great development prospect. This paper summarizes the plant resources, bioactivity and the structure-activity relationships (SARs) of xanthones from references published over the last few decades, which may be useful for new drug research and development on xanthones.

Kenganthranol F, a new Anthranol from Psorospermum aurantiacum

A new anthranol, kenganthranol F, was isolated from the ethyl acetate extracts of the seeds and the whole plant of the Cameroonian plant Psorospermum aurantiacum (Hypericaceae), together with fifteen known compounds viz., ferruginin B, vismin, vismion D, haronginanthrone, kenganthraquinone, kenganthranol B and kenganthranol E isolated from the fruits and 3-geranyloxyemodinanthrone, 2-geranylemodin, bianthrone A1, vismione D, 1,8-dihydroxy- 3-geranyloxy-6-methylanthraquinone, vismione M, vismiaquinone, vismiaquinone C being isolated from the whole plant. The structure of the new isomer of kenganthranol F was determined to be 1,8,10-trihydroxy-3,4-[2,2-dimethyldihydropyrano]-6-methyl-2,5-bis-(3,3-dimethylallyl)-anthrone.

Analysis of an inactive cyanobactin biosynthetic gene cluster leads to discovery of new natural products from strains of the genus Microcystis

Cyanobactins are cyclic peptides assembled through the cleavage and modification of short precursor proteins. An inactive cyanobactin gene cluster has been described from the genome Microcystis aeruginosa NIES843. Here we report the discovery of active counterparts in strains of the genus Microcystis guided by this silent cyanobactin gene cluster. The end products of the gene clusters were structurally diverse cyclic peptides, which we named piricyclamides. Some of the piricyclamides consisted solely of proteinogenic amino acids while others contained disulfide bridges and some were prenylated or geranylated. The piricyclamide gene clusters encoded between 1 and 4 precursor genes. They encoded highly diverse core peptides ranging in length from 7–17 amino acids with just a single conserved amino acid. Heterologous expression of the pir gene cluster from Microcystis aeruginosa PCC7005 in Escherichia coli confirmed that this gene cluster is responsible for the biosynthesis of piricyclamides. Chemical analysis demonstrated that Microcystis strains could produce an array of piricyclamides some of which are geranylated or prenylated. The genetic diversity of piricyclamides in a bloom sample was explored and 19 different piricyclamide precursor genes were found. This study provides evidence for a stunning array of piricyclamides in Microcystis, a worldwide occurring bloom forming cyanobacteria.

Antitumor psoropermum xanthones and sarcomelicope acridones: privileged structures implied in DNA alkylation

Fused isopropylfuran and dimethylpyran units are privileged structures present in numerous bioactive natural products exemplified, in the field of anticancer drugs, by the furanoxanthone psorospermin and the pyranoacridone acronycine. Psorospermin binds to the N-7 position of the guanine units in the presence of topoisomerase II. In contrast, acronycine derivatives such as cis-1,2-diacetoxy-1,2-dihydrobenzo[b]acronycine alkylate the 2-amino group of DNA guanine residues in the minor groove. Hybrid compounds associating the acridone or benzo[b]acridone chromophore of acronycine derivatives and the epoxyfuran alkylating unit present in psorospermin also display very potent antiproliferative activities, alkylating DNA guanine units at position N-7 in the major groove, as natural xanthones belonging to the psorospermin series.