(±)-Cyclopenin

Three new quinazoline derivatives (1-3), one new oxepin-containing natural product (4) and four new cyclopenin derivatives (5-7 and 9) have been isolated from an EtOAc extract of the Taiwan Kueishantao hydrothermal vent crab-associated fungus Aspergillus versicolor XZ-4. Their planar structures were established by HRMS, 1D and 2D NMR spectroscopic data analyses. The absolute configurations for compounds 1 and 4 were determined by chiral phase HPLC analysis of their hydrolysis products. The absolute configurations of 2, 3 and 7 were defined mainly by comparison of the quantum chemical TDDFT calculated and the experimental ECD spectra, and the absolute configuration of 5 was deduced from comparison of the optical rotation values reported in the literature. The presence of two atropisomers of 5 was established by NOE analyses. The Ile & Val units in compounds 1-3 allowed the assignment of a new quinazoline skeleton and it's the first time the configuration of isoleucine in the quinazoline skeleton was defined. A series of 7-methoxy cyclopenin derivatives were reported for the first time in this study. The bioevaluation of compounds 5, 7, 8 and 9 revealed inhibitory activities against E. coli at MIC values around 32 μg mL-1.

Balanced heterokarions were grown from Penicillium cyclopium aux-glu 1, a glutamic acid auxotroph producing benzodiazepine alkaloids of the cyclopenin-cyclopenol group, and P. viridicatum aux-met 1, a methionine auxotroph forming these alkaloids in traces only. In contrast to the hyphae of the parent strains, the hyphae of the heterokarions were dark orange-brown and grew well on media without the auxotrophic factors. In surface cultures they synthesized the benzodiazepine alkaloids cyclopenin and cyclopenol in amounts similar to those formed by the hyphae of P. cyclopium aux-glu 1. From the monokariotic conidiospores of the heterokarions homokariotic daughter strains were obtained which were similar to the parent strains in every respect. Hence no exchange of features of cyclopenin-cyclopenol biosynthesis took place between the parent strains at the stage of the heterokarion. This result indicates that the formation of cyclopenin and cyclopenol in P. cyclopium aux-glu 1 and the nearly complete lack of biosynthesis of these compounds in P. viridicatum aux-met 1 is encoded within the nucleus and is not influenced by plasmic genetic material.

In the course of screening lipopolysaccharide (LPS)-induced nitric oxide (NO) production inhibitors, two related benzodiazepine derivatives, cyclopenol and cyclopenin, were isolated from the extract of a deep marine-derived fungal strain, Aspergillus sp. SCSIOW2. Cyclopenol and cyclopenin inhibited the LPS-induced formation of NO and secretion of IL-6 in RAW264.7 cells at nontoxic concentrations. In terms of the mechanism underlying these effects, cyclopenol and cyclopenin were found to inhibit the upstream signal of NF-κB activation. These compounds also inhibited the expression of IL-1β, IL-6, and inducible nitric oxide synthase (iNOS) in mouse microglia cells, macrophages in the brain. In relation to the cause of Alzheimer's disease, amyloid-β-peptide is known to induce inflammation in the brain. Therefore, the present study investigated the ameliorative effects of these inhibitors on an in vivo Alzheimer's model using flies. Learning deficits were induced by the overexpression of amyloid-β42 in flies, and cyclopenin but not cyclopenol was found to rescue learning impairment. Therefore, novel anti-inflammatory activities of cyclopenin were identified, which may be useful as a candidate of anti-inflammatory agents for neurodegenerative diseases.