Pecilocin

Variotin (1) and three novel compounds, formosusin A (2), B (3), and C (4), were isolated from the cultures of the fungus Paecilomyces formosus, and their structures were determined by spectroscopic analyses. Compound 2 is (6Z,8E,10E)-variotin, a new cis-olefin analog of compound 1. Compound 2 selectively inhibited the activity of mammalian DNA polymerase β (pol β) in vitro, with an IC50 of 35.6μM. By contrast, compounds 1, 3, and 4 did not influence the activity of pol β. These four compounds showed no effect on the activities of other 10 mammalian pols (i.e., pols α, γ, δ, ε, η, ι, κ, λ, and μ, and terminal deoxynucleotidyl transferase). These compounds also did not inhibit the activities of fish, insect, plant, and prokaryotic pols and other DNA metabolic enzymes tested. These results suggested that compound 2 could be a selective inhibitor of mammalian pol β. The compound 2-induced inhibition of rat pol β activity was competitive and non-competitive with respect to the DNA template-primer substrate and the dNTP substrate, respectively. On the basis of these results, the relationship between the three-dimensional structure and pol β inhibitory mechanism of compound 2 is discussed.

Besides the antifungal agents variotin (1), wasabidienone B(0) (4), and phomaligin A (5), two new but inactive metabolites, viriditin (2) and O-methylviriditin (3), were isolated from extracts of the culture filtrate of liquid cultures of a strain of Aspergillus viridi-nutans. In addition, wasabidienone B(1) (6) was isolated and characterized by spectroscopy.

Aspergillus is well-known as the second-largest contributor of fungal natural products. Based on NMR guided isolation, three nitrogen-containing secondary metabolites, including two new compounds, variotin B (1) and coniosulfide E (2), together with a known compound, unguisin A (3), were isolated from the ethyl acetate (EtOAc) extract of the deep-sea fungus Aspergillus unguis IV17-109. The planar structures of 1 and 2 were elucidated by an extensive analysis of their spectroscopic data (HRESIMS, 1D and 2D NMR). The absolute configuration of 2 was determined by comparison of its optical rotation value with those of the synthesized analogs. Compound 2 is a rare, naturally occurring substance with an unusual cysteinol moiety. Furthermore, 1 showed moderate anti-inflammatory activity with an IC50 value of 20.0 µM. These results revealed that Aspergillus unguis could produce structurally diverse nitrogenous secondary metabolites, which can be used for further studies to find anti-inflammatory leads.