Virantmycin

In the course of our screening for activators of hypoxia-inducible factor (HIF), A-503451 A and virantmycin were isolated from the cultured broth of an actinomycete strain, Streptomyces sp. SANK 60101. From the same culture, the non-active homologs A-503451 B and D were also isolated. A-503451 A and virantmycin activated HIF-dependent reporter gene expression with EC50 values of 8 and 17 ng ml-1, respectively. They are highly potent activators of HIF and thus may be therapeutically useful for erythropoiesis and neural cell protection.

Two new antibiotics, designated virantmycin B (1) and C (2), were isolated from the cultured broth of Streptomyces sp. AM-2504. Compounds 1 and 2 were purified by Diaion HP-20, silica gel, and octadecylsilane chromatography, followed by high-performance liquid chromatography. The chemical structures of the new compounds, 1 and 2, were determined by nuclear magnetic resonance and mass spectrometry, as containing a terahydroquinoline and an indoline, respectively, each also containing a hydroxy cyclopentenone moiety. Both compounds demonstrated weak antimicrobial (both antibacterial and antifungal) activity and compound 1 also showed antiviral activity against the dengue virus, whereas compound 2 exhibited no antiviral properties.

Pseudorabies virus (PRV) is a pathogen that causes Aujeszky's disease (AD) in animals, leading to huge economic losses to swine farms. In order to discover anti-PRV compounds, we studied the extracts of the strain Streptomyces jiujiangensis NBERC-24992, which showed significant anti-PRV activity. Eight benzoheterocyclic secondary metabolites, including three new compounds (1-3, virantmycins D-G) and five known compounds (4-8, virantmycin, A-503451 D, A-503451 D acetylate, A-503451 A, and A-503451 B), were isolated from the broth of NBERC-24992. The structures of the new compounds were identified by using extensive spectroscopic data, including mass spectrometry (MS), nuclear magnetic resonance (NMR), and electronic circular dichroism (ECD). Compound 1 was found to be a novel heterocyclic compound with a tricyclic skeleton from natural product. All compounds were tested for antiviral activity, and 4 (virantmycin) showed an excellent effect against PRV and was better than ribavirin and acyclovir. Our study revealed that chlorine atom and tetrahydroquinoline skeleton were important active moiety for antiviral activity. Virantmycin could be a suitable leading compound for an antiviral drug against PRV.