• Natural Product Sciences
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• 제19권1호
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• pp.61-65
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• 2013

A bioassay-guided fractionation of the extract of the fungus Paecilomyces variotii, which was derived from the giant jellyfish Nemopilema nomurai, led to the isolation of antibacterial compounds viriditoxin and its monomeric subunit semi-viriditoxin. Viriditoxin showed significant antibacterial activity against several marine fish and human pathogens including MDR strains. Significant potencies against resistant pathogens such as VRE Enterococcus faecium, VRE Enterococcus faecalis, and MRSA were highly interesting. Viriditoxin also showed notable antibacterial activity against the fish pathogen Streptococcus iniae. Its potency was over 100-fold higher than oxytetracycline which is employed as a general antibiotic for aquaculture.

• Natural Product Sciences
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• 제21권4호
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• pp.282-288
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• 2015

Viriditoxin is a fungal metabolite isolated from Paecilomyces variotii, which was derived from the giant jellyfish Nemopilema nomurai. Viriditoxin was reported to inhibit polymerization of FtsZ, which is a key protein for bacterial cell division and a structural homologue of eukaryotic tubulin. Both tubulin and FtsZ contain a GTP-binding domain, have GTPase activity, assemble into protofilaments, two-dimensional sheets, and protofilament rings, and share substantial structural identities. Accordingly, we hypothesized that viriditoxin may inhibit eukaryotic cell division by inhibiting tubulin polymerization as in the case of bacterial FtsZ inhibition. Docking simulation of viriditoxin to ${\beta}-tubulin$ indicated that it binds to the paclitaxel-binding domain and makes hydrogen bonds with Thr276 and Gly370 in the same manner as paclitaxel. Viriditoxin suppressed growth of A549 human lung cancer cells, and inhibited cell division with G2/M cell cycle arrest, leading to apoptotic cell death.