Curvularin

Sumalarins A-C (1-3), the new and rare examples of sulfur-containing curvularin derivatives, along with three known analogues (4-6), were isolated and identified from the cytotoxic extract of Penicillium sumatrense MA-92, a fungus obtained from the rhizosphere of the mangrove Lumnitzera racemosa . Their structures were established by detailed interpretation of NMR and MS data, and compound 1 was confirmed by X-ray crystallographic analysis. Compounds 1-3 and 5 showed potent cytotoxicity against some of the tested tumor cell lines. Sulfur substitution at C-11 or a double bond at C-10 significantly increased the cytotoxic activities of the curvularin analogues.

Five curvularin macrolides (1-5) were isolated from the cultured broth of marine actinomycete Pseudonocardia sp. HS7 that was obtained from the cloacal aperture of sea cucumber Holothuria moebii. The structures of these isolates were characterized as (11S,15R)-11-hydroxycurvularin (1), (11R,15R)-11-hydroxycurvularin (2), curvularin-7-O-α-D-glucopyranoside (3), trans-dehydrocurvularin (4) and curvularin (5) based on their NMR and HRESIMS data as well as chemical degradation. Compound 3 is a new macrolide with a rare α-D-glucopyranose substituent. Compounds 1-4, 5a and 5c (the acyl products of 5), suppressed the proliferation of all six tested cancer cell lines and 4 is the most active compound with IC50 values ranging from 0.59 to 3.39 μM. The 11-hydroxycurvularins 1 and 2 also showed antibacterial activity inhibiting the growth of Escherichia coli.

TGF-β is a multifunctional cytokine that regulates cell proliferation, differentiation, apoptosis and extracellular matrix production. Deregulation of TGF-β production or signaling plays a pivotal role in a variety of pathological processes such as cancer, metastasis, angiogenesis and fibrosis. Therefore, TGF-β inhibitors should be promising therapeutic agents for the suppression of cancer progression and metastasis as well as fibrotic disorders. In a screening program of natural compounds from fungi inhibiting the TGF-β dependent expression of a reporter gene in HepG2 cells, we found that the fungal lactones (S)-curvularin, dehydrocurvularin, oxacyclododecindione and galiellalactone inhibited the binding of the activated Smad2/3 transcription factors to the DNA and antagonized the cellular effects of TGF-β including reporter gene activation and expression of TGF-β induced genes in HepG2 and MDA-MB-231 cells. The most active compound oxacyclododecindione inhibited TGF-β dependent reporter activity with IC50-values of 190-217 nM.

In previous studies, we identified the fungal macrocyclic lactone (S)-curvularin (SC) as an anti-inflammatory agent using a screening system detecting inhibitors of the Janus kinase/signal transducer and activator of transcription pathway. The objective of the present study was to investigate whether SC is able to decrease proinflammatory gene expression in an in vivo model of a chronic inflammatory disease. Therefore, the effects of SC and dexamethasone were compared in the model of collagen-induced arthritis (CIA) in mice. Total genomic microarray analyses were performed to identify SC target genes. In addition, in human C28/I2 chondrocytes and MonoMac6 monocytes, the effect of SC on proinflammatory gene expression was tested at the mRNA and protein level. In the CIA model, SC markedly reduced the expression of a number of proinflammatory cytokines and chemokines involved in the pathogenesis of CIA as well as human rheumatoid arthritis (RA).