Eupenifeldin, a novel cytotoxic bistropolone from Eupenicillium brefeldianum.

Abstract

Eupenifeldin was isolated from cultures of Eupenicillium brefeldianum ATCC741 84 by extraction and crystallization.The compoundwas identified as a pentacyclic bistropolone on the basis of spectral data and its complete structure was established by single-crystal X-ray analysis. The compound is cytotoxic against the HCT-1 16 cell line and has in vivo antitumor activity in the P388 leukemia model.Ongoing efforts to find new natural products with antitumor activity led to isolation of a novel cytotoxic bistropolone from a culture broth produced by Eupenicillium brefeldianum ATCC74184. The active principle of this culture was purified to homogeneity and namedeupenifeldin. Its spectral data showed that the molecule had partial symmetry due to the presence of two identically substituted tropolone units each fused in the same mannerto dihydropyran rings. The complete structure and relative stereochemical relationships were determined by single crystal X-ray analysis. Only one naturally occuring bistropolone with cytotoxic activity, fusariocin C, has been described previously in the literature.1>2) It was isolated from the culture filtrate of Fusarium moniliforme and had cytotoxic and antitumor activities. Bistropolones madeby chemical synthesis have also been reported to possess antitumor activity.3) This report describes isolation, physico-chemical characterization, biological properties and the structure of eupenifeldin. Materials and Methods Spectral DataMass spectra in the FABmodewere obtained on a Kratos MS25using m-nitrobenzylalcohol as matrix. El spectra were recorded on a Finnigan TSQ70. A Shimadzu UV2100Uspectrophotometer was used for UVspectra and a Perkin-Elmer FTIR Model 1800 spectrometer for IR spectra. All NMRspectra were recorded in CDC13with a drop ofDMSO-d6on a Bruker Model AM-500spectrometer. Proton-proton coupling constants were obtained by selective irradiations, and carbon-proton one-bond coupling constants were measured in the proton coupled carbon spectrum.El mass spectrum: major peaks at m/z 548, 384, 366, 175, 137. IR-spectrum (KBr): 3440, 3260, 2950, 2870, 1630, 1595, 1530, 1445, 1425, 1395, 1280, 1178, 1150, 1082 cm"1. Fermentation ConditionsTo prepare an inoculum for the production phase, 4 rnl of the frozen vegetative stock were transferred to a 500-ml Erlenmeyer flask containing 100ml of vegetative mediumconsisting of soluble starch 0.5%, glucose 0.5%, fishmeat extract 0. 1 %, yeast extract 0.1 %, NZ-case 0.2%, sodium chloride 0.2% and calcium

Aspergillus hancockii sp. nov., a biosynthetically talented fungus endemic to southeastern Australian soils

“…hancockii cultivation extracts, a distinctive non-polar metabolite was frequently but erratically observed. Purification using normal phase silica led to the identification of eupenifeldin [35] ( t R 7.65 min, N/A%; λ max 250, 324s, 363 nm; ESIMS m/z [M–H] – 547, [M+H] + 549) as an important co-metabolite of A . hancockii .…”

Chemistry and Biology of Biosynthetic Diels–Alder Reactions

“…Pycnidione (180), [87] eupenifeldin (181), [88] and epolone B (182) [89] are a group of recently isolated fungal metabolites that possess identical tropolone rings attached to a sesquiScheme 35. Biosynthetic studies on culantraramine (167).…”

Malettinin E, an antibacterial and antifungal tropolone produced by a marine Cladosporium strain

“…Representative structures of fungi are puberulic acid, puberulonic acid, stipitatic acid and related structures (Corbett et al, 1950;Iwatsuki et al, 2011). More complex known compounds are epolone A or B, pycnidione, eupenifeldin or fusariocin C (Ito et al, 1981;Mayerl et al, 1993;Cai et al, 1998), which structurally share the fused tropolone/dihydropyran ring structure with the malettinins. However, malettinins 1-4 are unique with regard to their linkage of the tropolone/dihydropyran ring to a furan.…”