Production of cladospirone bisepoxide, a new fungal metabolite

COX Inhibitory and Cytotoxic Naphthoketal-Bearing Polyketides from Sparticola junci

Axenic fermentation on solid rice of the saprobic fungus Sparticola junci afforded two new highly oxidized naphthalenoid polyketide derivatives, sparticatechol A (1) and sparticolin H (2) along with sparticolin A (3). The structures of 1 and 2 were elucidated on the basis of their NMR and HR-ESIMS spectroscopic data. Assignment of absolute configurations was performed using electronic circular dichroism (ECD) experiments and Time-Dependent Density Functional Theory (TDDFT) calculations. Compounds 1-3 were evaluated for COX inhibitory, antiproliferative, cytotoxic and antimicrobial activities. Compounds 1 and 2 exhibited strong inhibitory activities against COX-1 and COX-2. Molecular docking analysis of 1 conferred favorable binding against COX-2. Sparticolin H (2) and A (3) showed a moderate antiproliferative effect against myelogenous leukemia K-562 cells and weak cytotoxicity against HeLa and mouse fibroblast cells.

Catechol-Bearing Polyketide Derivatives from Sparticola junci

Sparticols A (1) and B (2), two catechol-bearing naphthalenedioxy derivatives, were isolated from the submerged culture of the Spanish broom inhabiting Dothideomycetes fungus, Sparticola junci. The structures of 1 and 2 were established by NMR spectroscopic analysis and high-resolution mass spectrometry. The 8S absolute configuration of their β-hydroxy functionalities was determined by ECD-TDDFT. Both compounds exhibited inhibitory activity against Staphylococcus aureus with an MIC value of 66.6 μg/mL. Polyketides 1 and/or 2 may be associated with pathways cascading to seco-spirodioxynapthalene derivatives.

Enhancement of Palmarumycin C12 and C13 Production by the Endophytic Fungus Berkleasmium sp. Dzf12 in an Aqueous-Organic Solvent System

The endophytic fungus Berkleasmium sp. Dzf12, isolated from Dioscorea zingiberensis, was found to produce palmarumycins C₁₂ and C₁₃ which possess a great variety of biological activities. Seven biocompatible water-immiscible organic solvents including n-dodecane, n-hexadecane, 1-hexadecene, liquid paraffin, dibutyl phthalate, butyl oleate and oleic acid were evaluated to improve palmarumycins C₁₂ and C₁₃ production in suspension culture of Berkleasmium sp. Dzf12. Among the chosen solvents both butyl oleate and liquid paraffin were the most effective to improve palmarumycins C₁₂ and C₁₃ production. The addition of dibutyl phthalate, butyl oleate and oleic acid to the cultures of Berkleasmium sp. Dzf12 significantly enhanced palmarumycin C₁₂ production by adsorbing palmarumycin C₁₂ into the organic phase. When butyl oleate was fed at 5% (v/v) in medium at the beginning of fermentation (day 0), the highest palmarumycin C₁₂ yield (191.6 mg/L) was achieved, about a 34.87-fold increase in comparison with the control (5.3 mg/L). n-Dodecane, 1-hexadecene and liquid paraffin had a great influence on the production of palmarumycin C₁₃. When liquid paraffin was added at 10% (v/v) in medium on day 3 of fermentation, the palmarumycin C₁₃ yield reached a maximum value (134.1 mg/L), which was 4.35-fold that of the control (30.8 mg/L). Application of the aqueous-organic solvent system should be a simple and efficient process strategy for enhancing palmarumycin C₁₂ and C₁₃ production in liquid cultures of the endophytic fungus Berkleasmium sp. Dzf12.

Enhancement of palmarumycin C12 and C13 production in liquid culture of the endophytic fungus Berkleasmium sp. Dzf12 by oligosaccharides from its host plant Dioscorea zingiberensis

Three crude oligosaccharides were respectively prepared by acid hydrolysis of three polysaccharides, which were water-extracted polysaccharide (WEP), sodium hydroxide-extracted polysaccharide (SEP) and acid-extracted polysaccharide (AEP) from the rhizomes of Dioscorea zingiberensis. Among the three oligosaccharides, the crude oligosaccharide prepared by acid hydrolysis of WEP was found to be the most efficient elicitor to enhance the production of palmarumycins C₁₂ and C₁₃ in liquid culture of endophytic fungus Berkleasmium sp. Dzf12. When OW was applied to the medium at 300 mg/L on day 3 of culture, the maximal yields of palmarumycin C₁₂ (87.96 mg/L) and palmarumycin C₁₃ (422.28 mg/L) were achieved on day 15 of culture, which were 9.83 and 3.24-fold in comparison with those (8.95 and 130.43 mg/L) of control, respectively. The results indicate that addition of the oligosaccharides from the host plant D. zingiberensis should be an effective strategy for enhancing production of palmarumycins C₁₂ and C₁₃ in liquid culture of endophytic fungus Berkleasmium sp. Dzf12.

Enhancement of diepoxin ζ production by yeast extract and its fractions in liquid culture of Berkleasmium-like endophytic fungus Dzf12 from Dioscorea zingiberensis

This study was to examine the effects of yeast extract (YE) and its fractions (YE1 and YE2) on the growth and diepoxin ζ (a spirobisnaphthalene with a diversity of bioactivities) production in liquid culture of Berkleasmium-like endophytic fungus Dzf12 from Dioscorea zingiberensis. When YE was applied to the liquid medium at 10 g/L on day 3 of culture, the diepoxin ζ production was most effectively enhanced 3.2-fold (378.70 mg/L versus 120.09 mg/L in control) after another 10 days culture. Feeding with 15 g/L of YE on day 9, the mycelia biomass reached 16.44 g/L, about 2.3-fold in comparison with the control (7.15 g/L). The polysaccharide fraction (YE1) was mainly responsible for stimulating diepoxin ζ accumulation, and the non-polysaccharide fraction (YE2) was mainly responsible for promoting mycelia growth. The results showed that the diepoxin ζ production in liquid culture of endophyte Dzf12 could be effectively enhanced by YE and its fractions.

Use of experimental design for the optimization of the production of new secondary metabolites by two Penicillium species

A fractional factorial design approach has been used to enhance secondary metabolite production by two Penicillium strains. The method was initially used to improve the production of bioactive extracts as a whole and subsequently to optimize the production of particular bioactive metabolites. Enhancements of over 500% in secondary metabolite production were observed for both P. oxalicum and P. citrinum. Two new alkaloids, citrinalins A (5) and B (6), were isolated and identified from P. citrinum cultures optimized for production of minor metabolites.

Unified route to the palmarumycin and preussomerin natural products. Enantioselective synthesis of (-)-preussomerin G

The total syntheses of eight members of the palmarumycin family have been achieved, with identification of the absolute stereochemistry for three of these natural products. In addition, the ras-farnesyl transferase inhibitor (-)-preussomerin G has been synthesized, achieving the first enantioselective route for accessing this family of natural products. Highlights of the synthetic work include an asymmetric epoxidation of a cyclic enone in excellent yield and enantiomeric excess and a potentially biomimetic oxidative spirocyclization for the introduction of the bis-spiroketal array unique to the preussomerin natural products.

Formal total synthesis of (+)-diepoxin sigma

The highly oxygenated antifungal anticancer natural product (+/-)-diepoxin sigma was prepared in 10 steps and in 15% overall yield from O-methylnaphthazarin. Highlights of the synthetic work include an Ullmann coupling and a possibly biomimetic oxidative spirocyclization for the introduction of the naphthalene ketal as well as the use of a retro-Diels-Alder reaction to unmask the reactive enone moiety in the naphthoquinone bisepoxide ring system. A novel highly bulky chiral binaphthol ligand was developed for a boron-mediated Diels-Alder reaction that constitutes a formal asymmetric total synthesis of (+)-diepoxin sigma.

UV mutagenesis and enzyme inhibitors as tools to elucidate the late biosynthesis of the spirobisnaphthalenes

The metabolite pattern of UV mutants of the spirobisnaphthalene producing fungus F-24'707 by TLC and HPLC analysis has been investigated. Mutants with differences in colony morphology or colour compared to the parent strain were isolated. Cultivation in shaking flasks and P flasks showed differences in the metabolite pattern of some of the strains. Furthermore, enzyme inhibitors were used to block the spirobisnaphthalene biosynthesis of the parent strain at different steps. Feeding of precursors and intermediates of cladospirone bisepoxide (15) led to a two-fold increase of the production of 15. From these data and preceding biosynthetic studies we deduced a general pathway for the biosynthesis of all spirobisnaphthalenes of the fungus F-24'707. This enables us to present the hypothesis that all bisnaphthalenes described so far are produced using a common pathway with only a few intermediates as central branching points.

Sphaerolone and dihydrosphaerolone, two bisnaphthyl-pigments from the fungus Sphaeropsidales sp. F-24'707

Two new bisnaphthalene compounds, sphaerolone (1) and dihydrosphaerolone (2), together with 2-hydroxyjuglone (9), were isolated from the culture broth of a Sphaeropsidales sp. (strain F-24'707) after inhibition of the regular proceeding 1,8-dihydroxynaphthalene (DHN) biosynthesis with tricyclazole. The structures of 1 and 2 were established by detailed spectroscopic analysis and present novel bisnaphthalenes. The biosynthetic origin of 1 and 2 as dimerization products of 1,3,8-trihydroxynaphthalene, an intermediate of the DHN biosynthesis, is discussed.