Oxygenated Hexylitaconates from a Marine Sponge-Derived Fungus Penicillium sp.

Abstract

Although dicarboxylic acids do not occur in appreciable amount as components of animal or vegetal lipids, generally they are important metabolic products of fatty acids. Especially the a,b-dicarboxylic acid and its derivatives, such as itaconic acid 1,2) and citraconic acid derivatives, 3) have been of much interest for their biosynthesis, stereochemistry, and chemical relationship. Furthermore, some of them were reported to exhibit various interesting bioactivities, such as plant growth-stimulation, 4) production of a cellulolytic active oxygen species, inhibition of the iron redox reaction, 5) inhibition of p53-HDM2 interaction which can induce apoptosis in human cancer cells, 6) and anti-trypanosomal activity. 7)In the course of search for bioactive metabolites from marine organisms, five hexylitaconic acid derivatives including four new ones (1-4) were isolated from a sponge-derived fungus Penicillium sp. Herein we describe the structure elucidation and the biological evaluation of the compounds. Results and DiscussionAccurate mass measurement (high resolution (HR)-FAB-MS) of compound 1 (m/z 259.1549 [MϩH] ϩ , Dϩ0.4 mmu) revealed the molecular formula to be C 13 H 22 O 5 with three degrees of unsaturation. Thirteen carbon signals were evident in the 13 C-NMR spectrum (Table 1) and deduced to be three methyl, five methylene, two methine, and three quaternary carbons from the distortionless enhancement by polarization transfer (DEPT)135 spectrum. According to 1 H-and In the course of our search for bioactive metabolites from marine organisms, new hexylitaconic acid derivatives (1-4), along with (3S)-hexylitaconic acid (5), were isolated from a sponge-derived fungus Penicillium sp. Based on the NMR and MS data, the structures of compounds 1-4 were defined as a a,b b-dicarboxylic acid derivatives, such as hexylitaconic acid and tensyuic acids which were previously reported as metabolite of Aspergillus niger, Penicillium striatisporum, or Apiospora montagnei. The isolated compounds were evaluated for cytotoxicity against a panel of five human solid tumor cell lines, and for anti-inflammatory activity gauged by their inhibitory effects on the production of major pro-inflammatory mediators (nitric oxide (NO), interleukin (IL)-6, tumor necrosis factor (TNF)-a a, and IL-1b b) in murine macrophage cells. Compounds 1 and 4 showed weak inhibition of IL-1b b production at the concentration of 200 m mM.

Biosynthesis of alkylcitric acids inAspergillus nigerinvolves both co-localized and unlinked genes

“…We used one-dimensional and two-dimensional NMR spectra to elucidate the structure of the two major metabolites produced by strain SP1: hexylaconitic acid and hexylitaconic acid (Supplemental information, Section on structural elucidation). Structures of the other compounds were determined by comparing their 1 H-and 13 C-NMR spectra with the major hexylaconitic acid and hexylitaconic acid, and with published data 24,[26][27]38 . Since all compounds in this study are derivatives of either hexylaconitic acid or hexylitaconic acid, we designate the major compounds as hexylaconitic acid A and hexylitaconic acid A.…”

“…To identify the candidate cis-aconitate decarboxylase, we examined orthologous gene clusters predicted to be involved in alkylcitric acids biosynthesis. Previous reports have shown that alkylcitric acids and the similar structured maleidrides are being produced not only in A. niger but also in other filamentous fungi including Penicillium striatosporum 27,41 and A. oryzae 42 . Therefore, we used the alkylcitric acid cluster of A. niger as query to search for orthologous gene clusters in the published Aspergilli genomes.…”

“…Alkylcitrates comprise two moieties; a saturated alkyl "tail" and a "head" derived from citric acid. Alkylcitrates isolated from filamentous fungi include the tensyuic acids (A-F) [22][23] , hexylaconitic acid anhydride [23][24] , hexylitaconic acid [24][25] , hexylcitric acid 26 and hydroxylated hexylitaconic acids 27 (Figure 1). Members of alkylcitric acids have been shown to possess useful bioactive properties including plant root growth promotion (hexylitaconic acid) 24 , anti-fungal (hexylaconitic acid anhydride) 28 , antibiotic, and anti-parasitic properties (tensyuic acid C) 22 .…”

“…Members of alkylcitric acids have been shown to possess useful bioactive properties including plant root growth promotion (hexylitaconic acid) 24 , anti-fungal (hexylaconitic acid anhydride) 28 , antibiotic, and anti-parasitic properties (tensyuic acid C) 22 . The production level of these bioactive alkylcitrates under laboratory conditions is low (ng-mg/L range) 22,24,[26][27] . In this work, we sought to use genomic information and chemical structure data to determine the SM gene cluster responsible for the production of the alkylcitric acid orphan compounds, manipulate their expression to increase the production of specific compounds, and to produce previously uncharacterized alkylcitric acids.…”

“…In this work, we sought to use genomic information and chemical structure data to determine the SM gene cluster responsible for the production of the alkylcitric acid orphan compounds, manipulate their expression to increase the production of specific compounds, and to produce previously uncharacterized alkylcitric acids. [22][23][24][26][27] showing two common moieties: a saturated hydrocarbon tail (thin bonds) and a citrate-derived head (thick bonds).…”