Cis-Trans Isomerization of Unsaturated Fatty Acid Methyl Ester by Natural Sulfur Compounds in Model Systems.

Growing evidence indicates that the intake of trans fatty acids (TFAs) increases the risk of numerous diseases, such as cardiovascular diseases. Recently, our group found that certain natural sulfur compounds (allyl isothiocyanate [AITC] and diallyl disulfide [DADS]) promote cis to trans isomerization of fatty acid esters during heat treatment. However, little information is available on the fatty acid isomerization with them. In this study, we investigated the effects of oxygen and α-tocopherol (antioxidant) on isomerization of oleic acid (18:1) methyl ester (OA-ME) in the presence of AITC and DADS. Furthermore, the effect of the simultaneous use of AITC and DADS was evaluated. Our results indicate that oxygen enhances the AITC-induced trans isomerization, and DADS was found to promote trans isomerization but inhibit AITC-induced trans isomerization during heating. Both AITC- and DADS-induced trans isomerization were inhibited by α-tocopherol. These results indicate that the trans isomerization of fatty acids induced by sulfur compounds can be controlled by devising a cooking process and the food ingredients used together.

Dietary fish oil enriched in very-long-chain polyunsaturated fatty acid reduces cardiometabolic risk factors and improves retinal function.

Very-long-chain polyunsaturated fatty acids (VLCPUFAs; C24-38) constitute a unique class of PUFA that have important biological roles, but the lack of a suitable dietary source has limited research in this field. We produced an n-3 C24-28-rich VLCPUFA-oil concentrated from fish oil to study its bioavailability and physiological functions in C57BL/6J mice. The serum and retinal C24:5 levels increased significantly compared to control after a single-dose gavage, and VLCPUFAs were incorporated into the liver, brain, and eyes after 8-week supplementation. Dietary VLCPUFAs resulted in favorable cardiometabolic changes, and improved electroretinography responses and visual performance. VLCPUFA supplementation changed the expression of genes involved in PPAR signaling pathways. Further in vitro studies demonstrated that the VLCPUFA-oil and chemically synthesized C24:5 are potent agonists for PPARs. The multiple potential beneficial effects of fish oil-derived VLCPUFAs on cardiometabolic risk and eye health in mice support future efforts to develop VLCPUFA-oil into a supplemental therapy.

Natural Sulfur Compounds, Allyl Isothiocyanate and Diallyl Disulfide, Promote Cis to Trans Isomerization of Fatty Acid Esters during Heat Treatment.

The effects of allyl isothiocyanate (AITC) and diallyl disulfide (DADS), widely found in edible vegetables, on thermal isomerization of unsaturated fatty acid esters (oleic acid methyl ester [OA-ME], linoleic acid methyl ester [LA-ME], and eicosapentaenoic acid ethyl ester [EPA-EE]) were investigated. Although heating with AITC and DADS significantly promoted cis to trans isomerization of all fatty acid esters, the isomerization trends varied greatly depending on the type of fatty acid. Specifically, AITC promoted thermal isomerization of OA-ME and LA-ME more efficiently than DADS; however, an opposite result was obtained for EPA-EE. For example, when OA-ME was heated at 180°C for 1 h with 1.0 equivalent of AITC and DADS, its trans isomer ratios reached 29.0 ± 7.1 and 7.6 ± 0.6%, respectively, and when EPA-EE was heated under the same conditions, its trans isomer ratios reached 4.2 ± 0.4 and 8.6 ± 0.2%, respectively. These results indicate that isothiocyanates and polysulfides would promote the formation of trans fatty acids in food processing under heating conditions.

Lincomycin at Subinhibitory Concentrations Potentiates Secondary Metabolite Production by Streptomyces spp.

Antibiotics have either bactericidal or bacteriostatic activity. However, they also induce considerable gene expression in bacteria when used at subinhibitory concentrations (below the MIC). We found that lincomycin, which inhibits protein synthesis by binding to the ribosomes of Gram-positive bacteria, was effective for inducing the expression of genes involved in secondary metabolism in Streptomyces strains when added to medium at subinhibitory concentrations. In Streptomyces coelicolor A3(2), lincomycin at 1/10 of its MIC markedly increased the expression of the pathway-specific regulatory gene actII-ORF4 in the blue-pigmented antibiotic actinorhodin (ACT) biosynthetic gene cluster, which resulted in ACT overproduction. Intriguingly, S. lividans 1326 grown in the presence of lincomycin at a subinhibitory concentration (1/12 or 1/3 of its MIC) produced abundant antibacterial compounds that were not detected in cells grown in lincomycin-free medium. Bioassay and mass spectrometry analysis revealed that some antibacterial compounds were novel congeners of calcium-dependent antibiotics. Our results indicate that lincomycin at subinhibitory concentrations potentiates the production of secondary metabolites in Streptomyces strains and suggest that activating these strains by utilizing the dose-response effects of lincomycin could be used to effectively induce the production of cryptic secondary metabolites. In addition to these findings, we also report that lincomycin used at concentrations for markedly increased ACT production resulted in alteration of the cytoplasmic protein (FoF1 ATP synthase α and ß subunits, etc.) profile and increased intracellular ATP levels. A fundamental mechanism for these unique phenomena is also discussed.

Biosynthesis of akaeolide and lorneic acids and annotation of type I polyketide synthase gene clusters in the genome of Streptomyces sp. NPS554.

The incorporation pattern of biosynthetic precursors into two structurally unique polyketides, akaeolide and lorneic acid A, was elucidated by feeding experiments with 13C-labeled precursors. In addition, the draft genome sequence of the producer, Streptomyces sp. NPS554, was performed and the biosynthetic gene clusters for these polyketides were identified. The putative gene clusters contain all the polyketide synthase (PKS) domains necessary for assembly of the carbon skeletons. Combined with the 13C-labeling results, gene function prediction enabled us to propose biosynthetic pathways involving unusual carbon-carbon bond formation reactions. Genome analysis also indicated the presence of at least ten orphan type I PKS gene clusters that might be responsible for the production of new polyketides.

Akaeolide, a carbocyclic polyketide from marine-derived Streptomyces.

Akaeolide, a novel polycyclic polyketide, was isolated from the culture extract of a marine-derived actinomycete belonging to the genus Streptomyces. The planar structure of the new compound was elucidated by spectroscopic analysis including NMR and MS, and the absolute configuration was determined by X-ray crystallographic analysis of its chlorinated derivative. Akaeolide possesses a 15-membered carbocyclic framework, apparently derived from the malonate pathway, with a tetrahydrofuran ring and a ß-keto-δ-lactone unit.

Neomaclafungins A-I: oligomycin-class macrolides from a marine-derived actinomycete.

Nine new 26-membered macrolides of the oligomycin subfamily, neomaclafungins A-I, were isolated from the fermentation broth of Actinoalloteichus sp. NPS702, which was isolated from marine sediment collected from Usa Bay, Kochi Prefecture, Japan. Their structures were identified through mass spectrometry and NMR experiments. They belong to the oligomycin class and have several distinct features including the presence of alkane or alkanol branches. Neomaclafungins A-I exhibited significant antifungal activity in vitro against Trichophyton mentagrophytes (ATCC 9533), showing MIC values between 1 and 3 µg/mL.

Usabamycins A-C: new anthramycin-type analogues from a marine-derived actinomycete.

New anthramycin-type analogues, designated usabamycin A-C (1, 2 and 3), have been isolated from cultures of Streptomyces sp. NPS853, a bacterium found in marine sediments. The structures of the new compounds were established on the basis of extensive spectroscopic analyses including 1D- and 2D-NMR ((1)H-(1)H COSY, HSQC, and HMBC) experiments. The usabamycins show weak inhibition of HeLa cell growth and selective inhibition of serotonin (5-hydroxytrypamine) 5-HT(2B) uptake.

Alstiphyllanines E-H, picraline and ajmaline-type alkaloids from Alstonia macrophylla inhibiting sodium glucose cotransporter.

Three new picraline-type alkaloids, alstiphyllanines E-G (1-3) and a new ajmaline-type alkaloid, alstiphyllanine H (4) were isolated from the leaves of Alstonia macrophylla together with 16 related alkaloids (5-20). Structures and stereochemistry of 1-4 were fully elucidated and characterized by 2D NMR analysis. Alstiphyllanines E and F (1 and 2) showed moderate Na(+)-glucose cotransporter (SGLT1 and SGLT2) inhibitory activity. A series of a hydroxy substituted derivatives 21-28 at C-17 of the picraline-type alkaloids have been derived as having potent SGLT inhibitory activity. 10-Methoxy-N(1)-methylburnamine-17-O-veratrate (6) exhibited potent inhibitory activity, suggesting that the presence of an ester side chain at C-17 may be important to show SGLT inhibitory activity. Structure activity relationship of alstiphyllanines on inhibitory activity of SGLT was discussed.

Gneyulins A and B, stilbene trimers, and noidesols A and B, dihydroflavonol-C-glucosides, from the bark of Gnetum gnemonoides.

Gneyulins A (1) and B (2), two new stilbene trimers consisting of oxyresveratrol constituent units, and noidesols A (3) and B (4), two new dihydroflavonol-C-glucosides, were isolated from the bark of Gnetum gnemonoides. The structures and configurations of 1-4 were elucidated on the basis of 2D NMR correlations and X-ray analysis. Gneyulins A (1) and B (2) showed inhibition of Na(+)-glucose transporters (SGLT-1 and SGLT-2).

Cyclic diarylheptanoids as Na+-glucose cotransporter (SGLT) inhibitors from Acer nikoense.

Two cyclic diarylheptanoids, acerogenins A (1) and B (2) have been isolated from the bark of Acer nikoense as inhibitors of Na(+)-glucose cotransporter (SGLT). Acerogenins A (1) and B (2) inhibited both isoforms, SGLT1 and SGLT2. Structure-activity relationship of acerogenin derivatives on inhibitory activity of SGLT as well as conformational analysis of 1 and 2 on the basis of J-resolved HMBC spectra and X-ray analysis were discussed.

Lorneic acids, trialkyl-substituted aromatic acids from a marine-derived actinomycete.

A marine-derived actinomyces strain (NPS554) isolated from a marine sediment sample collected from Miyazaki Harbor, Japan, at a depth of 38 m yielded two trialkyl-substituted aromatic acids, lorneic acid A (1) and lorneic acid B (2). The structures of the lorneic acids, which were elucidated by spectroscopic analysis, differed only in the side-chain, which contained either a conjugated double bond or a benzylic alcohol. Their structural differences affected inhibition activities against phosphodiesterase 5.

Indoxamycins A-F. Cytotoxic tricycklic polypropionates from a marine-derived actinomycete.

Six antitumor antibiotics of a new structure class, indoxamycins A-F (1-6), were isolated from a saline culture group of marine-derived actinomyces whose strains showed approximately 96% sequence homology of 16S rDNA with the family streptomycetaceae. The structures of these indoxamycins, which are unusual polyketides composed of six consecutive chiral centers, were assigned by combined spectral and chemical methods. In feeding experiments using a stable isotope label, indoxamycin A was assembled from propionate units initially forming the "aglycon" pentamethyl indeno furan. The discovery of these unprecedented compounds from marine-derived actinomycetes, a low gene homology genus, offers a significant opportunity for drug discovery.

Isolation and identification of antihypertensive peptides from antarctic krill tail meat hydrolysate.

Antarctic krill (Euphausia superba) obtained from the huge biomass in Antarctic waters is an important food product in Japan. Antarctic krill peptide powder (AKPP) prepared from the tail meat by enzymatic hydrolysis significantly decreased the systolic blood pressure in spontaneously hypertensive rats by a single oral administration (1, 10, or 100 mg). Presumably, the effect of AKPP was through inhibition of the conversion of angiotensin, which mediates blood pressure elevation, from its inactive propeptide to the mature angiotensin. Two potent angiotensin I-converting enzyme (ACE) inhibitory peptides were isolated from AKPP by high-performance liquid chromatography (HPLC) and identified as Val-Trp (IC(50)= 2.75 microg/mL; 12.9 microM) and Leu-Lys-Tyr (IC(50)= 4.26 microg/mL; 10.1 microM). Val-Trp and Leu-Lys-Tyr comprised 0.025%+/- 0.0023% (w/w) and 0.018%+/- 0.0023% (w/w) of AKPP, respectively, as measured by electrospray ionization mass spectrometry (ESI-MS). The contributions of Val-Trp and Leu-Lys-Tyr to the ACE inhibitor activity of AKPP were 17.7%+/- 1.60% and 8.04%+/- 1.03%, respectively, suggesting that these 2 peptides constitute a substantial portion of the overall ACE inhibitor potential of AKPP.

Na+-glucose cotransporter (SGLT) inhibitory flavonoids from the roots of Sophora flavescens.

The methanol extract of Sophora flavescens, which is used in traditional Chinese medicine (sophorae radix), showed potent Na(+)-glucose cotransporter (SGLT) inhibitory activity. Our search for active components identified many well-known flavonoid antioxidants: kurarinone, sophoraflavanone G, kushenol K, and kushenol N.