Identification of a novel target of sulforaphane: Sulforaphane binds to acyl-protein thioesterase 2 (APT2) and attenuates its palmitoylation.

Sulforaphane (SFaN) is a food-derived compound with several bioactive properties, including atherosclerosis, diabetes, and obesity treatment. However, the mechanisms by which SFaN exerts its various effects are still unclear. To elucidate the mechanisms of the various effects of SFaN, we explored novel SFaN-binding proteins using SFaN beads and identified acyl protein thioesterase 2 (APT2). We also found that SFaN binds to the APT2 via C56 residue and attenuates the palmitoylation of APT2, thereby reducing plasma membrane localization of APT2. This study reveals a novel bioactivity of SFaN as a regulator of APT2 protein palmitoylation.

Advancement in structure elucidation of natural medium-sized lactones through synthesis and theoretical calculations.

Medium-sized lactones are an important class of natural products with diverse biological activities. Unlike conventional organic compounds, these molecules exhibit elevated levels of conformational flexibility. This inherent structural feature occasionally exacerbates the complexities associated with determining their conformation, thereby posing challenges in deciphering their stereochemistry or, in certain instances, leading to incorrect structures. This review highlights specific scenarios in which synthetic studies and computational chemistry have assumed pivotal roles in unveiling the structures of lactones, which have previously eluded definitive elucidation.

Synthesis, growth inhibitory activity against tumor cells, and structure-activity relationship of CGK733 and its analogs.

CGK733 was reported as a compound that inhibited ATM/ATR kinase activities and blocked their checkpoint signaling pathways with great selectivity. However, this paper was subsequently retracted, and the truth about the activity of CGK733 remains unclear. We synthesized various analogs of CGK733 with a modification of the carboxylic acid moiety and/or the aniline derivative moiety to accumulate knowledge of the structure-activity relationship of this compound. Growth inhibitory activity of CGK733 and novel 35 analogs against HeLa S3 cells was evaluated, and the structure-activity relationship revealed that analogs with the 2-naphthyl or 4-fluorophenyl group instead of the benzhydryl group have activity comparable to CGK733 and that the 3-nitro group on the aniline moiety significantly affects the activity.

Divergent Synthesis of Stachyurin and Casuarinin Focusing on C-Glycosidic Bond Reactivity.

Stachyurin and casuarinin are ellagitannins, a class of polyphenols that exhibit various biological activities that have an impact on human health. Casuarinin is a stachyurin stereoisomer. These compounds contain the characteristic C-glycosidic bond between the open-chain d-glucose and the phenol aromatic ring. Therefore, chemical elucidation of the C-glycosidic bond reactivity is required to exploit their multiple bioactivities. This study developed a method for the divergent synthesis of stachyurin and casuarinin via the α-selective C-glycosylation as well as the ß-selective introduction of the oxygen functional group, focusing on structural specificity. The proposed method applies to the syntheses of stachyurin and casuarinin analogues, thereby facilitating the utilisation of their beneficial bioactivities.

Disproof of the Proposed Structures of Bradyoxetin, a Putative Bradyrhizobium japonicum Signaling Molecule, and HMCP, a Putative Ralstonia solanacearum Quorum-Sensing Molecule.

First, we revisited the reported NMR data of bradyoxetin, a putative cell density factor of Bradyrhizobium japonicum, and found some inconsistencies in the proposed structure. To elucidate the correct structure, we synthesized model oxetane compounds and confirmed that the NMR data of the synthetic compounds did not match those of the reported bradyoxetin. After reinterpreting the reported NMR data, we concluded that bradyoxetin must be chloramphenicol. Next, some derivatives of 2-hydroxy-4-((methylamino)(phenyl)methyl)cyclopentanone (HMCP), which is a putative quorum-sensing molecule of Ralstonia solanacearum, were synthesized. The NMR spectra of the synthesized compounds were completely different from those of the reported natural products. Based on theoretical studies, including the estimation of 1H and 13C NMR chemical shifts using density functional theory calculations, we confirmed the correctness of the structure of the synthesized compound. These results strongly suggest that the proposed structure of HMCP could be incorrect.

Studies on analogs of DAMASCENOLIDETM: Part 4. Synthesis and odor evaluation of sulfur-containing analogs of DAMASCENOLIDETM.

DAMASCENOLIDETM [1, 4-(4-methylpent-3-en-1-yl)furan-2(5H)-one], which is isolated from damask rose, is a useful aroma compound with a citrus-like odor. We have previously reported on the synthesis and odor properties of 34 analogs of 1 as part of our new aroma compound development project. In order to develop better aroma compounds and to gather more information on structure-odor relationships, 6 novel sulfur-containing analogs of 1 were synthesized. Odor evaluation revealed that their odors differed significantly from those of the corresponding sulfur-free compounds. The introduction of a sulfur atom does not necessarily result in a sulfur-like odor. In particular, the 2(5H)-thiophenone analogs gave waxy, oily, and lactone-like odors that are uncharacteristic of sulfur-containing compounds. In many synthesized analogs, the introduction of a sulfur atom led to an increase in odor intensity, as expected.

Studies on analogs of DAMASCENOLIDETM: Part 3. Synthesis and odor evaluation of dimethylated, cyclopropanated, and other analogs of DAMASCENOLIDETM.

DAMASCENOLIDETM [1, 4-(4-methylpent-3-en-1-yl)furan-2(5H)-one], which has a citrus-like odor, is an important aroma component of roses. We have previously reported on the synthesis and odor evaluation of 24 analogs of 1 as part of our new aroma compound developing project. To accumulate more information on structure-odor relationships, 10 more promising analogs such as dimethylated and cyclopropanated analogs were synthesized and subjected to odor evaluation. As a result, it was found that dimethylation of the furanone ring affected the odor. It was also found that cyclopropanation of 1 affected the odor, whereas cyclopropanation of the double bond isomer of 1 did not significantly affect the odor. The effects on the odor caused by ring size expansion and replacement of the side chain were also investigated.

Synthesis of both enantiomers of lycoperdic acid, an unusual mushroom-derived amino acid.

An efficient synthesis of both enantiomers of lycoperdic acid, a 4-hydroxyglutamic acid derivative from edible mushroom Lycoperdon perlatum, was achieved from a chiral aminoalcohol. The key steps were a stereoselective introduction of a C3 unit into a bicyclic ketone and oxidative cleavage of a cyclic vicinal diol into a dicarboxylic acid. This report provides the first synthesis of (-)-lycoperdic acid.

Identification of biosynthetic intermediates for the mating hormone α2 of the plant pathogen Phytophthora.

The heterothallic group of the plant pathogen Phytophthora can sexually reproduce between the cross-compatible mating types A1 and A2. The mating hormone α2, produced by A2 mating type and utilized to promote the sexual reproduction of the partner A1 type, is known to be biosynthesized from phytol. In this study, we identified 2 biosynthetic intermediates, 11- and 16-hydroxyphytols (1 and 2), for α2 by administering the synthetic intermediates to an A2-type strain to produce α2 and by administering phytol to A2 strains to detect the intermediates in the mycelia. The results suggest that α2 is biosynthesized by possibly 2 cytochrome P450 oxygenases via 2 hydroxyphytol intermediates (1 and 2) in A2 hyphae and secreted outside.

Enantioselective synthesis and stereochemical determination of the highly reduced polyketide ishigamide.

Ishigamide was isolated as a metabolite of a recombinant strain of Streptomyces sp. MSC090213JE08 and its unsaturated fatty acid moiety has been confirmed in vitro to be synthesized by a type II PKS. Biosynthesis of such a highly reduced polyketide by a type II PKS is worthy of note. However, absolute configuration of ishigamide remained unknown. (R)-Ishigamide was synthesized enantioselectively employing Stille coupling and Wittig reaction between three units, vinyl iodide, stannyldienal, and Wittig salt. Stereochemistry of natural ishigamide was determined to be R by chiral HPLC analysis comparing with the synthesized standard.

Analog synthesis of DAMASCENOLIDETM, an important aroma component of roses, and their odor properties.

DAMASCENOLIDETM [1, 4-(4-methylpent-3-en-1-yl)furan-2(5H)-one], which has a citrus-like odor, is an important aroma component of roses. We have previously reported on the synthesis and odor evaluation of double-bond isomers of 1 and concluded that the position and the geometric isomerism of the double-bond had a significant effect on the odor. For the purpose of deepening knowledge about structure-odor relationships, we synthesized 13 analogs of compound 1 and evaluated their odors. As a result, it was found that the presence of two double-bonds and branched methyl group at the terminal position in the side chain was essential in order to have a citrus-like odor. Substitution of the side chain with appropriate length at the appropriate 4-position of the 2(5H)-furanone ring was also an important factor in determining the quality of the odor.

Cucumis sativus secretes 4'-ketoriboflavin under iron-deficient conditions.

A new compound in cucumber, Cucumis sativus, nutrient solution that appears under iron-deficient conditions, but not under ordinary culture conditions, has been revealed by HPLC analysis. The chemical structure of this compound was identified using LC-MS and NMR techniques as that of 4'-ketoriboflavin. This is the first report to show that 4'-ketoriboflavin can be found in metabolites from organisms.

Synthesis and DFT-NMR-guided structure revision of cremenolide.

The structure of an anti-plant pathogenic and plant growth-promoting nonenolide, namely cremenolide, was revised by an efficient combination of DFT-based theoretical NMR calculations and synthesis of a target diastereomer. Initially, the planar structure of cremenolide was reconsidered by an individual analysis of the reported NMR spectra. Subsequently, the relative configuration was predicted using NMR calculations of all possible diastereomers based on the ωB97X-D functional. Finally, the relative configuration of cremenolide was unambiguously confirmed by preparation of the proposed structure.

Chrysin 7-O-ß-d-glucopyranoside increases hepatic low-density lipoprotein receptor expression through AMP-activated protein kinase activation.

Elevated plasma low-density lipoprotein (LDL) cholesterol level is a risk factor for developing atherosclerosis. Increased LDL receptor (LDLR) expression is expected to reduce the risk of atherosclerotic disease since hepatic LDLR is essential for clearing plasma LDL cholesterol. Here, we screened human LDLR promoter effectors and observed that extracts from peduncles of sweet cherry (Prunus avium) 'Sato-Nishiki' induce LDLR gene promoter activity. We used several analytical and chemical methods to show that chrysin 7-O-ß-d-glucopyranoside (chrysin-7G) is one of the compounds that stimulate LDLR gene promoter activity in cherry peduncle extracts. Furthermore, synthetic chrysin-7G increased the expression and activity of LDLR. The chrysin-7G-mediated increase in LDLR expression and activity was completely abolished by treatment with an AMP-activated protein kinase (AMPK) inhibitor, compound C. These results indicate that chrysin-7G increases LDLR expression through AMPK activation and may be a useful compound that can be recycled from waste parts of agricultural products.

Adjacent double branches exist in the branching structure of starch.

Starch is composed of two giant polymers of glucose-linked amylose and amylopectin but is not considered to have a branched structure with adjacent α-1,6-linkages (adjacent double branches). We previously discovered that the oligosaccharide DP6-1 contains adjacent double branches in sake, a Japanese rice wine. In this study, we analyzed the oligosaccharides generated from rice starch following porcine pancreatic α-amylase and glucoamylase digestion by hydrophilic interaction chromatography coupled with time-of-flight/mass spectrometry. We found that their elution times were identical to those of the oligosaccharides containing adjacent double branches observed in sake. Nuclear magnetic resonance (NMR) analysis confirmed that one of the oligosaccharides was identical to DP6-1. This indicates for the first time that adjacent double branches exist in the branching structure of starch. The adjacent double branches were estimated to be present at a ratio of approximately 1:100 of the total branching points in rice starch, suggesting that the contribution of the adjacent double branch to the entire structure of starch may be limited. Nonetheless, we found adjacent double branches in starch from rice, maize, wheat, and potato, which indicates that this novel branching pattern is universally present in starch.

Sulforaphane suppresses the activity of sterol regulatory element-binding proteins (SREBPs) by promoting SREBP precursor degradation.

Sterol regulatory element-binding proteins (SREBPs) are transcription factors that regulate various genes involved in cholesterol and fatty acid synthesis. In this study, we describe that naturally occurring isothiocyanate sulforaphane (SFaN) impairs fatty acid synthase promoter activity and reduces SREBP target gene (e.g., fatty acid synthase and acetyl-CoA carboxylase 1) expression in human hepatoma Huh-7 cells. SFaN reduced SREBP proteins by promoting the degradation of the SREBP precursor. Amino acids 595-784 of SREBP-1a were essential for SFaN-mediated SREBP-1a degradation. We also found that such SREBP-1 degradation occurs independently of the SREBP cleavage-activating protein and the Keap1-Nrf2 pathway. This study identifies SFaN as an SREBP inhibitor and provides evidence that SFaN could have major potential as a pharmaceutical preparation against hepatic steatosis and obesity.

Sulfoquinovosylglyceryl ether, a new group of ether lipids from lake ball-forming green alga Aegagropilopsis moravica (family Pithophoraceae).

Ether lipids are a minor group of glycerolipids but widespread in nature, playing a vital function as membrane lipids, signalling molecules, or buoyant material. We have discovered sulfoquinovosylchimyl alcohol (1), a sulfonate-substituted glyceroglycolipid, from a lake ball-forming green alga Aegagropilopsis moravica (family Pithophoraceae), with the guidance of antimicrobial activity. The structure of 1, including absolute configurations of all sterogenic centers, was established by extensive NMR analysis, chemical degradation studies, and finally by total synthesis. Lipid 1 is an ether variant of a lyso-form of sulfoquinovosyldiacylglycerol, a chloroplast-specific membrane lipid, and thus represents a new lipid class, sulfoquinovosylglyceryl ether. A high occurrence of mobile life form in the family Pithophoraceae and a unique behaviour of chloroplasts reported in closely related Aegagropila linnaei, the famous lake-ball alga, implies a possible role of lipid 1 or its acyl derivatives in ecological adaptation to dysphotic niches.

Novel glucoamylase-resistant gluco-oligosaccharides with adjacent α-1, 6 branches at the non-reducing end discovered in Japanese rice wine, sake.

Sake, a traditional Japanese rice wine, contains various oligosaccharides (Sake oligosaccharides; SAOs) derived from rice starch. We previously found that SAOs reach a high degree of polymerization (DP). In this study, we developed a hydrophilic interaction liquid chromatography-time-of-flight/mass spectrometry (HILIC-TOF/MS) based analytical method to separate isomeric SAOs. Isomers of SAOs with DP = 6, 7, and 8, which were named DP6-1, DP7-1, DP8-1 and DP8-2, respectively, were purified from sake and their structures were determined by two-dimensional NMR spectroscopy. These were novel oligosaccharides containing two α-1, 6 bonded branches on an α-1, 4-linked glucose main chain. Interestingly, adjacent double α-1, 6 branches that have not been identified in starch, were found in DP6-1, DP7-1, and DP8-1, suggesting the presence of the branching pattern in starch. DP6-1 was poorly digested by fungal glucoamylase, and this may be attributed to its adjacent double branches at the non-reducing end.

Synthesis of (2RS,8R,10R)-YM-193221 and an improved approach to tyroscherin, bioactive natural compounds from Pseudallescheria sp.

Short-step syntheses of (2RS,8R,10R)-YM-193221 (1) and tyroscherin (2), which are biologically active compounds isolated from Pseudallescheria sp., were accomplished in six and eight steps from L-tyrosine. The relative stereochemistry of natural YM-193221 was determined to be 8R*,10R*.

Transglycosylation Forms Novel Glycoside Ethyl α-Maltoside and Ethyl α-Isomaltoside in Sake during the Brewing Process by α-Glucosidase A of Aspergillus oryzae.

Sake, the Japanese rice wine, contains a variety of oligosaccharides and glucosides produced by fungal enzymes during the brewing process. This study investigates the effect of knocking out the Aspergillus oryzae α-glucosidase (agdA) gene on the transglycosylation products in brewed sake. In addition to α-ethyl glucoside and α-glyceryl glucoside, the amount of two compounds that have molecular mass values similar to that of ethyl maltose decreased by agdA gene knockout. Both compounds were synthesized, in vitro, from maltose and ethanol with purified agdA. Nuclear magnetic resonance analysis identified the two compounds as ethyl α-maltoside and ethyl α-isomaltoside, respectively, which are novel compounds in sake as well as in the natural environment. Quantitative analysis of 111 commercially available types of sake showed that these novel compounds were widely present at concentrations of several hundred mg/L, suggesting that both of them are ones of the common glycosides in sake.