Approach to the "Missing" Diarylsilylene: Formation, Characterization, and Intramolecular C-H Bond Activation of Blue Diarylsilylenes with Bulky Rind Groups.

The treatment of the bulky Rind-based dibromosilanes, (Rind)2SiBr2 (2) [Rind = 1,1,7,7-tetra-R1-3,3,5,5-tetra-R2-s-hydrindacen-4-yl: EMind (a: R1 = Et, R2 = Me) and Eind (b: R1 = R2 = Et)], with two equivalents of tBuLi in Et2O at low temperatures resulted in the formation of blue solutions derived from the diarylsilylenes, (Rind)2Si: (3). Upon warming the solutions above -20 °C, the blue color gradually faded, accompanying the decomposition of 3 and yielding cyclic hydrosilanes (4) via intramolecular C-H bond insertion at the Si(II) center. The molecular structures of the bulky Eind-based 3b and 4b were confirmed by X-ray crystallography. Thus, at -20 °C, blue crystals were formed (Crystal-A), which were identified as mixed crystals of 3b and 4b. Additionally, colorless crystals of 4b as a singular component were isolated (Crystal-B), whose structure was also determined by an X-ray diffraction analysis. Although the isolation of 3 was difficult due to their thermally labile nature, their structural characteristics and electronic properties were discussed based on the experimental findings complemented by computational results. We also examined the hydrolysis of 3b to afford the silanol, (Eind)2SiH(OH) (5b).

Role of the thiosugar ring in the inhibitory activity of salacinol, a potent natural α-glucosidase inhibitor.

Herein, ring-cleaved (24) and truncated (25) analogues of an azasugar, 1-deoxynojirimycin (23), exhibited inhibitory activity (Ki = 4-10 µM) equal to that of the parent compound (1, Ki = 14 µM). Based on this structure-activity relationship (SAR), four ring-cleaved (26a-26c and 27c) and three truncated (28a-28c) analogues of salacinol (1), a potent thiosugar-ring-containing α-glucosidase inhibitor, were synthesised. Bioassay results revealed that all the synthetics were inactive, indicating that the 5-membered thiosugar ring of 1 played an essential role in the potent activities of sulfonium-type inhibitors. The present findings are interesting and important in understanding the function of salacinol, considering that the observed inhibitory activity trend was contrary to the SAR observed in aza-compounds (23, 24, and 25) in a previous study, which suggested that the cyclic structure did not contribute to their strong inhibitory activity.

Total Synthesis of Calanthoside, a Potential Hair Growth Stimulant: A Facile Synthetic Approach via One-Pot S- and O-Glucosidic Bond Formation.

The first total synthesis of calanthoside (1), which exhibits potent proliferative activity against human hair follicle dermal papilla cells, has been achieved in seven steps with an overall yield of 43% on a gram scale starting from anthranilic acid (11). The synthetic strategy features a one-pot process involving thioglucoside bond formation via nucleophilic substitution reaction and enol-glucosylation for building the S-,O-bisdesmoside structure of 1. Moreover, the one-pot reaction showed broad substrate adaptability to several sugar donors other than d-glucose, thus affording S,O-bisglycoside intermediates in ∼84% yield.

Biosynthetic diversification of non-ribosomal peptides through activity-based protein profiling of adenylation domains.

We describe activity-based protein profiling for analyzing the adenylation domains of non-ribosomal peptide synthetases (ABPP-NRPS) in bacterial proteomes. Using a range of non-proteoinogenic amino acid sulfamoyladenosines, the competitive format of ABPP-NRPS provided substrate tolerance toward non-proteinogenic amino acids. When coupled with precursor-directed biosynthesis, a non-proteinogenic amino acid (O-allyl-L-serine) was successfully incorporated into gramicidin S.

Infused juice concentrate of Japanese plum Prunus mume attenuates inflammatory vascular remodeling in a mouse model of hypertension induced by angiotensin II.

Fruit from the Prunus mume tree is a traditional food in Japan. Recently, bainiku-ekisu, an infused juice concentrate of Japanese Prunus mume, is attracting attention as a health promoting supplement. Angiotensin II (Ang II) plays a central role in development of hypertension. It has been reported that bainiku-ekisu treatment attenuates the growth-promoting signaling induced by Ang II in vascular smooth muscle cells. However, whether bainiku-ekisu has any effect on an animal model of hypertension remains unknown. Therefore, this study was designed to explore the potential anti-hypertensive benefit of bainiku-ekisu utilizing a mouse model of hypertension with Ang II infusion. Male C57BL/6 mice were infused with Ang II for 2 weeks and given 0.1% bainiku-ekisu containing water or normal water for 2 weeks with blood pressure evaluation. After 2 weeks, mice were euthanized, and the aortas were collected for evaluation of remodeling. Aortic medial hypertrophy was observed in control mice after Ang II infusion, which was attenuated in bainiku-ekisu group with Ang II infusion. Bainiku-ekisu further attenuated aortic induction of collagen producing cells and immune cell infiltration. Development of hypertension induced by Ang II was also prevented by bainiku-ekisu. Echocardiograph indicated protection of Ang II-induced cardiac hypertrophy by bainiku-ekisu. In vascular fibroblasts, bainiku-ekisu attenuated vascular cell adhesion molecule-1 induction, an endoplasmic reticulum stress marker, inositol requiring enzyme-1α phosphorylation, and enhancement in glucose consumption in response to Ang II. In conclusion, Bainiku-ekisu prevented Ang II-induced hypertension and inflammatory vascular remodeling. Potential cardiovascular health benefit to taking bainiku-ekisu should be further studied.

A hydrolysate of poly-trans-[(2-carboxyethyl)germasesquioxane] (Ge-132) suppresses Cav3.2-dependent pain by sequestering exogenous and endogenous sulfide.

Poly-trans-[(2-carboxyethyl)germasesquioxane] (Ge-132), an organogermanium, is hydrolyzed to 3-(trihydroxygermyl)propanoic acid (THGP) in aqueous solutions, and reduces inflammation, pain and cancer, whereas the underlying mechanisms remain unknown. Sulfides including H2S, a gasotransmitter, generated from l-cysteine by some enzymes including cystathionine-γ-lyase (CSE), are pro-nociceptive, since they enhance Cav3.2 T-type Ca2+ channel activity expressed in the primary afferents, most probably by canceling the channel inhibition by Zn2+ linked via coordinate bonding to His191 of Cav3.2. Given that germanium is reactive to sulfur, we tested whether THGP would directly trap sulfide, and inhibit sulfide-induced enhancement of Cav3.2 activity and sulfide-dependent pain in mice. Using mass spectrometry and 1H NMR techniques, we demonstrated that THGP directly reacted with sulfides including Na2S and NaSH, and formed a sulfur-containing reaction product, which decreased in the presence of ZnCl2. In Cav3.2-transfected HEK293 cells, THGP inhibited the sulfide-induced enhancement of T-type Ca2+ channel-dependent membrane currents. In mice, THGP, administered systemically or locally, inhibited the mechanical allodynia caused by intraplantar Na2S. In the mice with cyclophosphamide-induced cystitis and cerulein-induced pancreatitis, which exhibited upregulation of CSE in the bladder and pancreas, respectively, systemic administration of THGP as well as a selective T-type Ca2+ channel inhibitor suppressed the cystitis-related and pancreatitis-related visceral pain. These data suggest that THGP traps sulfide and inhibits sulfide-induced enhancement of Cav3.2 activity, leading to suppression of Cav3.2-dependent pain caused by sulfide applied exogenously and generated endogenously.

A Gedunin-Type Limonoid, 7-Deacetoxy-7-Oxogedunin, from Andiroba (Carapa guianensis Aublet) Reduced Intracellular Triglyceride Content and Enhanced Autophagy in HepG2 Cells.

The seed oil of Carapa guianensis Aublet (Andiroba) has been used in folk medicine for its insect-repelling, anti-inflammatory, and anti-malarial activities. This study aimed to examine the triglyceride (TG) reducing effects of C. guianensis-derived limonoids or other commercially available limonoids in human hepatoblastoma HepG2 cells and evaluate the expression of lipid metabolism or autophagy-related proteins by treatment with 7-deacetoxy-7-oxogedunin (DAOG; 1), a principal limonoid of C. guianensis. The gedunin-type limonoids, such as DAOG (% of control at 20 µM: 70.9 ± 0.9%), gedunin (2, 74.0 ± 1.1%), epoxyazadiradione (4, 73.4 ± 2.0%), 17ß-hydroxyazadiradione (5, 79.9 ± 0.6%), 7-deacetoxy-7α-hydroxygedunin (6, 61.0 ± 1.2%), andirolide H (7, 87.4 ± 2.2%), and 6α-hydroxygedunin (8, 84.5 ± 1.1%), were observed to reduce the TG content at lower concentrations than berberine chloride (BBR, a positive control, 84.1 ± 0.3% at 30 µM) in HepG2 cells pretreated with high glucose and oleic acid. Andirobin-, obacunol-, nimbin-, and salannin-type limonoids showed no effect on the intracellular TG content in HepG2 cells. The TG-reducing effect of DAOG was attenuated by the concomitant use of compound C (dorsomorphin), an AMPK inhibitor. Further investigation on the detailed mechanism of action of DAOG at non-cytotoxic concentrations revealed that the expressions of autophagy-related proteins, LC3 and p62, were upregulated by treatment with DAOG. These findings suggested that gedunin-type limonoids from Andiroba could ameliorate fatty liver, and that the action of DAOG in particular is mediated by autophagy.

Structure-activity relationship study of 4,5-didehydroguadiscine, an aporphine alkaloid showing potent melanogenesis-inhibitory activity in B16 melanoma cells.

Although 4,5-didehydroguadiscine (12a), an alkaloid with potent melanogenesis-inhibitory activity isolated from Hornschuchia obliqua (Annonaceae), consists of an aporphine nucleus with an aromatized B-ring, to date, it has not been utilized as a template for structure-activity relationship (SAR) studies of pharmacological activities because of its exceptional structure. Accordingly, herein, five analogs (12b-12f) of 12a and five benzylisoquinoline analogs (13b-13f) lacking the C11a-C11b bond of 12b-12f were prepared. The inhibitory effects of 12b-12f and 13b-13f on melanogenesis in theophylline-stimulated B16 melanoma 4A5 cells were examined and compared with those of 12a. Melanogenesis-inhibitory activities of 12b-12f were the same as that of 12a, whereas the melanogenesis-inhibitory activities of 13b-13f were significantly inferior to those of 12a and 12b-12f. These results suggest that the C11a-C11b bond plays an essential role in the melanogenesis-inhibitory activities of 12a-12e.

Ligand compatibility of salacinol-type α-glucosidase inhibitors toward the GH31 family.

We show that salacinol-type α-glucosidase inhibitors are ligand-compatible with the GH 31 family. Salacinol and its 3'-O-benzylated analogs inhibit human lysosomal α-glucosidase at submicromolar levels. Simple structure-activity relationship studies reveal that the salacinol side-chain stereochemistry significantly influences binding to GH31 α-glucosidases.

Elongation of the side chain by linear alkyl groups increases the potency of salacinol, a potent α-glucosidase inhibitor from the Ayurvedic traditional medicine "Salacia," against human intestinal maltase.

Four chain-extended analogs (12a-12d) and two related de-O-sulfonated analogs (13a and 13c) by introducing alkyl groups (a: R = C3H7, b R = C6H13, c: R = C8H17, d: R = C10H21) to the side chains of salacinol (1), a natural α-glucosidase inhibitor from Ayurvedic traditional medicine "Salacia", were synthesized. The α-glucosidase inhibitory activities of all the synthesized analogs were evaluated in vitro. Against human intestinal maltase, the inhibitory activities of 12a and 13a with seven-carbon side chain were equal to that of 1. In contrast, analogs (12b-12d, and 13c) exhibited higher level of inhibitory activity against the same enzyme than 1 and had equal or higher potency than those of the clinically used anti-diabetics, voglibose, acarbose, and miglitol. Thus, elongation of the side chains of 1 was effective for specifically increasing the inhibitory activity against human intestinal maltase.

Identification of Compounds in Coleus forskohlii Extract Involved in the Induction of Hepatic CYP and Fatty Liver in Mice.

Coleus forskohlii extract (CFE), a popular weight-loss herbal product, induces hepatic cytochrome P450 (CYP) and fatty liver in mice; however, its main bioactive ingredient, forskolin, does not show such effects. To ensure the safety of CFE as a dietary supplement, identification of the compounds implicated in the induction of hepatic CYP and fatty liver is required. In this study, we separated a crude CFE extract into 5 fractions (Fr.) by column chromatography and administered the fractions to mice for one week to assess their ability to induce CYP and fatty liver. CYP induction was detected for all fractions, indicating that many compounds may be involved in CYP induction, while fatty liver was only detected for Fr. 2. Further isolation and purification of Fr. 2 by column chromatography identified 14-deoxycoleon U as a major compound and crocetin dialdehyde as a pigment compound. An in vivo mouse study revealed that crocetin dialdehyde had no effect on the liver and, as 14-deoxycoleon U was the major compound in Fr. 2, it is likely that the active compound inducing fatty liver in CFE is 14-deoxycoleon U. These findings will facilitate the preparation of standardized safe CFE ingredients for dietary supplements.

Biotransformation of (+)-isofraxinellone by Aspergillus niger and insect antifeedant activity.

The biotransformation of (+)-isofraxinellone (1) by Aspergillus niger was investigated. Compound 1 was transformed to only one new compound 2. The structure of 2 was identified as (-)-(4S)-4-hydroxyisofraxinellone which was regio- and stereo-selective hydroxylated at the C-4 position by IR, EI-MS 1D and 2D NMR. Absolute configuration of hydroxyl group at the C-4 position was detected by modified Mosher's method. Antifeedant activity of compounds 1 and 2 against larvae of Spodoptera litura was assayed. These compounds showed potent antifeedant activity and ED50 (50% of effective dose) values were 3.91 and 4.43 µg/cm2, respectively.

Antimutagenic activity of flavonoids from Sozuku.

Pinocembrin (1) and cardamonin (2) from Sozuku showed a suppressive effect on umu gene expression of SOS response in Salmonella typhimurium TA1535/pSK1002 against the mutagen furylfuramide. Compounds 1 and 2 suppressed 52% and 36% of SOS-inducing activity at a concentration of 0.20 µmol/mL. The ID50 value of 1 was 0.18 µmol/mL. These compounds showed the suppression of 2-amino-3,4-dimethylimidazo-[4,5-f]quinolone (MeIQ) and UV irradiation-induced SOS response. Pinostrobin (3) and 5,7-dimethoxyflavanone (4), methyl ethers of 1, showed similar activity to 1 against MeIQ-induced SOS response, but that of furylfuramide and UV irradiation were decreased. On the other hand, compounds 1-4 did not show the suppression of activated MeIQ-induced SOS response. Furthermore, compounds 1-4 showed potent antimutagenic activity against MeIQ mutagenesis in Ames test using the S. typhimurium TA100 and TA98 strains.

Biotransformation of (+)-Carvone and (-)-Carvone by the Common Cutworm Spodoptera litura Larvae.

Biotransformation of (+)- and (-)-carvone (1 and 2) by the larvae of common cutworm (Spodoptera litura) has been investigated. (+)-Carvone was transformed to (+)-(4S)-10-hydroxycarvone (1-1), (+)-(4S)-7- hydroxycarvone (1-2), and (-)-(4S)-8,9-dihydroxy-8,9-dihydrocarvone (1-3). (-)-Carvone (2) was transformed to (-)-(4R)-10-hydroxycarvone (2-1), (-)-(4R)-7-hydroxycarvone (2-2), (+)-(4R)-8,9-dihydroxy-8,9- dihydrocarvone (2-3), and (-)-(2R,4R)-10-hydroxycarveol (2-4). The results indicate that the main metabolic reaction of carvones by S. litura larvae is oxidation at vinyl group (C-8 and C-9).

Total Synthesis of γ-Alkylidenebutenolides, Potent Melanogenesis Inhibitors from Thai Medicinal Plant Melodorum fruticosum.

A hitherto unreported member of γ-alkylidenebutenolides in Melodorum fruticosum (Annonaceae), (4 E)-6-benzoyloxy-7-hydroxy-2,4-heptadiene-4-olide, named as isofruticosinol (4) was isolated from the methanol extract of flowers, along with the known related butenolides, namely, the (4 Z)-isomer (3) of 4, melodrinol (1), and its (4 E)-isomer (2). To unambiguously determine the absolute configuration at the C-6 position in these butenolides, the first total syntheses of both enantiomers of 2-4 were achieved over 6-7 steps from commercially available D- or L-ribose (D- and L-5). Using the same protocol, both enantiomers of 1 were also synthesized. Based on chiral HPLC analysis of all synthetic compounds ( S- and R-1-4), all naturally occurring butenolides were assigned as partial racemic mixtures with respect to the chiral center at C-6 (enantiomeric ratio, 6 S/6 R = ∼83/17). Furthermore, the melanogenesis inhibitory activities of S- and R-1-4 were evaluated, with all shown to be potent inhibitors with IC50 values in the range 0.29-2.9 µM, regardless of differences in the stereochemistry at C-6. In particular, S-4 (IC50 = 0.29 µM) and R-4 (0.39 µM) showed potent inhibitory activities compared with that of reference standard arbutin (174 µM).

Diastereoselective Synthesis of Salacinol-Type α-Glucosidase Inhibitors.

A facile and highly diastereoselective approach toward the synthesis of potent salacinol-type α-glucosidase inhibitors, originally isolated from plants of the genus "Salacia", was developed using the S-alkylation of thiosugars with epoxides in HFIP (∼90%, dr, α/ß = ∼ 26/1). The dr ratio of the product was significantly improved by the protocol as compared to that of the conventional S-alkylation of thiosugars (dr, α/ß = ∼ 8/1). The protocol could be used for gram scale synthesis of the desired compounds. The 3'-O-benzylated salacinol analogs, which are the most potent in vitro inhibitors to date, were synthesized and evaluated in vivo; all analogs suppressed blood glucose levels in maltose-loaded mice, at levels comparable to those of the antidiabetic agent, voglibose.

Comparison of Essential Oils from Three Kinds of Cryptotaenia japonica Hassk (Kirimitsuba, Nemitsuba, and Itomitsuba) used in Japanese Food.

The compositions of the essential oils from three kinds of Cryptotaenia japonica Hassk ("Mitsuba" in Japanese, Kirimitsuba (KM), Nemitsuba (NM), and Itomitsuba (IM)) were investigated by capillary GC/GC-MS. The oils contained 53 volatile components, of which 95% were terpenoids. The major constituents were sesquiterpenoids, which were α-selinene (KM: 39.1%; NM: 38.4%; IM: 13.2%), ß-selinene (15.5%, 15.2%, 4.8%), germacrene D (12.1%, 7.2%, 24.1%), trans-farnesene (11.1%, 6.0%, 10.9%), ß-elemene (2.9%, 2.9%, 6.8%), and trans-caryophyllene (1.7%, 1.7%, 2.6%). The main sesquiterpene found in KM and NM was α-selinene and in IM was germacrene D. The major monoterpenes found were ß-myrcene (3.8%, 6.7%, and 3.5%) and ß-pinene (2.8%, 0.2%, and 1.4%).

Biotransformation of (-)-(1R,4S)-Menthone and (+)-(1S,4R)-Menthone by the Common Cutworm Spodoptera litura Larvae.

Using biotransformation as a biocatalytic process has the advantage of being able to proceed under mild conditions and with high regio- and enantioselectivity. This study investigated the biotransformation of (-)-(1R,4S)-menthone (1) and (+)-(1S,4R)-menthone (2) by Spodoptera litura larvae. Compound 1 was converted to (-)-(1R,4S)-7-hydroxymenthone (1-1), (+)-(1R,3S,4S)-7-hydroxyneomenthol (1-2) and (-)-(1R,4S,8R)-p-menth-3-one-9-oic acid (1-3). The metabolism of substrate 2 generated three enantiomers of the above metabolites, designated as 2-1 to 2-3, respectively. The C-9 position of (-)-menthone and (+)-menthone was oxidized to carboxylic acid by S. litura, which is a metabolic pathway not observed in any other example of biocatalysis.

Inhibition of ß-Secretase Activity by Monoterpenes, Sesquiterpenes, and C13 Norisoprenoids.

Inhibition of ß-secretase (BACE1) is currently regarded as the leading treatment strategy for Alzheimer's disease. In the present study, we aimed to screen the in vitro inhibitory activity of 80 types of aroma compounds (monoterpenes, sesquiterpenes, and C13 norisoprenoids), including plant-based types, at a 200-µM concentration against a recombinant human BACE1. The results showed that the most potent inhibitor of BACE1 was geranyl acetone followed by (+)-camphor, (-)-fenchone, (+)-fenchone, and (-)-camphor with the half-maximal inhibitory concentration (IC50) values of 51.9 ± 3.9, 95.9 ± 11.0, 106.3 ± 14.9, 117.0 ± 18.6, and 134.1 ± 16.4 µM, respectively. Furthermore, the mechanism of inhibition of BACE1 by geranyl acetone was analyzed using Dixon kinetics plus Cornish-Bowden plots, which revealed mixed-type mode. Therefore aroma compounds may be used as potential lead molecules for designing anti-BACE1 agents.

In Vitro Regio- and Stereoselective Oxidation of ß-Ionone by Human Liver Microsomes.

The metabolism of the norisoprenoid ß-ionone was investigated in vitro using human liver microsomes and 11 different recombinant cytochrome P450 enzymes expressed in Trichoplusia ni cells. ß-Ionone was found to be oxidized via 4S-hydroxylation by CYP2B6 in human liver microsomes. CYP1A2 also regioselectively catalyzed the hydroxylation of ß-ionone to yield 4-hydroxylation; this conversion was not stereoselective. Further kinetic analysis revealed that CYP2B6 exhibited the highest activity for ß-ionone 4-hydroxylation. Kinetic analysis showed that Km and Vmax for oxidation of ß-ionone by CYP1A2 and CYP2B6 was 107.9 ± 36.0 µM and 3200.3 ± 323.0 nmol/min/nmol P450 and 5.6 ± 1.2 µM and 572.8 ± 29.8 nmol/min/nmol P450, respectively. The reaction rates observed using human liver microsomes and recombinant CYP2B6 were very high compared with those of other CYP2B6 substrates reported thus far. These results suggest that ß-ionone, a norisoprenoid present in nature, is one of the effective substrates for CYP2B enzymes in human liver microsomes. To the best of our knowledge, this is the first time that 4-hydroxy ß-ionone has been described as a human metabolite of ß-ionone.