Isolation and identification of S(+)-3-hydroxyisobutyric acid in the urine of rats loaded with isobutyric acid.

3-Hydroxyisobutyric acid has been isolated from the urine of rats loaded with sodium isobutyrate. An optical rotation measurement of the methyl ester derivative shows this compound to be the S(+) stereoisomer. This is the same stereoisomer that has been previously identified in cultures of bacteria incubated with ammonium isobutyrate (Aberhart, D.J. (1977) Bioorg. Chem. 6, 191--201).     

Anaerobic Degradation of Normal- and Branched-Chain Fatty Acids with Four or More Carbons to Methane by a Syntrophic Methanogenic Triculture

Syntrophic degradation of normal- and branched-chain fatty acids with 4 to 9 carbons was investigated with a mesophilic syntrophic isobutyrate-butyrate-degrading triculture consisting of the non-spore-forming, syntrophic, fatty acid-degrading, gram-positive rod-shaped strain IB, Methanobacterium formicicum T1N, and Methanosarcina mazei T18. This triculture converted butyrate and isobutyrate to methane and converted valerate and 2-methylbutyrate to propionate and methane. This triculture also degraded caproate, 4-methylvalerate, heptanoate, 2-methylhexanoate, caprylate, and pelargoate. During the syntrophic conversion of isobutyrate and butyrate, a reversible isomerization between butyrate and isobutyrate occurred; isobutyrate and butyrate were isomerized to the other isomeric form to reach nearly equal concentrations and then their concentrations decreased at the same rates. Butyrate was an intermediate of syntrophic isobutyrate degradation. When butyrate was degraded in the presence of propionate, 2-methylbutyrate was synthesized from propionate and isobutyrate formed from butyrate. During the syntrophic degradation of valerate, isobutyrate, butyrate, and 2-methylbutyrate were formed and then degraded. During syntrophic degradation of 2-methylbutyrate, isobutyrate and butyrate were formed and then degraded.     

Phytoecdysones from Diplazium donianvm

From Diplazium donianum, makisterone A, makisterone D, and an unidentified stereoisomer of makisterone B have been isolated. The presence of two other unidentified phytoecdysones has been noted.     

Effects of isobutyrate supplementation in pre- and post-weaned dairy calves diet on growth performance,rumen development,blood metabolites and hormone secretion

Isobutyrate supplements could improve rumen development by increasing ruminal fermentation products, especially butyrate, and then promote the growth performance of calves. The objective of this study was to evaluate the effects of isobutyrate supplementation on growth performance, rumen development, blood metabolites and hormone secretion in pre- and post-weaned dairy calves. In total, 56 Chinese Holstein male calves with 30 days of age and 72.9±1.43 kg of BW, blocked by days of age and BW, were assigned to four groups in a randomized block design. The treatments were as follows: control, low-isobutyrate, moderate-isobutyrate and high-isobutyrate with 0, 0.03, 0.06 and 0.09 g isobutyrate/kg BW per calf per day, respectively. Supplemental isobutyrate was hand-mixed into milk of pre-weaned calves and the concentrate portion of post-weaned calves. The study consisted of 10 days of an adaptation period and a 50-day sampling period. Calves were weaned at 60 days of age. Seven calves were chosen from each treatment at random and slaughtered at 45 and 90 days of age. BW, dry matter (DM) intake and stomach weight were measured, samples of ruminal tissues and blood were determined. For pre- and post-weaned calves, DM intake and average daily gain increased linearly (P<0.05), but feed conversion ratio decreased linearly (P<0.05) with increasing isobutyrate supplementation. Total stomach weight and the ratio of rumen weight to total stomach weight tended to increase (P=0.073) for pre-weaned calves and increased linearly (P=0.021) for post-weaned calves, whereas the ratio of abomasum weight to total stomach weight was not affected for pre-weaned calves and decreased linearly (P<0.05) for post-weaned calves with increasing isobutyrate supplementation. Both length and width of rumen papillae tended to increase linearly for pre-weaned calves, but increased linearly (P<0.05) for post-weaned calves with increasing isobutyrate supplementation. The relative expression of messenger RNA for growth hormone (GH) receptor and 3-hydroxy-3-methylglutaryl-CoA synthase 1 in rumen mucosa increased linearly (P<0.05) for pre- and post-weaned calves with increasing isobutyrate supplementation. Blood concentrations of glucose, acetoacetate, β-hydroxybutyrate, GH and IGF-1 increased linearly (P<0.05) for pre- and post-weaned calves, whereas blood concentration of insulin decreased linearly with increasing isobutyrate supplementation. The present results indicated that isobutyrate promoted growth of calves by improving rumen development and its ketogenesis in a dose-dependent manner.     

Reciprocal Isomerization of Butyrate and Isobutyrate by the Strictly Anaerobic Bacterium Strain WoG13 and Methanogenic Isobutyrate Degradation by a Defined Triculture

Isomerization of butyrate and isobutyrate was investigated with the recently isolated strictly anaerobic bacterium strain WoG13 which ferments glutarate to butyrate, isobutyrate, CO₂, and small amounts of acetate. Dense cell suspensions converted butyrate to isobutyrate and isobutyrate to butyrate. ¹³C-nuclear magnetic resonance experiments proved that this isomerization was accomplished by migration of the carboxyl group to the adjacent carbon atom. In cell extracts, both butyrate and isobutyrate were activated to their coenzyme A (CoA) esters by acyl-CoA:acetate CoA-transferases. The reciprocal rearrangement of butyryl-CoA and isobutyryl-CoA was catalyzed by a butyryl-CoA:isobutyryl-CoA mutase which depended strictly on the presence of coenzyme B₁₂. Isobutyrate was completely degraded via butyrate to acetate and methane by a defined triculture of strain WoG13, Syntrophomonas wolfei, and Methanospirillum hungatei.     

Thymol derivatives from Calea nelsonii

Calea nelsonii yielded, besides the two known thymol derivatives 8,9-epoxy-7-isobutyryloxythymol isobutyrate and 10-acetoxy-8,9-epoxythymol isobutyrate, the five new thymol derivatives 10-acetoxy-8,9-epoxy-7- isobutyryloxythymol isobutyrate, 10-acetoxy-8,9-epoxy-7-hydroxythymol isobutyrate, 8-hydroxy-9-acetoxy-10-isobutyryloxythymol 7-acetoxy-8-hydroxy-9,10-diisobutyryloxythymol and 7-isobutyryloxy-8,9-dihydroxythymol, while C. zacatechichi provided the known flavones 5-hydroxy-7,4′-dimethoxy flavone and 5,7-dihydroxy-4′-methoxyflavone and a known epoxysesquiterpene lactone. The structures of the new compounds were established by spectral methods. Some chemotaxonomic aspects are discussed.     

Isolation of isodihydroquinamine from Isertia hypoleuca

A new dihydroindole alkaloid, isodihydroquinamine, has been isolated from the leaves of Isertia hypoleuca Benth. Chemical and spectroscopic data show it to be a stereoisomer of dihydroquinamine, which was previously isolated from the same plant.     

Chromatography of Cytokinins on a Neutral Polystyrene Resin: A Simple Procedure for the Separation of the cis and trans Isomers of Zeatin or Ribosylzeatin

A simple procedure for the separation of the cis and trans isomers of zeatin and ribosylzeatin by column chromatography on a neutral polystyrene resin, Porapak Q, in aqueous ethanol solutions is reported. The method has been used to examine the stereoisomer composition of ribosylzeatin isolated from wheat germ transfer RNA. Chromatographic data for several other cytokinins are also presented.     

A stereochemical study on the metabolism of isobutyrate in Pseudomonas putida

Ammonium[2-³H,1-¹⁴C]isobutyrate was converted by Pseudomonas putida ATCC 21244 into S(+)-β-hydroxyisobutyric acid (β-HIBA) with loss of the α-tritium atom. The recovered isobutyrate had the same ${}^3\text{H}{}^{14}\text{C}$ as the starting material. Ammonium (2S)-[3-¹³C]isobutyrate was synthesized and converted by P. putida into β-HIBA. The ¹³C-nmr of the corresponding methyl ester benzoate showed ¹³C enrichment in the hydroxymethyl carbon atom. The results therefore indicate that isobutyrate metabolism in this organism proceeds via an unsaturated intermediate (probably methacrylyl-CoA) formed by dehydrogenation of the 2-pro-S-methyl group of the precursor (isobutyryl-CoA). Hydration of the intermediate proceeds with addition of a proton at C-2 from the same side as the hydrogen removed in the dehydrogenation.     

Thymol derivatives from schizogyne glaberrima

An investigation of Schizogyne glaberrima afforded in addition to known compounds 3-(acetoxy-methyl)-6-methyl-5-methoxy-benzofuran,10-acctoxy-8,9-epoxy-6-methoxy-thymol isobutyrate, 10-acetoxy-8-hydroxy-9-isobutyryloxy-6-methoxy-thymol,8-hydroxy-9,10-isobutyryloxy-thymol and 8,10-dihydroxy-9-isobutyryloxy-thymol, five new thymol derivatives, 8-ethoxy-9-isobutyryloxy-thymol, 10-acetoxy-8,9-dehydro-6-methoxy-thymol isobutyrate, 6-acetoxy-8,9-dehydro-9-carbomethoxy-10-hydroxy-thymol and 8,9-dihydroxy-10-isobutyryloxy-6-methoxy-thymol.     

Identification of a selective inhibitor of human monocarboxylate transporter 4

The human monocarboxylate transporters (hMCTs/SLC16As) mediate the uptake of various monocarboxylates. Several isoforms of hMCTs are expressed in cancerous tissue as well as in normal tissue. In cancerous tissue, hypoxia induces the expression of hMCT4, which transports the energetic metabolite l-lactate across the plasma membrane. Since hMCT4 is involved in pH regulation and the transport of l-lactate in cancer cells, an hMCT4 inhibitor could function as an anticancer agent. Although several non specific hMCT inhibitors have been developed, a selective hMCT4 inhibitor has not yet been identified. The aim of this study was therefore to identify a selective hMCT4 inhibitor for use as a pharmacological tool for studying hMCT4. The heterologous expression system of the Xenopus oocyte was used to assess the effects of test compounds on hMCT4, whereupon isobutyrate derivatives, fibrates, and bindarit (2-[(1-benzyl-1H-indazol-3-yl)methoxy]-2-methylpropanoic acid) were demonstrated to exhibit selective inhibitory effects against this transporter. It is suggested that the structure formed from the joining of an isobutyrate moiety and two aromatic rings by appropriate linkers is important for acquiring the selective hMCT4-inhibiting activity. These findings provide novel insights into the ligand recognition of hMCT4, and contribute to the development of novel anticancer agents.     

Effects of isobutyrate on rumen fermentation, lactation performance and plasma characteristics in dairy cows

The objective of this study was to evaluate effects of isobutyrate supplementation on rumen fermentation, lactation performance and plasma characteristics of dairy cows. Twenty multiparous second filial generation (F2) cows of a cross between Chinese Jinnan Yellow and Holstein cows at 148 ± 4.5 days in milk and 22.3 ± 0.81 kg milk production were used in a replicated 4 × 4 Latin square experiment. The treatments were: control (without isobutyrate), low (LIB), medium (MIB) and high (HIB) isobutyrate supplementation of 20, 40 and 60 g per cow per day, respectively. Experimental periods were 30 days with 15 d of adaptation and 15 d of data collection. Dry matter (DM) intake was not affected by increasing isobutyrate supplementation, but milk yields were highest for the 40 g/d isobutyrate supplementation level, where proportion of milk fat, true protein and lactose were minimized. Ruminal pH (6.38–6.24) and ammonia N (13.8–11.1 mg/100 ml) were linearly (P<0.01) decreased, whereas total VFA concentration (124–131 mM) increased at a decreasing rate with increasing isobutyrate supplementation. The ratio of acetate to propionate increased linearly (P<0.01) from 2.77 to 4.43 as isobutyrate supplementation increased due to the increase in acetate production and decrease in propionate production. Digestibilities of OM in the total tract increased linearly (P<0.01) as isobutyrate supplementation increased, digestibilities of DM and EE were highest for the 40 g/d isobutyrate supplementation level, digestibilities of CP, aNDF and ADF increased at a decreasing rate with increasing isobutyrate supplementation. Plasma concentrations of glucose and growth hormone linearly (P<0.03) increased, whereas concentrations of non-esterified fatty acids linearly (P<0.01) decreased. Results indicate that supplementation of this diet with isobutyrate changed the rumen fermentation pattern towards acetate production, improved digestion and modified plasma concentrations of glucose and growth hormone. This suggests that isobutyrate stimulated digestive microorganisms or enzymes in a dose-dependent manner with the optimum isobutyrate dose at about 40 g per cow per day in terms of improved digestion.     

Propylthiouracil-induced hypothyroid hyperlipidemic chick: A model for clofibrate-induced toxicity

1. An animal model for clinically observed clofibrate (p-chlorophenoxy isobutyrate, CPIB)-induced toxicity has been tested.2. It is demonstrated that propylthiouracil-induced hypothyroid-hyperlipidemic chick develops severe toxic manifestations following clofibrate administration.3. Toxic symptoms are characterized by listlessness, drowziness, and extreme muscular weakness.4. This is associated with elevation of blood urea nitrogen, creatine phosphokinase, uric acid and glutamic oxaloacetic transaminase.5. Histological examination of muscle specimen from chicks exhibiting toxic syndrome showed degeneration and vacuolization of muscle fibers.6. The biochemical and histological changes observed are quite similar to those reported in clinical practice in some patients given clofibrate.7. It is suggested that this chick model could be used to investigate the biochemical basis of clofibrate toxicity.     

Mikanokryptin,a new guianolide from Mikania

The isolation and structure determination of mikanokryptin, a stereoisomer of 11,13-dehydrogeigerin, from what appears to be a previously undescribed Mikania species is reported. Mikania micrantha HBK. yielded mikanolide and dihydromikanolide.     

Perturbation of syntrophic isobutyrate and butyrate degradation with formate and hydrogen

The effect of formate and hydrogen on isomerization and syntrophic degradation of butyrate and isobutyrate was investigated using a defined methanogenic culture, consisting of syntrophic isobutyrate-butyrate degrader strain IB, Methanobacterium formicicum strain T1N, and Methanosarcina mazeii strain T18. Formate and hydrogen were used to perturb syntrophic butyrate and isobutyrate degradation by the culture. The reversible isomerization between isobutyrate and butyrate was inhibited by the addition of either formate or hydrogen, indicating that the isomerization was coupled with syntrophic butyrate degradation for the culture studied. Energetic analysis indicates that the direction of isomerization between isobutyrate and butyrate is controlled by the ratio between the two acids, and the most thermodynamically favorable condition for the degradation of butyrate or isobutyrate in conjunction with the isomerization is at almost equal concentrations of isobutyrate and butyrate. The degradation of isobutyrate and butyrate was completely inhibited in the presence of a high hydrogen partial pressure (>2000 Pa) or a measurable level of formate (10 muM or higher). Significant formate (more than 1 mM) was detected during the perturbation with hydrogen (17 to 40 kPa). Resumption of butyrate and isobutyrate degradation was related to the removal of formate. Energetic analysis supported that formate was another electron carrier, besides hydrogen, during syntrophic isobutyrate-butyrate degradation by this culture. (c) 1996 John Wiley & Sons, Inc.     

Actinomycetales from Corn

Mesophilic Actinomycetales were isolated from whole corn, brewer's grits, and break flour received from three different mills. In addition, strains were isolated from high-moisture (27%) field corn; high-moisture, silo-stored corn (untreated); and high-moisture corn treated with ammonia, ammonium isobutyrate, or propionic-acetic acid. According to standard techniques, 139 strains were extensively characterized and 207 additional strains were partially characterized. On the basis of these characterizations, the streptomycete strains were identified by both the systems of Pridham et al. and Hütter because these systems are rapid and accurate. In general, only Streptomyces griseus (Krainsky) Waksman and Henrici was isolated from high-moisture whole corn (treated or untreated) except from grain exposed to ammonium isobutyrate. Strains isolated from high-moisture corn subjected to that treatment represented both S. griseus and S. albus (Rossi Doria) Waksman and Henrici. The strains isolated from corn and corn products from the three mills were identified with a number of streptomycete species. Of all Actinomycetales isolated, only three were not streptomycetes—two from brewer's grits and one from break flour.     

Effects of isobutyrate on rumen fermentation,urinary excretion of purine derivatives and digestibility in steers

The objective of this study was to evaluate the effects of isobutyrate supplementations on rumen fermentation, urinary excretion of purine derivatives and feed digestibility in steers. Eight ruminally cannulated Simmental steers were used in a replicated 4 × 4 Latin square experiment. On DM basis, diet consisted of 60% corn stover and 40% concentrate. Dry matter intake (averaged 9 kg/d) was restricted to 90% of ad libitum intake. The four treatment groups received a daily dose of 0 (control), 8.4, 16.8 or 25.2 g isobutyrate per steer. With increasing isobutyrate supplementation total VFA concentration (range 64.2–74.0 mM) was significantly enhanced. The ratio of acetate to propionate (range 2.72–4.25) was also significantly increased due to the increase in actate production and decrease in propionate production. With increasing isobutyrate supplementation the ruminal degradation of NDF from corn stover was improved but the CP degradability of soybean meal was decreased. Furthermore, the isobutyrate supplementation caused a significantly increased urinary excretion of purine derivatives. Similarly, digestibilities of OM, NDF and CP in the total tract were significantly increased. The present results indicate that dietary supplementation with isobutyrate improved rumen fermentation and feed digestion in beef cattle in a dose-dependent manner. According to the conditions of this experiment, the optimum daily dose of isobutyrate was about 16.8 g/animal.     

Cationic iridium complexes with C2-symmetry binaphthalene-core disulfide ligands: Synthesis and catalytic activity in the hydrogenation of alkenes

Mononuclear cationic Ir(I)-cyclooctadiene complexes containing three different C₂-symmetrical binaphthalene-templated sulfide ligands, featuring alkyl groups of increasing steric demand onto the donor centres, have been prepared and characterized. Variable temperature NMR spectra provide evidence that, regardless of the bulk of the alkyl substituent on the sulfur, the chelate coordination of the ligands proceeds in all cases with complete stereoselectivity at the newly generated S-stereocentres affording just one stereoisomer. This species features a seven-membered chelate ring in a frozen conformation where the diequatorial S-alkyl substituents are disposed in anti-relationship and the stereogenic S-donors display the same configuration. The oxidative addition of hydrogen to these complexes proceeds smoothly affording in every case one single cis-dihydride complex whose structure in one case has been cleared by correlated NMR spectra. The cationic complexes derived from these ligands are catalysts of modest value for the hydrogenation of α,β-unsaturated acid derivatives where they produce nearly racemic products in moderate yields.     

The biosynthesis of valine from isobutyrate by Peptostreptococcus elsdenii and Bacteroides ruminicola

1. Growing cultures of Peptostreptococcus elsdenii and Bacteroides ruminicola incorporate (14)C from [1-(14)C]isobutyrate into the valine of cell protein. With P. elsdenii some of the (14)C is also incorporated into leucine. 2. Crude cell-free extracts of both organisms in the presence of glutamine, carbon dioxide and suitable sources of energy and electrons incorporate (14)C from [1-(14)C]isobutyrate into valine but not into leucine. 3. With extracts of P. elsdenii treated with DEAE-cellulose the reaction is dependent on ATP, CoA, thiamin pyrophosphate, molecular hydrogen and a low-potential electron carrier (ferredoxin, flavodoxin or benzyl viologen). 4. The same extracts incorporate (14)C from NaH(14)CO(3) into valine in the presence of isobutyrate plus ATP, CoA, glutamine and ferredoxin; isobutyryl-CoA or isobutyryl phosphate plus CoA will replace the isobutyrate plus CoA and ATP. With acetyl phosphate in place of isobutyryl phosphate, (14)C is incorporated into alanine. With isovalerate or 2-methylbutyrate in place of isobutyrate, (14)C is incorporated into leucine and isoleucine respectively. 5. When carrier 2-oxoisovalerate is added to the carboxylating system (14)C from [1-(14)C]isobutyrate passes into the oxo acid fraction. 6. It is concluded that these two organisms form valine from isobutyrate by the sequence isobutyrate-->isobutyryl-CoA-->2-oxoisovalerate-->valine and that the reductive carboxylation of isobutyrate is catalysed by a system similar to the pyruvate synthetase of clostridia and photosynthetic bacteria.     

Sesquiterpene lactones from Eremanthus species

The investigation of three Eremanthus species afforded, in addition to known compounds, several new sesquiterpenelactones, a cumambrin B isobutyrate, four lactones related to the eremantholides, two to zexbrevin and one to goyazensolide. Furthermore, a new coniferyl alcohol derivative was isolated. The overall picture of the genus is very uniform. The occurrence of eremanthine and germacranolides with a furanone ring seems to be especially typical.