Chirality of the γ-lactones produced by Sporidiobolus salmonicolor grown in two different media

Sporidiobolus salmonicolor is an aroma-producing yeast which gives a peach-like smell to the culture media. The enantiomeric ratios of the five γ-lactones produced by this yeast cultivated in two different media were determined by multidimensional gas chromatography (MDGC) on a fused silica capillary column coupled to a modified β-cyclodextrin column. These ratios remain constant during growth and are not affected by the composition of the medium. The (R)-enantiomer is highly predominant (99%) for γ-decalactone and predominant (68–88%) for γ-octalactone, γ-nonalactone, and (Z6)-γ-dodecenolactone. A ratio close to racemic was found for γ-dodecalactone. A discussion on the metabolic origin of these lactones is based on the analysis of the enantiomeric ratios obtained. With respect to consumers' preference for products considered as “natural,” microbial lactone production may represent a valuable alternative to fruit flavors. The enantiomeric lactone ratios produced by Sporidiobolus salmonicolor are compared with those reported from some fruits. Chirality 9:667–671, 1997. © 1997 Wiley-Liss, Inc.     

Enantiodifferentiation of four γ-lactones produced by Penicillium Roqueforti

Identification and enantiodifferentiation of γ-lactones produced during the bioconversion of soy bean fatty acids by Penicillium roqueforti spores in the presence of an exogenous lipase was performed using gas chromatography-mass spectrometry (GC-MS) in selected ion monitoring (SIM) mode. It was shown that 4-dodecanolide and 4-hexanolide were first produced with an enantiomeric excess (99%) in favor of the (R) form, whereas an enantiomeric excess in favor of the (S) form (94%) is found for (6Z)-dodecen-4-olide, the major lactone produced by the fungus. If incubation was continued, mixtures of both enantiomers were found, more particularly for 4-decanolide (R/S:40/60), which was produced only after 120 hr of incubation. The results obtained can be explained by the stereoselective hydroxylation by a 10-hydratase and/or a 10-lipoxygenase of the unsaturated fatty acid precursors, oleic and linoleic acids, and by competition between different pathways. The results point out the limitations of chiral GC analysis as a criterion for the natural origin of relevant lactones, and the complexity of mechanisms involved in γ-lactone formation by microorganisms. Chirality 10:786–790, 1998. © 1998 Wiley-Liss, Inc.     

Lactones 29. Enzymatic resolution of racemic γ-lactones

Studies on the application of commercially available enzymes to resolution of the racemic unsaturated γ-lactones: 5-(3-methylbutylidene)-4-methyl-tetrahydrofuran-2-one (1a) and 5-(3,3-dimethylbutylidene)-4-methyl-tetrahydrofuran-2-one (2a) are presented. Lipase PS, Rhizopus niveus lipase, Rhizopus arrhizus lipase, porcine pancreas lipase and hog liver esterase transformed substrates into their respective γ-keto acids with good efficiency (50–75%). Three of them hydrolysed the studied lactones with moderate enantioselectivity. Enantiomeric excesses determined by GC for the unreacted lactones were in the range of 20–60%. Lipase PS preferentially hydrolysed the (+) enantiomers of lactones 1a and 2a whereas R. niveus lipase hydrolysed the (?) enantiomers, respectively.     

Lactones 29 . Enzymatic resolution of racemic γ-lactones

Studies on the application of commercially available enzymes to resolution of the racemic unsaturated γ-lactones: 5-(3-methylbutylidene)-4-methyl-tetrahydrofuran-2-one (1a) and 5-(3,3-dimethylbutylidene)-4-methyl-tetrahydrofuran-2-one (2a) are presented. Lipase PS, Rhizopus niveus lipase, Rhizopus arrhizus lipase, porcine pancreas lipase and hog liver esterase transformed substrates into their respective γ-keto acids with good efficiency (50-75%). Three of them hydrolysed the studied lactones with moderate enantioselectivity. Enantiomeric excesses determined by GC for the unreacted lactones were in the range of 20-60%. Lipase PS preferentially hydrolysed the (+) enantiomers of lactones 1a and 2a whereas R. niveus lipase hydrolysed the (-) enantiomers, respectively.     

A single-host fermentation process for the production of flavor lactones from non-hydroxylated fatty acids

Lactone flavors with fruity, milky, coconut, and other aromas are widely used in the food and fragrance industries. Lactones are produced by chemical synthesis or by biotransformation of plant-sourced hydroxy fatty acids. We established a novel method to produce flavor lactones from abundant non-hydroxylated fatty acids using yeast cell factories. Oleaginous yeast Yarrowia lipolytica was engineered to perform hydroxylation of fatty acids and chain-shortening via β-oxidation to preferentially twelve or ten carbons. The strains could produce γ-dodecalactone from oleic acid and δ-decalactone from linoleic acid. Through metabolic engineering, the titer was improved 4-fold, and the final strain produced 282 mg/L γ-dodecalactone in a fed-batch bioreactor. The study paves the way for the production of lactones by fermentation of abundant fatty feedstocks.     

Composition of the leaf, stem bark and root bark oils of Isolona cooperi investigated by GC (retention index), GC-MS and 13C-NMR spectroscopy

The leaf, stem bark and root bark oils of Isolona cooperi Hutchinson & Dalziel from the Ivory Coast have been analysed by GC (retention index), GC-MS and 13C-NMR spectroscopy. Two types of essential oil were produced by the plant. The leaf and stem bark oils were monoterpene-rich, containing principally (Z)-beta-ocimene and gamma-terpinene and three lactones, 5-[(E and Z)-hexylidene]-5H-furan-2-ones and massoia lactone, were present in appreciable amounts. Conversely, the root bark oil was dominated by 5-isopentenylindole and (E)-beta-caryophyllene. The strategy for the analysis of each oil was adapted according to the nature of the components.     

Short and simple synthesis of (R)- and (S)-4-hydroxypentylaminoacetamide: both enantiomers of the (ω-1)-hydroxylated metabolite of milacemide

Both (R)- and (S)-4-hydroxypentylaminoacetamide have been synthesized by reductive amination of glycinamide on the γ-valerolactols corresponding to (R)- and (S)-γ-valerolactone, respectively. These enantiomeric lactones were readily obtained in high enantiomeric excess (ee) by enzymic porcine pancreatic lipase (PPL) kinetic resolution of rac-methyl γ-hydroxyvalerate. © 1992 Wiley-Liss, Inc.     

Lactones in the Flavor of Heated Pork Fat

Pork fat was heated at 160~170°C for 3 hr under bubbling with air, and the volatile compounds were collected in the cold trap. After the acidic compounds were removed from the volatile compounds by extraction with 3% aqueous sodium carbonate solution, lactones were obtained from the nonacidic compounds by saponification. Gas chromatographic analyses of lactones were carried out on the PEG-20M and Apiezon L packed columns, and then each lactone was fractionated by repeated gas chromatography. Each isolated lactone was identified by infrared spectrometry, and also three major lactones were identified by mass spectrometry. Consequently, γ-C₅—C₁₂ and δ-C₉, δ-C₁₀, δ-C₁₂ and δ-C₁₄ lactones were found in the flavor of heated pork fat. Gamma-lactones, especially γ-C₇, γ-C₈ and γ-C₉, were predominant in the flavor, and unsaturated lactones were not detected. Mechanisms for the formation of the lactones were discussed.     

Genetic and biochemical characterization of a novel monoterpene epsilon-lactone hydrolase from Rhodococcus erythropolis DCL14

A monoterpene epsilon-lactone hydrolase (MLH) from Rhodococcus erythropolis DCL14, catalyzing the ring opening of lactones which are formed during degradation of several monocyclic monoterpenes, including carvone and menthol, was purified to apparent homogeneity. It is a monomeric enzyme of 31 kDa that is active with (4R)-4-isopropenyl-7-methyl-2-oxo-oxepanone and (6R)-6-isopropenyl-3-methyl-2-oxo-oxepanone, lactones derived from (4R)-dihydrocarvone, and 7-isopropyl-4-methyl-2-oxo-oxepanone, the lactone derived from menthone. Both enantiomers of 4-, 5-, 6-, and 7-methyl-2-oxo-oxepanone were converted at equal rates, suggesting that the enzyme is not stereoselective. Maximal enzyme activity was measured at pH 9.5 and 30 degrees C. Determination of the N-terminal amino acid sequence of purified MLH enabled cloning of the corresponding gene by a combination of PCR and colony screening. The gene, designated mlhB (monoterpene lactone hydrolysis), showed up to 43% similarity to members of the GDXG family of lipolytic enzymes. Sequencing of the adjacent regions revealed two other open reading frames, one encoding a protein with similarity to the short-chain dehydrogenase reductase family and the second encoding a protein with similarity to acyl coenzyme A dehydrogenases. Both enzymes are possibly also involved in the monoterpene degradation pathways of this microorganism.     

Quorum-sensing molecules: Sampling,identification and characterization of N-acyl-homoserine lactone in Vibrio sp

Quorum sensing (QS) is a mechanism by which gram-negative bacteria regulate their gene expression by making use of cell density. QS is triggered by a small molecule known as an autoinducer. Typically, gram-negative bacteria such as Vibrio produce signaling molecules called acyl homoserine lactones (AHLs). However, their levels are very low, making them difficult to detect. We used thin layer chromatography (TLC) to examine AHLs in different Vibrio species, such as Vibrio alginolyticus, Vibrio parahemolyticus, and Vibrio cholerae, against a standard- Chromobacterium violaceum. Further, AHLs were characterised by high-performance liquid chromatography (HPLC) and gas chromatography-mass spectrometry (GC–MS). C4-HSL (N- butanoyl- L- homoserine lactone), C6-HSL (N- hexanoyl- L- homoserine lactone), 3-oxo-C8-HSL (N-(3-Oxooctanoyl)-DL-homoserine lactone), C8-HSL (N- octanoyl- L- homoserine lactone), C₁10-HSL (N- decanoyl- L- homoserine lactone), C12-HSL (N- dodecanoyl- L- homoserine lactone) and C14-HSL (N- tetradecanoyl- L- homoserine lactone) were identified from Vibrio. These results may provide a basis for blocking the AHL molecules of Vibrio, thereby reducing their pathogenicity and eliminating the need for antimicrobials.     

槐庶尺蛾性信息素腺体EAG活性成分绝对构型的鉴定(英文)

槐庶尺蛾Semiothisa cinerearia Bremer et Grey （鳞翅目： 尺蛾科）是我国北方国槐Sophora japonica L.上的重要食叶害虫。本研究的主要目的是阐明槐庶尺蛾性信息素成分化学结构的绝对构型, 为在城市地区环境友好地防控槐庶尺蛾的为害提供一种新方法。经与标准品比较气相色谱保留时间和质谱特征离子, 从槐庶尺蛾处女雌蛾（2-3日龄）性信息素腺体溶剂提取物中检测到顺6, 顺9-顺-3, 4-环氧-十七碳二烯烃和顺3, 顺6, 顺9-3, 6, 9-十七碳三烯烃2种成分, 在腺体中以100∶4.8±1.3 （N=12）的比例存在。槐庶尺蛾性信息素腺体提取物进一步经手性毛细管色谱柱（CycloSil-B, 30 m×0.25 mm×0.25 μm 液膜厚）分离, 在优化的程序升温条件下发现腺体成分顺6, 顺9-顺-3, 4-环氧-十七碳二烯烃具有3R, 4S的绝对构型。两种合成的对映异构体混合物顺6, 顺9-3R, 4S-环氧-十七碳二烯烃和顺6, 顺9-3S, 4R-环氧-十七碳二烯烃以1.28∶1的比例加到腺体提取物中, 比例变为1.55∶1。根据这一分析, 腺体成分顺6, 顺9-顺-3, 4-环氧-十七碳二烯烃进一步确认具有3R, 4S的绝对构型。该研究结论将为生产上研发高效的槐庶尺蛾性信息素诱芯奠定坚实的基础。     

High resolution proton NMR studies of gangliosides. Structure of two types of GD3 lactones and their reactivity with monoclonal antibody R24

Ganglioside GD3 was converted at room temperature to two stable lactones, denoted as GD3 lactones I and II. The reaction sequence was presumed to be GD3----GD3 lactone I----GD3 lactone II based on the time course of their production. Lactone I behaved as a monosialoganglioside and lactone II as a neutral species. The two lactones were isolated by DEAE-Sephadex column chromatography. The positions of the inner ester linkages were investigated by two-dimensional J-correlated proton NMR spectroscopy. An ester linkage was most likely formed between the carboxyl group of the external sialic acid residue and C9-OH of the internal sialic acid residue in lactone I. In addition to this ester linkage, a second ester linkage between the carboxyl group of the internal sialic acid and C2-OH of the galactose residue was likely formed in lactone II. The structural changes induced by lactonization were further examined by their reactivity with the monoclonal antibody R24 (Puckel, C. S., Lloyd, K. O., Travassos, L. R., Dippold, W. G., Oettgen, H. F., and Old, L. J. (1982) J. Exp. Med. 155, 1133-1147), which reacted with GD3. R24 was found to bind weakly to GD3 lactone I, but not to GD3 lactone II. The results suggest that the monoclonal antibody requires both sialic acid residues for high affinity binding, and the complete lactonization results in a loss of negative charges and/or a change in the overall conformation of the oligosaccharide moiety which may account for the loss of binding.     

Taraxacoside,a type of acylated γ-butyrolactone glycoside from taraxacum officinale

In addition to the four new sesquiterpene lactones previously identified, a new acylated γ-butyrolactone glucoside, taraxacoside, was isolated from the roots of Taraxacum officinale. Its structure was elucidated mainly by ¹H and ¹³C NMR studies as β-O-[4-O-(p-hydroxyphenylacetyl]β-D-glucopyranosyl]-β-hydroxy-γ-butyrolactone. This seems to be the first instance of the detection of a monocyclic five-membered, saturated lactone O-glycoside. Additionally, p-hydroxyphenylacetic acid was identified for the first time as an acylating acid in a sugar ester.     

Production and characterization of a monoclonal antibody (BBH5) directed to ganglioside lactone

The occurrence of lactones in various ganglioside preparations has been clearly demonstrated, yet the natural occurrence of ganglioside lactones in cells and tissues has been the subject of long debate, since lactones can be formed readily during preparation of gangliosides. We now report the generation of a monoclonal antibody (BBH5) that reacts specifically with lactones of disialogangliosides having the NeuAc2-8NeuAc2-3Gal sequence, but does not crossreact with the parent ganglioside. The specificity of the antibody resides on the first lactone ring between two sialic acid residues but not on the second lactone ring between sialic acid and galactose, as evidenced by reactivity with lactonized GD_1b having the first lactone ring (L1), and by reactivity with lactonized polysialic acid homo-oligomers ([NeuAc2-8] _n NeuAc). The sialic acid carboxyl involved in the lactone ring was unequivocally determined after ammonolysis followed by methylation and fast atom bombardment mass spectrometry. The antibody BBH5 thus provides a novel tool for studies of the natural occurrence of lactones in cells and tissues.Abbreviations BSA bovine serum albumin - CM chloroform-methanol - CMW chloroform-methanol-water - FAB-MS fast atom bombardment mass spectrometry - IHW isopropanol-hexane-water - MAb monoclonal antibody - PBS phosphate-buffered saline - TLC thin layer chromatography     

Conversion of Some Saturated Fatty Acids,Aldehydes, and Alcohols into γ- and δ-Lactones

A series or γ- and δ-lactones could be found in the thermal oxidative products of normal saturated acids, aldehydes, and alcohols (C₉, C₁₀, and C₁₂, respectively) heated at 180°C in the presence of 0.1% KMnO₄. Their lactones were identified by gas chromatography, infrared spectroscopy, and mass spectroscopy. And they could be detected also in the volatile compounds occurred by heating of C₁₀ acid, aldehyde, and alcohol mixed with pork fat. So it was expected that lactones in meat fat flavor described in the earlier papers could be secondary products converted from saturated acids, aldehydes, and alcohols formed by oxidative degradation of meat fats. This process was presumed to be one of the mechanisms of the lactone formation.

It was discussed that lactones might be derived through mono or dihydroperoxides of acids, aldehydes, and alcohols.     

Haloenol lactones as inactivators and substrates of aldehyde dehydrogenase

Human aldehyde dehydrogenase (EC 1.2.1.3) isozymes E1 and E2 were irreversibly inactivated by stoichiometric concentrations of the haloenol lactones 3-isopropyl-6(E)-bromomethylene tetrahydro-pyran-2-one and 3-phenyl-6(E)-bromomethylene tetrahydro-pyran-2-one. No inactivation occurred with the corresponding nonhalogenated enol lactones. Both the dehydrogenase and esterase activities were abolished. Activity was not regained on dialysis or treatment with 2-mercaptoethanol. The inactivation was subject to substrate protection: NAD afforded protection which increased in the presence of the aldehyde-substrate competitive inhibitor chloral. Saturation kinetics gave positivey-axis intercepts, allowing the determination of binding constants. Inactivation stiochiometry determined with¹⁴C-labeled 3-(1-naphthyl)-6(E)-iodomethylene tetrahydropyran-2-one was found to correspond to the active-site number. The nonhalogenated lactone, 3-(1-naphthyl)-6(E)-methylene tetrahydropyran-1-one was shown to be a substrate for aldehyde dehydrogenase via its esterase function. Inactivation and enzymatic hydrolysis occurred within a similar time frame. Opening of the lactone ring to form enzyme-acyl intermediate with active site cysteine appears to be a necessary prerequisite to inactivation, since halogen in the lactone ring is nonreactive. Thus, the inactivation of aldehyde dehydrogenase by haloenol lactones is mechanism-based. Inactivation by haloenol lactones occurs in a manner analogous to that of chymotrypsin with which aldehyde dehydrogenase shares esterase activity and binding of haloenol lactones at the active site.     

Terpenoid lactones as plant growth regulators

Plant growth regulating activity of dehydrocostus lactone possessing an α-methylene-γ-lactone moiety has been compared with its two derived C-16 lactones, in which a trisubstituted double bond and a cyclopropane ring are conjugated with the lactone carbonyl. The results show that the two latter compounds are slightly more active than dehydrocostus lactone.     

Isolation of 2-Isopropyl-4,4-dimethyl-5-vinylidene-2-cyclopenten-1-one and 2-Isopropyl-3-isopentyl-maleic Anhydride from the Pyrolytic Products of 2-Isopropylmalic acid

(R)-[2-¹⁴C]-Mevalonic acid (MVA) lactone was incorporated into (-)-4′-hydroxy-y-ionylideneacetic acid (4?-hydroxy-y-acid), which was first isolated from the culture broth of Cercospora cruenta. 4?-Hydroxy-γ-acid was then metabolized to (+)-(2Z,4E)-4′-oxo-α-ionylideneacetic acid and (+)-(2Z,4E)-′14′-dihydroxy-γ-ionylideneacetic acid. The latter was converted to (+)-abscisic acid (ABA) with a high incorporation ratio by the fungus.     

Structure and functions of γ-dodecalactone isolated from Antrodia camphorata for NK cell activation

The preserved fungal species Antrodia camphorata has diverse health-promoting effects and has been popularly used in East Asia as a traditional herb. We isolated a volatile compound from the culture medium of A. camphorata and identified it as γ-dodecalactone (γ-DDL). Cytomic screening for immune-modulating activity revealed that γ-DDL can activate human NK cells to express the early activation marker CD69. Further experiments showed that γ-DDL not only can induce NK cells to express CD69 but also stimulate NK cells to secrete cytotoxic molecules (FasL and granzyme B) and Th1 cytokines (TNF-α and INF-γ).Measuring the distribution of γ-DDL in the subcellular compartments of NK cells revealed that γ-DDL has been converted to 4-hydroxydodecanoic acid (an acyclic isomer of γ-DDL) in a time-dependent manner in the cytoplasm.Synthetic (R,S)-4-hydroxydodecanoic acid activated NK cells to express CD69 mRNA within 10 min, in contrast to γ-DDL, which activated NK cells to express CD69 within 50 min. This faster activation suggests that γ-DDL has converted to 4-hydroxydodecanoic acid and to stimulate the NK cells to express CD69.Optically pure (R)-(+)-4-hydroxydodecanoic acid and (S)-(?)-4-hydroxydodecanoic acid were obtained via: (1) synthesis of its diastereomeric esters of (R,S)-4-hydroxydodecanoic (R)-(?)-2-phenylpropionate; (2) separation of diastereomers via preparative HPLC, and (3) subsequent hydrolysis of the obtained optical pure ester of (R)-(+)-4-hydroxydodecanoic acid (R)-(?)-2-phenylpropionate and (R)-(?)-4-hydroxydodecanoic acid (R)-(?)-2-phenylpropionate, respectively. Further assays of NK cells activation using each enantiomer showed that only the (R)-(+)-4-hydroxydodecanoic acid can activate NK cells.     

Syntheses of Unsaturated Lactones

6-Pentyl-α-pyrone, 6-propyl-α-pyrone and 4-decenoic acid-δ-lactone were prepared, and the nature of their flavors was investigated. Unsaturated lactones having the best flavorous nature as a butter or butter cake flavor among the lactones having double bond at various site, were 2-ene-δ-lactones which have a double bond at the α-position of the lactone ring and α-pyrones which have two double bonds at the α- and γ-positions. The flavor of 4-deceno-δ-lactone which has a double bond at the γ-position was the worst of them.