Biotransformation of alpha-terpineol by the larvae of common cutworm (Spodoptera litura)

Biotransformation of alpha-terpineol by the common cutworm (Spodoptera litura) larvae was investigated. alpha-Terpineol was mixed in an artificial diet, and the diet was fed to the larvae (fourth-fifth instar) of S. litura. Metabolites were isolated from the frass and analyzed spectroscopically. Main metabolites were 7-hydroxy-alpha-terpineol (p-menth-1-ene-7,8-diol) and oleuropeic acid (8-hydroxy-p-menth-1-en-7-oic acid). Intestinal bacteria from the frass of larvae did not participate in the metabolism of alpha-terpineol. alpha-Terpineol was preferentially oxidized at the C-7 position (allylic methyl group) by S. litura larvae.     

Biotransformation of gamma-terpinene and (-)-alpha-phellandrene by the larvae of common cutworm (Spodoptera litura)

gamma-Terpinene was mixed in artificial diet at a concentration of 1 mg/g of diet, and the diet was fed to the last instar larvae of common cutworm (Spodoptera litura). Metabolites were recovered from frass and analyzed spectroscopically. gamma-Terpinene was transformed mainly to p-mentha-1,4-dien-7-oic acid and p-cymen-7-oic acid (cumic acid). Similarly, (-)-alpha-phellandrene was transformed mainly to (4R)-p-mentha-1,5-dien-7-oic acid and p-cymen-7-oic acid (cumic acid). The C-7 position (allylic methyl group) of gamma-terpinene and (-)-alpha-phellandrene was preferentially oxidized.     

Isolation and identification of steroidal saponins in Taiwanese yam cultivar (Dioscorea pseudojaponica Yamamoto)

A new furostanol pentaoligoside and spirostanol tetraoligoside were isolated for the first time from yam tubers (Dioscorea pseudojaponica Yamamoto) from Taiwan, together with four known yam saponins, methyl protodioscin, methyl protogracillin, dioscin, and gracillin. Their structures were characterized as 26-O-beta-D-glucopyranosyl-22alpha-methoxyl-(25R)-furost-5-en-3beta,26-diol, 3-O-alpha-L-rhamnopyranosyl-(1-->2)-O-([alpha-L-rhamnopyranosyl-(1-->4)]-O-[alpha-L-rhamnopyranosyl-(1-->4)])-beta-D-glucopyranoside, and (25R)-spirost-5-en-3beta-ol 3-O-alpha-L-rhamnopyranosyl-(1-->2)-O-([alpha-L-rhamnopyranosyl-(1-->4)]-O-[alpha-L-rhamnopyranosyl-(1-->4)])-beta-D-glucopyranoside. The structural identification was performed using LC-MS and 1H and 13C NMR. The methanol extract of yam tubers was fractionated by XAD-2 column chromatography using a methanol/water gradient elution system to yield furostanol and spirostanol glycoside fractions. Preparative high-performance liquid chromatography, employing a C18 column and a mobile phase of methanol/water (69:31, v/v), was used to separate each furostanol glycoside, whereas a mobile phase of methanol/water (79:21, v/v) was used to resolve the individual spirostanol glycosides. The conversions from steroid saponins to diosgenin after acid hydrolysis were around 68 and 90% for furostanol and spirostanol glycosides, respectively.     

Hemisynthesis of dihydroumbellulols from umbellulone: new cooling compounds

Although menthol is a common ingredient used in food products, other molecules also evoke coolness through stimulation of the somatosensory system. To discover new molecules having cooling properties, we virtually screened the chemical structures of terpenes and sesquiterpenes to find structures that are similar to (-)-menthol. We realized that dihydroumbellulols could be good candidates. Although their occurrence was reported in Hyptis pectinata Poit, we were unable to obtain these molecules from the plant or to prove their natural occurrence. Therefore, we extracted (-)-(R)-umbellulone from Umbellularia californica Nutt. The (-)-(R)-umbellulone was reduced to prepare (1R,2R/S)-1-isopropyl-4-methylbicyclo[3.1.0]hex-3-en-2-ol, (1R,4R/S)-1-isopropyl-4-methylbicyclo[3.1.0]hexan-2-one, and (1R,2RS,4RS)-1-isopropyl-4-methylbicyclo[3.1.0]hexan-2-ols, named dihydroumbellulols. Sensory analysis suggested that (1R,2R,4S)-dihydroumbellulol has a pleasant, trigeminal cooling effect, about 2-3 times less cooling than (-)-menthol, with a weak odor slightly reminiscent of eucalyptol. In addition, a previously unreported compound was discovered, (-)-(1R)-1-isopropyl-4-methylenebicyclo[3.1.0]hexan-2-one.     

Chemoenzymatic synthesis of homochiral (R)- and (S)-karahanaenol from (R)-limonene

Terpinolene oxide, a monoterpene belonging to the p-menthane group, is easily derived from naturally abundant (R)-limonene. It was isomerized with montmorillonite clay catalyst to karahanaenone (2,2, 5-trimethylcyclohept-4-en-1-one) by ring enlargement. The enantiomers of the corresponding alcohol, karahanaenol (2,2, 5-trimethylcyclohept-4-en-1- ol), known for their individual organoleptic properties, were resolved through Pseudomonas cepacia lipase mediated enantiospecific alcoholysis of its acetate derivative.     

Phytotoxic activity of bibenzyl derivatives from the orchid Epidendrum rigidum

A whole plant chloroform-methanol extract of the orchid Epidendrum rigidum inhibited radicle growth of Amaranthus hypochondriacus seedlings (IC50 = 300 microg/mL). Bioassay-guided fractionation furnished four phytotoxins, namely, gigantol (1), batatasin III (2), 2,3-dimethoxy-9,10-dihydrophenathrene-4,7-diol (9), and 3,4,9-trimethoxyphenanthrene-2,5-diol (11), along with the known flavonoids apigenin, vitexin, and isovetin and the triterterpenoids 24,24-dimethyl-9,19-cyclolanostane-25-en-3beta-ol (14) and 24-methyl-9,19-cyclolanostane-25-en-3beta-ol (15). Stilbenoids 1, 2, 9, and 11 inhibited radicle growth of A. hypochondriacus with IC50 values of 0.65, 0.1, 0.12, and 5.9 microM, respectively. Foliar application of gigantol (1) at 1 microM to 4 week old seedlings of A. hypochondriacus reduced shoot elongation by 69% and fresh weight accumulation by 54%. Bibenzyls 1 and 2, as well as synthetic analogues 4'-hydroxy-3,3',5-trimethoxybibenzyl (3), 3,3',4',5-tetramethoxybibenzyl (4), 3,4'-dihydroxy-5-methoxybibenzyl (5), 3'-O-methylbatatasin III (6), 3,3',5-trihydroxybibenzyl (7), and 3,4',5-trihydroxybibenzyl (8), were tested for phytotoxicity in axenic cultures of the small aquatic plant Lemna pausicostata. All bibenzyls derivatives except 7 and 8 inhibited growth and increased cellular leakage with IC50 values of 89.9-180 and 89.9-166 microM, respectively. The natural and synthetic bibenzyls showed marginal cytotoxicity on animal cells. The results suggest that orchid bibenzyls may be good lead compounds for the development of novel herbicidal agents.     

Isolation and identification of terpene chlorohydrins found in cold-pressed orange oil

Three terpene chlorohydrins found in cold-pressed orange oil were concentrated by silica adsorption chromatography and purified by preparative HPLC. Formation of these chlorohydrins was determined to be the result of a reaction of d-limonene, the major component of cold-pressed oil, with hypochlorous acid, found in chlorinated treatment water used in the oil recovery process. NMR analyses indicated that the major chlorohydrin present was the diequatorially substituted (1R,2R,4R)-2-chloro-8-p-menthen-1-ol (1). The other two compounds were the diaxial trans stereoisomer, (1S,2S,4R)-2-chloro-8-p-menthen-1-ol (2), and the dichlorohydrin, (1R,2R,4R)-2,9-dichloro-8-p-menthen-1-ol (3).     

Novel 1,3-dioxanes from apple juice and cider

Extracts obtained by XAD solid-phase extraction of apple juice and cider were separated by liquid chromatography on silica gel. Several new 1,3-dioxanes including the known 2-methyl-4-pentyl-1,3-dioxane and 2-methyl-4-[2'(Z)-pentenyl]-1,3-dioxane, were identified in the nonpolar fractions by GC/MS analysis and confirmed by chemical synthesis. The enantioselective synthesis of the stereoisomers of the 1,3-dioxanes was performed using (R)- and (R,S)-octane-1,3-diol and (R)- and (R,S)-5(Z)-octene-1,3-diol as starting material. Comparison with the isolated products indicated that the natural products consisted of a mixture of (2S,4R) and (2R,4R) stereoisomers in the ratio of approximately 10:1, except for 1,3-dioxanes generated from acetone and 2-butanone. It is assumed that the 1, 3-dioxanes are chemically formed in the apples and cider from the natural apple ingredients (R)-octane-1,3-diol, (R)-5(Z)-octene-1, 3-diol, (3R,7R)- and (3R,7S)-octane-1,3,7-triol, and the appropriate aldehydes and ketones, which are produced either by the apples or by yeast during fermentation of the apple juice.     

Biotransformation of (+)- and (-)-menthol by the larvae of common cutworm (Spodoptera litura).

(+)-Menthol was mixed in an artificial diet at a concentration of 1 mg/g of diet, and the diet was fed to the last instar larvae of common cutworm (Spodoptera litura). Metabolites were recovered from frass and analyzed spectroscopically. (+)-Menthol was transformed mainly to (+)-7-hydroxymenthol. Similarly, (-)-menthol was transformed mainly to (-)-7-hydroxymenthol. The C-7 position of (+)- and (-)-menthol was preferentially oxidized.     

Generation of (E)-1-(2,3,6-trimethylphenyl)buta-1,3-diene from C13-norisoprenoid precursors

Three C(13)-norisoprenoid compounds, 3,6,9-trihydroxymegastigma-4,7-diene (6), 3,4,9-trihydroxymegastigma-5,7-diene (4), and the actinidols (8), have all been synthesized and subjected to acid hydrolysis. All three were shown to generate (E)-1-(2,3,6-trimethylphenyl)buta-1,3-diene (1) under wine conservation conditions. At 45 degrees C, approximately 4000-5000 ng/L of 1 was formed from 1.0 mg/L of precursor, after 173 days, while at 25 degrees C more wine-like amounts (200-600 ng/L) were observed. A glucoside, 4,5-dihydrovomifoliol-C(9)-beta-d-glucopyranoside (9b), was isolated from grapevine leaves by multilayer coil countercurrent chromatography (MLCCC), and its stereochemistry was deduced as being (5R, 6S, 9R) by NMR and CD spectroscopy. Hydrolysis of this glucoside produced 1, but in quantities insufficient to account for the levels observed in wine.     

Quantitative studies and sensory analyses on the influence of cultivar, spatial tissue distribution, and industrial processing on the bitter off-taste of carrots (Daucus carota l.) and carrot products

Although various reports pointed to 6-methoxymellein (1) as a key player imparting the bitter taste in carrots, activity-guided fractionation experiments recently gave evidence that not this isocoumarin but bisacetylenic oxylipins contribute mainly to the off-taste. Among these, (Z)-heptadeca-1,9-dien-4,6-diyn-3-ol (2), (Z)-3-acetoxy-heptadeca-1,9-dien-4,6-diyn-8-ol (3), and (Z)-heptadeca-1,9-dien-4,6-diyn-3,8-diol (falcarindiol, 4) have been successfully identified. In the present study, an analytical procedure was developed enabling an accurate quantitation of 1-4 in carrots and carrot products. To achieve this, (E)-heptadeca-1,9-dien-4,6-diyn-3,8-diol was synthesized as a suitable internal standard for the quantitative analysis of the bisacetylenes. On the basis of taste activity values, calculated as the ratio of the concentration and the human sensory threshold of a compound, a close relationship between the concentration of 4 and the intensity of the bitter off-taste in carrots, carrot puree, and carrot juice was demonstrated, thus showing that compound 4 might offer a new analytical measure for an objective evaluation of the quality of carrot products. Quantitative analysis on the intermediate products in industrial carrot processing revealed that removing the peel as well as green parts successfully decreased the concentrations in the final carrot puree by more than 50%.     

Sphingolipid and other constituents from almond nuts (Prunus amygdalus Batsch)

One sphingolipid, 1-O-beta-D-glucopyranosyl-(2S,3R,4E,8Z)-2-[(2R)-2-hydroxyhexadecanoylamino]-4,8-octadecadiene-1,3-diol, and four other constituents, beta-sitosterol, daucosterol, uridine, and adenosine, have been isolated from the nuts of almond (Prunus amygdalus). Complete assignments of the proton and carbon chemical shifts for the sphingolipid were accomplished on the basis of high-resolution 1D and 2D NMR data. All of these compounds are being reported from almond nuts (P. amygdalus)for the first time.     

Four new steroidal saponins from the seeds of Allium tuberosum

Four new steroidal saponins, 26-O-beta-D-glucopyranosyl-(25S,20R)-20-O-methyl-5alpha-furost-22(23)-en-2alpha,3beta,20,26-tetraol 3-O-alpha-L-rhamnopyranosyl-(1-->2)-[alpha-L-rhamnopyranosyl-(1-->4)]-beta-D-glucopyranoside (1); 26-O-beta-D-glucopyranosyl-(25S,20R)-5alpha-furost-22(23)-en-2alpha,3beta,20,26-tetraol 3-O-alpha-L-rhamnopyranosyl-(1-->2)-[alpha-L- rhamnopyranosyl-(1-->4)]-beta-D-glucopyranoside (2); 26-O-beta-D-glucopyranosyl-(25S,20S)-5alpha-furost-22(23)-en-2alpha,3beta,20,26-tetraol 3-O-alpha-L-rhamnopyranosyl-(1-->2)-[alpha-L- rhamnopyranosyl-(1-->4)]-beta-D-glucopyranoside (3); and 26-O-beta-D-glucopyranosyl-(25S,20S)-5alpha-furost-22(23)-en-3beta,20,26-triol 3-O-alpha-L-rhamnopyranosyl-(1-->2)-[alpha-L-rhamnopyranosyl-(1-->4)]-beta-D-glucopyranoside (4), have been isolated from the seeds of Allium tuberosum. Their structures were established by spectroscopic studies such as MS, IR, NMR, and 2D-NMR and the results of acid hydrolysis and named tuberosides F, G, H, and I, respectively.     

Constituents of the leaves of Peucedanum japonicum Thunb. and their biological activity

In the course of our study on the isolation and structure determination of constituents in tropical plants, we focused on Peucedanum japonicum Thunb., belonging to the family Umbelliferae. In this study, a new C(13) norisoprenoid glucoside, (3S)-O-beta-d-glucopyranosyl-6-[3-oxo-(2S)-butenylidenyl]-1,1,5-trimethylcyclohexan-(5R)-ol (1), and two new phenylpropanoid glucosides, 3-(2-O-beta-d-glucopyranosyl-4-hydroxyphenyl)propanoic acid (3) and methyl 3-(2-O-beta-d-glucopyranosyl-4-hydroxyphenyl)propanoate (4), were isolated from the n-butanol soluble fraction of this plant's leaves, together with five known compounds. The structures of these compounds were determined on the basis of spectroscopic evidence. In addition, all isolated compounds were examined for scavenging activity against 1,1-diphenyl-2-picrylhydrazyl radical and inhibitory activity against mushroom tyrosinase. These results suggested that 2-(4-hydroxy-3-methoxyphenyl)propane-1,3-diol (7) and 3-O-beta-d-glucopyranosyl-2-(4-hydroxy-3-methoxyphenyl)propanol (8) showed an appreciable activity in both assay systems.     

In vivo studies on the metabolism of the monoterpene pulegone in humans using the metabolism of ingestion-correlated amounts (MICA) approach: explanation for the toxicity differences between (S)-(-)- and (R)-(+)-pulegone

The major in vivo metabolites of (S)-(-)-pulegone in humans using a metabolism of ingestion-correlated amounts (MICA) experiment were newly identified as 2-(2-hydroxy-1-methylethyl)-5-methylcyclohexanone (8-hydroxymenthone, M1), 3-hydroxy-3-methyl-6-(1-methylethyl)cyclohexanone (1-hydroxymenthone, M2), 3-methyl-6-(1-methylethyl)cyclohexanol (menthol), and E-2-(2-hydroxy-1-methylethylidene)-5-methylcyclohexanone (10-hydroxypulegone, M4) on the basis of mass spectrometric analysis in combination with syntheses and NMR experiments. Minor metabolites were be identified as 3-methyl-6-(1-methylethyl)-2-cyclohexenone (piperitone, M5) and alpha,alpha,4-trimethyl-1-cyclohexene-1-methanol (3-p-menthen-8-ol, M6). Menthofuran was not a major metabolite of pulegone and is most probably an artifact formed during workup from known (M4) and/or unknown precursors. The differences in toxicity between (S)-(-)- and (R)-(+)-pulegone can be explained by the strongly diminished ability for enzymatic reduction of the double bond in (R)-(+)-pulegone. This might lead to further oxidative metabolism of 10-hydroxypulegone (M4) and the formation of further currently undetected metabolites that might account for the observed hepatotoxic and pneumotoxic activity in humans.     

Isolation, characterization, and antioxidant activity of bromophenols of the marine red alga Rhodomela confervoides

A total of 19 naturally occurring bromophenols, with six new and 13 known structures, were isolated and identified from the methanolic extract of the marine red alga Rhodomela confervoides. The new compounds were identified by spectroscopic methods as 3,4-dibromo-5-((methylsulfonyl)methyl)benzene-1,2-diol (1), 3,4-dibromo-5-((2,3-dihydroxypropoxy)methyl)benzene-1,2-diol (2), 5-(aminomethyl)-3,4-dibromobenzene-1,2-diol (3), 2-(2,3-dibromo-4,5-dihydroxyphenyl)acetic acid (4), 2-methoxy-3-bromo-5-hydroxymethylphenol (5), and (E)-4-(2-bromo-4,5-dihydroxyphenyl)but-3-en-2-one (6). Each compound was evaluated for free radical scavenging activity against DPPH (α,α-diphenyl-β-dipicrylhydrazyl) and ABTS [2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid)diammonium salt] radicals. Most of them exhibited potent activities stronger than or comparable to the positive controls butylated hydroxytoluene (BHT) and ascorbic acid. The results from this study suggest that R. confervoides is an excellent source of natural antioxidants, and inclusion of these antioxidant-rich algal components would likely help prevent the oxidative deterioration of food.     

Isolation and structural elucidation of some glycosides from the rhizomes of smaller galanga (Alpinia officinarum Hance)

Glycosidically bound compounds were isolated from the methanol extract of fresh rhizomes of smaller galanga (Alpinia officinarum Hance). Nine glycosides (1-9) were finally obtained by reversed-phase HPLC and their structures were elucidated by MS and NMR analyses. They were the three known glycosides, (1R,3S,4S)-trans-3-hydroxy-1,8-cineole beta-D-glucopyranoside (1), benzyl beta-D-glucopyranoside (3), and 1-O-beta-D-glucopyranosyl-4-allylbenzene (chavicol beta-D-glucopyranoside, 4); and the six novel glycosides, 3-methyl-but-2-en-1-yl beta-D-glucopyranoside (2), 1-hydroxy-2-O-beta-D-glucopyranosyl-4-allylbenzene (5), 1-O-beta-D-glucopyranosyl-2-hydroxy-4-allylbenzene (demethyleugenol beta-D-glucopyranoside, 6), 1-O-(6-O-alpha-L-rhamnopyranosyl-beta-D-glucopyranosyl)-2-hydroxy-4-allylbenzene (demethyleugenol beta-rutinoside, 7), 1-O-(6-O-alpha-L-rhamnopyranosyl-beta-D-glucopyranosyl)-4-allylbenzene (chavicol beta-rutinoside, 8), and 1,2-di-O-beta-D-glucopyranosyl-4-allylbenzene (9). Compounds 2-9 were detected for the first time as constituents of galanga rhizomes.     

Uptake and transformation of pesticide metabolites by duckweed (Lemna gibba)

Uptake and transformation of 14C-labeled metabolites from several pesticides, 3-methyl-4-nitrophenol (1), 3,5-dichloroaniline (2), 3-phenoxybenzoic acid (3), (R,S)-2-(4-chlorophenyl)-3-methylbutanoic acid (4), and (1RS)-trans-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropanecarboxylic acid (5), were examined by using duckweed (Lemna gibba) in Hoagland's medium. More uptake into duckweed from the exposure water at pH 7.0 was observed for non-ionized 1 and 2 than for 3-5 in an ionized form, and their hydrophobicity accounted for these differences. While carboxylic acids 4 and 5 were scarcely transformed in duckweed, 1-3 mainly underwent phase II conjugation with glucose for 1 and 2, malic acid for 3, glutamic acid for 2, and malonylglucose for 3, the chemical identities of which were confirmed by various spectrometric analyses (LC-MS, LC-MS/MS, and NMR) and/or HPLC cochromatography with reference synthetic standards.     

Spiro cross-links: representatives of a new class of glycoxidation products

Covalently cross-linked proteins are among the major modifications caused by the advanced Maillard reaction. So far, the chemical nature of these aggregates is largely unknown. Investigations are reported on the isolation of 6-[2-[[(4S)-4-amino-4-carboxybutyl]amino]-6,7-dihydroxy-6,7-dihydroimidazo[4,5-b]azepin-4(5H)-yl]-L-norleucine (10) and N-acetyl-6-[(6R,7R)-2-[[4-(acetylamino)-4-carboxybutyl]amino]-6,7,8a-trihydroxy-6,7,8,8a-tetrahydroimidazo[4,5-b]azepin-4(5H)-yl]-L-norleucine (12) formed by oxidation of the major Maillard cross-link glucosepane 1. Independent synthesis and unequivocal structural characterization are given for 10 and 12. Spiro cross-links, representing a new class of glycoxidation products, were obtained by dehydrogenation of the amino imidazolinimine compounds N6-[2-[[(4S)-4-ammonio-5-oxido-5-oxopentyl]amino]-5-[(2S,3R)-2,3,4-trihydroxybutyl]-3,5-dihydro-4H-imidazol-4-ylidene]-L-lysinate (DOGDIC 2) and N6-[2-[[(4S)-4-ammonio-5-oxido-5-oxopentyl]amino]-5-[(2S)-2,3-dihydroxypropyl]-3,5-dihydro-4H-imidazol-4-ylidene]-L-lysinate (DOPDIC 3). These new oxidation products were synthesized, and their unambiguous structural elucidation proved the formation of the spiro imidazolimine structures N6-[(7R,8S)-2-[[(4S)-4-ammonio-5-oxido-5-oxopentyl]amino]-8-hydroxy-7-(hydroxymethyl)-6-oxa-1,3-diazaspiro[4.4]non-1-en-4-ylidene]-L-lysinate (16), N6-(8R,9S)-2-[(4S)-4-ammonio-5-oxido-5-oxopentyl]amino]-8,9-dihydroxy-6-oxa-1,3-diazaspiro[4.5]dec-1-en-4-ylidene)-L-lysinate (19), and N6-[(8S)-2-[(4-amino-4-carboxybutyl)amino]-8-hydroxy-6-oxa-1,3-diazaspiro[4.4]non-1-en-4-ylidene]-L-lysinate (18), respectively. It was shown that reaction of the imidazolinone 15 led to the formation of spiro imidazolones, structurally analogous to 16 and 19.     

Biotransformation of beta-myrcene by the larvae of common cutworm (Spodoptera litura)

beta-Myrcene was mixed in an artificial diet at a concentration of 1 mg/g of diet, and the diet was fed to the last instar larvae of common cutworm (Spodoptera litura). Metabolites were recovered from frass and analyzed spectroscopically. beta-Myrcene was transformed mainly to myrcene-3(10)-glycol and myrcene-1,2-glycol. Each pair of double bonds of beta-myrcene was converted to the corresponding diol by oxidation, respectively. The 3,10- and 1,2-double bonds of beta-myrcene were respectively oxidized.