Jan St. Pyrek

2,3-Dihydrofarnesoic acid, a unique terpene from trichomes ofLycopersicon hirsutum, repels spider mites

Lycopersicon hirsutum, a wild relative of the tomato, is highly resistant to arthropod herbivores. Both botanic forms ofL. hirsutum, L. hirsutum f.glabratum (C.H. Mull.) andL. hirsutum f.typicum (Humb. & Bonpl.), are resistant to two-spotted spider mites,Tetranychus urticae Koch. However, leaves and trichome secretions from f.typicum repel mites more so than those from f.glabratum. We have previously demonstrated that trichome secretions from LA 1363 and LA 1927, accessions of f.typicum, repelled mites. In this paper we report the identification of the primary component of trichome secretions responsible for repellency. Leaflet washes having compositions similar to trichome secretions were collected and separated into neutral and acid fractions; repellency was mainly associated with the acid fraction, which, when applied to nonrepellent leaflets of f.glabratum, rendered them repellent. Separation of leaflet washes by HPLC allowed purification and subsequent identification by gas chromatography-mass spectrometry and nuclear magnetic resonance of 2,3-dihydrofamesoic acid (3,7,11-trimethyl-6, 10-dodecadienoic acid) as the primary chemical component responsible for repellency. Application of this acid to leaflets ofL. esculentum rendered them repellent. Other volatile compounds present in minor amounts in the acid fractions were farnesoic acid and 16∶0, 16∶3, 18∶0, 18∶2, and 18∶3 fatty acids. This is the first report of the natural occurrence of 2,3-dihydrofarnesoic acid.

A synthesis of C-23 and C-24 diastereomers of 5α-dinosterane

Abstract Stereoselective routes for the preparation of C-23 and C-24 diastereomers of the C30 biological marker, 5α-dinosterane (1), involved the alkylation of (20S)-20-(iodomethyl)-4α-methyl-5α-pregnane (7) with either a saturated ester, methyl 3,4-dimethylpentanoate (9), followed by reduction to give principally the erythro-diastereomers or the alkylation of 7 with an α,β-unsaturated ester, methyl 3,4-dimethylpentenoate (12), followed by reduction to give principally the threo-diastereomers.

Hepatic metabolism of 3-oxoandrost-4-ene-17β-carboxylic acid in the adult rat: formation of carboxyl-linked glucuronides both in vivo and in vitro

The hepatic metabolism of 3-oxoandrost-4-ene-17 beta-carboxylic acid (etienic acid), a probable acidic catabolite of deoxycorticosterone, was investigated using rats prepared with an external biliary fistula. Metabolic products were identified by GC-MS after hydrolysis with beta-glucuronidase and by proton nuclear magnetic resonance after chromatographic purification of protected glucuronides. About 80% of the injected dose was secreted into bile in 20 hours. Three fully reduced etianic acids (3 alpha-hydroxy-5 alpha-, 3 beta-hydroxy-5 alpha-, 3 alpha-hydroxy-5 beta-androstan-17 beta-carboxylic acids) were identified as were several of their di- and trihydroxylated congeners. Glucuronides of these reduced and/or hydroxylated metabolites constituted over half of the recovered dose, with carboxyl-linked glucuronides predominating over 3-hydroxyl-linked glucuronides. The mode of glucuronidation correlated well with the ability of liver microsomes to form the corresponding compounds in vitro from the set of four 3,5-diastereomeric etianic acids.

Mass Spectrometry in the Chemistry of Natural Products

Mass spectrometry (MS) is one of the very first spectral methods dating back to the beginning of this century (1913, J.J. Thomson, parabola spectrograph; 1918, A.J. Dempster, spectrometer, and 1919, F.W. Aston, spectrograph).1 It measures mass, one of the two basic properties of matter, as the mass-to-charge-ratio of ions, (m/z in atomic mass units, scale relative to 12C) while other spectral methods usually measure frequency, either absorbed or emitted. Thus, in a sense, the mass spectrometer is an extension of the balance, the principal tool of a chemical laboratory. Sensitivity of mass spectral measurements approaches single ion detection and the accuracy of mass determination may be in order of ppm. The quest for this precise information characterizes all three major phases of the application and development of mass spectrometry: detection of isotopes, “inorganic phase”, followed by extensive analysis of molecules of relatively low molecular weight, “organic phase”, and the most recent “biological phase” in which ionization and analysis of ions derived from a much wider variety of polar and large organic molecules becomes possible. Immense developments of instrumentation, increasing analytical applications, and an ever increasing range of compounds accessible to measurement do not change the heart of mass spectrometry and the simplicity of the fundamental information provided.

Mass spectrometry at low and high mass.

The introduction of novel methods as well as expanding applications to diverse areas highlight truly impressive progress in mass spectrometry. These developments are illustrated here by two seemingly different areas of research: new methods designed for the determination of isotopic enrichment and novel ionization methods; and mass analyzers which have enabled the precise determination of the molecular weight of proteins and large oligonucleotides.

Metabolites of Nuatigenin ((22S,25S)22,25-Epoxy-3β,26-Dihydroxy-Furost-5-Ene) Accumulate in the Bile of Rabbits Fed Oats

In spite of frequent occurrence of steroidal saponins in nutritionally important plants, little is known about metabolism of the corresponding sapogenols. Only relatively recent data indicate that certain saponins are of a considerable health significance to livestock and this toxicity seems to be related to discrete metabolites of sapogenols identified in the bile. It has been noted that lambs grazing on a kleingrass, Panicum coloratum, develop photosensitization secondary to the hepatic dysfunction with lesions, necrosis of hepatocytes and obstruction of small bile ducts with a crystalline material.1 Similar material, accumulating in sheep fed Agave lecheguilla, has been identified as either smilagenin ((25R)3β-hydroxy-5β-spirostane) la or sarsapogenin ((25S)3β-hydroxy-5β-spirostane) 2a.2 Diosgenin ((25R)3β-hydroxyspirost-5-ene) 3 and yamogenin ((25R)3β-hydroxyspirost-5-ene) 4, released from saponins of P. coloratum upon hydrolysis, may give rise to these insoluble products.3 Two related species, P. dichotomiflorum and P. schinzii, are also hepatotoxic to sheep and their intake causes accumulation of a calcium salt of β-D-glucuronide of epi-smilagenin ((25R)3α-hydroxy-5β-spirostane) lb.4,5,6,7 Subsequently, however, the true sapogenol of P. dichotomiflorum has been identified as (25R)-3β,22α,26-trihydroxy-furost-5-ene 5.8 Thus, in case of Panicum, furostanols and not spirostanols may serve as precursors of these bile-insoluble products. In addition, it has been found that in case of the intoxication of sheep grazing on signal grass Brachiaria decumbens, epi-sarsapogenin ((25S)3α-hydroxy-5β-spirostane) 2b and epi-smilagenin lb accumulate in the rumen content,9,10 whereas feeding furostanol saponins of Trigonella foenum graecum to dogs results in the fecal excretion of smilagenin la, diosgenin 3, and gitogenin ((25R)2α, 3β-dihydroxy-5α-spirostane) 6.11