A sulfated, myotropic neuropeptide termed leucosulfakinin (Glu-Gln-Phe-Glu-Asp-Tyr(SO3H)-Gly-His-Met-Arg-Phe-NH2) was isolated from head extracts of the cockroach Leucophaea maderae. The peptide exhibits sequence homology with the hormonally active portion of the vertebrate hormones human gastrin II and cholecystokinin, suggesting that these peptides are evolutionarily related. Six of the 11 amino acid residues (55 percent) are identical to those in gastrin II. In addition, the intestinal myotropic action of leucosulfakinin is analogous to that of gastrin.

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Formylation of solasodine results in the formation of two different 3,N-diformylsolasodines whose isomerism is due to a difference in stereochemistry at C22 rather than restricted rotation about the C = N partial double bond of the amide or nitrogen inversion as previously proposed. Mass spectra, 'H and I3C n.m.r. spectra have shown the isomers to possess 22R,25R (major) and 22S,25R (minor) stereochemistry. The 22S,25R isomer is thermodynamically preferred at elevated temperatures while the 2212,2513 isomer is kinetically favoured upon recyclization of the ring-F opened intermediate which forms upon heating of either isomer. A non-chair ring-P conformation is proposed for each isomer on the basis of 13C and 'H n.m.r. spectra. mixture of the isomeric N-formylsolasodines. This study reports a detailed investigation of the isomeric (25R)-N-formyl-22N-spiroso1-5-en-3j3-y1 formates (3,Ndiformylsolasodines) by mass spectrometry, 13C and 'H n.m.r. spectroscopy which has led to assignment of structures (1) and (2) to these compounds. Results and DiscussionAddition of formic-acetic anhydride to a chloroform solution of solasodine yielded isomeric diformylsolasodines in a ratio of approximately 2 : 1. The major isomer (I) gave a 'H n.m.r. spectrum corresponding to that reported1 for isomer (B) while the minor isomer (2) afforded a 'H n.m.r. spectrum resembling that reported1 for isomer (A). Formylation of tomatidine under similar conditions yielded a single diformyl derivative (3). 'H and 13C N.M.R. SpectraDue to conflicting assignments reported by two groups of ~o r k e r s ' ,~ for 'H n.m.r. signals of the H21 and H27 [see structure (4) for numbering] methyl groups of (1) and (2), proton decoupling experiments were performed in order to unequivocally establish the position of the resonance for each methyl group (Table 1). Irradiation of (2), in CDCl,, at 6 2.30 (H20) collapsed only the downfield methyl doublet at 6 1.14 while irradiation at 6 1.80 (H 25) collapsed signals due to each of the H26 protons at 6 3.88 and 3.13 in addition to the upfield methyl doublet at 6 0.94. Similar results were obtained for (1) in C,D,, a solvent in which the upfield H26 resonance moved downfield relative to its position in CDCl, enabling it to be observed. These results confirm the assignments originally reported1 by Toldy and Radics and enable assignment of H 27 to the upfield methyl doublet. Furthermore, we have confirmed the report1 that the upfield H 26 has a trans (7-9 Hz) coupling to the H 25 proton in (1) and (2).

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Two methods for mass spectral (MS) confirmation of aflatoxins in agricultural products and in physiological fluids are described. In the first method, electron ionization (EI) mass spectra are obtained following isolation by thin layer chromatography (TLC) and compared with available reference mass spectra to provide structural confirmation. Extensive sample cleanup is required for confirmation at the 10—1000 ppb level and minimum sample size is 10—50 ng aflatoxin isolated by TLC. The second method restricts the MS scanning to particular ions which are characteristic of the suspected aflatoxins and requires spectrometer resolution above 5000. The latter method, called high resolution selected ion monitoring (HRSIM), has a sensitivity below 0.0001 μg for aflatoxin B1 and makes possible direct analysis of complex mixtures. Employing HRSIM analysis on complex mixtures lowers the detection limit for aflatoxins M1 and B1 by 100-fold or more below the limit for highly purified samples. We attribute this dramatic sensitivity enhancement to a reduction in surface bonding between the aflatoxins and the glass sample containers used to introduce the samples. The HRSIM is generally applicable to compounds that cannot be separated by gas chromatography prior to MS analysis.