Naoto Shimizu

Sterols of the Cucurbitaceae

Abstract The sterol constituents of 32 seed and mature plant (leaves and stems, pericarp of the fruit and roots) materials from the 12 genera of the family Cucurbitaceae were investigated, and 44 sterols were identified or newly characterized. The sterols found were those possessing the following 7 types of skeletons: saturated, and Δ 5 -, Δ 7 -, Δ 8 -, Δ 8(14) - and 14α-methyl-Δ 9(11) -unsaturated, and 14α-methyl-9β,19-cyclo skeletons, with the side chains of 24-unsubstituted, Δ 24 -, 24-methyl-, 24-methyl-Δ 22 -, 24-methylene-, 24-ethyl-, 24-ethyl-Δ 22 -, 24-ethyl-Δ 24(250 -, 24-ethylidene-, 24-ethyl-Δ 25 - and 24-ethyl-δ 22,25 -substituted, 24-methylene-25-methylated and 24,24-dimethylated (24,24-dimethyl-, 24,24-dimethyl-Δ 22 - and 24,24-dimethyl-Δ 25 -substituted) structures. The configurations at C-24 of the 24-alkylsterols were examined by high resolution 1 H NMR and 13 C NMR spectroscopy. The 24-methyl- and 24-ethylsterols lacking a Δ 25 -bond examined (i.e. 24-methyl-, 24-methyl-Δ 22 -, 24-ethyl- and 24-ethyl-Δ 22 -sterols) were shown to occur as the C-24 epimeric mixtures, or as a single diastereoisomer, either 24α- and 24β-epimer. The 24-ethylsterols bearing a Δ 25 -bond (i.e. 24-ethyl-δ 25 - and 24-ethyl-Δ 22,25 -sterols) were, on the other hand, composed of only 24β-epimers. The possible biosynthetic sequences to the cucurbitaceous sterols are discussed.

(24S)-14α,24-dimethyl-9β,19-cyclo-5α-cholest-25-en-3β-ol: A new sterol and other sterols inMusa sapientum

The structure of a new sterol isolated fromMusa sapientum has been shown by chemical and spectroscopic methods to be (24S)-14α,24-dimethyl-9α,19-cyclo-5α-cholest-25-en-3β-ol. In addition, several known (24S)-24-methyl-Δ25-sterols, their 24-methylene isomers and other sterols (4,4-dimethyl-, 4α-methyl- and 4-demethyl-sterols) together with 3-oxo-4α-methylsteroids were isolated from the plant and identified. The biogenetic implication of these sterols and 3-oxosteroids is discussed.

4α-methylvernosterol and other sterols from Vernonia anthelmintica seeds

Abstract A novel 4α-methylsterol isolated from the seeds of Vernonia anthelmintica was shown to have the structure 4α-methyl-5α-stigmasta-8,14,24(24′) Z -trien-3β-ol (4α-methylvernosterol) based on spectroscopic methods. The 4-demethylsterol and 4,4-dimethylsterol fractions from the seed material were also investigated. The 4-demethylsterol fraction contained 5α-stigmasta-8,14,24(24′) Z -trien-3β-ol (vernosterol) and 5α-stigmasta-7,24(24′) Z -dien-3β-ol (avenasterol) as the dominant sterols. 4α-Methylvernosterol is the possible intermediate in the biosynthesis of vernosterol in V. anthelmintica seeds.

The 24α- and 24β-epimers of 24-ethylcholesta-5,22-dien-3β-ol in two Clerodendrum species

Abstract 13 C NMR spectroscopy of the 24-ethylcholesta-5,22 E -dien-3β-ol isolated from the aerial parts of Clerodendrum fragrans and C. infortunatum demonstrated the occurrence of a minor amount of the 24β-epimer, poriferasterol, in addition to,the dominant 24α-epimer, stigmasterol. This was confirmed by 400 MHz 1 H NMR spectroscopy after enrichment of the 24p-epimer by repetitive reverse-phase HPLC. The ratios (24α:24β) of the C-24 epimeric mixtures were estimated to be 23:2 for the C. fragrans sterol and 19:1 for the C. infortunatum sterol.

(24R-14α-methyl-24-ethyl-5α-cholest-9(11)-en-3β-ol: A new 14α-methylsterol fromCucumis sativus

The structure of a new 14α-methylsterol isolated fromCucumis sativus has been shown to be (24R)-14α-methyl-24-ethyl-5α-cholest-9(11)-en-3β-ol. Characterization of the 14α-methyl-Δ9(11) skeletal structure was undertaken based on the comparison with 14α,24-dimethyl-5α-cholest-9(11)-en-3β-ol obtained from 24-methylpollinastanol by acid-catalyzed isomerization. Isolation and identification of an additional 14α-methylsterol, 24-methylene-pollinastanol, from the plant also is described.

Structures of three new 24,24-dimethyl-Δ7-sterols fromGynostemma pentaphyllumfromGynostemma pentaphyllum

The structures of three new sterols isolated fromGynostemma pentaphyllum (Cucurbitaceae) have been shown by chemical and spectroscopic methods to be 24,24-dimethyl-5α-cholest-7-en-3β-ol, (22E)-24,24-dimethyl-5α-cholesta-7,22-dien-3β-ol and 24,24-dimethyl-5α-cholesta-7,25-dien-3β-ol.

Elution behaviour of polyamic acid and polyamide-imide in size-exclusion chromatography

Abstract The causes of the peculiarities of the elution behaviour of thermoresistant resins, when N,N-dimethylformamide (DMF) is used as the mobile phase were investigated. In order to establish whether the peculiarities are caused by the properties of DMF, by the interactions between the stationary phase and DMF, or by the generation of specific properties of the solutes in DMF, tetrahydrofuran (THF)-soluble polyamic and polyamide—imide resins were prepared. Two stationary phases, hydrophobic polystyrene gel and hydrophilic polymer gel, were used and DMF, THF and a mixture of DMF and THF with or without H 3 PO 4 and LiBr were used as the mobile phases. The peculiarities are discussed from the point of dissociation of carboxylic groups of the solutes and of the hydrophilic stationary phase. Adsorption of the resins on the columns or early elution from the columns were prevented by the addition of H 3 PO 4 and early elution of the neutral polyamide—imide from the column was prevented by the addition of LiBr. The early elution of the resins was not due to the intramolecular chain expansion of the resins in DMF, but to the interactions between carboxylic groups of the resins and of the hydrophilic polymer gels. The addition of H 3 PO 4 suppressed the dissociation of carboxylic groups of the resins. DMF partially controls the dissociation of the carboxylic groups.

Retention behavior of methylamines, ethylenediamine and N-methyl-substituted ethylenediamines on a cation-exchange resin having a polycarboxylic acid as the functional group

The retention behavior of ethylenediamine and N-methyl-substituted ethylenediamines on a polycarboxylic acid-type cation-exchange resin was investigated. These diamines were retained as 2+ cations on the polycarboxylic acid-type cation-exchange resin using nitric acid solution as the eluent. The capacity factor of the N-methyl-substituted ethylenediamines increased with increasing number of methyl groups. The retention of these diamine compounds was only slightly affected by adding CH 3 CN to the eluent. On the other hand, the retention of methylamines was strongly affected. This result would be due to the difference in the hydrophobic effect of the methyl group for the hydration state of the amines.