Pectic polysaccharides were obtained from chalkumra (Benincasa hispida) fruit by sequential extraction with ammonium oxalate (fraction BOX), dilute acid (fraction BHCl), and cold dilute alkali (fraction BOH). The highest yield of polysaccharides was obtained with oxalate and HCl. BOX was enriched in partly methyl-esterified galacturonic acid, whereas BHCl and BOH contained mostly galactose. All of the extracts showed similar elution patterns in size exclusion chromatography although the intrinsic viscosities (eta) were different (132 +/- 6, 100 +/- 5, and 285 + 10 mL/g for BOX, BHCl, and BOH, respectively). From fractionation by anion exchange chromatography, homogalacturonan (as seen from sugar analysis and Fourier transform infrared spectrum) accounted for more than half of BOX and 11% of BHCl. Methylation analyses and hydrolysis of BHCl with endo-beta-(1-->4)-d-galactanase showed the presence of beta-(1-->4)-d-galactan. The neutral galactan represented more than 76% of BHCl and approximately 40% of BOH. The other polysaccharides were complex galactans in BOH and an acidic arabinan (<1%) in BOX and BHCl.

The major sterols of the seeds ofBenincasa cerifera, Cucumis sativus, Cucurbita maxima, C. pepo andTrichosanthes japonica and of the mature plant tissues (leaves and stems) ofCitrullus battich, Cucumis sativus andGynostemma pentaphyllum of the family Cucurbitaceae were 24-ethyl-Δ(7)-sterols which were accompanied by small amounts of saturated and Δ(5)-and Δ(8)-sterols. The 24-ethyl-Δ(7,22),Δ(7,25(27)) and Δ(7,22,25(27))-sterols constituted the predominant sterols for the seed materials, whereas the 24-ethyl-Δ(7) and Δ(7,22)-sterols were the major ones for the mature plant tissues. The configurations of C-24 of the alkylsterols were examined by high resolution(1)H NMR and(13)C NMR spectroscopy. Most of the 24-methyl- and 24-ethylsterols examined which lack a Δ(25(27))-bond (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 in which the 24α-epimers predominated in most cases. The 24-ethylsterols which possess a Δ(25(27)) (i.e., 24-ethyl-Δ(25(27))-and 24-ethyl-Δ(7,22,25(27))-sterols) were, on the other hand, composed of only 24β-epimers. The Δ(8)-sterols identified and characterized were four 24-ethyl-sterols: 24α-and 24β-ethyl-5α-cholesta-8,22-dien-3β-ol, 24β-ethyl-5α-cholesta-8,25(27)-dien-3β-ol and 24β-ethyl-5α-cholesta-8,22,25(27)-trien-3β-ol. This seems to be the first case of the detection of Δ(8)-sterols lacking a 4-methyl group in higher plants, and among the four Δ(8)-sterols the latter two are considered to be new sterols. The probable biogenetic role of the Δ(8)-sterols and the possible biosynthetic pathways leading to the 24α- and 24β-alkylsterols in Cucurbitaceae are discussed.

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