In-situ identification of major metabolites in the red alga Gracilariopsis lemaneiformis using high-resolution magic angle spinning nuclear magnetic resonance spectroscopy

The content of low-molecular-weight compounds in the red alga Gracilariopsis lemaneiformis [(Bory) Dawson, Acleto, et Foldvik] has been analysed in-situ using high-resolution magic angle spinning (HR-MAS) nuclear magnetic resonance (NMR) spectroscopy. The major heteroside was shown to be floridoside, but digeneaside and isofloridoside were also detected in the alga. Other major components were isethionic acid and the amino acids taurine and citrulline. The results from the HR-MAS NMR analysis were confirmed with high-resolution NMR spectroscopy, high-resolution fast atom bombardment mass spectrometry (FABMS) and GC-MS, on material isolated from the studied alga, but also on authentic samples. Received: 2 February 1998 / Accepted: 9 April 1998     

Structural studies on some saponins from Lecaniodiscus cupanioides

Four triterpenoid saponins isolated from the stem bark of Lecaniodiscus cupanioides and denoted S-2,S-3,S-4 and S-5, were identified as follows. S-2:3-O-[α-l-arabinopyranosyl-(1→3)-α-l-rhamnopyranosyl-(1→2)-α-l-arabinopyranosyl]-hederagenin; S-3:3-O-[α-d-xylopyranosyl-(1→3)-α-l-rhamnopyranosyl-(1→2)-α-l-arabino-pyranosyl ]-hederagenin; S-4:3-O- [α-l-arabinopyranosyl-(1→3)-α-l-rhamnopyranosyl-(1→ 2)-α-l-arabinopyranosyl]-hederagenin; S-5:3-O- [α-l-rhamnopyranosyl-(1→2)-α-l-arabinopyranosyl ]-hederagenin. Of these, S-2 and S-4 are new substances.     

RecA-like activity in mammalian cell extracts of different origin

The occurrence of a RecA-like activity similar to the one detected in the fibroblast cell line GM1492 derived from a patient suffering from the autosomal recessive disease Bloom's syndrome has been investigated in cell extracts of different origin. The formation of D-loop containing joint molecules from phi X174 RFI DNA and fragments of phi X174 single-stranded DNA by partially purified extracts was measured by a filter binding assay. The RecA-like activity, dependent on ATP and Mg2+, was detected at an elevated level only in the human and rodent cell lines, GM1492 and CHO respectively. The level of activity in DNA-cellulose-purified cell extracts from these cell lines was 4-7-fold higher compared to normal human fibroblasts. Low levels of activity were also detected in extracts from two additional Bloom's syndrome fibroblast cell lines, Fanconi's anemia fibroblasts, virus- (Epstein-Barr virus, Simian virus 40) transformed human cells and human placenta. Cell extracts from rat testis, spleen and calf thymus were also of low activity.     

Structural analysis of two 2-deoxy analogues of alpha- and beta-KDO and the methyl alpha- and beta-glycosides of KDO, and determination of their metal-ion-binding properties

Ammonium 2,6-anhydro-3-deoxy-D-glycero-D-talo-octonate (1), a potent inhibitor of the enzyme CMP-KDO synthetase, its C-2 epimer 2, and the methyl beta- (3) and alpha-glycoside (4) of KDO were studied by 1H- and 13C-n.m.r. spectroscopy. Compound 1 was also analysed by X-ray crystallography. Each compound adopted a 5C2 chair conformation with the side chain equatorial. The preponderant side-chain conformation of 1 in solution was the same as that in the crystal and was stabilised by an intramolecular hydrogen bond from HO-8 to the carboxylate group. This hydrogen bond appeared to be present also in 3. However, the side-chain conformation of 2 and 4 was different from that in 1 and 3. The metal-ion-binding properties, determined on the basis of the line-broadening effects of Mn2+ on the 13C-n.m.r. signals, showed that the carboxylate group was involved in the binding with O-8 in 1 and 3 and with O-6 and O-8 in 2 and 4.