Stimulating effect of both 4’- O -methylnorbelladine feeding and temporary immersion conditions on galanthamine and lycorine production by Leucojum aestivum L. bulblets

International audienceBulb cultures of Leucojum aestivum and L. aestivum ‘Gravety Giant’ were subcultured in medium containing the precursor 4’‐O‐methylnorbelladine (MN) at various concentrations [0 (control), 0.15 and 0.3 g/L]. The cultures were conducted in bioreactor RITA® and lasted for 15, 30, 40 and 50 days. The growth rate and the alkaloid accumulation in bulblets were studied. For this latter purpose, a purification method was developed. It comprised a highly selective solid phase extraction using on the one hand, UPTI‐CLEAN SI and SCX cartridges for plant extracts and on the other hand, 2H cartridges for culture media. Pure alkaloidal fractions were, thus, analyzed by LC‐ESI‐MS allowing the quantitative evaluation of galanthamine and lycorine from culture extracts. Precursor feeding along with temporary immersion conditions was found to significantly improve the accumulation of both galanthamine and lycorine. The maximal concentrations of galanthamine (0.81 mg/g DW) and lycorine (0.54 mg/g DW) in L. aestivum bulblets were reached, respectively, after 40 days of culture with 0.15 g/L of precursor and after 30 days of culture with 0.3 g/L of precursor. In L. aestivum ‘Gravety Giant’ bulb cultures, 0.3 g/L of precursor was the best condition for both galanthamine (0.6 mg/g DW after 50 days) and lycorine (1.13 mg/g DW after 30 days)

Characterization of the molecular structure of two highly isotactic polypropylenes

Two polypropylenes, PP1 and PP2, produced with different heterogeneous Ziegler-Natta catalytic systems were studied in this work. Preliminary characterization of the non-fractionated materials showed that a low difference in their average tacticity (PP2 > PP1) leads to an important modification of their rigidity properties. In order to establish correlation between the molecular structure parameters and the rigidity properties of these polymers, fractionation of the materials according to crystallizability was performed by means of temperature rising elution fractionation (TREF). Analysis of the fractions of both PP1 and PP2 was carried out by means of C-13 NMR, size exclusion chromatography (SEC), differential scanning calorimetry (DSC) and atomic force microscopy (AFM). The results first showed that TREF does not strictly fractionate PP according to tacticity, but according to the longest crystallizable sequence in a chain. C-13 NMR, SEC and DSC analysis of the fractions demonstrated that the inter-chain tacticity distributions of the polypropylenes is affected by the change of the polymerization conditions, which, in turn, modifies the rigidity properties of the materials. Some results also seem to indicate that the intrachain tacticity distributions are different for the two PP. An AFM study of the elastic modulus was carried out for the first time on the TREE fractions. It showed that the rigidity or the fractions strongly increases as the TREF elution temperature increases in accordance with a concomitant increase of isotacticity and the crytallinity of the fractions. PP2 TREE fractions were, moreover, found to exhibit a higher elastic modulus than PP1 TREF fractions at all elution temperatures. This study allowed us to further identify the TREF fractions that were responsible for differences in rigidity. To summarize, it is shown how the experimentally observed increase of the average rigidity of one of these two polypropylenes can be rationalized via information collected from a TREF fractionation. (C) 2000 Published by Elsevier Science Ltd

New method for the study of Amaryllidaceae alkaloid biosynthesis using biotransformation of deuterium-labeled precursor in tissue cultures.

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