Biosynthese des produits volatils de la pomme: Formation des alcools et des esters a partir des acides gras

The biosynthesis of apple volatiles (alcohols and esters) was studied using disks of aged tissues. After adding each substrate, the volatiles formed were analysed and estimated by GLC and their qualitative and quantitative composition compared with those of the control. Alcohols were formed from aliphatic acids having either the same number of carbon atoms, or from higher homologues through β-oxidation. Fatty acids with an even carbon number gave rise to butanol and hexanol, while odd carbon fatty acids generated propanol and pentanol. Esters were synthesized from the corresponding acid and alcohol and the yield was very high. Volatile profiles differed from one variety to another, yellow-skinned varieties producing chiefly acetic acid esters and the red-skinned mainly butyric acid esters. Provided the right substrates were given, all the esters were synthesized by the different tissues assayed, and the nature of the volatiles produced by each variety depends on the substrates present in the fruit. However, in Golden Delicious apples, which have a low content of butyric esters, erogenous butyrate was rapidly and completely transformed into acetate.     

Role de la phenylalanine dans la biosynthese des flavonoides et acides “cinnamique” dans les tiges volubiles de Periploca Graeca

Phenylalanine is the precursor of the cinnamic acids and coumarins in the stems and leafs of P. graeca L. Esterification of p-coumaric acid by quinic acid is required before oxidation to chlorogenic acid. In our experiments, we did not obtain radioactive flavonols from ¹⁴C phenylalanine. PAL activity varies as a result of light and temperature in the same manner as the level of flavonoids (especially the phenolic acids). This enzyme, therefore, plays a regulatory role in the synthesis of these phenolic substances. The variation in PAL activity during illumination does not follow the same course as described for other plants.     

Etude de melanges binaires de triglycerides derives des acides palmitique et stearique

The phase diagrams of the SSS—PSP, PSP—SPP and SSS—SPP systems have been established, using DTA and X-ray diffraction, In all cases, a demixtion was found in the solid state, and an intermediate phase was evidenced for the PSP—SPP and SSS—SPP systems.Relations between the diagrams of stable and unstable forms are considered for the system SSS—PSP. Moreover, the influence of structuration in the liquid state on the drawing of liquidus is discussed.     

Influence de la température sur la biosynthèse des acides gras de deux champignons filamenteux, Aspergillus ochraceus et Mucor mucedo

The two moulds, Mucor mucedo and Aspergillus ochraceus, grow very rapidly at 22°; when transferred to 12°, Mucor shows a regular growth and sporulation while Aspergillus development is almost entirely inhibited. ¹⁴C Acetate was supplied to both fungi at 12° and 22°. In both, the total radioactivity of saturated fatty acids was less important at the lowest temperature. In contrast, C 18:1 radioactivity rose in Mucor while it was C 18:2 radioactivity which rose in Aspergillus at the lowest temperature. There was an increase in phosphatidylethanolamine (PE) and phosphatidylcholine (PC) radioactivities in Mucor while the phosphatidylserine (PS) radioactivity decreased at low temperature. By contrast, when Aspergillus was placed in the same cultural conditions, PE and PC radioactivities decreased while PS radioactivity increased. Based on these results, a tentative explanation of the improved cold-resistance of M. mucedo is presented.     

Variations circadiennes des acides aminés libres de l'hemolymphe de Penaeus japonicus

The non-essential free amino acids of Peneaus japonicus hemolymph (asp, ser, glu, pro, gly, tyr, arg, ala, cys, tau) are more common than the essential ones: 750 pmol μl^?1 of hemolymph vs 330 pmol. Under a light-dark (L-D); 12-12 photoperiod, tricircadian variations of males or tetracircadian variations of females are more pronounced for non-essential amino acids then for essential ones. In the first case, free amino acid concentrations of hemolymph can be multiplied by a factor of three, and in the second case by a factor of six; but circadian variations of females are greater than those of males. Differences between the maximum and minimum of essential free amino acid concentrations of male and female hemolymph are more frequent than for non-essential amino acids. A differences of 2 h between the minimum of essential and non-essential amino acid concentrations in males only appeared during the afternoon. The more concentrated free amino acids in P. japnicus hemolymph are glycine, proline, histidine, and alanine; the less concentrated are lysine, cysteine and glutamic acid while others, like leucine, isoleucine, phenylalanine and tyrosine can only be estimated at 10.00 and 24.00 h.     

Influence d'un choc osmotique sur la composition des feuilles de cotonnier en acides amines libres

The effect of water stress on the free amino acids in cotton leaves has been investigated. The water deficit, obtained by lowering of osmotic potential through the use of polyethylene glycol (PEG-600) as the osmotic agent, induces an accumulation of free amino acids.Significant modifications in the composition of this fraction are observed. The major differences from treated and untreated leaves are in the levels of γ-aminobutyric acid, asparagine, proline, and glutamic acid and its amide.     

Variations circadiennes des acides aminés libres du muscle de Penaeus kerathurus

Free amino acids of the abdominal muscle of Penaeus kerathurus show circadian variations which are proportionally more important in the case of essential amino acids (valine, leucine, isoleucine, threonine, lysine, histidine, phenylalanine, methionine) than in the case of non-essential amino acids. Total concentration of essential amino acids shows two diurnal peaks, at times which are dependent on environmental factors. In winter conditions, these peaks occur earlier (06 and 18 h) than in summer conditions (09 and 21 h). These 12-12 rhythms may be related to the circadian variations of digestive enzyme activities.     

Alcoxyhalogenation d'acides gras ethyleniques. IV: Cas des octadécadienoates de méthyle 9c, 12c et 9t, 11t et de composés apparentés

Methoxybromination, with HBBT, of long chain methylene interrupted dienes led to simultaneous formation of methoxybromides and dimethoxydibromides. Formation of dimethoxydibromides in which methoxy groups are both internal is limited by steric hindrance.Methoxybromination of long chain conjugated dienes forms, in nearly equal quantities, methoxybromides resulting from a 1,4 addition and methoxybromides from 1,2 addition in which the methoxy group is adjacent to the double bond.     

Structure des acides isomuronique et neuropogolique,nouveaux acides aliphatiques du lichen Neuropogon trachycarpus

The structures of two new aliphatic acids, isomuronic and neuropogolic acid, from the lichen Neuropogon trachycarpus, were established by spectroscopic (MS, ¹H and ¹³C NMR) and chemical evidence. Circular dichroism data allowed the configuration of isomuronic acid to be assigned as 2R.     

Triterpenoïdes nouveaux de Napoleonaea imperialis

Besides protoaescigenin, the seed saponin of Napoleonaea imperialis yields on hydrolysis a new sapogenol. Its structure has been deduced from spectral data. Controlled hydrolysis of this saponin yielded a new prosapogenin, the structure of which has been established. The names napoleogenol and napoleogenin are respectively proposed for the sapogenol and prosapogenin.     

Etude du métabolisme des acides nucléiques et des protéines au cours de l'initiation de racines adventives

Summary Changes in the metabolism of nucleic acids and proteins were followed during the initiation of adventitious roots of Cicer arietinum. During the first 24 h, several phases of activation of the metabolism were found. The use of inhibitors of RNA synthesis showed that an early phase of incorporation of precursors into RNA is essential for the initiation phenomena. This phase is more sensitive to inhibitors and activators (hormones) than all other phases. The rapid turn-over of RNA synthesized during the first 6 h and the inefficience of inhibitors after this time suggested that a stable (non-RNA) factor maintains the activation. This factor must be synthesized soon after the stimulus of cutting.     

Composition en lipides et acides gras de deux esèces de Taphrina parasites de Prunus domestica

Four strains of both Taphrina pruni and T. institiae were cultivated under identical conditions and and lipids and fatty acids were quantitatively analysed at two stages of their development. Tri- and diglycerides are the major neutral lipids in both species. Phosphatidylcholine and phosphatidylethanolamine are the most abundant polar lipids. Qualitatively, the two species show identical fatty acid contents, except for margaric acid (17:0) which was only found in Taphrine pruni. Quantitatively there are several differences: palmitoleic acid (16:1) occurs in reasonable amounts regularly and only in Taphrina pruni. The ratios 16:0/18:0 and 18:1/18:2 are generally higher for T. insititiae whereas the degree of unsaturation of fatty acids is higher in the former. The results are discussed with regard to data on other fungal species.     

Differentiation des hydroxy-5 dimethoxy-6,7 ou 7,8 et des triméthoxy-5,6,7 ou 5,7,8 flavones par spectrometrie de masse

The relative abundance of M and M-15 peaks in the mass spectrum allows the differentiation of 5-hydroxy-6,7-dimethoxy- and 5,7,8-trimethoxyflavones (M > M-15) from 5-hydroxy-7,8-dimethoxy and 5,6,7-trimethoxy-flavones (M < M-15) respectively, thus affording a solution to the 5,6,7- or 5,7,8-orientation problem on microscale.     

Differentiation des dihydroxy-5, 7 methoxy-6 ou 8 flavones flavonols et methyl-3 flavonols par spectrometrie de masse

5,7-Dihydroxy flavones and flavonols variously methoxylated in the 3-, 6- and/or 8-positions give characteristic fragmentation peaks. The relative abundance of M, M-1 and M-15 peaks and the presence of M-18 peak makes it possible to differentiate the 6-methoxy from the 8-methoxy isomers and three types of 6-methoxyflavones from each other.     

Les polysaccharides des graines de quelques liliacees et iridacees

The alkali-soluble polysaccharides have been surveyed in the seeds of 7 species of the Liliaceae and 2 species of the Iridaceae. All appear to contain galactoglucomannans and/or glucomannans. The structure of the water-soluble galactoglucomannan from the endosperm of Asparagus officinalis has been studied in detail. It contains residues of glucose, mannose and galactose in the ratio 43:49:7. Hydrolysis of the fully methylated polysaccharide released 2,3,4,6-tetra-O-methyl-d-hexoses (mannose and glucose), 2,3,4,6-tetra-O-methyl-d-galactose, 2,3,6-tri-O-methyl-d-mannose, 2,3,6-tri-O-methyl-d-glucose, 2,3-di-O-methyl-d-mannose and 2,3-di-O-methyl-d-glucose in the molar proportions of 1:4.5:50:41:2:1·5. The following oligosaccharides were identified on partial hydrolysis of the galactoglucomannan: mannobiose, mannotriose, mannotetraose, cellobiose, glucopyranosylmannose, mannopyranosylglucose and a trisaccharide composed of two mannosyl residues and one glucosyl residue. The galactoglucomannan consists of a linear chain of β(1 → 4)-Iinked d-mannosyl and d-glucosyl residues, to which are attached single-unit galactosyl side chains. The galactose residues are linked 1 → 6, probably α. The terminal, non-reducing residues of the main chain may be either glucosyl or mannosyl units but the former predominate.