Galactolipids and phospholipids of orange peel and juice chromoplasts

Chromoplasts from yellow orange (Citrus sinensis) fruit peel contain monogalactosyl diglycerides (MGDG), digalactosyl diglycerides (DGDG) and phosphatidyl glycerol (PG) in amounts similar to those found in chloroplasts from green fruit peel. Juice chromoplasts contain relatively little MGDG and no DGDG with high levels of phosphatidyl choline and phosphatidyl ethanolamine but no PG.     

Lipid composition of the fat body and haemolymph and its relation to lipid release in Oncopeltus fasciatus

Lipid composition of the fat body and haemolymph of male milkweed bug, Oncopeltus fasciatus, was determined. Triglycerides were the predominant lipids of the fat body while diglycerides accounted for the major lipid in the haemolymph. Sterols, sterol esters, and non-esterified fatty acids were present in both fat body and haemolymph besides triglycerides and diglycerides. Only traces of monoglycerides were detected.Gas chromatographic analysis of the fatty acids revealed a difference in the fatty acid composition between fat body and haemolymph glycerides and sterol esters. Oleate and linoleate were the predominant unsaturated fatty acids in both fat body and haemolymph lipids and in the milkweed seeds as well.When fat body was labelled in vivo and in vitro with ¹⁴C-palmitate, the fatty acid was incorporated largely into the triglycerides. When the prelabelled fat body was incubated with a medium containing haemolymph the fat body released lipids mainly as diglycerides. Some radioactivity was observed in the triglycerides and non-esterified fatty acids also.Electrophoretic analysis of the incubation medium containing the haemolymph revealed that the released lipids were bound to three haemolymph lipoprotein bands. Lipid mobilization, release, and transport in Oncopeltus are discussed in relation to studies on other insects.     

Incorporation of palmitic acid-1-14C into lipids of pharate adult tissues of Bombyx mori

Incorporation of palmitic acid-1-¹⁴C into pharate adult tissues and their lipid components of Bombyx mori was investigated. Rapid incorporation of radioactivity took place predominantly in fat body and haemolymph lipids, and partially in ovarian lipids immediately after the injection at the middle stage of pharate adult development. The major parts of the radioactivities in fat body, haemolymph and ovary were distributed in triglycerides and phospholipids, diglycerides, and triglycerides, respectively. The patterns of time course of incorporation of radioactivity into lipid components of pharate adult tissues suggest that the major form of lipid released from fat body may be diglycerides and the diglycerides in haemolymph are probably the main source of ovarian triglycerides.     

Hypolipidemic constituents from the aerial portion of Sibiraea angustata

Two new monoterpene acylglucosides (1–2) and one new aromatic glycoside (3), together with five known compounds (4–8), were isolated from 95% ethanol extract of Sibiraea angustata. The structures of these compounds were characterized by 2D-NMR and mass spectrometry. Compounds were evaluated for their hypolipidemic activity using oleic acid-induced lipid accumulation in HepG2 cells. RT-PCR analysis revealed that compound 5 could decrease the expression level of fatty acid synthase (FASN). Lipidomics analysis indicated that compound 5 significantly decreased the levels of 11 lipids in oleic acid-induced lipid accumulation, including triglycerides (TG), diglycerides (DG), phosphatidylcholines (PC) and 1-acyl-sn-glycero-3-phosphocholines (lysoPC). These data demonstrated that terpene acylglucosides are the major active constituents in Sibiraea angustata.     

Synthesis of erythro-5,6-diacetoxyhexadecanoic acid,a novel fatty acid from mosquito eggs

The synthesis of erythro-5,6-diacetoxyhexadecanoic acid, a major component of diglycerides isolated from the eggs of Culex tarsalis and related species and reported to influence oviposition of these mosquitoes, is described.     

Chlorinated phenolic sesquiterpenoids from the Arctic fungus Nectria sp. B-13

Seven chlorinated phenolic sesquiterpenoids, together with one prenylated 2-pyridyl ketone alkaloid (9) and two monophenols (10 and 11), were isolated from the fungus Nectria sp. B-13 obtained from an Arctic soil sample. Their chemical structures were elucidated using a combination of spectroscopic data (ESI-MS, ¹H, and ¹³C NMR) and comparisons with the published data. This is the first report on the isolation of compounds from pole-derived Nectria sp. B-13. The chemotaxonomic significance of these compounds is discussed.     

Isolation and structures of diomuscinone and diomuscipulone from Dionaea muscipula

From the fresh leaves and roots of Dionaea muscipula, two new substances (diomuscinone and diomuscipulone) have been isolated together with the known naphthoquinone plumbagin. The structures of the new compounds have been elucidated on the basis of their spectral data coupled with some chemical evidence.     

Manipulation of galactolipid Fatty Acid composition with substituted pyridazinones

The fatty acid composition of the major lipids of the chloroplast membranes, the mono- and digalactosyl diglycerides, can be definably altered with various substituted pyridazinones. Galactolipid fatty acid composition of wheat (Triticum aestivum L.) can be altered so that there is a decrease in linolenic acid accompanied by an increase in linoleic acid without a shift in the relative proportion of saturated to unsaturated fatty acids; the fatty acid composition can be shifted toward a higher proportion of saturated fatty acids; or the fatty acid composition of the monogalactosyl diglycerides can be altered in preference to the digalactosyl diglycerides. Also, the light-mediated parallel accumulation of chlorophyll and linolenic acid can be separated with a substituted pyridazinone. The substituted pyridazinones may be useful tools in clarifying the role the galactolipids and their component fatty acids play in the structure and function of chloroplast membranes in higher plants.     

Biosynthesis of lipids in chloroplasts isolated from jack pine needles

Suspensions of isolated pine needle chloroplasts were shown to incorporate galactose from UDP galactose-[¹⁴C] into galactolipids. The incorporation of the label among galactolipids was always considerably higher in the monogalactosyl diglycerides than in the digalactosyl diglycerides. The galactosyl incorporation into both galactolipid fractions was optimal at pH 8.0 and was inhibited by sulphydryl reagents (p-chloromercuribenzoate, N-ethyl maleimide and CdCl₂). The chloroplast preparations were also able to biosynthesize various phospholipids and galactolipids from palmitoyl-[1-¹⁴C]-CoA; the major portion of the label appeared in phosphatidyl choline. The incorporation of palmitic-[1-¹⁴C] acid into various lipids was very poor compared to that of palmitoyl-[1-¹⁴C]-CoA. However, addition of ATP and CoA markedly stimulated lipid biosynthesis from palmitic-[1-¹⁴C] acid, suggesting the presence of activating enzymes. These chloroplast suspensions did not show any de novo fatty acid synthesis.     

Biochemical aspects of the visual process. XXXVII. Evidence for lateral aggregation of rhodopsin molecules in phospholipase C-treated bovine photoreceptor membranes

Photoreceptor membranes derived from isolated bovine rod outer segments, are subjected to treatment with phospholipase C (Bacillus cereus). This results in varying degrees of hydrolysis of the membrane phospholipids into diglycerides and water soluble phosphate esters without loss of rhodopsin. Electron microscopic observations of thin sections and freeze-fractured preparations indicate extrusion of diglycerides from the membranes and their coalescence to lipid droplets, beginning at 20% hydrolysis of phospholipids. After 90% hydrolysis of phospholipids membranous structures are still present. The rhodopsin is located in these structures, presumably in the form of two-dimensional lateral aggregates. This explains the cross-fracturing of the membranous structures, regularly observed upon freeze-fracturing of the phospholipase-treated photoreceptor membranes.     

Lipids of Fontinalis antipyretica

Fatty acid compositions of the lipids of Fontinalis antipyretica shows the presence of octadeca-9, 12-dien-6-ynoic, octadeca-9,12,15-trien- 6-ynoic and eicosa-11,14-dien-8-ynoic acids as the major components of the triglycerides. These acetylenic acids were not present in the galactosyl diglycerides. The moss lipids also contained relatively large amounts of two novel acetylenic methyl ketones with an unsaturation pattern analogous to that of the C₁₈ acetylenic acids.     

Isoflavonoid phytoalexins of the genus Medicago

Detached leaves of 25 annual and perennial Medicago species have been inoculated with the fungus, Helminthosporium carbonum, and examined for subsequent production of isoflavonoid phytoalexins. Hydroxylated pterocarpan (medicarpin) and isoflavan (vestitol, sativan and isosativan) phytoalexins were obtained from most of the species investigated. Although large quantities of two flavonoid derivatives, isoliquiritigenin and liquiritigenin, were isolated from leaves of M. lupulina, this species was apparently unable to produce isoflavonoid compounds. Traces of 7-hydroxy-2′,4′-dimethoxyisoflavanone (a substance not previously recorded in the tribe Trifolieae) were obtained (together with medicarpin, vestitol and sativan) from M. sativa cv Du Puits. Some taxonomic aspects of phytoalexin induction are discussed with reference to the generic location of certain controversial Medicago species including M. (Trigonella) radiata.     

Almond (Prunus dulcis (Mill.) D.A. Webb) polyphenols: From chemical characterization to targeted analysis of phenolic metabolites in humans

In this paper, a survey of our studies on almond polyphenols including their chemical characterization and further bioavailability in humans is reported. Combination of analytical techniques (LC-DAD/fluorescence, LC/ESI-MS and MALDI-TOF-MS) allowed us, for the first time, the identification of A- and B-type procyanidin, propelargonidin and prodelphinidin polymers in almond skins. Glucuronide, O-methyl glucuronide, sulfate and O-methyl sulfate derivatives of (epi)catechin, as well as the glucuronide conjugates of naringenin and isorhamnetin, and sulfate conjugates of isorhamnetin, together with conjugates of hydroxyphenylvalerolactones were detected in plasma and urine samples after the intake of almond skin polyphenols. In addition, numerous microbial-derived metabolites, including hydroxyphenylpropionic, hydroxyphenylacetic, hydroxycinnamic, hydroxybenzoic and hydroxyhippuric acids were also identified. Depending of the type of metabolite, maximum urinary excretion was attained at different time in comparison to the control group in the course of the 24-h period of urine excretion, allowing us to establish the onset of microbial metabolism.     

Galactolipid Synthesis in Vicia faba Leaves: I. Galactose, Glycerol, and Fatty Acid Labeling after CO(2) Feeding

The galactose, glycerol, and fatty acids of mono- and digalactosyl diglycerides (MGDG and DGDG) have been separated and analyzed for ¹⁴C activity after ¹⁴CO₂ feeding of Vicia faba leaf discs. Fully expanded and developing leaves were analyzed at time intervals following feeding during continuous illumination. In addition, fully expanded leaves were analyzed after similar times in complete darkness. In all cases, ¹⁴C was incorporated very rapidly into galactose, whereas glycerol and fatty acids were labeled much more slowly and over a longer period of time. The data are consistent with the galactosylation of a diglyceride to MGDG which is in turn galactosylated to DGDG. The data suggest that the formation of diglycerides suitable for galactosylation to MGDG is slow in comparison to the galactosylation process. It is also suggested that DGDG may be formed from more than one pool of MGDG. The complete analysis of the ¹⁴C incorporation into galactose appears to represent the only satisfactory method of comparing galactolipid synthesis by ¹⁴C incorporation. Estimates of comparative rates of synthesis of MGDG and DGDG have been made on this basis.     

Kinetic study of possible intermediates in the biosynthesis of chlorogenic acid in Cestrum poeppigii

p-Coumaric and 3-O-p-coumarylquinic acid seem to be important precursors of chlorogenic acid in the leaves of Cestrum poeppigii. 3-O-Cinnamylquinic acid, which has a very small metabolic activity, is of little importance in this respect. The kinetics of incorporation of radioactivity from t-cinnamic acid-3-[¹⁴C] into p-coumaric, 3-O-p-coumarylquinic, chlorogenic and 3-O-cinnamylquinic acid showed that the biosynthetic rates for these products decrease in the order shown. For p-coumaric acid, which has a markedly high metabolic activity, a turnover rate of 28 μg/hr and per gram fresh plant leaf, was calculated. Some trapping experiments with caffeic acid, and the acids mentioned above and using either t-cinnamic acid-3-[¹⁴C] or p-coumaric acid-2-[¹⁴C] as precursor, are discussed. A HPLC method for the rapid determination of phenolic acids in plant extracts, is described.     

Lipid Composition of Some Species of Arthrobacter

The lipids from Arthrobacter crystallopoietes, A. pascens, and A. globiformis were investigated. Each strain contained three glycolipids, a monogalactosyl diglyceride, a digalactosyl diglyceride, and a dimannosyl diglyceride, and traces of triand tetraglycosyl diglycerides. The phospholipids in all three strains consisted of bisphosphatidylglycerol, phosphatidylglycerol, and phosphatidylmyoinositol. No evidence could be obtained for the occurrence of mannophosphoinositides. Analysis of the fatty acids by gas-liquid chromatography showed that they are predominantly C_15:0anteiso and C_17:0anteiso compounds. No significant differences were observed in the composition of lipids extracted from homogeneous cell preparations of the rod and sphere forms of A. crystallopoietes.     

Gas-liquid chromatography of plant galactolipids and their deacylation and methanolysis products.

The gas-liquid chromatography of monogalactosyl diglyceride (MGDG) and digalactosyl diglyceride (DGDG) and their deacylation and methanolysis products is reported. MGDG and DGDG and their galactosyl monoglycerides were chromatographed as their trimethylsilyl derivatives. Galactosyl monoglycerides were produced by partial deacylation of the diglycerides with Grignard's reagent and pancreatic lipase. The products of complete deacylation, mono- and digalactosyl glycerols, were separated as O-methyl, O-acetyl, O-trimethylsilyl and O-trifluoroacetyl derivatives. Gas-liquid chromatography of derivatives of the methanolysis products of MGDG and DGDG and the methylated galactosyl glycerols allowed the separation and quantitative recovery of the galactose and glycerol of both lipids and the two galactoses of DGDG.     

Continuous interesterification of oils and fats using dried fungus immobilized in biomass support particles

The industrial feasibility of an interesterification process using acetone-dried fungus (as a lipase catalyst) immobilized in biomass support particles (BSPs) was examined by continuous interesterification between olive oil and methyl stearate, where the water content of the reaction mixture (C_w) was controlled at a given value. The C_w affected not only the inactivation rate of lipase in the cells but also the production rate of the by-product (diglycerides). The optimal C_w was determined as about 100 ppm. The half-life of lipase in the cells was about 1200 h at the optimal C_w, suggesting that the interesterification process using the immobilized fungus is industrially feasible.     

The phenolics and a hydrolysable tannin polyphenol oxidase of Medinilla magnifica

The production of viable meristem cultures of Medinilla magnifica has proved to be very difficult. This may be due, in part, to a pronounced ‘browning’ response of the tissues on cutting. For this reason the phenolic compounds and the hydrolysable-tannin polyphenol oxidase from Medinilla were studied. The distribution of the compounds was: simple phenols 19% , flavonoids 5% , hydrolysable tannins 69% , condensed tannins 7%. Amongst the simple phenols and phenolic acids, the following were identified: phloroglucinol, p-hydroxybenzoic acid, vanillic acid, protocatechuic acid, gallic acid (both in free and bound form the most abundant simple phenol), syringic acid, trans-p-coumaric acid, trans-ferulic acid and trans-caffeic acid. No kaempferol or quercetin or their derivatives were detected but condensed tannins are present. Methods for the extraction, fractionation and quantitative determination of phloroglucinol and the phenolic acids, as well as correction factors for losses during the extraction, alkali treatment and derivatization, are presented in a supplementary publication. With regard to the hydrolysable tannin polyphenol oxidase activity of Medinilla stems, the enzyme(s) is rather specific since at neither of its two pH optima (6 and 7) could a classical polyphenol oxidase activity be detected. The enzyme was strongly inhibited by 2-mercaptoethanol. Preliminary experiments have further shown that in addition to the hydrolysable tannins of the tissue, the ferrous ions of the medium, and oxygen together with the hydrolysable tannin polyphenol oxidase could play a role in the browning response. Ways to overcome this difficulty have been suggested.     

Glucolipids of Zea mays and Pisum sativum

The glucolipids formed upon feeding (U-¹⁴C)glucose to embryos of Zea mays were partially characterized with respect to: (a) metabolic turnover, (b) acid lability, (c) phosphorus content, (d) chromatographic properties, and (e) hydrolysis products. The chloroform-methanol-soluble assimilated radioactivity was examined specifically for occurrence of a glycosylated prenol phosphate. With the extraction conditions used, no evidence was found for formation of a glucosylated prenol phosphate. Several, as yet unidentified, acid-labile glucolipids undergoing metabolic turnover were observed. Four diglycerides were characterized as hydrolysis products of a fraction that contained ¹⁴C-glucose and phosphorus, and was subject to metabolic turnover. Examination of the 1-butanol-soluble glucolipids from pea (Pisum sativum) seedlings also demonstrated anionic glucolipids, evidencing metabolic turnover but none with the properties of glucosylated prenol phosphate.