Acylglycerols Containing Trihydroxy Fatty Acids in Castor Oil and the Regiospecific Quantification of Triacylglycerols

Ricinoleate, a monohydroxy fatty acid in castor oil, has many industrial uses. Dihydroxy and trihydroxy fatty acids can also be used in industry. We report here the identification of diacylglycerols (DAG) and triacylglycerols (TAG) containing trihydroxy fatty acids in castor oil. The C₁₈ HPLC fractions of castor oil were used for mass spectrometry of the lithium adducts of acylglycerols to identify trihydroxy fatty acids and the acylglycerols containing trihydroxy fatty acids. Two DAG identified were triOH18:1–diOH18:1 and triOH18:0–OH18:1. Four TAG identified were triOH18:1–OH18:1–OH18:1, triOH18:0–OH18:1–OH18:1, triOH18:1–OH18:1–diOH18:1 and triOH18:0–OH18:1–diOH18:1. The structures of these two newly identified trihydroxy fatty acids were proposed as 11,12,13-trihydroxy-9-octadecenoic acid and 11,12,13-trihydroxyoctadecanoic acid. The locations of these trihydroxy fatty acids on the glycerol backbone were almost 100% at the sn-1,3 positions or at trace levels at the sn-2 position. The content of these acylglycerols containing trihydroxy fatty acids was at the level of about 1% or less in castor oil.     

Ratios of Regioisomers of Triacylglycerols Containing Dihydroxy Fatty Acids in Castor Oil by Mass Spectrometry

The triacylglycerols (TAG) containing dihydroxy fatty acids have been recently identified by mass spectrometry in castor oil. These new dihydroxy fatty acids were proposed as 11,12-dihydroxy-9-octadecenoic acid (diOH18:1), 11,12-dihydroxy-9,13-octadecadienoic acid (diOH18:2) and 11,12-dihydroxyoctadecanoic acid (diOH18:0). The ratios of regioisomers of the TAG were estimated by fragment ions from the loss of fatty acids at the sn-2 position as α,β-unsaturated fatty acids by electro spray ionization-mass spectrometry of the lithium adducts (MS³). The content of regioisomeric diOH18:1-OH18:1-diOH18:1 (ABA, with two different fatty acids) was about 92% in the total of stereoisomeric diOH18:1-OH18:1-diOH18:1, OH18:1-diOH18:1-diOH18:1 and diOH18:1-diOH18:1-OH18:1 combined. The approximate contents of other regioisomers were as follows: diOH18:1-OH18:1-OH18:1 (92%), diOH18:1-diOH18:0-diOH18:1 (91%), diOH18:2-OH18:1-OH18:1 (80%) and diOH18:0-OH18:1-OH18:1 (96%). The ratios of regioisomers of TAG (ABC) containing three different fatty acids were estimated as about 7:1:2 (OH18:1:diOH18:1:diOH18:2) and about 7:2:1 (OH18:1:diOH18:0:diOH18:1). Ricinoleate (OH18:1) was predominately at the sn-2 position of TAG (both AAB and ABC) containing dihydroxy fatty acids and ricinoleate. Dihydroxy fatty acids were mainly at the sn-1,3 positions of TAG containing dihydroxy fatty acids and ricinoleate in castor oil. The ratios of the three regioisomers of TAG (ABC) containing three different fatty acids by mass spectrometry are first reported here.     

Clickable Lipids: Azido and Alkynyl Fatty Acids and Triacylglycerols

Hydroxy fatty acids (FAs), which were isolated from glycolipids that can be prepared fermentatively from fats and oils, have been synthetically modified to contain azide and alkyne functional groups. These particular functional groups were chosen because they can participate in a copper-catalyzed reaction that combines them to form a 1,4-triazole, known as a “click” reaction, which has been widely used in a variety of fields but remains underutilized in FA chemistry. Depending on the starting hydroxy FA, these groups can be close to the carboxy unit (using 3-hydroxydecanoate) and hence the polar glycerol group, or distant from it (using 17-hydroxyoctadecanoate). These structural alternatives will impart different properties to the triacylglycerols that are subsequently prepared from the modified FA. Finally, the click reaction was used to conjugate triacylglycerols to each other and to other molecules such as a glycolipid or a protected amine.     

Distribution of Isomeric Octadecenoic Fatty Acids in Commercially Hydrogenated Olive Oil

Samples of cooking fats and margarines prepared from hardened olive oil were analyzed for positional isomers of the cis and trans monoene fraction. The fats were transesterified and the methyl esters were separated by silver nitrate thin layer chromatography. The monoene fraction was recovered from the plates and the positional isomers were determined by epoxidation, cleavage of methyl epoxy-octadecanoates and gas chromatographic analysis of the aldehyde esters. Hydrogenated olive oil products contain 70–75% monoenes. 25–27% of the fatty acids are in the form of trans 18:1 isomers. The position of the double bond appears to be distributed from Δ7 to Δ13. This distribution over the carbon chain is 2–4 times higher in the trans fraction of the monoenes.     

鱼油不饱和脂肪酸的自由基氧化规律

从东海小杂鱼鱼油中鉴定出43种脂肪酸,主要16种脂肪酸占总脂肪酸95．01％。测定了鱼油加入自由基后在不同的时间及不同光照条件下的脂肪酸的氧化规律,并进行分析发现无论在光照还是避光条件下所有不饱和脂肪酸都随着时间的推移,含量都有下降的趋势,说明不断的被氧化,特别是EPA、DHA被氧化的更快。在光照条件下鱼油中的脂肪酸氧化比在避光条件下要快。在实验过程中,通过在鱼油加入自由基后再加入不同的抗氧化剂,利用TBA值的测定,筛选出对鱼油中的脂肪酸氧化有较好的抗氧化性的各种抗氧化剂的有效浓度。同时可以发现4-己雷琐辛的抗氧化性最强,由于此实验中用的TBHQ是食品级的,因此BHA的抗氧化性比TBHQ强。并且对鱼油在添加抗氧化剂前后脂肪酸的自由基氧化规律进行比较。     

Quantification of Fatty Acids and their Regioisomeric Distribution in Triacylglycerols from Porcine and Bovine Sources Using 13C NMR Spectroscopy

The uptake of specific fatty acids in humans is dependent on their position on the glycerol backbone. There is a great interest in methods that can access this information fast and accurately. By way of high-resolution NMR, we have analyzed TAG extracted from pig and beef tissues and obtained quantitative data for the composition and regioisomeric distribution of all major unsaturated fatty acids usually found in these source materials, using a combination of manual integration and deconvolution of ¹³C NMR spectra. In addition, we have developed a method for determining composition and regioisomeric distribution of the two main saturated fatty acids found in pork (16:0, 18:0). The results are discussed in relation to species-specific genetic characteristics of fatty acid and TAG biosynthesis. The developed method could support decisions related to breeding for desired fatty acid profiles, and stimulate further methodology developments using high field NMR.     

TiO2光催化氧化亚甲基蓝的动力学研究

探讨了二氧化钛（TiO2）光催化氧化亚甲基蓝水溶液的动力学规律。结果表明,该反应符合Langmuir-Hin-shelwood（L-H）动力学模型,且光催化氧化过程为一级反应,反应速率常数（k）与亚甲基蓝初始浓度（c0）的关系是k∝c0^-1.1805。反应前后的紫外可见图谱和红外图谱表明,·OH破坏了亚甲基蓝的结构。     

Synthesis and Physical Properties of Symmetrical and Non-symmetrical Triacylglycerols Containing Two Palmitic Fatty Acids

A series of symmetrical (ABA) and non-symmetrical (AAB) triacylglycerol (TAG) isomers containing “A,” palmitic (P; 16:0) acid, and “B,” either oleic (O; 9c-18:1), elaidic (E; 9t-18:1), linoleic (L; 9c,12c-18:2) or linolenic (Ln; 9c,12c,15c-18:3) fatty acids were synthesized by esterification of the thermodynamically more-stable 1,3-di- or 1(3)-monoacylglycerols [1,3-DAG or 1(3)-MAG], respectively. 1,3-dipalmitoylglycerol (1,3P-DAG) was esterified with O, L or Ln acid to prepare the symmetrical TAG isomers POP, PLP and PLnP, while the O- E-, L- and Ln-1(3)MAG precursors, synthesized or obtained commercially, were esterified with P acid to prepare the non-symmetrical TAG isomers OPP, EPP, LPP and LnPP, respectively. The drop point(s), solid fat content and melting point values of the synthesized TAG were determined. The 1,3-dipalmitoylglycerol (1,3P-DAG) and 1(3)P-MAG precursors were prepared, in multi-gram quantities, by partial glycerolysis (glycerol/p-toluenesulfonic acid) of tripalmitin. After fractionation by silica gel chromatography, the 1(3)P-MAG and 1,3P-DAG isomers (ca. 80% of total MAG or DAG) were purified (>98%) by crystallization from acetone [silver ion-HPLC was utilized to determine the structural purities of the DAG (or MAG) precursors, and the synthesized TAG]. Esterification of the appropriate, thermodynamically more-stable MAG or DAG precursors was found to be a very versatile method for synthesis (in 80–90% yields) of multi-gram (3–5 g) quantities of symmetrical and non-symmetrical TAG isomers, in chemical and structural purities of >96 and 97–99%, respectively. The 1- and 3- positions on the glycerol backbone of the MAG, DAG and TAG molecules are assumed to be equivalent. Mention of trade names or commercial products in this (publication) is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the US Department of Agriculture.     

Concentration of Stearidonic Acid in Free Fatty Acids Form from Modified Soybean Oil by Selective Esterification with Dodecanol

The concentration of stearidonic acid (SDA, 18:4 n-3) in free fatty acids (FFA) formed by selective esterification with dodecanol (lauryl alcohol) was studied. For this purpose, modified soybean oil (initial SDA content, ~23 %) was converted into its corresponding FFA by chemical hydrolysis. In a second step, the resulting FFA were esterified with dodecanol. Process variables such as the type of biocatalyst (lipase), substrate molar ratio and amount of lipase were evaluated. The best SDA concentration (58 %) and recovery (94 %) were attained by performing the esterification reaction for 4 h, with 1:1 molar ratio (dodecanol:FFA), and 5 % (w/w) Candida rugosa lipase as biocatalyst. It was observed that SDA was concentrated in the unesterified fraction.     

Analysis of Triacylglycerols and Free Fatty Acids in Algae Using Ultra-Performance Liquid Chromatography Mass Spectrometry

To assess the suitability of microalgal strains for biodiesel production the lipid content and composition, especially individual triacylglycerols (TAG) and free fatty acids (FFA) must be determined. In this study, the compositions and concentrations of TAG and FFA were analysed in four halophytic algal species, Dunaliella salina, D. tertiolecta, D. bardawil, and D. granulata. These species were selected as part of a larger screen to identify species suitable for biofuel feedstocks. An accelerated solvent extraction instrument was used for lipids and fatty acid extraction using a dichloromethane–hexane solvent system. Ultra-performance liquid chromatography coupled with mass spectrometry (MS) detection was optimized and applied to the quantitative analysis of TAG and FFA in the different algal extracts. Individual TAG were characterized structurally using direct electrospray ionization (ESI) MS and MS/MS techniques. Cationic adducts (NH₄ ⁺) of TAG were detected and quantified in the positive ESI MS and MS/MS modes, while the negative ESI mode was used for FFA analysis. Over 20 TAG were identified and quantified in the four Dunaliella strains. Analysis of FFA compositions demonstrated that the most abundant FFA in these four algal species were palmitic, linolenic, linoleic, and oleic acids.     

Impact of Free Fatty Acids and Phospholipids on Reverse Micelles Formation and Lipid Oxidation in Bulk Oil

Association colloids such as phospholipid reverse micelles could increase the rate of lipid oxidation in bulk oils. In addition to phospholipids, other surface active minor components in commercial oils such as free fatty acids may impact lipid oxidation rates and the physical properties of reverse micelles. In this study, the effects of free fatty acids on changes in the critical micelle concentration (CMC) of 1,2-Dioleoyl-sn-glycero-3-phosphocholine (DOPC) in stripped corn oil (SCO) were determined by using the 7,7,8,8-tetracyanoquinodimethane solubilization technique. Different free fatty acids including myristoleic, oleic, elaidic, linoleic and eicosenoic were added at 0.5 % by wt along with the DOPC into the bulk oils. There was no significant effect of free fatty acids with different chain length, configuration and number of double bonds on the CMC value for DOPC in bulk oil. However, increasing concentrations of oleic acid (0.5 to 5 % by wt) caused the CMC value for DOPC in bulk oils to increase from 400 to 1,000 μmol/kg oil. Physical properties of DOPC reverse micelles in the presence of free fatty acids in bulk oils were also investigated by the small angle X-ray scattering technique. Results showed that free fatty acids could impact on the reverse micelle structure of DOPC in bulk oils. Moreover, free fatty acid decreased pH inside reverse micelle as confirmed by the NMR studies. The oxidation studies done by monitoring the lipid hydroperoxide and hexanal formation revealed that free fatty acids exhibited pro-oxidative activity in the presence and absence of DOPC. Different types of free fatty acids had similar pro-oxidative activity in bulk oil.     

Simultaneous Determination of Free Fatty Acids and Esterified Fatty Acids in Rice Oil by Gas Chromatography

Free fatty acids (FFA) in crude rice oil were selectively and stoichiometrically derivatized to fatty acid N,N-dimethylamides (FADMA) by catalytic condensation at 45 °C, and then esterified fatty acids (eFA) were directly converted to fatty acid methyl esters (FAME) at 37 °C. The mixture of FADMA and FAME formed in a single test tube was injected into the capillary column of a gas chromatograph (GC). No mutual contamination occurred between FFA and eFA, and reliability of the method was confirmed by comparison between GC data obtained by this method and by a conventional isolation method. The advantages of the present method are that no FFA isolation procedures are required, the reactions proceed under mild temperature conditions, and FFA and eFA can be analyzed simultaneously by GC.     

Synthesis and Physical Properties of EOE and EEO,Triacylglycerols Containing Elaidic and Oleic Fatty Acids

Symmetrical and non-symmetrical triacylglycerols (TAG) containing oleic (O; 9c-18:1) and elaidic (E; 9t-18:1) acids were required as part of a study relating the physical characteristics and functionality of trans-containing TAG with the mouth feel, taste characteristics and related characteristics desired by consumers in frying oils and pastries. To replace the trans isomers in frying oils—a significant part of frying oils prepared by partial hydrogenation of vegetable oils—without loss of the sensory properties desired by consumers, required the initiation of a study relating the structure of trans-containing TAG with such characteristics as melting range, drop points, and other crystalline properties. Elaidic acid was esterified to trielaidin (EEE), and the EEE partially converted (glycerol/p-toluenesulfonic acid) to a mixture containing ca. 40% DAG (the 1,3- and 1,2-isomers). The DAG fraction was separated by silica gel chromatography, the 1,3-dielaidylglycerol (1,3EE-DAG) isomer isolated (structural purity >99%) by crystallization from acetone and esterified with oleic acid (O) to yield EOE. The 1(3)O-MAG was purchased commercially and esterified with E acid to prepare OEE. Both syntheses yielded multi-gram quantities of EOE and EEO, in 80–85% yields, and with structural purities >99%. Thus, by careful selection of the thermodynamically more-stable MAG or DAG precursors, the symmetrical EOE and non-symmetrical EEO isomers could be readily synthesized, and their drop point and melting point values determined. The 1- and 3- positions on the glycerol backbone of the MAG, DAG and TAG molecules are assumed to be equivalent.     

Aspects of Positional Distribution of Fatty Acids in Triacylglycerols of Skin,White and Dark Muscle of Mackerel Scomber scombrus in Relation to Hypertension

The triacylglycerols from skin, white and dark muscle of Atlantic mackerel Scomber scombrus were isolated and the distribution of fatty acids on the glycerol examined with pancreatic lipase. The dark muscle, which is the smallest dietary fat source of the three tissues, had less EPA and more DHA than the other two tissues. The EPA deficiency was located in the 2-position. The DHA was similar in both the 2-and 1,3-positions. The white muscle triacylglycerol showed a much higher proportion of DHA in the 2-position than in the 1,3-positions. The skin triacylglycerol was relatively undifferentiated in respect to distribution of EPA and DHA. Saturated acids were least in the 2-position of the white muscle triacylglycerol and highest in the 1,3-position of the same fat. Not unexpectedly, the monoethylenic fatty acids of exogenous origin were located in the 1,3-positions and the highest level was in the dark muscle triacylglycerol. The distribution of the whole of the EPA and DHA is not dissimiliar from that projected from literature of fish triacylglycerols. It is concluded that benefits attributed to supplement of dietary mackerel, relative to herring, in certain types of hypertension follow from the total ω-3 fatty acid intake and not from any special distribution on glycerol of mackerel fatty acids.     

Positional Distribution of Fatty Acids in Oilseed Lecithins

Positional distribution of fatty acids in the lecithins (phosphatidyl choline) of cottonseed, groundnut, mustard and sesame seeds was studied. GLC analysis of the methyl esters showed the total lecithins to contain 60–80% of unsaturated fatty acids. The fatty acids liberated by phospholipase A hydrolysis consisted mainly of unsaturated (oleic and linoleic) acids. Estimates of lecithin classes in terms of saturated and unsaturated fatty acids in the α- and β-position, viz. SS, SU, US and UU, were made in these lecithins. The amount of disaturated (SS) lecithin was negligible and the content of US species was very low. Mustard, sesame, groundnut and cottonseed lecithins contained 27, 47, 56 and 60% of SU species respectively. The diunsaturated (UU) lecithin content was high in mustard (69%) and medium in sesame (49%), groundnut (43%) and cottonseed (31%).     

Fe-5A催化亚甲基蓝溶液湿式H2O2氧化

以九水硝酸铁[Fe(NO3)3?9H2O]和柱状5A分子筛为原料采用湿法浸渍法制备Fe?5A催化剂,催化湿式H2O2氧化亚甲基蓝溶液,考察了间歇反应器中pH值和温度对亚甲基蓝转化率的影响及在连续固定床反应器中床层催化剂装填量、进料液流量、温度和亚甲基蓝入口浓度对亚甲基蓝降解性能的影响. 结果表明,在间歇反应中,在亚甲基蓝浓度50 mg/L、温度70℃、pH为2、反应20 min的条件下,亚甲基蓝的转化率为95.9%. 固定床反应中,随温度降低及进料液流量增加,亚甲基蓝转化率降低;随亚甲基蓝入口浓度增加,亚甲基蓝和化学需氧量(COD)的转化率变化幅度很小. 在温度70℃及pH=2、进料液流量4 mL/min、Fe?5A催化剂装填量1.25 g、亚甲基蓝浓度50?300 mg/L、固定床连续运转5 h的条件下,亚甲基蓝的转化率超过98%,COD转化率大于82%,铁浸出浓度低于3.5 mg/L,相同条件下,装填2.5 g 5A分子筛的固定床中50 mg/L亚甲基蓝的转化率仅为73.3%.     

Occurrence of Conjugated Linolenic Acids in Purified Soybean Oil

A high-performance liquid chromatographic (HPLC) method is described for the determination of conjugated linoleic acids (CLA) and conjugated linolenic acids (CLN). Methyl esters prepared from purified lipid fractions of soybean oil were analyzed using an HPLC system equipped with photodiode-array detector to detect peaks having maximum absorption around 233 and 275 nm. These peaks were concentrated by AgNO₃-silicic acid column chromatography and reversed-phase HPLC. The structural analysis, of dimethyloxazoline (DMOX) derivatized methyl esters, using gas chromatography–mass spectrometry (GC–MS) showed the occurrence of 9,11- and 10,12-CLA and 8,10,13-, 8,10,12-, and 9,11,13-CLN. The comparison of these conjugated fatty acids with authentic isomers by HPLC revealed the presence of isomeric mixtures of CLA [cis (c),trans(t) or t,c and t,t] and CLN (c,t,t or t,t,c and t,t,t). Traces of 9,11- and 10,12-CLA (c,t or t,c) were found in crude oil. CLN isomers (8,10,12-18:3 and 9,11,13-18:3) were found to be forming during the bleaching phase of soybean oil processing. 8,10,13-CLN and 9,11- and 10,12-CLA (t,t) were only found in soybean oil after the deodorization step. CLN contents in commercial soybean oil varied from 387 to 1,316 mg/kg oil. A decreased level of bleaching earth and temperature resulted in a reduced CLN content. It is possible that CLN would be derived from the linoleate hydroperoxides formed during the processing and storage of soybean oil.     

The Component Fatty Acids and Glycerides of Castor Oil

Gas-liquid chromatographic analysis of methyl esters of two samples of castor oil gave the following (as wt %): palmitate 1.2, 0.9; stearate 0.7, 1.2; arachidate 0.3, 0.2; hexadecenoate 0.2, 0.2; oleate 3.2, 3.3; linoleate 3.4, 3.7; linolenate 0.2, 0.2; ricinolE'ate 89.4, 89.0; and dihydroxystearate 1.4, 1.3. Oxidative cleavage of purified methyl ricinoleate indicated that the double bond was exclusively in the 9舑10 position. Castor oil glycerides were fractionated in a 100-tube CCD apparatus using 90% ethanol and commercial hexane as solvents. Analysis of pooled fractions showed (as mole %) triricinolein 68.2, diricinoleins 28.0, mono-ricinoleins 2.9 and nonricinoleins 0.9. These results coupled with lipase hydrolysis of the whole oil and of the fractions agree well with the distribution pattern proposed by Vander Wal.     

Oxidation of Branched Chain Fatty Acids by Chromic Acid

The kinetics of oxidation of isobutyric and isovaleric acids by chromic acid in sulphuric acid medium have been studied. The end product acetic acid is supposed to be derived from the ketones which are the initial oxidation products of the corresponding branched chain fatty acids. The influence of acetic acid on the oxidation velocity has been examined and a marked effect on the rate constants with increasing acetic acid concentration has been observed. A mechanism involving the electrophilic attack of the oxidant on the tertiary carbon atom of the fatty acid to yield a carbonium ion has been postulated.