Dietary fat saturation and gender/hormonal status modulate plasma lipids and lipoprotein composition(1)

Male, female and ovariectomized (to mimic menopause) guinea pigs were fed a saturated (SFA) or a polyunsaturated (PUFA) fat diet for 4 weeks to determine the effects of dietary fat saturation on lipoprotein levels and composition and to assess whether gender and hormonal status modulate the cholesterolemic response. Both diets contained 15g/100 g fat and 0.04 g/100 g cholesterol and were identical in composition except for the type of fat. The SFA diet contained 50% saturated fat (25% lauric + myristic fatty acids), 25% PUFA and 25% monounsaturated fatty acids while the PUFA diet had 50% PUFA (linoleic acid), 25% monounsaturated and 25% SFA fatty acids. Plasma LDL cholesterol (LDL-C) was an average 21% lower in guinea pigs fed PUFA compared to those fed SFA (P < 0.05). In addition, ovariectomized guinea pigs, both in the SFA and PUFA groups, had 20–33% higher LDL-C than either males or females (P < 0.01). VLDL cholesterol was 70% higher in the PUFA-fed animals (P < 0.0001). A gender effect was observed in plasma HDL cholesterol (HDL-C) with females and ovariectomized guinea pigs having 30–42% higher HDL-C than males (P < 0.01). LDL susceptibility to oxidation was not affected by dietary fat saturation or gender. In contrast, VLDL and LDL composition were significantly influenced by diet and gender. VLDL particles were larger in size in guinea pigs fed the SFA diets (P < 0.01) while LDL particles were larger in female guinea pigs (P < 0.001). Hepatic lipids were influenced by the interaction between diet and group. Hepatic cholesterol (P < 0.01) and TAG concentrations (P < 0.0001) were highest in female guinea pigs fed the PUFA diet. Since the liver is the major site of lipoprotein synthesis and catabolism, these results suggest that not only diet but also gender may play a major role in determining the composition and size of lipoproteins.     

Phytosterols and lecithin do not have an additive effect in lowering plasma and hepatic cholesterol levels in diet-induced hypercholesterolemic rats

Both plant sterols and lecithin are used as dietary supplements for lowering blood cholesterol in Western countries. This study evaluated the possibility of an additive effect of these ingredients on the regulation of lipid concentrations and cholesterol metabolism. Male Sprague-Dawley rats were randomly divided into three groups, and fed one of the following diets for 5 weeks; high cholesterol diet (HCD), phytosterol mixture-supplemented diet (PD, HCD+0.25% phytosterols), or phytosterol mixture and lecithin-supplemented diet (PLD, PD+0.15% lecithin). Feeding the PD for 5 weeks resulted in a 34% and 41% decrease in plasma total- and VLDL+LDL-cholesterol levels, respectively, and a 23% decrease in hepatic cholesterol content compared to those for the HCD rats (p < 0.05). These cholesterol-lowering properties of the phytosterol mixture were also associated with the down-regulation of hepatic acyl CoA:cholesterol acytransferase (ACAT) activity (p < 0.05). Addition of lecithin plus phytosterol mixture to the hypercholesterolemic diet did not significantly affect blood and hepatic lipid concentrations (with the exception of 36% decrease in hepatic triglyceride level, p < 0.05) as well as hepatic ACAT activity compared to feeding the hypercholesterolemic diet supplemented with phytosterol alone. These results indicate that combining lecithin, at a 0.15% level, with a phytosterol mixture-supplemented diet does not exhibit an additive effect in regulating hepatic ACAT activity or lowering blood cholesterol in hypercholesterolemic rats.     

Moderate intake of myristic acid in sn-2 position has beneficial lipidic effects and enhances DHA of cholesteryl esters in an interventional study

Among the saturated fatty acids (SFA), myristic acid is known to be one of the most atherogenic when consumed at high levels. Our purpose was to compare the effects of two moderate intakes of myristic acid on plasma lipids in an interventional study. Twenty-five male monks without dyslipidemia were given two isocaloric diets for 5 weeks each. In diet 1, 30% of the calories came from fat (8% SFA, 0.6% myristic acid) and provided 200 mg cholesterol/day. Calories of diet 2 were 34% fat (11% SFA, 1.2% myristic acid) with the same levels of oleate, linoleate, alpha-linolenate and cholesterol. A baseline diet was provided before each diet. In comparison with baseline, diets 1 and 2 induced a decrease in total cholesterol, LDL-cholesterol and triglycerides (P<.001); HDL-cholesterol was not modified and the apo A-I/apo B ratio increased (P<.001). Plasma triglycerides were lower after diet 2 than after diet 1 whereas HDL-cholesterol was higher (P<.05). In phospholipids, myristic acid, oleic acid, linoleic acid, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) increased after diet 2 vs. baseline (P<.01) and diet 1 (P<.05). Both diets were associated with an increase in alpha-linolenate of cholesteryl esters (P<.05), but only diet 2 was associated with an increase in DHA of cholesteryl esters (P<.05). In diet 2, myristic acid intake was positively correlated with myristic acid of phospholipids, and alpha-linolenic acid intake was correlated with alpha-linolenic acid of cholesteryl esters. Moderate intake (1.2% of total calories) of myristic acid has beneficial lipidic effects and enhances DHA of cholesteryl esters.     

Effect of oleic, lauric and myristic acids on phenylephrine-induced contractions of isolated rat vas deferens

D-004, a lipid extract of Roystonea regia fruits that contains oleic, lauric and myristic acids as major components inhibits alpha1-adrenoreceptors-mediated contractile responses in isolated rat vas deferens and prostate trips; no study has demonstrated a similar effect for oleic, lauric or myristic acids individually. Therefore, the effects of D-004 (250 microg/mL), oleic (100 microg/mL), lauric (50 microg/mL) or myristic (25 microg/mL) acids and their combined effects on phenylephrine (PHE: 10(-7)-10(-4) mol/L) induced contractions has been studied. No treatment changed the basal tone of the preparations, but all inhibited PHE-induced contractions. D-004 produced the highest inhibition, followed by lauric acid, which was more effective than myristic and oleic acids against PHE-induced contractions of control group. D-004 and the mixture of the three acids produced similar inhibitions.     

Lipid and sterol composition of the pollen of the west african oilpalm, Elaeis guineensis

The lipid classes, fatty acid methyl esters and the sterols of oilpalm pollen were analysed. The neutral lipid fraction consisted of triglycerides, esterified and free sterols and trace amounts of hydrocarbons. Monogalactosyl and digalactosyl diglycerides, phosphatidyl choline, phosphatidyl inositol and phosphatidyl ethanolamine represented the polar lipids. The major fatty acids were linoleic, palmitic and linolenic acids together with small to trace amounts of oleic, stearic, arachidic, myristic, lauric, palmitoleic and margaric acids. Unsaturated fatty acids predominated over saturated ones in the ratio of 3:2. The 4-desmethyl sterols were the major phytosterols in the free form but they constituted a lower proportion of the sterols in the esterified state. 28-Isofucosterol was isolated and characterized as the principal sterol.     

Beta-oxidation of medium chain (C8-C14) fatty acids studied in isolated liver cells

The beta-oxidation and esterification of medium-chain fatty acids were studied in hepatocytes from fasted, fed and fructose-refed rats. The beta-oxidation of lauric acid (12:0) was less inhibited by fructose refeeding and by (+)-decanoyl-carnitine than the oxidation of oleic acid was, suggesting a peroxisomal beta-oxidation of lauric acid. Little lauric acid was esterified in triacylglycerol fraction, except at high substrate concentrations or in the fructose-refed state. With [1-14C]myristic acid (14:0), [1-14C]lauric acid (12:0), [1-14C]octanoic acid (8:0) and [2-14C]adrenic acid (22:4(n - 6] as substrate for hepatocytes from carbohydrate-refed rats, a large fraction of the 14C-labelled esterified fatty acids consisted of newly synthesized palmitic acid (16:0), stearic acid (18:0) and oleic acid (18:1) while intact [1-14C]oleic acid substrate was esterified directly. With [9,10-3H]myristic acid as the substrate, small amounts of shortened 3H-labelled beta-oxidation intermediates were found. With [U-14C]palmitic acid, no shortened fatty acids were detected. It was concluded that when the mitochondrial fatty acid oxidation is down-regulated such as in the carbohydrate-refed state, medium-chain fatty acids can partly be retailored to long-chain fatty acids by peroxisomal beta-oxidation followed by synthesis of C16 and C16 fatty acids which can then stored as triacylglycerol.     

Differential effects of saturated fatty acids on low density lipoprotein metabolism in the guinea pig.

Studies have shown that dietary fat saturation affects guinea pig plasma low density lipoprotein (LDL) levels by altering both LDL receptor-mediated catabolism and flux rates of LDL (Fernandez et al. 1992. J. Lipid Res. 33: 97-109). The present studies investigated whether saturated fatty acids of varying chain lengths have differential effects on LDL metabolism. Guinea pigs were fed 15% (w/w, 35% calories) fat diets containing either palm kernel oil (PK), 52% lauric acid/18% myristic acid; palm oil (PO), 43% palmitic acid/4% stearic acid; or beef tallow (BT), 23% palmitic acid/14% stearic acid. Plasma LDL cholesterol levels were significantly higher for animals fed the PK diet (P < 0.001) with values of 83 +/- 19 (n = 12), 53 +/- 8 (n = 12) and 44 +/- 16 (n = 10) mg/dl for PK, PO, and BT diets, respectively. The relative percentage composition of LDL was modified by fat type; however, LDL diameters and peak densities were not different between diets, indicating no effect of saturated fatty acid composition on LDL size. ApoB/E receptor-mediated LDL fractional catabolic rates (FCR) were significantly lower in animals fed the PK diet (P < 0.01) and LDL apoB flux rates were reduced (P < 0.01) in animals fed the BT diet. A correlation was found between plasma LDL levels and receptor-mediated LDL catabolism (r = -0.66, P < 0.01). A higher apoB/E receptor number (Bmax), determined by in vitro LDL binding to guinea pig hepatic membranes, was observed for animals fed BT versus PK or PO diets and Bmax values were significantly correlated with plasma LDL levels (r = -0.776, P < 0.001). These results indicate that saturated fatty acids of varying chain length have differential effects on hepatic apoB/E receptor expression and on LDL apoB flux rates which in part account for differences in plasma LDL cholesterol levels of guinea pigs fed these saturated fats.     

Fatty acid composition of the depot fats of the Polynesian rat,Rattus exulans,Tokelau Islands

The fatty acid composition of the stomach contents, adipose tissue, and perinephric fat of Polynesian rats (Rattus exulans Peale), from the Tokelau Is indicated that the dietary fat consisted mainly, if not exclusively, of coconut oil. Lower ratios of lauric : myristic acids were found in the depot fats of the Polynesian rats than in the dietary coconut oil. These results were consistent with chain elongation of lauric to myristic acid after ingestion, as previously reported in rats and other mammals.     

Pectin and psyllium decrease the susceptibility of LDL to oxidation in guinea pigs

These studies were undertaken to determine whether pectin (PE) and psyllium (PSY) intake affect the circulating levels of alpha-tocopherol and the susceptibility of low density lipoprotein (LDL) to oxidation. For that purpose, male Hartley guinea pigs were fed 19 g/100 g of a fat mix with a 2:1:1 ratio of saturated:polyunsaturated:monounsaturated fatty acids and 35 g/100 g total carbohydrate with 80% of the carbohydrate energy contributed by sucrose. Diets were identical in composition except for the fiber source: cellulose (control diet), PE, or PSY. Guinea pigs fed PE or PSY had 36% and 67% lower plasma cholesterol concentrations, respectively, compared with controls (P < 0.001). This plasma cholesterol lowering was associated with both very low density lipoproteins and LDL cholesterol fractions. Intake of PE or PSY resulted in 54% lower plasma triacylglycerol (TAG) concentrations compared with the control group (P < 0.001). LDL from PE and PSY fed guinea pigs contained fewer molecules of cholesteryl ester, and alpha-tocopherol concentrations in this particle were 49% and 66% higher, respectively, compared with controls. In addition, LDL from guinea pigs fed soluble fiber exhibited less susceptibility to oxidation than those from the control group, as determined by thiobarbituric acid-reactive substances formation. Hepatic free and esterified cholesterol were 32% lower and hepatic TAG was 25% lower in guinea pigs fed PE and PSY compared with controls. The data from these studies confirm that PE and PSY reverse the hyperlipidemia associated with high fat-sucrose diets and demonstrate a potential antioxidant effect of soluble fiber on circulating LDL.     

Injected phytosterols/stanols suppress plasma cholesterol levels in hamsters

Although plant sterols are known to suppress intestinal cholesterol absorption, whether plasma and hepatic lipid levels are influenced through non-gut related internal mechanisms has not been established. To examine this question 50 male hamsters were divided into 5 groups and fed semi-purified diets containing 20% energy as fat and 0.25% (w/w) cholesterol ad libitum for 60 days. The control group (i) received diet alone, while four additional groups consumed the diet plus one of four equivalent phytosterol mixtures (5 mg/kg/day) given either as (ii) tall oil phytosterols/stanols mixed with diet (oralSA), (iii) tall oil phytosterols/stanols subcutaneously injected (subSA), (iv) soybean oil phytosterols alone mixed with diet (oralSE), or (v) soybean oil subcutaneous injected phytosterols alone (subSE). The control group and both orally supplemented groups also received placebo subcutaneous sham injections. Neither food consumption, body weight, nor liver weight differed across treatment groups. Subcutaneous administration of SA and SE decreased plasma total cholesterol levels by 21% and 23% (p < 0.0001) and non-apolipoprotein-A cholesterol concentrations by 22% and 15% (p < 0.0002), respectively, compared to control. HDL cholesterol and TG concentrations remained unchanged across all groups, except for a decline of 25% (p < 0.0001) in HDL concentration in the subSE group versus control. Plasma campesterol levels were lower (p < 0.05) in the subSA group relative to all other groups. Plasma campesterol:cholesterol and campesterol:sitosterol ratios were, however, higher (p < 0.0001) for both the oral and subSE groups. Hepatic cholesterol levels were higher (p < 0.0001) in the oral and subSE phytosterol groups by 30% and 31%, respectively, relative to control. We conclude that low doses of subcutaneously administered plant sterols reduce circulating cholesterol levels through mechanisms other than inhibiting intestinal cholesterol absorption.     

The influence of 5% and 10% dietary apple pectin on parameters of fermentation in faeces and caecal digesta of weaning pigs

In order to determine the effect of pectin on fermentation parameters in the faeces and caecal digesta of weaned pigs 18 castrated male crossbred pigs with an average body weight of 8 kg were fitted with T-cannulas at the caecum. The animals were randomly distributed into three groups and fed with diets supplemented with 0, 5 and 10% pectin. Faeces were collected over a period of 3 days. Thereafter the diets were withdrawn for 24 h followed by ad libitum feeding to enhance the feed intake. Caecal chyme was collected 0, 8 and 24 h postprandial. In the faeces the addition of 5% pectin to the diet lowered the content of dry matter and lactic acid. The pH and the digestibility of pectins, the concentration of total SCFA, acetate, propionate, butyrate, bicarbonate and chloride increased. Dietary pectin of 10% increased the content of total SCFA and acetate further. When the diets were withdrawn and fed ad libitum 24 h later, a decline of the pH and an increased concentration of lactate in the caecal chyme could be observed in all groups up to 8 h after feeding. With an interval of 8 to 24 h after feeding, a further decline in pH and a rise of lactate only occurred when the diet was not supplemented with pectin. It was concluded that pectin might be beneficial for the development of fermentative processes in the large intestine.     

Influence of chain length and unsaturation on the effects of fatty acids on phosphoglyceride biosynthesis in isolated rat and pig hepatocytes.

Hepatocytes isolated from rat or pig by collagenase perfusion were incubated with [3H]glcyerol and different albumin-bount fatty acids. Among C22 fatty acids docosahexaenoic acid stimulated phosphatidylethanolamine synthesis in rat hepatocytes most effectively. Addition of docosahexaenoic acid plus either palmitic or stearic acid resulted almost in the same stimulation whereas combinations of this acid with lauric or myristic acid had no effect. Lauric acid and myristic acid alone inhibited phosphatidylethanolamine synthesis. The chain length specificity for monoenoic fatty acids was similar, the hexadecenoic and octadecenoic acids (both cis and trans) being most stimulatory. The addition of 0.2 mM ethanolamine markedly stimulated phosphatidylethanolamine synthesis, but most effects of fatty acids were similar in its presence or absence.     

The influence of 5% and 10% dietary apple pectin on parameters of fermentation in faeces and caecal digesta of weaning pigs

In order to determine the effect of pectin on fermentation parameters in the faeces and caecal digesta of weaned pigs 18 castrated male crossbred pigs with an average body weight of 8?kg were fitted with T-cannulas at the caecum. The animals were randomly distributed into three groups and fed with diets supplemented with 0, 5 and 10% pectin. Faeces were collected over a period of 3 days. Thereafter the diets were withdrawn for 24?h followed by ad libitum feeding to enhance the feed intake. Caecal chyme was collected 0, 8 and 24?h postprandial. In the faeces the addition of 5% pectin to the diet lowered the content of dry matter and lactic acid. The pH and the digestibility of pectins, the concentration of total SCFA, acetate, propionate, butyrate, bicarbonate and chloride increased. Dietary pectin of 10% increased the content of total SCFA and acetate further. When the diets were withdrawn and fed ad libitum 24?h later, a decline of the pH and an increased concentration of lactate in the caecal chyme could be observed in all groups up to 8?h after feeding. With an interval of 8 to 24?h after feeding, a further decline in pH and a rise of lactate only occurred when the diet was not supplemented with pectin. It was concluded that pectin might be beneficial for the development of fermentative processes in the large intestine.     

Impact of dietary sterols on life-history traits of a caterpillar

Although lepidopteran larvae have been shown to metabolise a number of different phytosterols, their life-history traits in response to these different phytosterols may vary with the species. Using the specialist moth, Plutella xylostella (Linaeus) (Lepidoptera), growth, development and fecundity on artificial diets containing host and non-host phytosterols were measured over two generations. Because of the nature of the experimental design, maternal effects linked to dietary sterol could be assessed. In both generations, survival was highest on diets containing sitosterol as the primary phytosterol. A significant decrease in survival on stigmasterol, a non-host phytosterol, was observed between generations. As expected, survival on a control diet with only trace-sterols decreased between generations. Larval duration and pupal duration in both generations was longest on the diets containing the non-host phytosterols, stigmasterol and spinasterol, and on the trace-sterol diet. Finally, fecundity was affected by dietary sterol. In the first generation, fewer viable eggs were produced on the stigmasterol and trace-sterol diets than on wheatgerm control diet. In both generations, dietary sterol significantly influenced percentage egg viability. Overall, these results indicate that differences in phytosterol structure can have pronounced effects on life-history traits, especially when they are projected to the population level. The implications of these results are discussed with respect to phytosterol use by phytophagous insects and their host plant affiliations.     

Phytosterols inhibit the tumor growth and lipoprotein oxidizability induced by a high-fat diet in mice with inherited breast cancer

Dietary phytosterol supplements are readily available to consumers since they effectively reduce plasma low-density lipoprotein cholesterol. Several studies on cell cultures and xenograft mouse models suggest that dietary phytosterols may also exert protective effects against common cancers. We examined the effects of a dietary phytosterol supplement on tumor onset and progression using the well-characterized mouse mammary tumor virus polyoma virus middle T antigen transgenic mouse model of inherited breast cancer. Both the development of mammary hyperplastic lesions (at age 4 weeks) and total tumor burden (at age 13 weeks) were reduced after dietary phytosterol supplementation in female mice fed a high-fat, high-cholesterol diet. A blind, detailed histopathologic examination of the mammary glands (at age 8 weeks) also revealed the presence of less-advanced lesions in phytosterol-fed mice. This protective effect was not observed when the mice were fed a low-fat, low-cholesterol diet. Phytosterol supplementation was effective in preventing lipoprotein oxidation in mice fed the high-fat diet, a property that may explain — at least in part — their anticancer effects since lipoprotein oxidation/inflammation has been shown to be critical for tumor growth. In summary, our study provides preclinical proof of the concept that dietary phytosterols could prevent the tumor growth associated with fat-rich diet consumption.     

The solid-liquid phase diagrams of binary mixtures of consecutive, even saturated fatty acids: differing by four carbon atoms

The complete solid-liquid phase diagrams for four binary mixtures of saturated fatty acids are presented, for the first time, in this work. These mixtures are formed by caprylic acid (C_8:0) + lauric acid (C_12:0), capric acid (C_10:0) + myristic acid (C_14:0), lauric acid (C_12:0) + palmitic acid (C_16:0) and myristic acid (C_14:0) + stearic acid (C_18:0). The phase diagrams were obtained by differential scanning calorimetry (DSC) and X-ray diffraction (XRD). FT-Raman spectrometry and polarized light microscopy were used to complement the characterization for a complete understanding of the phase diagram. All of the phase diagrams here reported show the same global behavior that is far more complex than previously accepted. They present not only peritectic and eutectic reactions, but also metatectic reactions, due to solid-solid phase transitions common in fatty acids, and regions of solid solution not previously reported. This work contributes to the elucidation of the phase behavior of these important biochemical molecules with implications in various industrial applications.     

Effect of crude protein concentration and sugar-beet pulp on nutrient digestibility, nitrogen excretion, intestinal fermentation and manure ammonia and odour emissions from finisher pigs

A 2 × 2 factorial experiment was conducted to investigate the interaction between high and low dietary crude protein (CP) (200 v. 150 g/kg) and sugar-beet pulp (SBP) (200 v. 0 g/kg) on nutrient digestibility, nitrogen (N) excretion, intestinal fermentation and manure ammonia and odour emissions from 24 boars (n = 6, 74.0 kg live weight). The diets were formulated to contain similar concentrations of digestible energy (13.6 MJ/kg) and lysine (10.0 g/kg). Pigs offered SBP-containing diets had a reduced (P < 0.05) digestibility of dry matter, ash, N, gross energy and an increased (P < 0.001) digestibility of neutral-detergent fibre compared with pigs offered diets containing no SBP. There was an interaction between CP and SBP on urinary N excretion and the urine : faeces N ratio. Pigs offered the 200 g/kg CP SBP-based diet had reduced urine : faeces N ratio (P < 0.05) and urinary N excretion (P < 0.05) compared with those offered the 200 g/kg CP diet without SBP. However, there was no effect of SBP in pigs offered 150 g/kg CP diets. Manure ammonia emissions were reduced by 33% from 0 to 240 h (P < 0.01); however, odour emissions were increased by 41% (P < 0.05) when pigs were offered SBP diets. Decreasing dietary CP to 150 g/kg reduced total N excretion (P < 0.001) and ammonia emissions from 0 to 240 h (P < 0.05). There was an interaction between dietary CP and SBP on branched-chain fatty acids (P < 0.001) in caecal digesta. Pigs offered the 200 g/kg CP SBP-containing diet reduced branched-chain fatty acids in the caecum compared with pigs offered the 200 g/kg CP diet containing no SBP. However, there was no effect of SBP in the 150 g/kg CP diet. In conclusion, pigs offered SBP-containing diets had a reduced manure ammonia emissions and increased odour emissions compared with diets containing no SBP. Pigs offered the 200 g/kg CP SBP-containing diet had a reduced urine : faeces N ratio and urinary N excretion compared with those offered the 200 g/kg CP diet containing no SBP.     

Myristic acid increases delta6-desaturase activity in cultured rat hepatocytes

In order to study the effects of saturated fatty acids on delta6-desaturase activity, rat hepatocytes in primary culture were incubated with lauric (C12:0), myristic (C14:0) or palmitic (C16:0) acids. After optimization, the standard in vitro conditions for the measurement of delta6-desaturase activity were as follows: 60 micromol x L(-1) alpha-linolenic acid (C18:3n-3), reaction time of 20 min and protein content of 0.4 mg. Data showed that cell treatment with 0.5 mmol x L(-1) myristic acid during 43 h specifically increased delta6-desaturase activity. This improvement, reproducible for three substrates of delta6-desaturase, i.e. oleic acid (C18:1n-9), linoleic acid (C18:2n-6) and alpha-linoleic acid (C18:3n-3) was dose-dependent in the range 0.1-0.5 mmol x L(-1) myristic acid concentration.     

Critical temperatures for the interaction of free fatty acids with the erythrocyte membrane

Non-esterified long-chain fatty acids reduce the extent of hypotonic hemolysis at a certain low concentration range but cause hemolysis at higher concentrations. This biphasic behavior was investigated at different temperatures (0-37 degrees C) for lauric (12:0), myristic (14:0), palmitoleic (16:1), oleic (cis-18:1) and elaidic (trans-18:1) acids. The results are summarized as follows: (A) the fatty acids examined exhibit a high degree of specificity in their thermotropic behavior; (B) oleic acid protects against hypotonic hemolysis even at the highest concentrations, up to 15 degrees C, when it becomes hemolytic, but only in a limited concentration range; (C) elaidic acid does not affect the osmotic stability of erythrocytes up to 20 degrees C, when it starts protecting: above 30 degrees C, it becomes hemolytic at the highest concentrations; (D) palmitoleic acid is an excellent protecting agent at all temperatures in a certain concentration range, becoming hemolytic at higher concentrations; (E) lauric acid protects up to 30 degrees C and becomes hemolytic only above this temperature; (F) myristic acid exhibits an extremely unusual behavior at 30 and 37 degrees C by having alternating concentration ranges of protecting and hemolytic effects; (G) there is a common critical temperature for hemolysis at 30 degrees C for saturated and trans-unsaturated fatty acids; (H) the initial slope of Arrhenius plots of percent hemolysis at the concentration of maximum protection is negative for cis-unsaturated fatty acids and positive for saturated and trans-unsaturated fatty acids.     

The solid–liquid phase diagrams of binary mixtures of consecutive, even saturated fatty acids

For the first time, the solid–liquid phase diagrams of five binary mixtures of saturated fatty acids are here presented. These mixtures are formed of caprylic acid (C_8:0) + capric acid (C_10:0), capric acid (C_10:0) + lauric acid (C_12:0), lauric acid (C_12:0) + myristic acid (C_14:0), myristic acid (C_14:0) + palmitic acid (C_16:0) and palmitic acid (C_16:0) + stearic acid (C_18:0). The information used in these phase diagrams was obtained by differential scanning calorimetry (DSC), X-ray diffraction (XRD), FT–Raman spectrometry and polarized light microscopy, aiming at a complete understanding of the phase diagrams of the fatty acid mixtures. All of the phase diagrams reported here presented the same global behavior and it was shown that this was far more complex than previously imagined. They presented not only peritectic and eutectic reactions, but also metatectic reactions, due to solid–solid phase transitions common in fatty acids and regions of solid solution not previously reported. This work contributes to the elucidation of the phase behavior of these important biochemical molecules, with implications in various industrial applications.