Inhibitory activities of hydroxyphenolic acid–amino acid conjugates on tyrosinase

The inhibitory effects of hydroxyphenolic acid–aromatic amino acid conjugates on the activity of mushroom tyrosinase were investigated. Amongst the hydroxyphenolic acid–amino acid derivatives, protocatechuic acid–amino acid amide (PA-AA-NH₂) showed highly increased tyrosinase inhibitory activity. The results show that it could strongly inhibit both the monophenolase and diphenolase activities of tyrosinase. The IC₅₀ values, inhibition type, and K_I values of these hydroxyphenolic acid derivatives (PA-F-NH₂, PA-W-NH₂, PA-Y-NH₂) were evaluated and compared. Kinetic analyses of PA-AA-NH₂ as a tyrosinase inhibitor revealed that it acted as a reversible mixed-? type inhibitor, possibly by chelating copper at the active site of tyrosinase. These results suggest that aromatic amino acid conjugation assisted PA in binding to the active site of mushroom tyrosinase where it interrupted access to the substrate.     

Effects of dietary α-lipoic acid enantiomers on hepatic fatty acid metabolism in rats

Effects of dietary α-lipoic acid enantiomers on hepatic and serum lipid concentrations and the activity and mRNA levels of enzymes involved in hepatic fatty acid metabolism were examined in rats. Rats were fed experimental diets containing 0 or 2.5 g/kg of α-lipoic acid enantiomers (a racemic mixture of R/S-, S- or R-α-lipoic acid) for 21 days. Various α-lipoic acid preparations decreased serum and liver concentrations of triacylglycerol, and also lowered serum concentrations of cholesterol and phospholipid and the concentration of cholesterol in the liver. α-Lipoic acid decreased the activity and mRNA levels of various hepatic lipogenic enzymes and also decreased the activities of carnitine acyltransferase and 3-ketoacyl-CoA thiolase and mRNA levels of carnitine palmitoyltransferase 1a involved in fatty acid oxidation in the liver; however, R- and S-enantiomers of α-lipoic acid as well as well as a racemic mixture of R/S-α-lipoic acid were indistinguishable in altering these indices for lipid metabolism.     

Effect of acid concentration and treatment time on acid–alcohol modified jackfruit seed starch properties

The properties of starch extracted from jackfruit (Artocarpus heterophyllus Lam.) seeds, collected from west Assam after acid–alcohol modification by short term treatment (ST) for 15–30 min with concentrated hydrochloric acid and long term treatment (LT) for 1–15 days with 1 M hydrochloric acid, were investigated. Granule density, freeze thaw stability, solubility and light transmittance of the treated starches increased. A maximum decrease in the degree of polymerisation occurred in ST of 30 min (2607.6). Jackfruit starch had 27.1 ± 0.04% amylose content (db), which in ST initially decreased and then increased with the severity of treatment; in LT the effect was irregular. The pasting profile and granule morphology of the treated samples were severely modified. Native starch had the A-type crystalline pattern and crystalline structure increased on treatment. FTIR spectra revealed slight changes in bond stretching and bending. Colour measurement indicated that whiteness increased on treatment. Acid modified jackfruit seed starch can have applications in the food industry.     

Effects of fatty acid chain length on properties of potato starch–fatty acid complexes under partially gelatinization

A series of starch–fatty acid samples were prepared using potato starch and four fatty acids differing in their chain length, including lauric (C12), myristic (C14), palmitic (C16), and stearic (C18) acids. The results indicated that the fatty-acid chain length played a significant role in altering the properties of potato starch–fatty acid complexes. The complexing index of potato starch–fatty acid complexes decreased from 0.38 to 0.18 with increasing carbon-chain length. V-type crystalline polymorphs were formed between starch and four fatty acids, with shorter chain fatty acids preserving more crystalline structure. X-ray diffraction studies revealed that the degree of crystallinity exhibited by the starch samples was dependent on the fatty-acid chain length. In the Fourier transformed infrared spectrum of the samples, the new spikes at 2917, 2850, 1018, and 720 cm^?1 were assumed to be related to the presence of fatty long chains. The formation of amylose–fatty acid complex inhibited granule swelling of potato starch, w\ith longer chain fatty acids showing greater inhibition. Scanning electron microscopy microscopic examination indicated that amylose–fatty acid interactions taken place during starch gelatinization retarded the destruction of the granules.     

Why is sialic acid attracting interest now? Complete enzymatic synthesis of sialic acid with N-acylglucosamine 2-epimerase

N-Acetylneuraminic acid (NeuAc), the representative of the family of sialic acids, is an important molecule in biological recognition systems. Currently, NeuAc-based novel pharmaceutical agents and diagnostic reagents for influenza viruses are highly required in medical fields, and larger amounts of NeuAc are in demand worldwide. NeuAc had been prepared either from colominic acid (a homopolymer of NeuAc) produced by fermentation or from natural sources such as edible bird's nests, milk or eggs. However, the drawbacks of such conventional methods make them unsuitable for large-scale production of NeuAc. Recently, the N-acylglucosamine 2-epimerase (AGE) gene from porcine kidney was cloned in E. coli, and a strain with a high AGE expression level was constructed for practical applications, which enabled the complete enzymatic synthesis of NeuAc with a high conversion rate from the substrates, namely, N-acetylglucosamine and pyruvate. In addition, NeuAc of highest purity could be produced economically via its direct crystallization from the reaction mixture without any column purification processes. Such a simple procedure promises to be applicable to the mass production of sialic acid at the lowest cost.     

Effect of added α-ketoglutaric acid,pyruvic acid or pyridoxal phosphate on proteolyis and quality of Cheddar cheese

Cheddar cheese curds were supplemented with 1, 5 or 20 g of α-ketoglutarate or pyruvic acid or 1.2 g pyridoxal-5¹-phosphate/kg cheese curd. The higher levels of keto-acids (5 or 20 g/kg curd) caused undesirable changes in the physico-chemical properties of resultant cheese. All levels of α-ketoglutarate reduced the pH of the cheese and promoted syneresis during pressing, while pyruvic acid increased the pH of the cheese. The numbers of starter and non-starter lactic acid bacteria were not affected by the addition of keto-acids or pyridoxal-5¹-phosphate. α-Ketoglutarate or pyruvic acid, at 1 g/kg, or pyridoxal-5¹-phosphatase, at 1.2 g/kg cheese curd, did not influence primary proteolysis in the cheese. The highest and lowest concentrations of total and individual free amino acids were found in the cheeses treated with pyruvic acid or α-ketoglutarate, respectively. The concentrations of most amino acids were lower in the cheeses treated with pyridoxal-5¹-phosphate than in the control. The results of this study suggest that α-ketoglutarate and pyridoxal-5¹-phosphate enhanced the degradation of most amino acids in Cheddar cheese while pyruvic acid promoted the formation of amino acids. The cheeses treated with α-ketoglutarate were more mature than the control cheese of the same age while pyruvic acid-treated cheese had a better flavour than the control.     

Characterization of chitosan–oleic acid composite films

Edible films based on high molecular weight chitosan (CH) and different concentrations of oleic acid (OA) were prepared. Film-forming dispersions (FFD) were characterized in terms of rheological properties, surface tension, particle size distribution and ζ-potential. In order to study the impact of the incorporation of OA into the CH matrix, the water sorption isotherms, water vapour permeability (WVP), mechanical properties, and optical properties of the dry films were evaluated. Results showed that the increase in OA promoted changes in the size and surface charge of the FFD particles, which had an impact on the rheological properties of the FFD. As regards the film properties, the higher the OA content, the lower the WVP and the moisture sorption capacity. In general, the addition of OA into the CH matrix leads to a significant increase in gloss and translucency and a decrease in the tensile strength, elongation at break and elastic modulus of the composite films. The mechanical and optical properties of the films were related with their microstructure, which was observed by SEM.     

High γ-aminobutyric acid production from lactic acid bacteria: Emphasis on Lactobacillus brevis as a functional dairy starter

γ-Aminobutyric acid (GABA) and GABA-rich foods have shown anti-hypertensive and anti-depressant activities as the major functions in humans and animals. Hence, high GABA-producing lactic acid bacteria (LAB) could be used as functional starters for manufacturing novel fermented dairy foods. Glutamic acid decarboxylases (GADs) from LAB are highly conserved at the species level based on the phylogenetic tree of GADs from LAB. Moreover, two functionally distinct GADs and one intact gad operon were observed in all the completely sequenced Lactobacillus brevis strains suggesting its common capability to synthesize GABA. Difficulties and strategies for the manufacture of GABA-rich fermented dairy foods have been discussed and proposed, respectively. In addition, a genetic survey on the sequenced LAB strains demonstrated the absence of cell envelope proteinases in the majority of LAB including Lb. brevis, which diminishes their cell viabilities in milk environments due to their non-proteolytic nature. Thus, several strategies have been proposed to overcome the non-proteolytic nature of Lb. brevis in order to produce GABA-rich dairy foods.     

Effects of dietary α-linolenic acid on the fatty acid composition, storage stability and sensory characteristics of pork loin

Effects of dietary α-linolenic acid on the fatty acid composition, storage stability and sensory characteristics of cooked pork were studied. Dietary α-linolenic acid (LNA) significantly (p < 0.05) increased the proportion of n−3 fatty acids and the degree of unsaturation in the neutral lipids and phospholipids. The increases in n−3 fatty acids were observed in the total lipids, triglycerides, phosphatidylethanolamine and phosphatidylcholine, and mainly consisted of C18:3n3, C20:5n3 and/or C22:5n3.The thiobarbituric acid reactive substances (TBARS) values (mg malondialdehyde per kg meat) of cooked vacuum packaged loins remained below 1.5, but in loose packaged loins TBARS values increased more than 3 times those of 0 time values during 2-day storage at 4 °C. The TBARS values of loins after LNA-enrichment were significantly higher than those of the control in both vacuum and loose packaging, and the increase of unsaturation in fatty acids had a strong prooxidant effect. The increase in dietary LNA enrichment increased oxidation (TBARS values) and had a detrimental effect on the acceptability of cooked pork loins held for 2 days in loose packaging.     

Effect of γ-radiation on green onion DNA integrity: Role of ascorbic acid and polyphenols against nucleic acid damage

The effect of γ-radiation on green onion DNA integrity, phenol content, oxygen radical absorbance capacity, employing pyrogallol red and fluorescein as probes, as well as ascorbic acid content has been evaluated. Measurements using thiazole orange-DNA fluorescence and agarose gel electrophoresis show that γ-radiation does not lead to an apparent DNA change in green onion. However, it was readily cleaved upon irradiation from the previously isolated nucleic acid. Furthermore, green onion exposure to γ-radiation produces slight increases in the polyphenol concentrations (163–188 μM Trolox eq.) and a decrease in the oxygen radical absorbance using fluorescein (from 245 to 200 Trolox eq.) Interestingly, a high ascorbic acid content (364 μM), which decreases by 40% after γ-ray exposure was measured by using pyrogallol-red-based oxygen radical absorbance capacity induction times from green onion aqueous extracts. Thus, our results suggest that ascorbic acid present in green onion plays a fundamental role in the plant antioxidant response toward γ-radiation exposure, while polyphenols remain largely unchanged, as revealed from oxygen radical absorbance capacity, employing pyrogallol red.     

Use and abuse of ascorbic acid—A review

The antiscorbutic¹ and ‘extra-antiscorbutic’ functions of ascorbic acid are reviewed. Although megatherapy remains unproven there is substantial evidence that ascorbic acid may affect metabolism in other ways, e.g. by enhancing heavy metal absorption from the alimentary canal. There is little generally accepted evidence that megadoses of ascorbic acid are of themselves toxic.     

Exfoliation for sensitive skin with neutralized salicylic acid?

Citation: IFSCC Magazine, 11 (2008) (2) 115–119 Abstract: Hydroxy acids enjoy tremendous interest in cosmetology thanks to their skin anti‐ageing and water barrier enhancing activities. One of their actions is to promote the natural stratum corneum (stratum corneum) desquamatory process. However, their use is limited due to an inherent pH‐related irritancy potential which is even more exacerbated on sensitive skin. Clearly there is an opportunity for improvement. In this research we evaluated in humans the efficacy of salicylic acid, and its salts, as a corneodesmolytic agent using the dihydroxyacetone method and measuring the reduction in skin staining with treatment over time using a chromameter. Salicylic acid at 2% in a preparation of pH 3.12 significantly increased exfoliation by 10.9% compared with placebo (P < 0.05), confirming its desquamatory enhancing properties. Then the effect of vehicle cream pH on salicylic acid activity was studied. Salicylic acid at close to neutral pH (mostly in its neutralized form as salicylate, pH 6.50) exerted a corneodesmolytic activity as good as that of salicylic acid in an acidic vehicle (pH 3.12) after only two days of application. Furthermore, the performance of glycolic acid and salicylic acid salts as exfoliants were compared at pH 6.50. When these two hydroxyl acids were formulated at the same molar level in a cosmetic base (14.47mmol L^‐1), the salicylic acid preparation gave an 8.2% increase in stratum corneum desquamation compared with the glycolic acid preparation (P < 0.05). The corneodesmolytic effects were confirmed using a tape‐stripping assay combined with a quantitative protein assay. Neutralized salicylic acid was found to enhance the removal of stratum corneum proteins significantly more than the vehicle after 25 sequential tape strippings (14%; P < 0.05). Finally, salicylic acid had no significant influence on skin water barrier properties after 22 days of treatment. In the second phase of this research we assessed the suitability of neutralized salicylic acid as an ingredient for sensitive skin. A stinging test was performed according to the Frosch & Kligman method to evaluate the influence of the formulation base‐pH on stinging potential. Salicylic acid formulated at pH 6.50 induced no stinging sensation (score 0) in contrast to salicylic acid at pH 3.12 (score 19; P < 0.05). In addition, a clinical study was conducted to assess the erythema induced on volunteers’ cheeks after a single application of a neutralized salicylic acid (1%) formulation compared with placebo. Visual redness was assessed by a dermatologist and then measured with a Mexameter. No significant differences were observed. Moreover, half of the panel had sensitive skin and no correlation could be established between redness and/or abnormal sensation and sensitive skin. In conclusion, neutralized salicylic acid at a 1% concentration is a suitable exfoliant agent for subjects with sensitive skin. Keywords: exfoliation, hydroxy acids, Salicylic acid, stratum corneum Paper presented at the IFSCC Conference 2007, Amsterdam, The Netherlands.     

Influence of preprocessing methods and fermentation of adzuki beans on γ-aminobutyric acid (GABA) accumulation by lactic acid bacteria

The effects of pre-processes (immersing, germinating, and cold shock) and fermentation conditions of adzuki beans on γ-aminobutyric acid (GABA) accumulation using mixed cultures of Lactococcus lactis and Lactobacillus rhamnosus were investigated in this study. Among the preprocessing methods, cold shock treatment resulted in the highest observed GABA content (201.2 mg/100 g); a 150-fold increase compared to the non-treated adzuki beans. The LAB strains grew rapidly in cold-treated adzuki bean substrates and reached 10⁸ cfu/ml after 24 h of fermentation at 30 °C. After optimization, the GABA yield reached 68.2 mg/100 ml; a 20-fold increase compared to the non-fermentation yield. The viable cell counts of LAB remained above 10⁸ cfu/ml after 28 days of storage at 4 °C. Our results suggest that the combination of cold shock pretreatment and fermentation by LAB may be used for the preparation of adzuki beans with high GABA content, which can then be used as a natural resource of functional foods.     

Effect of dietary α-linolenic acid and vitamin E on the fatty acid composition, storage stability and sensory traits of rabbit meat

The synergistic effect of dietary linolenic acid and vitamin E on the oxidative stability and nutritional and eating characteristics of fresh and stored rabbit meat was studied. One-hundred hybrid male rabbits were divided into two homogenous groups and fed ad libitum two diets differing in the amount of sunflower and flaxseed and in the level of α-tocopherol, as follows: control diet: 0.08 kg kg(-1) sunflower, 50 mg kg(-1) α-tocopheryl-acetate and LNA-VE diet: 0.08 kg kg(-1) flaxseed, 200 mg kg(-1) α-tocopheryl-acetate. At 85 days, 20 rabbits per group were slaughtered and the thiobarbituric-acid reactive substances (TBA-RS), chemical composition, fatty acid profile and sensory quality were assessed on the longissimus dorsi muscles (fresh and stored for 8 days at 4?°C). The proximate composition of the fresh muscle was not significantly affected by the dietary treatment. Rabbits fed the LNA-VE diet showed a good capability to elongate and desaturate linolenic acid and this diet enriched the n-3 PUFA content of the meat without affecting its peroxidative stability. The sensory quality of the fresh and stored muscle was slightly affected by the dietary treatment, even though final tenderness (fresh meat) and overall acceptability (stored meat) of the LNA-VE rabbits showed significantly higher scores.     

Dynamics of γ-aminobutyric acid in wheat flour bread making

The dynamics of the health-improving non-protein amino acid γ-aminobutyric acid (GABA) during bread making were studied. Wheat flour contains trace levels of GABA (<15 ppm) and ca. 160–175 ppm of its precursor, glutamic acid (GA). During dough mixing, the levels of both GA and GABA largely increased. While wheat flour endogenous glutamic acid decarboxylase (GAD) performs some minor conversion of GA into GABA, yeast is the main contributor to GABA formation. Comparison of amino acid levels of dough samples, without or with yeast, indicated that yeast favours both GA and GABA formation already during mixing. Fermentation decreased both GA and GABA contents, due to amino acid consumption by the yeast, which used more GA than GABA. Proofing and baking resulted in large GABA losses, the latter probably in Maillard browning reactions during baking. Thermal loss of GA was less pronounced than that of GABA. Breads contained only trace levels of GABA and ca. 90–130 ppm of its precursor. Exogenous supplementation of recombinantly produced GAD of Yersinia intermedia decreased GA levels in mixed and fermented dough and increased GABA levels. The highest GAD dosage used resulted in fermented doughs with ca. 300 ppm of GABA, i.e. three times higher than the level present in the reference sample (no GAD added). After baking, a significant GABA level was left in the bread samples (ca. 115 ppm) and GABA-enriched breads were obtained. Addition of sodium glutamate (100–380 ppm) to a bread recipe containing no added GAD clearly indicated that its precursor was not the limiting factor for GABA conversion during bread making since the resulting breads contained no GABA, or only trace levels (ca. 20 ppm).     

Conjugated linoleic acid synthesis-related protein proteasome subunit α 5 (PSMA5) is increased by vaccenic acid treatment in goat mammary tissue

This study was conducted to identify proteins associated with the endogenous synthesis of conjugated linoleic acid (CLA) from trans-vaccenic acid (TVA; trans-11 C18:1, a precursor for CLA endogenous synthesis) in mammary tissues. Six lactating goats were divided into 2 groups. One group was given an intravenous bolus injection of TVA (150mg) twice daily over 4 d; the other group received saline injections. Treatment with TVA increased the concentration of cis-9,trans-11 CLA and TVA in goat milk. Additionally, TVA treatment increased the expression of stearoyl-CoA desaturase (SCD) in mammary tissue. Using 2-dimensional gel electrophoresis and electrospray ionization quadrupole time-of-flight mass spectrometry, 3 proteins affected by infusions of TVA were identified. Proteasome (prosome, macropain) subunit α type 5 (PSMA5) was upregulated, whereas peroxiredoxin-1 and translationally controlled tumor protein 1 were downregulated in TVA-treated animals compared with the vehicle-injected controls. Only the effect of TVA on PSMA5 could be confirmed by Western blot analysis. To further explore the regulation of PSMA5 in mammary epithelial cells when TVA is converted into CLA, we used a differentiated bovine mammary epithelial cell line treated with TVA for 6h. Changes in cis-9,trans-11 CLA concentrations and mRNA expression patterns of both SCD and PSMA5 were monitored. The concentration of cis-9,trans-11 CLA increased after TVA treatment. The mRNA expression level of PSMA5 was significantly elevated to 6h, but SCD mRNA expression only increased in 2h after TVA treatment. These results indicate that PSMA5 is highly expressed in goat mammary tissue and bovine mammary epithelial cells when TVA is converted into CLA. Our data suggest that PSMA5 protein is associated with CLA biosynthesis in mammary tissue.     

Fatty acid profile, trans-octadecenoic, α-linolenic and conjugated linoleic acid contents differing in certified organic and conventional probiotic fermented milks

Development of dairy organic probiotic fermented products is of great interest as they associate ecological practices and benefits of probiotic bacteria. As organic management practices of cow milk production allow modification of the fatty acid composition of milk (as compared to conventional milk), we studied the influence of the type of milk on some characteristics of fermented milks, such as acidification kinetics, bacterial counts and fatty acid content. Conventional and organic probiotic fermented milks were produced using Bifidobacterium animalis subsp. lactis HN019 in co-culture with Streptococcus thermophilus TA040 and Lactobacillus delbrueckii subsp. bulgaricus LB340. The use of organic milk led to a higher acidification rate and cultivability of Lactobacillus bulgaricus. Fatty acids profile of organic fermented milks showed higher amounts of trans-octadecenoic acid (C18:1, 1.6 times) and polyunsaturated fatty acids, including cis-9 trans-11, C18:2 conjugated linoleic (CLA-1.4 times), and α-linolenic acids (ALA-1.6 times), as compared to conventional fermented milks. These higher levels were the result of both initial percentage in the milk and increase during acidification, with no further modification during storage. Finally, use of bifidobacteria slightly increased CLA relative content in the conventional fermented milks, after 7 days of storage at 4 °C, whereas no difference was seen in organic fermented milks.     

Effect of slaughter season on fatty acid composition, conjugated linoleic acid isomers and nutritional value of intramuscular fat in Barrosã-PDO veal

This paper describes the influence of slaughter season on lipid content, fatty acid composition, conjugated linoleic acid (CLA) isomeric profile and nutritional value of fat in Barrosã veal from calves reared according to the specifications of the Protected Designation of Origin (PDO). Barrosã purebred calves (n = 27) were raised in a traditional production system and slaughtered in early autumn (October) and late spring (June). Barrosã-PDO veal only presented seasonal differences in the levels of some minor fatty acids and CLA isomers, as well as in the PUFA/SFA ratio. Based on the analysed grass intake indicators, it was shown that veal-PDO has similar values to pasture-fed cattle for both slaughter seasons. From a human nutrition perspective, intramuscular fat in Barrosã-PDO veal has a high nutritional value throughout the year, since CLA contents and the percentages of the c9,t11 isomer are relatively high, and the n − 6/n − 3 ratios are within the recommended values for the human diet.     

Transfer rate of α-linolenic acid from abomasally infused flaxseed oil into milk fat and the effects on milk fatty acid composition in dairy cows

The objectives of the present study were to evaluate the transfer efficiency of α-linolenic acid (ALA) from the abomasum into milk fat, its interaction with milk fat content and yield, and the relationship between ALA and C16:0 in milk fat. Three rumen-fistulated multiparous Holstein cows at midlactation were used in a 3×3 Latin square design. Treatments consisted of abomasal infusion of (1) 110mL of water/d (control), (2) 110mL of flaxseed oil/d (low flaxseed oil, LFO), and (3) 220mL of flaxseed oil/d (high flaxseed oil, HFO). Experimental periods were continued for 2 wk and fat supplements were infused abomasally during the last 7 d of each period. Average dry matter intake and milk yield were not affected by oil infusion. Milk fat and lactose content tended to be greater with flaxseed infusion compared with the control. Plasma ALA was 2.9- and 4.0-fold greater with LFO and HFO, respectively. The apparent transfer efficiency of ALA to milk was 44.8 and 45.7% with LFO and HFO, respectively. The C16:0 content in milk fat was decreased by 3.59 and 5.25 percentage units, whereas the ALA content was increased by 1.68 and 3.09 percentage units with LFO and HFO, respectively. Similarly, C18:2n-6 was increased by 0.95 and 1.31 percentage units with LFA and HFO, respectively, without changes in other fatty acids (FA). Total polyunsaturated FA was 4.4 and 2.7% lower in the HFO and LFO, respectively, than in the control. Furthermore, C16:0 content in the milk fat was reduced to a greater extent than the increase in ALA content, as a 1.68 and 3.09 percentage unit increase occurred in ALA compared with a 3.6 and 5.25 percentage unit decrease in C16:0 for LFO and HFO, respectively, such that a negative correlation existed between ALA and C16:0 (r=-0.72). In conclusion, abomasal infusion of flaxseed oil dramatically increased the ALA content in plasma and milk fat. Because the replacement of C16:0 with ALA and C18:2n-6 occurred without changes in other FA presumed to be synthesized de novo in the mammary gland, this suggests that the preformed C16:0 was replaced, rather than being caused, by an overall suppression of de novo FA synthesis in the mammary gland.