Inhibition of benzo(a)pyrene-induced mouse forestomach neoplasia by conjugated dienoic derivatives of linoleic acid.

Grilled ground beef contains factors that inhibit the initiation of mouse epidermal carcinogenesis by 7,12-dimethylbenz(a)anthracene. Previously we isolated an active principal and characterized it as an isomeric mixture of conjugated dienoic derivatives of linoleic acid (CLA). We now show that synthetic CLA inhibits the initiation of mouse forestomach tumorigenesis by benzo(a)pyrene. Four and 2 days prior to p.o. treatment with benzo(a)pyrene, female ICR mice were given (a) CLA in olive oil, (b) linoleic acid in olive oil, or (c) olive oil alone or plus 0.85% saline (control groups). Three days later the cycle was repeated for a total of 4 times. At 30 wk of age, the mice were sacrificed. In three independent experiments, mice treated with CLA developed only about half as many neoplasms/animal as mice in the control groups (P less than 0.025); in two of the experiments tumor incidence was also reduced (P less than 0.05). There were no significant differences in food intake or body weight among the groups. High-performance liquid chromatography/gas chromatography analysis established that, following intubation, only the c-9, t-11 CLA isomer was incorporated into forestomach phospholipids. In studies aimed at elucidating the mechanism of action, we found that CLA is an effective antioxidant. Under the conditions of the test CLA was more potent than alpha-tocopherol and almost as effective as butylated hydroxytoluene. These observations indicate that CLA might serve as an in situ defense mechanism against membrane attack by free radicals and may, at least in part, explain the anticarcinogenic properties of CLA.

Two-dimensional atmospheric transport and chemistry model: numerical experiments with a new advection algorithm.

Extensive testing of the advective scheme, proposed by Prather (1986), has been carried out in support of the California Institute of Technology-Jet Propulsion Laboratory two-dimensional model of the middle atmosphere. We generalize the original scheme to include higher-order moments. In addition, we show how well the scheme works in the presence of chemistry as well as eddy diffusion. Six types of numerical experiments including simple clock motion and pure advection in two dimensions have been investigated in detail. By comparison with analytic solutions it is shown that the new algorithm can faithfully preserve concentration profiles, has essentially no numerical diffusion, and is superior to a typical fourth-order finite difference scheme.

Conjugated linoleic acid isomers in partially hydrogenated soybean oil obtained during nonselective and selective hydrogenation processes.

Partially hydrogenated soybean oil samples were collected during selective and nonselective hydrogenation processes. The formation of conjugated linoleic acids (CLAs) during hydrogenation was greatly dependent on the types and duration of hydrogenation processes. During hydrogenation processes, CLA contents increased initially. After reaching maximum CLA content, the content decreased during hydrogenation. Selective hydrogenation was much more favorable for the formation of conjugated linoleic acids. With nonselective hydrogenation process, the total CLA content was a maximum (9.06 mg total CLA/g oil) at 35 min. However, with the selective hydrogenation process, the total CLA content was a maximum (98.27 mg total CLA/g oil) at 210 min. The CLA contents in some of the tested selectively hydrogenated soybean oils were among the highest ever reported in foods.

Improvement of oxidative stability of conjugated linoleic acid (CLA) by microencapsulation in cyclodextrins.

Oxidative stability of conjugated linoleic acid (CLA) encapsulated in alpha-, beta-, and gamma-cyclodextrins (designated CLA/CDs microencapsules) was studied by measuring the headspace-oxygen depletion in airtight serum bottles and by measuring the peroxide values (POV). The rate of oxygen depletion was reduced from 41.0 (control) to 21.5, 2.1, 1.2, and 1.1 micromol/L.h(-)(1) by CLA/alpha-CD microencapsules at 1:1, 1:2, 1:4, and 1:6 mole ratios, respectively, indicating that CLA oxidation was completely protected by a 1:4 mole ratio of CLA/alpha-CD. Such a protective effect by CLA/beta-CD or CLA/gamma-CD microencapsules was achieved at a 1:6 mole ratio, but the effect by CLA/beta-CD was slightly greater than that by CLA/gamma-CD. The protective effect of alpha-, beta-, and gamma-CDs for CLA oxidation was confirmed by their POV-reducing abilities in CLA/CDs. These results suggest that alpha-CD was the most effective for the protection of CLA oxidation by microencapsulation, followed by beta-CD and gamma-CD.

Separation of alpha-tocopherol and its oxidation products by high performance liquid chromatography.

A very sensitive high performance liquid chromatographic (HPLC) method was developed for the separation of alpha-tocopherol (alpha-T) and its five oxidation products: alpha-tocopheryl quinone (TQ), dimer (D), dihydroxy dimer (DHD), trimer (T) and 9-methoxy-alpha-tocopherone commonly called alpha-tocopheroxide (TO). The separation was achieved on a normal-phase silica-based column (Ultrasphere-Si), using a mobile phase of hexane/chloroform/isopropanol (95:4.5:0.5, v/v/v) at a flow rate of 0.4 ml/min, and the eluants were monitored simultaneously at their maximum absorptions using a variable-wavelength UV detector. The minimum detection limit is 0.01 microgram for alpha-T, TQ and TO, 0.05 microgram for DHD and D, and 0.1 microgram for T/injection. This normal-phase method has the combined advantages of being very sensitive, fast and capable of separating all six compounds at the same time.

alpha-Tocopherol oxidation mediated by superoxide anion (O2-). I. Reactions in aprotic and protic conditions.

The reaction of alpha-tocopherol (alpha-T) with superoxide anion (O2-) in both dry acetonitrile and in aqueous acetonitrile solution is described. The O2- was generated by the electrochemical reduction of molecular oxygen in acetonitrile, using tetrabutylammonium bromide as an electrolyte. alpha-T was reacted with O2- either in dry acetonitrile or in a 10% aqueous acetonitrile solution. In dry acetonitrile, alpha-T was oxidized to a very unstable primary intermediate, which was further oxidized to a secondary, more stable intermediate. The formation of the secondary intermediate depended upon the presence of molecular oxygen. This intermediate readily converted into two compounds in equimolar amounts (designated A and B). The primary, very unstable intermediate was readily reduced again to alpha-T by treatment with LiAlH4 or ascorbic acid. However, the secondary intermediate or the stable oxidation products could not be reduced to alpha-T. In the 10% aqueous acetonitrile, alpha-T was oxidized to alpha-tocopheryl quinone, alpha-tocopherol dimer and alpha-tocopherol dihydroxy dimer, and an unknown compound. In the aqueous medium, no intermediates were formed by the action of O2-. The results of this study indicate that the reaction of alpha-T with O2- under aprotic conditions is different from that observed under protic conditions.

alpha-Tocopherol oxidation mediated by superoxide anion (O2-). II. Identification of the stable alpha-tocopherol oxidation products.

The present paper describes the identification of two stable end products of alpha-tocopherol oxidation that were previously detected among the products of the reaction of alpha-tocopherol with superoxide anion (O2-) under aprotic conditions. One compound, previously designated compound A, was identified as trans-7-hydroxy-trans-8,8a-epoxy-alpha-tocopherone, and the other, designated compound B, was identified as cis-7-hydroxy-cis-8,8a-epoxy-alpha-tocopherone. It was also observed that under protic conditions (10% water in acetonitrile) the reaction of alpha-tocopherol with O2- did not produce compounds A and B, but rather alpha-tocopheryl quinone, alpha-tocopherol dimer, alpha-tocopherol dihydroxy dimer, and the previously designated compound C. Compound C was identified in the present study as alpha-tocopheryl-quinone-2,3-epoxide.

Separation of α-tocopherol and its oxidation products by high performance liquid chromatography.

A very sensitive high performance liquid chromatographic (HPLC) method was developed for the separation of α-tocopherol (α-T) and its five oxidation products: α-tocopheryl quinone (TQ), dimer (D), dihydroxy dimer (DHD), trimer (T) and 9-methoxy-α-tocopherone commonly called α-tocopheroxide (TO). The separation was achieved on a normal-phase silica-based column (Ultrasphere-Si), using a mobile phase of hexane/chloroform/isopropanol (95∶4.5∶0.5, v/v/v) at a flow rate of 0.4 ml/min, and the eluants were monitored simultaneously at their maximum absorptions using a variable-wavelength UV detector. The minmum detection limit is 0.01 µg for α-T, TQ and TO, 0.05 µg for DHD and D, and 0.1 µg for T/injection. This normal-phase method has the combined advantages of being very sensitive, fast and capable of separating all six compounds at the same time.

Calculated hydroxyl A2 sigma --> X2 pi (0, 0) band emission rate factors applicable to atmospheric spectroscopy.

A calculation of the A2 sigma --> X2 pi (0, 0) band emission rate factors and line center absorption cross sections of OH applicable to its measurement using solar resonant fluorescence in the terrestrial atmosphere is presented in this paper. The most accurate available line parameters have been used. Special consideration has been given to the solar input flux because of its highly structured Fraunhofer spectrum. The calculation for the OH atmospheric emission rate factor in the solar resonant fluorescent case is described in detail with examples and intermediate results. Results of this calculation of OH emission rate factors for individual rotational lines are on average 30% lower than the values obtained in an earlier work.

Formation and action of anticarcinogenic fatty acids.

Conjugated dienoic derivatives of linoleic acid (referred to by the acronym CLA) constitute a newly recognized class of anticarcinogenic fatty acids. Of the eight major CLA isomers, the cis-9, trans-11 isomer alone is incorporated into phospholipid and may be the most biologically relevant isomer. CLA exhibits potent antioxidant activity; evidence is presented indicating that CLA acts both as an in vitro and in vivo antioxidant. The formation of CLA in foods, and its possible biological significance in cell membranes, is discussed.

Effects of dietary conjugated linoleic acid on fatty acid composition, lipid oxidation, color, and water-holding capacity of pork loin.

The effects of dietary conjugated linoleic acid (CLA) on fatty acid composition, lipid oxidation, and pork quality were investigated. Pigs (n = 20) were fed a diet containing 0, 1, 2.5, or 5% CLA for 4 wk and slaughtered at 105 kg. The longissimus thoracis et lumborum muscle was collected at 24 h postmortem. Pork loin chops (3 cm thick) were packaged aerobically and stored at 4 degrees C for 7 d. Samples were analyzed for ultimate pH, intramuscular fat content, fatty acid composition, thiobarbituric acid-reactive substances, color (L*, a*, b*), and water-holding capacity. Dietary CLA reduced the concentration of linoleic acid and increased CLA concentration in intramuscular fat of pork loin (P < 0.05). The concentration of CLA in muscle was increased with dietary CLA level and did not change during storage. Thiobarbituric acid-reactive substance value of control was higher than that of the CLA-fed groups (P < 0.05). Intramuscular fat content was increased by dietary CLA, and less purge loss was observed with samples from CLA-fed pigs (P < 0.05). Dietary CLA improved the color stability of pork loin during cold storage. After 7 d, lightness (L*) and yellowness (b*) of the 5% CLA-fed group were significantly lower than those of control (P < 0.05). The results indicated that the water-holding capacity of pork loin was increased with increased intramuscular fat content apparently caused by dietary CLA. Also, the data indicated that color stability of pork was improved with inhibition of lipid oxidation and changing of fatty acid composition by dietary CLA.

Effects of conjugated linoleic acid on color and lipid oxidation of beef patties during cold storage.

The effects of conjugated linoleic acid (CLA) on color and lipid oxidation of beef patties were investigated. Ground beef was divided into three batches. The control patties were prepared with 90% lean meat and 10% tallow. The second treatment consisted of 90% lean meat with 9.5% tallow+0.5% CLA sources. The third treatment consisted of 90% lean meat with 8% tallow+2% CLA sources. The patties were wrap-packaged and then stored at 4° for 14 days. The CLA concentration significantly increased (P<0.05) by substituting CLA sources for fat. Storage of the patties did not alter the CLA concentration in beef patties. The treatment substituted with CLA sources had significantly lower TBARS (2-thiobarbituric acid-reactive substances) values (P<0.05) than the control. For oxymyoglobin contents and a* value, substituted CLA sources treatments had significantly higher values than the control. However, L* value significantly increased by substituting CLA sources for fat.

Inhibition of 7,12-dimethylbenz[a]anthracene induced mouse skin carcinogenesis by Artemisia capillaris.

Anticarcinogenic activity of medicinal herbs (Artemisia capillaris, Taxus cuspidata, Anthriscus sylveatris, and Curcuma longa) was examined for 7,12-dimethylbenz[a]anthracene (DMBA)-induced mouse skin carcinogenesis. Four types of solvent fractions (hexane, chloroform, ethyl acetate, and butanol) were prepared from the methanolic extract of medicinal herbs. The cytotoxicity and anticarcinogenic activities of solvent fractions were examined for mouse leukemia L1210 cancer cells and for female ICR mouse epidermal carcinogenesis induced by DMBA, respectively. The chloroform fraction of Artemisia capillaris, Taxus cuspidata, and Anthriscus sylveatris was more toxic to L1210 cells than other solvent fractions. The chloroform fraction of Artemisia capillaris markedly reduced the number of tumors/mouse and tumor incidence relative to that of other medicinal herbs tested. Major active chemical constituents in the chloroform fraction of Artemisia capillaries were found to be camphor, 1-borneol, coumarin, and achillin when analyzed by TLC and GC-MS. These results suggest that Artemisia capillaris was the most effective anticarcinogenic medicinal herb for DMBA-induced mouse epidermal carcinogenesis among 4 medicinal herbs tested, and the effect might be attributed to chemical compounds of camphor, 1-borneol, coumarin, and achillin.

Growth inhibition of osteosarcoma cell MG-63 by a mixture of trans,trans conjugated linoleic acid isomers: possible mechanistic actions.

The growth inhibitory effect of a mixture of t,t conjugated linoleic acid isomers (t,t CLA) was investigated in the human osteosarcoma cell MG-63, with references to c9,t11 and t10,c12 CLA isomers. The t,t CLA effectively induced a cytotoxic effect in a time-dependent (0 to 6 d) and concentration-dependent (0 to 40 microM) manner, as compared to the reference and control treatments. The apoptosis and cell cycle related parameters were measured on the cells treated with 40 microM t,t CLA for 4 d. Flow cytometric analysis revealed that the t,t CLA treatment effectively increased the proportion of apoptotic cells with a low DNA content (sub G0/G1) and a marked loss of cells from the G0/G1 phase of the cell cycle, relative to other treatments. The occurrence of the characteristic morphological changes and DNA fragmentation confirmed the apoptosis. The level of Bax protein was increased, whereas the Bcl-2 expression was reduced. In addition, cytochrome c was released from the mitochondria into the cytosol, and the activation of caspase-3 led to the cleavage of poly (ADP-ribose) polymerase (PARP). Moreover, the composition of linoleic and arachidonic acids in membrane was decreased by increase in t,t CLA. These findings suggest that t,t CLA incorporation in membrane activates a mitochondria-mediated apoptosis pathway that can enhance the antiproliferative effect of t,t CLA in the osteosarcoma cells.

Antibacterial compounds from Rose Bengal-sensitized photooxidation of beta-caryophyllene.

The bactericidal activity of beta-caryophyllene photooxidized in acetonitrile was examined for 5 Gram-positive and 4 Gram-negative foodborne bacteria. The beta-caryophyllene (5 x 10(-3) M) was photooxidized in acetonitrile containing Rose Bengal (6.25 x 10(-4) M) for 24 h under fluorescent light. The antimicrobial activities of samples were determined by the agar-disc diffusion method. Active compounds from the photooxidized beta-caryophyllene were isolated by silica gel open-column chromatography in conjunction with recyclic high-performance liquid chromatography (HPLC), and were identified by infrared spectroscopy, mass spectrometry, and nuclear magnetic resonance spectroscopy. The antimicrobial activity of the photooxidized beta-caryophyllene was strongly enhanced against Streptococcus aureus and Vibrio parahaemolyticus, relative to that of beta-caryophyllene, but was weakly enhanced against other tested bacteria. The photooxidized beta-caryophyllene contained 3 active compounds specific for these 2 bacteria, and the compounds were identified as 5-alpha-hydroxycaryophylla-4(12),8(13)-diene, 5-alpha-hydroxycaryophylla-3(4),8(13)-diene, and 5-beta-hydroxycaryophylla-3(4),8(13)-diene. The efficacies of these compounds were similar, but the efficacy of 5-beta-hydroxycaryophylla-3(4),8(13)-diene was slightly higher than that of the other 2 compounds. The results suggest that the antibacterial activities of beta-caryophyllene for S. aureus and V. parahaemolyticus could be enhanced by dye-sensitized photooxidation, and the photooxidized beta-caryophyllene and the isolated individual compounds could be useful antimicrobial agents to control the growth of S. aureus and V. parahaemolyticus in certain food systems.

Conjugated dienoic derivatives of linoleic acid: a new class of anticarcinogens.

Evidence establishing the anticarcinogenic activity of the conjugated dienoic derivatives of linoleic acid (CLA) is reviewed. Our findings demonstrate that CLA is a potent antioxidant and that the c-9,t-11 CLA isomer is selectively incorporated into cellular phospholipid, which may at least in part explain the anticarcinogenic activity of CLA. Dietary sources of CLA include grilled beef, cheese, and related foods. Another source of CLA is its endogenous generation via the carbon centered free radical oxidation of linoleic acid. We propose that the formation and action of CLA represents a previously unrecognized in situ defense mechanism against membrane attack by oxygen radicals.

Newly recognized anticarcinogenic fatty acids.

Evidence leading to the recognition of the anticarcinogenic activity of the conjugated dienoic derivatives of linoleic acid (CLA) is reviewed. New data indicate that CLA has potent antioxidant activity. Because the c-9, t-11 CLA isomer is esterified in phospholipid, it may represent a heretofore unrecognized in situ defense mechanism against membrane attack by oxygen radicals.

Anticarcinogens from fried ground beef: heat-altered derivatives of linoleic acid.

Fried ground beef contains substances that inhibit mutagenesis in bacteria and the initiation of epidermal carcinogenesis in mice by 7,12-dimethylbenz [a]anthracene (DMBA). The inhibitors apparently act at least in part via inhibition of cytochrome P-450 activity. A highly purified fraction that inhibited cytochrome P-450 activity in vitro was isolated by HPLC and characterized by GC-MS, and by UV and proton NMR spectroscopy. The fraction contained four isomeric derivatives of linoleic acid each containing a conjugated double-bond system (designated CLA). Synthetically prepared CLA (containing all four isomers) was tested for anti-initiation activity in the two-stage mouse epidermal carcinogenesis system. Seven days, 3 days and 5 min prior to DMBA application, CLA was applied at doses of 20, 20 and 10 mg respectively. Control mice were treated similarly with linoleic acid or solvent (acetone). One week after initiation, and twice weekly thereafter, all mice were treated with 12-O-tetradecanoylphorbol-13-acetate to effect tumor promotion. There was no difference in tumor incidence or yield between linoleic acid-treated mice and solvent-treated control mice. By contrast, the CLA-treated mice developed only about half as many papillomas and exhibited a lower tumor incidence compared with the control mice.

Dietary conjugated linoleic acid (CLA) induces apoptosis of colonic mucosa in 1,2-dimethylhydrazine-treated rats: a possible mechanism of the anticarcinogenic effect by CLA.

One of the objectives of the present study was to investigate whether 1 % conjugated linoleic acid (CLA) in the diet reduced tumour incidence in the colon of 1,2-dimethylhydrazine (DMH)-treated rats. Colon cancer was induced by injecting 6-week-old, male, Sprague-Dawley rats with 15 mg/kg DMH twice per week for 6 weeks. They were fed either 1 % CLA or a control diet ad libitum for 30 weeks. Dietary CLA significantly decreased colon tumour incidence (P<0.05). Our second objective was to investigate whether apoptosis in the colon mucosa of DMH-treated rats was affected by the amount of dietary CLA and whether the changes in apoptosis were related to those in fatty acid-responsive biomarkers. For this purpose, rats were killed after being fed a diet containing 0 %, 0.5 %, 1 % or 1.5 % CLA for 14 weeks. CLA was undetected in the mucosa of rats fed the 0 % CLA diet and increased to 5.9 mg/g phospholipid in rats fed the 0.5 % diet. The apoptotic index estimated by the terminal deoxynucleotidyl transferase-mediated dUTP nick and labelling technique was increased by 251 % and the 1,2-diacylglycerol content was decreased by 57 % in rats fed 0.5 % CLA. No further changes in these variables were observed when CLA in the diet was raised to 1.0 % or 1.5 %. However, dietary CLA decreased mucosal levels of prostaglandin E2, thromboxane B2 and arachidonic acid in a dose-dependent manner. The present data indicate that dietary CLA can inhibit DMH-induced colon carcinogenesis by mechanisms probably involving increased apoptosis.