Prooxidant and antioxidant activity of vitamin E analogues and troglitazone

The order of antioxidant effectiveness of low concentrations of vitamin E analogues, in preventing cumene hydroperoxide-induced hepatocyte lipid peroxidation and cytotoxicity, was 2,2,5,7,8-pentamethyl-6-hydroxychromane (PMC) > troglitazone > Trolox C > alpha-tocopherol > gamma-tocopherol > delta-tocopherol. However, vitamin E analogues, including troglitazone at higher concentrations, induced microsomal lipid peroxidation when oxidized to phenoxyl radicals by peroxidase/H2O2. Ascorbate or GSH was also cooxidized, and GSH cooxidation by vitamin E analogue phenoxyl radicals was also accompanied by extensive oxygen uptake and oxygen activation. When oxidized by nontoxic concentrations of peroxidase/H2O2, vitamin E analogues except PMC also caused hepatocyte cytotoxicity, lipid peroxidation, and GSH oxidation. The prooxidant order of vitamin E analogues in catalyzing hepatocyte cytotoxicity, lipid peroxidation, and GSH oxidation was troglitazone > Trolox C > delta-tocopherol > gamma-tocopherol > alpha-tocopherol > PMC. A similar order of effectiveness was found for GSH cooxidation or microsomal lipid peroxidation but not for ascorbate cooxidation. Except for troglitazone, the toxic prooxidant activity of vitamin E analogues was therefore inversely proportional to their antioxidant activity. The high troglitazone prooxidant activity could be a contributing factor to its hepatotoxicity. We have also derived equations for three-parameter quantitative structure-activity relationships (QSARs), which described the correlation between antioxidant and prooxidant activity of vitamin E ananlogues and their lipophilicity (log P), ionization potential (E(HOMO)), and dipole moment.     

Molecular and cellular mechanisms of apolipoprotein E4 neurotoxicity and potential therapeutic strategies

Apolipoprotein (apo) E is a multifunctional protein that has central roles in lipid metabolism and neurobiology. It has three common isoforms (apoE2, apoE3 and apoE4) that have different effects on lipid and neuronal homneostasis. Unlike apoE3, tie most common isoform, apoE4 is a major risk factor for Alzheimer's disease (AD). Although the mechanisms underlying the actions of apoE4 in AD pathogenesis are still poorly understood, emerging data strongly suggest that apoE4, with its multiple cellular origins and multiple structural and biophysical properties, contributes to this disease by interacting with different factors through various pathways. Thus, multiple molecular and cellular mechanisms should be considered in developing anti-AD drugs that target apoE4.     

高效液相色谱法测定复方维胺酯维E乳膏中维生素E的含量

目的　采用HPLC测定复方维胺酯维E乳膏中维生素E的含量。方法　以Symmetry C18为分析柱,甲醇为流动相,检测波长为285nm。结果　平均回收率分别为99.8%。结论　方法简便,结果准确,可用于该制剂质量控制     

气相色谱法测定尿素维E乳膏中维生素E的含量

目的建立一种用气相色谱法测定尿素维E乳膏中维生素E含量的方法。方法采用硅酮OV-17填充柱(涂布浓度为2%);柱温:275℃;进样口温度:295℃;FID检测器,检测器温度320℃。结果维生素E在2.00~6.06μg范围内呈良好线性关系(r=0.9992),平均加样回收率为97.1%,RSD为1.4%(n=9)。结论该法简便快速,结果准确,可以有效地控制该药品的质量。     

Protease-inhibitory activities of leupeptin analogues

Thirty analogues of leupeptin were synthesized and examined for their inhibitory activities against trypsin, papain, plasmin, kallikrein, thrombin and urokinase in vitro. Benzoyl- and alpha-naphthalenesulfonyl-L-leucyl-L-argininal were 8 times more inhibitory to papain, benzyloxycarbonyl-L-pyroglutamyl-L-leucyl-L-argininal 10 times more to trypsin and plasmin, and DL-2-pipecolyl-L-leucyl-L-argininal 25 times more to kallikrein than leupeptin. Against urokinase, only L-pyroglutamyl-L-leucyl-L-argininal exhibited a potent inhibitory activity. alpha-Naphthalensulfonyl-, dansyl- and benzyloxycarbonyl-(2S,3R)-3-amino-2-hydroxy-4-phenylbutyryl-L-leucyl-L- argininal were inhibitory to thrombin.     

Inhibitory effects of ascorbic acid,vitamin E,and vitamin B-complex on the biological activities induced by Bothrops venom

Context: Natural compounds have been widely studied with the aim of complementing antiophidic serum therapy.

Objective: The present study evaluated the inhibitory potential of ascorbic acid and a vitamin complex, composed of ascorbic acid, vitamin E, and all the B-complex vitamins, on the biological activities induced by snake venoms.

Material and methods: The effect of vitamins was evaluated on the phospholipase, proteolytic, coagulant, and fibrinogenolytic activities induced by Bothrops moojeni (Viperidae), B. jararacussu, and B. alternatus snake venoms, and the hemagglutinating activity induced by B. jararacussu venom.

Results: The vitamin complex (1:5 and 1:10 ratios) totally inhibited the fibrinogenolytic activity and partially the phospholipase activity and proteolytic activity on azocasein induced by the evaluated venoms. Significant inhibition was observed in the coagulation of human plasma induced by venoms from B. alternatus (1:2.5 and 1:5, to vitamin complex and ascorbic acid) and B. moojeni (1:2.5 and 1:5, to vitamin complex and ascorbic acid). Ascorbic acid inhibited 100% of the proteolytic activities of B. moojeni and B. alternatus on azocasein, at 1:10 ratio, the effects of all the venoms on fibrinogen, the hemagglutinating activity of B. jararacussu venom, and also extended the plasma coagulation time induced by all venoms analyzed.

Discussion and conclusion: The vitamins analyzed showed relevant in vitro inhibitory potential over the activities induced by Bothrops venoms, suggesting their interaction with toxins belonging to the phospholipase A₂, protease, and lectin classes. The results can aid further research in clarifying the possible mechanisms of interaction between vitamins and snake enzymes.     

高效液相色谱法测定维生素E乳中维生素E的含量

目的建立测定维生素E乳中维生素E含量测定的方法。方法采用SHISEIDO CAPCELL PAK MGⅡ C18色谱柱,以甲醇为流动相;流速：1.0ml/min;检测波长：285nm。结果维生素E在浓度在0.133～0.931mg/ml内与峰面积具有良好的线性关系,平均回收率为100.5%,RSD=1.0%。结论本方法测定维生素E乳中维生素E含量简便、快速、准确。     

HPLC法测定维生素E乳膏中维生素E的含量

目的:建立HPLC测定维生素E乳膏中维生素E含量的方法.方法:采用反相高效液相色谱法.色谱柱为DiamonsilTM C18柱(200 mm×4.6mm,5 um),流动相为甲醇-异丙醇(80:20),流速为1.0 ml/min.检测波长为284 nm.结果:维生素E在149.39-448.16ug/ml范围内,峰面积与浓度呈良好线性(r=0.999 9),测得维生素E平均回收率为100.84%,RSD为0.56%(n=9).结论:本方法准确可靠,可有效控制产品质量.     

Prostaglandin E receptor subtypes in smooth muscle: agonist activities of stable prostacyclin analogues.

The agonist activities of a range of prostaglandin analogues on smooth muscle preparations sensitive to prostaglandin E2 (PGE2) have been investigated. When necessary thromboxane-like activity was eliminated using the thromboxane receptor antagonists EP 045 and EP 092. On the bullock iris sphincter, rat stomach fundus and guinea-pig trachea, (+/-) omega-tetranor-16-p-chlorophenoxy PGE2 (ICI 80205) and 16,16-dimethyl PGE2 were more active contractile agents than PGE2, whereas for relaxant activity on the cat trachea, guinea-pig trachea and dog hind limb arterial vessels in vivo the order of potency was reversed. 11-Deoxy PGE1 exhibited greater relaxant than contractile activity when compared to PGE2. Iloprost and 6a-carba-delta 6,6aPGI1 (potent mimetics of PGI2) showed high contractile activity on the PGE-sensitive preparations. PGI2 was less active and another potent PGI2 mimetic, ZK 96480, showed only very weak activity. When tested, the dibenzoxazepines SC 19220 and SC 25191 blocked the contractile actions of iloprost and 6a-carba-delta 6,6aPGI1 and those of PGE2 and 16,16-dimethyl PGE2 to similar extents. Each of the PGI2 analogues showed weak activity on the relaxant systems. On the proximal portion of the ascending colon of the rat, PGI2, iloprost, 6a-carba-delta 6,6aPGI1 and ZK 96480 always inhibited spontaneous activity at nanomolar concentrations. PGE2 and PGE1 showed weak contractile activity. The distal portion of the ascending colon was more responsive to the contractile action of PGE analogues: both iloprost and 6a-carba-delta 6,6aPGI1 showed evidence of contractile activity, whereas PGI2 and ZK 96480 always inhibited spontaneous activity. Evidence was obtained that the rat stomach fundus also contains a PGF receptor; (+/-) omega-tetranor-16-m-trifluoromethylphenoxy PGF2 alpha (ICI 81008) acted as a specific agonist. PGF2 alpha and its omega-tetranor-16-p-fluorophenoxy analogue produced a higher maximum response that ICI 81008 probably due to their additional agonist action at the PGE receptor. The data support the hypothesis that there are two subtypes of the PGE receptor. ZK 96480 has minimal activity on both receptor subtypes and appears to be a highly specific PGI2 mimetic.     

用RP-HPLC法同时测定珍珠维E乳膏中维生素B6和维生素E的含量

目的:建立同时测定珍珠维E乳膏中维生素B6和维生素E的RP-HPLC法。方法:色谱柱为Kromasil-C18柱(150 mm×4.6 mm,5μm),流动相为甲醇-0.2%磷酸溶液,梯度洗脱,检测波长285 nm,流速1.0 ml/min。样品在90%乙醇中用超声破碎仪破碎10 min,然后50℃水浴加热5 min处理。结果:维生素B6和维生素E的线性范围分别为1~50μg/ml(r=0.999 9,n=5)和1~50μg/ml(r=0.999 8,n=5);平均回收率分别为(95.32±0.27)%(n=9)和(96.91±0.85)%(n=9)。3批样品中维生素B6和维生素E的含量分别为标示量的(94.91±0.77)%和(96.87±0.85)%。结论:该方法适用于珍珠维E乳膏中维生素B6和维生素E的含量测定。     

用HPLC法测定维生素E乳剂中维生素E的含量

维生素E乳剂是第二军医大学长征医院药学部研制的皮肤科制剂，主要用于修复破损细胞、溶解角质、保护皮肤，是治疗各种季节性皮炎、激素依赖性皮炎、鱼鳞病、剥脱性角质疏松症、老年性外阴瘙痒、放射性皮炎以及剥脱性唇炎等皮肤疾病的有效药物。该制剂的主要成分为维生素E，对维生素E的含量测定的方法有一阶导数光谱法、二阶导数光谱法、气相色谱法及HPLC法等。本研究采用HPLC法测定维生素E乳剂中维生素E的含量，操作简单、准确，具有良好的重现性，为该制剂的质量控制提供方法。     

Biological activities of Bv8 analogues

1 The small protein Bv8, secreted by the skin of the frog Bombina variegata, belongs to a novel family of secreted proteins whose orthologues have been identified in snakes (MIT) and in mammals (prokineticins (PKs)). A characteristic feature of this protein family is the same N-terminal sequence, AVITGA, and the presence of 10 cysteines with identical spacing in the C-terminal domain. Two closely related G protein-coupled receptors that mediate signal transduction of Bv8/PKs have been cloned (PK-R1 and PK-R2). In mammals, the Bv8/PK protein family is involved in a number of biological activities such as ingestive behaviours, circadian rhythms, angiogenesis and pain sensitization. 2 In an attempt to identify the structural determinants required for the pronociceptive activity of Bv8, we prepared Bv8 derivatives lacking one (des-Ala-Bv8) or two (des-Ala-Val-Bv8) residues from the N-terminus. 3 des-Ala-Bv8 displayed a receptor affinity five times lower than that of Bv8, it was five times less potent in inducing [Ca(2+)](i) transients and in causing p42/p44 MAPK phosphorylation in CHO-cells expressing PK-R1 and PK-R2. Moreover, dA-Bv8 was about 20 times less potent than Bv8 in inducing hyperalgesia in rats. 4 The deletion of the first two amino acids of Bv8 abolished any biological activity both 'in vitro' and 'in vivo'; however, des-AlaVal-Bv8 is able to antagonize the Bv8-induced hyperalgesia, binding the PK-Rs on peripheral and central projections of the primary sensitive neurons.     

Immunological properties of vitamin D analogues and metabolites.

This commentary has attempted to describe some of the new aspects of our knowledge of the immunological properties of 1 alpha,25(OH)2D3, the physiologically active metabolite of vitamin D3, and its new analogues. These analogues will, in the future, serve as tools to increase our understanding of the role of vitamin D in immunobiology, not only in basal research but also, hopefully, in the therapy of immune-mediated diseases.     

Effect of natural analogues of trans-resveratrol on cytochromes P4501A2 and 2E1 catalytic activities

The aim was to assess the inhibitory effect of a series of naturally occurring trans-resveratrol analogues on cytochromes P450, namely CYP1A2 and CYP2E1, in vitro in order to analyse any structure-activity relationships. 3,5-Dimethoxy-4'-hydroxy-trans-stilbene (pterostilbene), 3,4',5-trimethoxy-trans-stilbene (TMS), 3,4'-dihydroxy-5-methoxy-trans-stilbene (3,4'-DH-5-MS) and 3,5-dihydroxy-4'-methoxy-trans-stilbene (3,5-DH-4'-MS) inhibited the activity of CYP1A2, with K(i) = 0.39, 0.79, 0.94 and 1.04 microM, respectively. Piceatannol (3,3',4,5'-tetrahydroxy-trans-stilbene) was the least potent inhibitor of CYP1A2 with a K(i) = 9.67 microM. Piceatannol and TMS in the concentration range 1-100 microM did not inhibit CYP2E1 activity. The activity of this enzyme likewise was not significantly influenced by pterostilbene and 3,5-DH-4'-MS with IC(50) > 100 microM, whereas 3,4'-DH-5-MS appeared to be a moderately potent, competitive inhibitor of CYP2E1 (K(i) = 42.6 microM). Structure-activity relationship analysis leads to the conclusion that the substitution of hydroxy groups of resveratrol with methoxy groups increases the inhibition of CYP1A2, yet the number and position of methylation are not essential. However, the 4'-hydroxy group in trans-resveratrol and its analogues may play an important role in the interaction with a binding site of CYP2E1.     

Effect of natural analogues of trans-resveratrol on cytochromes P4501A2 and 2E1 catalytic activities

The aim was to assess the inhibitory effect of a series of naturally occurring trans-resveratrol analogues on cytochromes P450, namely CYP1A2 and CYP2E1, in vitro in order to analyse any structure–activity relationships. 3,5-Dimethoxy-4′-hydroxy-trans-stilbene (pterostilbene), 3,4′,5-trimethoxy-trans-stilbene (TMS), 3,4′-dihydroxy-5-methoxy-trans-stilbene (3,4′-DH-5-MS) and 3,5-dihydroxy-4′-methoxy-trans-stilbene (3,5-DH-4′-MS) inhibited the activity of CYP1A2, with K_i?=?0.39, 0.79, 0.94 and 1.04?µM, respectively. Piceatannol (3,3′,4,5′-tetrahydroxy-trans-stilbene) was the least potent inhibitor of CYP1A2 with a K_i?=?9.67?µM. Piceatannol and TMS in the concentration range 1–100?µM did not inhibit CYP2E1 activity. The activity of this enzyme likewise was not significantly influenced by pterostilbene and 3,5-DH-4′-MS with IC₅₀?>?100?µM, whereas 3,4′-DH-5-MS appeared to be a moderately potent, competitive inhibitor of CYP2E1 (K_i?=?42.6?µM). Structure–activity relationship analysis leads to the conclusion that the substitution of hydroxy groups of resveratrol with methoxy groups increases the inhibition of CYP1A2, yet the number and position of methylation are not essential. However, the 4′-hydroxy group in trans-resveratrol and its analogues may play an important role in the interaction with a binding site of CYP2E1.     

Pharmacology and therapeutic use of vitamin D and its analogues

The term vitamin D is generally used to describe a number of chemically related compounds with common antirachitic properties, but which have differences in the rapidity of their action, the way they are produced in the body, and the conditions under which their results are optimal. Ergocalciferol, cholecalciferol, 25-hydroxycholecalciferol (calcifediol), dihydrotachysterol, 1 alpha-hydroxycholecalciferol (alfacalcidol), and 1,25-dihydroxycholecalciferol (calcitriol) are currently the most commonly used vitamin D metabolites. In man, cholecalciferol produced on the skin and the fraction obtained from the diet in the gastrointestinal tract are converted in the liver to 25-hydroxycholecalciferol and then in the kidney to 1,25-dihydroxycholecalciferol. The demonstration of these metabolic pathways has helped to elucidate the aetiology of such conditions a hepatobiliary osteodystrophy, drug-induced anticonvulsant osteomalacia, the hypocalcaemia of hypoparathyroidism and above all azotaemic osteodystrophy. In the therapy of azotaemic osteodystrophy, the period of 'vitamin D resistance' when large doses of vitamin D2 and D3 had to be used is now over, and these patients can be efficiently and successfully treated with almost physiological doses of 1 alpha-hydroxycholecalciferol and 1,25-dihydroxycholecalciferol. Attention to diet, calcium supplements and oral phosphate binders are also important. During repetitive haemodialysis, the above principles still hold true, but in some of these patients an osteomalacic syndrome resistant to 1,25-dihydroxycholecalciferol has been recognised. These patients readily become hypercalcaemic when given 1,25-dihydroxycholecalciferol and their fractures and osteomalacia do not improve. Aluminium intoxication, possibly related to the use of impure dialysis fluid, is currently thought to be the most likely explanation of this dialysis osteomalacic syndrome.