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Chapter 7 Vitamins 维生素

Chapter 7 Vitamins 维生素. 主要介绍各种维生素的结构、性质和 功能 ， 维生素与辅酶的关系 , 维生素缺乏症。. 广州中医药大学 生化教研室 吴映雅. Introduction.

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Chapter 7 Vitamins 维生素

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  1. Chapter7Vitamins 维生素 主要介绍各种维生素的结构、性质和功能，维生素与辅酶的关系,维生素缺乏症。 广州中医药大学 生化教研室 吴映雅

  2. Introduction Definition：Vitaminsare organic nutrients that are required in small quantities for a variety of biochemical functions and which, generally, cannot be synthesized by the body and must therefore be supplied by the diet食物.

  3. history The early history of vitamins can be traced to observations that certain disease could be cured by a supplement of another foodstuff. Eg: the ancient Arab physicians and their successors valued the use of liver to cure night blindness, the North America Indian knew that scurvy(坏血病） could be treated by a tea made from cedar(雪松 ) leaves. In seventeenth century, it was standard procedure for the British Navy to provide lemon juice for its sailors to prevent scurvy.

  4. history • Thiamine was discovered in 1912 & was thought to be a vital amine compound & thus the term vitamin was invented • Vita=vital for life • Min=amine

  5. Properties 特点： • 1. They are not used for energy supply, but have Important roles in regulating metabolism and maintaining physiological functions of the body. 2. They are low-molecular-weight organic compounds. • 3. Generally, they cannot be synthesized in body and must be supplied by the diet in small amounts . • 4. Absence or relative deficiency of vitamins leads to characteristic deficiency states and diseases. But if any vitamin is so much in excess of the body’s metabolic capacity, there maybe signs of toxicity.

  6. Classification分类 • lipid-soluble vitamin: soluble in non-polar organic solvents • water-soluble vitamin: soluble in aqueous solvents

  7. Essential Vitamins For Human Being vitamins water -soluble lipid-soluble Vit C Vit B A, D, E, K B1, B2, B6, B12, PP, patothenic acid泛酸，folic acid叶酸,biotin生物素, lipoic acid硫辛酸

  8. 维生素缺乏病的原因 • 1、进食量不足2、吸收障碍3、需要量增加4、服用某些药物 5、生物体特异缺陷

  9. Section I Water-soluble Vitamins水溶性维生素 Common features: ﹡1.Water soluble ﹡2.Easy to be discharged through urine. Rarely accumulated to the toxic concentrations. ﹡3.Their storage is limit. Must be provided regularly. Vitamin B12 is the only water-soluble vitamin that can be stored in the liver for many years.

  10. （一）维生素C（抗坏血酸 ascorbic acid） • Water soluble • sour taste (acid) • Six-carbon polyhydroxy compound • Strong antioxidant 六碳、多羟基化合物.酸性 、强还原性

  11. 1535 Jacques Cartier and his sailors were cured by Newfoundland Indians by drinking the extract from spruce云杉treeneedles. • 1747, British naval surgeon prescribed lime酸橙to sailors to prevent scurvy. Thus the slang limey for British sailor.

  12. 1.Structure 结构 或 Ascorbic acid ( vitamin C )

  13. 2．性质 易被氧化（较强的抗氧化剂） 水溶液极不稳定，易被热及氧化破坏 在组织中有两种形式存在：还原型与脱氢型。可以通过氧化还原反应互变，因而都具有生理活性。若脱氢型继续氧化或水解，则其活性丧失。

  14. Vitamin C Reduced state Dehydro-vitaminC Oxidation state

  15. 3．食物来源(Food Sources of Vitamin C) When dietitians say “vitamin C,” people think “oranges.”

  16. Food Sources of Vitamin C----fresh fruit and vegetables新鲜蔬菜、水果 But these foods are also rich in vitamin C.

  17. 4.生化功能 • (1.)Hydroxylation参与体内的羟化作用 Ascorbic acid is required for the activities of some hydroxylase羟化酶. 代谢物的羟基化是生物氧化biological oxidation的一种方式。而Vit C在羟基化中起着必不可少的辅助因子的作用。 • 胶原collagen的合成： 维生素C

  18. 羟脯氨酸hydroxyproline和羟赖氨酸hydroxylysine为胶原蛋白collagen所特有，羟脯氨酸是维持胶原蛋白四级结构的关键物质。羟脯氨酸hydroxyproline和羟赖氨酸hydroxylysine为胶原蛋白collagen所特有，羟脯氨酸是维持胶原蛋白四级结构的关键物质。 • 二者分别是在胶原脯氨酸羟化酶hydroxylase和胶原赖氨酸羟化酶的作用下由脯氨酸proline和赖氨酸lysine羟化而成。Vit C是这两种酶的辅助因子。故缺乏Vit C可造成胶原蛋白合成障碍。

  19. Collagen Synthesis

  20. Vitamin C deficiency维生素C缺乏症： • scurvy 坏血病: • It's syptoms included swollen and bleeding gums and loose teeth, brittle脆hair and nails, tiredness, problem in the joints • 毛细血管脆性capillary fragility增加； • 牙龈肿胀、出血； • 鼻衄、月经过多menorrhagia； • 骨钙化calcification不正常及伤口愈合缓慢

  21. Vitamin C Deficiency Signs 齿龈炎 瘀斑 出血

  22. Pinpoint Bleeding in Scurvy 1

  23. Pinpoint Bleeding from Scurvy 2

  24. Hydroxylation参与体内的羟化作用 • 胶原的合成： • 参与胆固醇cholesterol的转化transformation： • Cholesterol → →→bile acid Hydroxylation 维生素C

  25. 参与芳香族氨基酸aromatic amino acids 代谢： 在苯丙氨酸phenylalanine转变为酪氨酸tyrosine，酪氨酸转变为羟苯丙酮酸hydroxyphenylpyruvatate，经羟化、脱羧、移位等步骤转变为尿黑酸homogentisate 时亦需Vit C参与。所以当Vit C缺乏时将导致苯酮尿症，黑尿酸症等。 • Vit C还参与肝脏生物转化biological transformation过程中的许多羟化反应。

  26. (2)参与体内的氧化还原反应 ① Vit C能起到保护巯基mercapto的作用： 溶酶体膜

  27. ②促进抗体antibody的生成 • 促进造血作用 ----使难以吸收的Fe3+还原成易吸收的Fe2+

  28. (3)其它生化功能 ①降低血浆胆固醇 ②防癌：理论上推测

  29. THERAPEUTIC USES • Cardiovascular diseases • Cataracts白内障 • Diabetes Mellitus • Cancer prevention • Common cold • Lead铅toxicity

  30. 二、Vitamin B1（硫胺素thiamine） （一）structure & properties化学结构及性质 硫胺素: 含S、-NH2 性质： 白色、耐热，加碱破坏 （烹调不当易损失）

  31. Active form活性形式：thiamin pyrophosphate 焦磷酸硫氨素（ＴＰＰ） • Thiamin is rapidly converted to TPP in the brain and liver by a specific enzymes, thiamin diphosphotransferase硫胺素二磷酸转移酶.

  32. Food Sources of thiamin 来源： • Unrefined cereal grains and meat；seeds, nuts, legums豆类 • Recommended Dietary Allowance(RDA): M:1.2mg/d， F:1.1mg/d

  33. （三）生化作用： • 1、Vit B1→TPP→α酮酸脱氢酶系的辅酶→糖代谢等。 eg: TPP是丙酮酸脱羧酶pyruvate decarboxylase和α-酮戊二酸脱羧酶α-ketoglutarate decarboxylase的辅酶，参与α-酮酸的氧化脱羧。 • 2、 TPP is necessary as a cofactor for the reactions of the pentose phosphate pathway 是戊糖磷酸途径中转酮酶的辅助因子 • 3、抑制胆碱酯酶choline esteraseVit B1可抑制胆碱酯酶活性，使神经传导所需的乙酰胆碱acetylcholine不被破坏，保持神经的正常传导功能

  34. DEFICIENCY & USES • Severe thiamin deficiency can lead to: • Beri-Beri • Wernicke-Korsakoff syndrome综合征 臨床上會有神智不清、眼動障礙、眼振及厲害的搖晃等表现 • Thiamin is used for treatment of congestive充血性的heart failure心力衰竭& Alzheimer's disease as well as in cancer prevention.

  35. beriberi脚气病,末梢神经炎 脚气病，主要表现为神经血管系统的损害。 根据其典型症状临床上分为三型： 1.湿型脚气病：主要表现为心界扩大、心动过速、呼吸窘迫和下肢水肿。 2.干型脚气病：表现为腱反射异常、上行性多发性神经炎、肌肉乏力和疼痛、腓肠肌压痛等。 3.混合型脚气病：同时出现神经和心血管系统症状，见于严重缺乏者。

  36. Wet Beri-Beri

  37. RISK OF THIAMIN DEFICIENCY • Low intake & alcoholism酒精中毒 • Increased consumption: Malaria疟疾& AIDS • Excessive loss: hemodialysis血液透析and diuretics利尿剂 • Anti-thiamin factors: tea & coffee. • Thiaminases found in raw fish, raw shellfish & in silkworms.

  38. 三．Vitamin B2 (riboflavin核黄素) • （1）结构 含核醇ribitol，异咯嗪环isoalloxazine ring.可逆的氧化还原特性 碱性条件 + 光照，易破坏 核醇 异咯嗪环

  39. Food Sources of riboflavin ： Adequate amounts of B2 is present in eggs, milk, meat & cereals. • 广泛，动植物，动物性食物（肝、肾、心多） • 真菌类、紫菜、奶类、蛋类 • 酵母yeast RDA：M: 1.4mg/d， F: 1.2mg/d

  40. Active form： FMN，FAD • 生化作用：Vit B2→FMN、FAD→黄素酶类的辅基→受氢、脱氢、递氢作用→生物氧化. 有助于脂肪、糖类、蛋白质转化为能量，是修复和维护身体内部和外部皮肤健康必需的营养物质。 与视网膜感光作用有关。 FMN：Flavin mononucleotide黄素单核苷酸 FAD：Flavin adenine dinucleotide黄素腺嘌呤二核苷酸 ① 氧化型的FMN或FAD是黄色的，还原后成无色。 ② FMN或FAD有强烈的黄绿色荧光，还原后荧光消失。

  41. 缺乏症： Symptoms associated with riboflavin deficiency include, glossitis舌炎, seborrhea脂溢性皮炎, angular stomatitis口角炎, cheilosis唇炎 ， scrotitis阴囊炎 and photophobia畏光

  42. glossitis

  43. 四、VitPP/niacin,也称抗癞皮病维生素） （一）化学结构及性质 1、结构： 吡啶pyridine衍生物derivative： 尼克酸（烟酸, nicotinic acid） 尼克酰胺（烟酰胺, nicotinamide） 2、性质： 稳定，一般食物中含量较多 肝脏：色氨酸tryptophan→尼克酸，仍不足

  44. 尼克酸(烟酸) 尼克酰胺(烟酰胺) 吡啶-3-酰胺 nicotinamide 吡啶-3-羧酸 nicotinic acid

  45. Food Sources of Vit PP 食物来源： • Niacin is available in both animal & plant food and is made in the body from tryptophane色氨酸. 豆类、粮食、肝脏、肾、瘦肉、鱼、酵母、蘑菇 色氨酸在体内合成烟酸： 60mg色氨酸 = 1mg烟酸

  46. 生化作用：Vit PP→NAD、NADP→不需氧脱氢酶辅酶→递氢→生物氧化 缺乏症：癞皮病(pellagra) 皮炎dermatitis 腹泻diarrhea 痴呆dementia

  47. Pellagra

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