Vitamin natural sources

Several substances having vitamin K. activity have been isolated from natural sources. Vitamin Ki from alfalfa oil, is 2-methyl-3-phytyl-1,4-naphthoquinone. 

Pyridine carboxamide [98-92-0] (nicotinamide) (1) and 3-pyridine carboxylic acid [59-67-6] (nicotinic acid) (2) have a rich history and their early significance stems not from their importance as a vitamin but rather as products derived from the oxidation of nicotine. In 1867, Huber prepared nicotinic acid from the potassium dichromate oxidation of nicotine. Many years later, Engler prepared nicotinamide. Workers at the turn of the twentieth century isolated nicotinic acid from several natural sources. In 1894, Su2uki isolated nicotinic acid from rice bran, and in 1912 Funk isolated the same substance from yeast (1). 

As vitamin Bg is mainly located in the germ and aleurone layer in cereal grains polishing for the production of flour removes a substantial portion. White bread is therefore a poor source unless fortified. Some nonedible yeasts contain up to 38 mg/100 g dry weight vitamin B, the highest level of the natural sources (4,27). As a rule, these amounts are too low for cost-effective isolation. 

Fish-hver oil, Hver, milk, and eggs are good natural sources of the D vitamin. Most milk sold in the United States is fortified with manufactured vitamin D. Fish oil is the only commercial source of natural vitamin D, and the content of the vitamin varies according to species as well as geographically, ie, Adantic cod contain 100 lU/g where lU (International Unit) = 0.025 /ig of vitamin D, whereas oriental tuna (Percomofpk) contain 45,000 lU/g oil. 

Why put such extraordinary effort into the laboratory synthesis of a molecule so easily obtained from natural sources There are many reasons. On a basic human level, a chemist might be motivated primarily by the challenge, much as a climber might be challenged by the ascent of a difficult peak. Beyond the pure challenge, the completion of a difficult synthesis is also valuable for the way in which it establishes new standards and raises the field to a new level. If vitamin Bj2 can t>e made, then why can t any molecule found in nature be made Indeed, the three and a half decades that have... 

Vitamin C occurs as L-ascorbic acid and dihydroascorbic acid in fruits, vegetables and potatoes, as well as in processed foods to which it has been added as an antioxidant. The only wholly undisputed function of vitamin C is the prevention of scurvy. Although this is the physiological rationale for the currently recommended intake levels, there is growing evidence that vitamin C may provide additional protective effects against other diseases including cancer, and the recommended dietary allowance (RDA) may be increased in the near future. Scurvy develops in adults whose habitual intake of vitamin C falls below 1 mg/d, and under experimental conditions 10 mg/d is sufficient to prevent or alleviate symptoms (Bartley et al., 1953). The RDA is 60 mg per day in the USA, but plasma levels of ascorbate do not achieve saturation until daily intakes reach around 100 mg (Bates et al., 1979). Most of the ascorbate in human diets is derived from natural sources, and consumers who eat five portions, or about 400-500 g, of fruits and vegetables per day could obtain as much as 200 mg of ascorbate. 

SRB contains high-quality protein, oil, dietary fiber, polysaccharides, fat-soluble phytochemicals (plant derived bioactive compounds) and other bran nutrients. Rice bran and germ are the richest natural sources of B complex vitamins as well as E vitamins, polyphenols, several antioxidants and minerals. It is now available in the commercial food ingredient market as a safe and effective functional food and dietary supplement. 

Rice bran is the richest natural source of B-complex vitamins. Considerable amounts of thiamin (Bl), riboflavin (B2), niacin (B3), pantothenic acid (B5) and pyridoxin (B6) are available in rice bran (Table 17.1). Thiamin (Bl) is central to carbohydrate metabolism and kreb s cycle function. Niacin (B3) also plays a key role in carbohydrate metabolism for the synthesis of GTF (Glucose Tolerance Factor). As a pre-cursor to NAD (nicotinamide adenine dinucleotide-oxidized form), it is an important metabolite concerned with intracellular energy production. It prevents the depletion of NAD in the pancreatic beta cells. It also promotes healthy cholesterol levels not only by decreasing LDL-C but also by improving HDL-C. It is the safest nutritional approach to normalizing cholesterol levels. Pyridoxine (B6) helps to regulate blood glucose levels, prevents peripheral neuropathy in diabetics and improves the immune function. 

In the synthesis of vitamin A, the dependence on natural sources as well as steadily increasing production via /3-ionone as an intermediate have led to the development of a method for synthesizing citral from dehydrolinalool (see p. 37). More recent routes employ dehydrolinalool as the starting material for pseudoionone. Dehydrolinalool is converted into pseudoionone by using either diketene [92] or a suitably substituted acetoacetate (Carroll reaction) [93] ... 

The major dietary sources of retinol are dairy products, eggs and liver, while important sources of /3-carotene are spinach and other dark-green leafy vegetables, deep orange fruits (apricots, cantaloupe) and vegetables (squash, carrots, sweet potatoes, pumpkin). The richest natural sources of vitamin A are fish liver oils, particularly halibut and shark. 

Vitamin C Is the Synthetic Vitamin as Good as the Natural One A claim put forth by some purveyors of health foods is that vitamins obtained from natural sources are more healthful than those obtained by chemical synthesis. For example, pure L-ascorbic acid (vitamin C) extracted from rose hips is better than pure L-ascorbic acid manufactured in a chemical plant. Are the vitamins from the two sources different Can the body distinguish a vitamin s source ... 

Neither folic acid nor vitamin Bt is produced by humans in adequate amounts the substances must he absorbed from food. Natural sources of folic acid include ... 

Oily substances are. by far. the best natural sources of vitamin E. 

In the only known human study of vitamin D bioavailability from natural sources (43), the average relative bioavailability of vitamin D2 from meat sources was estimated to be about 60% as compared to a vitamin supplement. 

Once a structure is known, organic chemists try to synthesize the compound in the laboratory. If the starting materials are inexpensive and the synthesis process is simple enough, it may become more economical to manufacture a compound than to isolate it from a plant or bacterium. In the case of vitamin C, a complete synthesis was achieved in 1933, and it is now much cheaper to synthesize it from glucose than to extract it from citrus or other natural sources. Worldwide, more than 80 million pounds are synthesized each year. 

Like other fat-soluble vitamins, vitamin D is absorbed in the gut with other lipids. The two major natural sources of vitamin D are cholecalciferol... 

Vitamin E is required for normal growth and reproduction. The most important natural source is a-tocopherol found in plant oils and seeds. The ester form (e.g. vitamin E acetate) can be synthesized and is used for feed supplementation. One international unit is defined as being equivalent to the activity of 1 mg DL-a-tocopherol acetate. The nutritional role of vitamin E is closely interrelated with that of selenium and is involved mainly in the protection of lipid membranes such as cell walls from oxidative damage. Although these signs are similar to those of selenium deficiency, it is not possible to substitute selenium completely for vitamin E. Both nutrients are required in the diet. 

Despite increasing acceptance by scientists, some people viewed the synthesis of natural compounds as unnatural. Indeed proponents of the vital force theory can still be found on a quick scan of the Internet more than 100 years after it was discredited as a scientific theory. For example, vestiges of the vital force theory linger in the belief that vitamins from natural sources are somehow healthier than vitamins that are synthesized. 

Vitamin A, or retinol, is one of the major fat-soluble vitamins. It is present in many foods the best natural sources are liver, butter, margarine, egg yolk, carrots, spinach, and sweet potatoes. Vitamin A is the precursor of retinal, the essential component of the visual pigment rhodopsin. 

All industrial vitamin A syntheses use p-ionone as the starting compound (36, see page 14) 3S). This monocyclic C13 ketone can be obtained either completely synthetically from acetone and acetylene by consequent use of the C2 and C3 addition reaction, or via citral (59, see page 14) obtainable from natural sources (lemongrass oil). 

Few natural sources are rich in vitamin B12. However, only very small amounts are required in the diet. Good sources are lean meat, liver, kidney, fish, shellfish, and milk (Table 9-23). In milk, the vitamin occurs as cobalamine bound to protein. 

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