Application background and overview of chromium picolinate
Chromium Picolinate, also known as chromium picolinate and chromium picolinate. Molecular formula: Cr (C6H4NO2) 3, relative molecular mass 418.33, purple-red crystalline fine powder, stable at room temperature, slightly soluble in water, insoluble in ethanol. Chromium picolinate, as organic trivalent chromium, is of great significance to the biological activity of Glucose Tolerance Facto Ultrafine Calcium Carbonate (GTF), and is widely used as a nutritional additive in food and livestock and poultry production. Studies have found that chromium picolinate can reduce blood sugar and blood lipid levels, and relieve symptoms related to sugar metabolism and lipid metabolism disorders. In human nutrition and health care products, chromium picolinate has become the second largest nutritional supplement after calcium supplements. In livestock and poultry production, supplementing chromium picolinate can promote the growth of pigs and increase the lean meat rate of pigs, improve the immunity of livestock and poultry, enhance the body’s anti-stress ability, and improve the reproductive capacity of female livestock. However, since Stearns et al. first reported in 1995 that chromium picolinate could cause ovarian cell distortion in Chinese hamsters, research on the safety of chromium picolinate has attracted much attention.
Applied biological functions of chromium picolinate
The physiological functions of trivalent chromium are mainly as a glucose tolerance factor, an activator of insulin, and a stabilizer of DNA and RNA (nucleic acids). It affects the metabolism of sugar, lipids, proteins and nucleic acids in the body, thereby acting on the body. of reproductive growth and immunity.
1. Metabolism of chromium and sugar
The glucose tolerance factor and insulin in the body are two important active substances that maintain the blood sugar concentration balance system. As a component of the glucose tolerance factor, trivalent chromium can activate the disulfide bond activity of insulin and cell membranes to improve animal health. Tolerance to glucose and insulin combine with its specific receptors to stimulate tissue uptake of glucose and increase glucose absorption.
2. Metabolism of fat
The main effect of chromium on lipid metabolism is to maintain normal blood cholesterol levels, affect the synthesis and clearance of fat and cholesterol in animal livers, and increase the content of high-density lipoprotein (HDL) in the blood.
3. Chromium and stress and immunity
Chromium has the ability to resist stress and improve the body’s immunity. Stress can increase the content of cortisol in the serum, and glucocorticoids are steroids that inhibit growth and immune system function. In addition, stress causes Zn, Cu , Fe, Mn, Cr and other trace elements increase. Chromium can reduce the body’s serum cortisol concentration, avoid the additional loss of Zn, Gu, Fe, Mn, Cr and other trace elements, and increase the content of immunoglobulins. and antibody titers to enhance the immunity of animals.
4.Chromium and reproduction
Chromium has a significant impact on pig reproduction and can significantly increase the number of litters in primiparous sows.
5. Application of chromium picolinate in aquaculture
1) Anti-stress: Intensively farmed animals face a large number of stresses, such as nutritional stress, environmental stress, immune stress, metabolic stress. Stress can lead to changes in animal sugar metabolism and mineral metabolism. , the sugar level will drop
Enhanced proteoneogenesis and enhanced glucose utilization will lead to an increase in tissue chromium, which will eventually be excreted from the body. Chromium supplementation can reduce mortality caused by stress, improve endocrine, improve production performance, and reduce other mineral elements. of excretion.
2) It can significantly improve carcass quality: Since the 1990s, the chromium source that has been studied more in animal nutrition, especially pig nutrition, is mainly chromium picolinate. In the feed of growing and finishing pigs, adding 200 × 10-9 inorganic chromium (supplied in the form of CrCl3 .6H2O) failed to improve pig growth and carcass composition. Adding 200 × 10– 9 Organic chromium significantly improved carcass quality, reduced backfat thickness, and increased lean meat rate.
Study on applied toxicity of chromium picolinate
1. Acute toxicity
30 healthy Wistar rats (weight 180~200 g, half male and half female) were randomly selected. A chromium picolinate suspension with a dose of 500 mg/mL was prepared with 0.05% sodium carboxymethylcellulose and administered into the stomach. After a few hours, some rats showed signs of mental depression and slow movements. They gradually returned to normal within 24 hours without any symptoms. Death status. The oral LD50 of chromium picolinate in Wistar rats is greater than 5 000 mg/kg BW, indicating that the substance has low toxicity and is safe to use.
2. Subchronic toxicity
Animal study data indicate that chromium picolinate has extremely low oral toxicity. Rats were fed diets containing chromium picolinate 5, 25, 50 and 100 !g·g-1 for 20 weeks to observe the toxicity of chromium picolinate. The results showed that at 7, 14 and 20 weeks of the test, there was no significant difference in body weight, organ weight and clinical biochemical indicators between the animals in each group. Compared with the control group, adding chromium picolinate to the diet increased the concentration of trivalent chromium in the liver and kidneys, but had no effect on the morphology of the liver and kidney tissues. According to this, chromium methoxypyridine picolinate in the diet is non-toxic to rats when it reaches 100g/g.
3. Reproductive toxicity
Research has found that the gradient addition of chromium picolinate to the culture medium of fruit flies can significantly reduce the number and survival rate of fruit fly offspring, delay their emergence time, and even lead to infertility. Chromium picolinate 200, 20 and 2 mg·kg-1 was added to the diet of Wistar rats. After 90 days of mating, the pregnant rats continued to feed diets containing chromium picolinate and were killed after 20 days of pregnancy. The results found that, Stillbirth rate, live birth rate, reabsorption rate and…The respective increases were 7.5%, 11.9%, and 6.5%, indicating that supplementing chromium to broiler chickens raised under high temperature conditions (30-35°C) can improve weight gain and feed conversion rate. On the basis of the control group, 0.25 mg/kg chromium picolinate, 0.50 mg/kg chromium picolinate, 0.25 mg/kg chromium citrate, and 0.50 mg·kg-1 chromium citrate were added. The experiment was divided into two stages: pre-growth period (1-28 days old) and growth period (29-42 days old). During the growth period, compared with the control group, only 0.50 mg/kg chromium picolinate significantly increased the daily weight gain and reduced the feed-to-weight ratio. It had the same results throughout the period. Compared with the control group, 0.50 mg/kg chromium citrate and 0.50 mg/kg chromium picolinate significantly increased the leg muscle rate of broiler chickens in the early growth period, but had no significant effect in the growth period. The research on chromium picolinate mainly focuses on common farmed animals. Most of the research on the use of organic chromium in ruminants is cattle, and its anti-stress and immunity-improving effects are mainly studied. As for research on other smaller animals, there have been reports one after another, but the research on pigs and chickens is far less in-depth, and many practical issues still need to be discussed in the future.
Application and preparation of chromium picolinate [3]
Overview of research on chromium picolinate and its application progress
Chromium picolinate is generally formed by oxidizing picolidine to picolinic acid and then complexing with a trivalent chromium compound. At present, there are many methods for methylpyridine oxidation, the main ones are:
1. Chemical oxidation method
Chemical oxidation method includes potassium permanganate, ozone and nitric acid as oxidants. Many manufacturers dissolve 2-methylpyridine in water, add potassium permanganate and other oxidants in batches under vigorous stirring, then add hydrochloric acid to adjust the pH value, and then extract with benzene. The product yield is 65%. By adding phase transfer catalysts and glacial acetic acid extractants and other improved methods, the reaction yield was increased by more than 15%, and the yield of 2-picolinic acid reached 82.37%. The use of chemical oxidation to produce picolinic acid is costly and produces a large amount of waste liquid during production, which pollutes the environment. The oxidant corrodes equipment under acid and alkali conditions, and has been gradually phased out in developed countries. The ozone oxidation method does not corrode equipment, has less waste, and has a higher yield. The disadvantage is that it requires a special ozone generator and is difficult to produce on a large scale.
2. Microbial fermentation and oxidation method
Using microbial bacterial fermentation, the methyl group on the heterocyclic ring can be oxidized into a carboxyl group. In Rhodococcus roseus sp·
In the presence of NS156, fermentation at 30°C for 230h, and picolinic acid fermentation under the same conditions, the yield of picolinic acid can reach more than 90%. Microbial fermentation produces picolinic acid under mild conditions, low cost, high conversion rate, and does not pollute the environment. However, its production cycle is too long and large-scale production has certain difficulties.
3. Vapor phase oxidation method
The gas phase oxidation method is to turn methylpyridine into steam at 300~450°C, and then mix it with ammonia, water vapor, air or oxygen through the catalyst layer to oxidize it to form picolinitrile, which is hydrolyzed to form picolinylmethyl. Amides and picolinic acid. The gas phase oxidation method has high temperature, high energy consumption, difficult to control the reaction, and is prone to produce tar and harmful gases. The catalyst requires high purity of raw materials.
4. Electrolytic oxidation method
The preparation of picolinic acid by electrolytic oxidation is carried out at the anode of an electrolytic cell with a diaphragm. The electrolyte and separator are very important, and the conductivity and corrosion resistance of the electrode affect the electrolysis efficiency and electrode life. The effects of these two aspects were not solved until the 1980s. A flat mesh PbO2/Ti (1cm×2.5cm) was used as the anode, a Ni plate (1cm×3cm) was used as the cathode, the anode chamber and the cathode chamber were separated by a domestic CM-001 proton exchange membrane, and a saturated KCl calomel electrode was used as the reference. The electrode is connected to the anode through a Lukin capillary. The anolyte is an aqueous solution of 2-methylpyridine and H2SO4. The catholyte is a 10% NaOH aqueous solution. 2-methylpyridine is electrolytically oxidized with a selectivity of 96.88%. For selectivity, the optimal conditions for the electrolysis reaction should be: 40°C, 1.0mol/LH2SO4, 0.5mol/L 2-methylpyridine and anode potential 1.95V. The electrolytic oxidation method has the advantages of mild conditions, low production cost, and less waste. It is one of the directions for the development of chemical industry in the future.
