Curcumin compounds, namely total curcumin, are active components extracted from the roots and stems of ginger and araceae plants, mainly including curcumin, demethoxylcurcumin and dimethoxylcurcumin. At present, curcumin is generally considered to be a mixture of these three components, of which curcumin accounts for 70% of the total curcumin, and is also the main component of curcumin compounds to play its function.
Curcumin has multiple phenolic hydroxyl groups and is orange yellow crystalline powder insoluble in water. Of curcumin in food is mainly used in sausage products, canned, sauce LuZhiPin coloring, such as in medicine, curcumin in anti-tumor, anti-inflammatory, antioxidant, scavenging free radicals, antimicrobial and the cardiovascular system, digestive system and other aspects have a wide range of pharmacological effects, and its security is good, but the chemical structure of curcumin is not stable, fast metabolism in the body, As a result, its bioavailability is very low and it is not widely used in clinical practice. In this paper, the bioavailability of curcumin, the methods to improve the bioavailability of curcumin and the process of biotransformation, absorption and metabolism of curcumin in human body are reviewed.
01 Structure of curcumin
The molecular formula of curcumin is C21H206, the molecular weight is 368.37g/mol, and the melting point is 183℃. Curcumin is crystallized. It is a rare pigment with diketone in the plant world, which is composed of two o-methylated phenols and a β -diketone. The β -diketone structure has the enol-one tautomatic structure, but the spectral structure proves that curcumin mainly exists in the enol form in solid and solution.
The solubility and stability of curcumin depend on the kind of solvent and pH. Curcumin is extremely insoluble in water, but soluble in organic solvents. Curcumin is more stable under acidic to neutral conditions. Under alkaline conditions, curcumin is very unstable and easily broken down to a yellow or tan color.
02 Physiological activity of curcumin
Curcumin contains a number of double bonds, as well as phenolic hydroxyl and carbonyl groups, so it has strong physiological activity. Studies have shown that curcumin has anti-tumor, anti-inflammatory, antioxidant, free radical scavenging, anti-microbial and cardiovascular system, digestive system and many other effects.
2.1 antitumor
Clinical studies have shown that curcumin, as a natural compound, has great anticancer potential, and the National Cancer Institute (NCI) has listed it as the third generation of cancer chemoprevention agents. A large number of studies have shown that curcumin can inhibit the proliferation of a variety of cancer cells, and no obvious toxic and side effects were found when the oral dose was 5g/kg in mice. In vitro, in vivo, and human clinical trials have confirmed the efficacy and potential of curcumin for many types of cancer. Its anticancer mechanism is mainly through inducing apoptosis of tumor cells, and its anticancer molecular mechanism has been widely studied.
2.2 anti-inflammatory
Anti-inflammatory acute and chronic inflammation is a major factor in the development of obesity, type ii diabetes, arthritis, pancreatitis, cardiovascular disease, neurodegenerative diseases and metabolic syndrome, and many types of cancer. Curcumin has been used as an anti-inflammatory drug for hundreds of years. A large number of studies have confirmed its anti-inflammatory effect and mechanism, and it has different degrees of inhibition on inflammation caused by a variety of causes, and has very small side effects and adverse reactions, which has obvious advantages compared with other anti-inflammatory drugs.
2.3 antioxidant
Curcumin, as a natural compound, can directly scavenge free radicals in vivo and in vitro, and its antioxidant activity can be compared with β -carotene, anthocyanin and other natural pigments, and some studies have shown that curcumin has better antioxidant ability than conventional vitamins. Curcumin's preventive and therapeutic potential for a number of diseases is also thought to be related to its antioxidant effects.
2.4 Neuroprotection
Neurodegenerative diseases are a kind of diseases caused by central nervous system dysfunction, including Alzheimer's disease, Parkinson's disease and other diseases, there is no effective treatment at present. Recent studies have shown that curcumin has a neuroprotective effect. Curcumin protects PC12 cells against beta-amyloid toxicity by inhibiting oxidative damage and tau hyperphosphorylation. Ma et al. injected curcumin, mecobalamin and normal saline into the intraperitoneal cavity of mice with nerve injury respectively for 4 weeks for comparison. Axonal regeneration was analyzed by retrograde labeling and morphometry, and motor function recovery was evaluated by electrophysiology, behavior, histological appearance and other indicators. Data analysis showed that both curcumin and mecobalamin treatment groups achieved good nerve regeneration and functional recovery.
2.5 Anti-fibrosis
Fibrosis can lead to organ structure destruction, dysfunction, failure, seriously affect the quality of life of patients. Studies have shown that curcumin has obvious anti-fibrosis physiological activity and has therapeutic effects on liver fibrosis, pulmonary fibrosis and renal fibrosis, etc. However, its anti-fibrosis mechanism needs to be further explored, and how to improve the bioavailability of curcumin to enhance the curative effect is also a problem that needs to be solved jointly by domestic and foreign scholars.
2.6 Improve intestinal microflora disorder
The bacteria living in the human intestine are called "intestinal flora", which plays an important role in digestion, immunity and disease resistance. They are in a dynamic balance under normal conditions. However, once the intestinal flora is maladjusted, it will have adverse effects on the body, such as obesity, diabetes, hypertension and other diseases related to the disorder of intestinal flora. Studies have shown that curcumin can regulate intestinal flora such as Escherichia coli and Bacteroidetes to restore their dynamic balance. Li Yun et al proved that curcumin can improve depression and intestinal microflora disorder caused by intermittent sleep in rats. In addition, turmeric root also has physiological activities such as lowering blood sugar, improving allergic asthma, anti-microbial and anti-HIV.
03 Application of curcumin
Curcumin, as a natural yellow acid phenolic pigment, is widely used and has great potential for development. Curcumin, as a representative of natural pigments, is safer than synthetic pigments. Currently, curcumin is one of the seven largest selling natural food pigments in the world. It is recognized as a natural food additive by WHO and FDA, and is mainly used in food coloring of candy, powder wrapping and instant rice and noodles. And because of its anti-cancer, antioxidant and other physiological activities, can be used as drugs to treat diseases. At present, the curcumin capsule has entered into health care products market, clinical studies have shown that curcumin capsule for cardiovascular system disease, gastrointestinal disease, and cancer have certain curative effect, can also be curcumin used in cosmetics and health products, but because of the curcumin poorly soluble in water, very low bioavailability, limits the curcumin pharmacological action of the play.
