Study on the Use of Marigold Flower Extract Lutein Powder

Xanthophylls are a type of natural carotenoid pigment that is not active in terms of VA. Also known as “phyto-lutein”, they are widely found in nature. This natural pigment is attracting more and more attention because of its bright color, strong coloring power, safety and non-toxicity, strong antioxidant capacity, ability to prevent human aging, and nutritional value without side effects. It is now fashionable internationally to add a certain amount of lutein to foods to make “lutein vegetarian foods”, which can prevent a series of diseases caused by the aging of organs in the human body. A large amount of epidemiological evidence shows that lutein has a protective effect on vision and has the effect of preventing cataracts, atherosclerosis, and enhancing immunity. In particular, it plays an important role in preventing the occurrence of cancer and delaying the development of cancer. It is currently a hot spot in the research of functional food ingredients internationally. Therefore, as a new type of health food additive, lutein has broad development prospects in the processing of health foods in the 21st century. This paper will summarize the research progress of lutein at home and abroad and look forward to its future application prospects.

1 Physiological effects and preparation of lutein

1.1 Composition of lutein

Lutein, also known as 3'3-dihydroxy-alpha-carotene, has the molecular formula C40H56O2 and a molecular weight of 568.85. Research has shown that the basic structure of lutein is two hexagonal carbon rings connected by a long chain containing an eighteen-carbon atom conjugated double bond. It has three chiral centers with eight stereoisomers, making it difficult to synthesize chemically. It can only be extracted from natural plants to date.

1.2 Lutein's effects

1.2.1 Protecting eyesight

Lutein plays an important protective role in the macula of the retina. A lack of lutein can easily lead to macular degeneration and blurred vision, which in turn can lead to symptoms such as vision degradation and myopia. Lutein is a precursor of VA and can be converted to VA in the human body. The main physiological functions of lutein in the eye are as an antioxidant and for photoprotection. The optic nerve is non-regenerative and is extremely vulnerable to harmful free radicals. Lutein's antioxidant effect can inhibit the formation of harmful free radicals. Lutein can absorb a large amount of blue light. The wavelength of blue visible light is close to ultraviolet light, and it is the most potentially harmful type of visible light that can reach the retina. Before reaching the sensitive cells on the retina, the light first passes through the area with the highest concentration of lutein. If the lutein content in the macula is high, this damage can be minimised.

1.2.2 Antioxidant effect

Lutein powder has a strong antioxidant effect, inhibiting the activity of active oxygen free radicals and preventing them from damaging normal cells. Experiments have shown that active oxygen radicals can react with DNA, proteins and lipids, impairing their physiological functions and causing chronic diseases such as cancer, atherosclerosis and macular degeneration of the eye. Lutein can inactivate singlet oxygen through physical or chemical quenching, thereby protecting the body from damage and enhancing its immune function.

1.2.3 Coloring effect

Lutein has a bright yellow color, is insoluble in water, soluble in oil and ethanol, has strong coloring power, and is resistant to light, heat, acid, and alkali. It can be widely used to color pastries, candies, seasonings, pickles, and feed. It can also be used to color health products, tablet coatings, and capsules. It is already used as a natural coloring agent in feed additives in China. Some European and American countries have also listed lutein as a food coloring agent, giving food a beautiful golden yellow color.

1.2.4 Anti-atherosclerosis effect

Recent research findings show that lutein has a delaying effect on the early stages of the hardening of the arteries. The main factor is the relationship between changes in the thickness of the inner lining of the main arteries and the lutein content in the blood. A low lutein content in the blood is very likely to cause the arterial walls to thicken. As the lutein content gradually increases, the tendency for the arterial walls to thicken decreases, and arterial blockages are significantly reduced. At the same time, lutein in the cells of the arterial wall can also reduce the oxidation of LDL cholesterol.

1.2.5 Anti-cancer effect

Many studies have shown that lutein has an inhibitory effect on a variety of cancers, such as breast cancer, prostate cancer, rectal cancer, skin cancer, etc. According to a recent study by the College of Pharmacy at New York University, there is a strong correlation between a lower incidence of breast cancer and lutein intake. The study found that the incidence of breast cancer in the experimental group with low lutein intake was 2.08 to 2.21 times that of the experimental group with high lutein intake. This effect may involve indirect immunomodulatory effects in synergy with other organ tissues. The study concluded that dietary lutein intake not only suppresses tumors, but may even prevent tumorigenesis. Relevant institutions recommend that a daily intake of 400–600 g of fruits and vegetables per capita can reduce the relative risk of cancer by 50%.

1.2.6 Prevention and treatment of diabetic retinopathy

Diabetic retinopathy is caused by long-term damage to the capillaries of the retina of the eye by high blood sugar: blood flow slows, tissues become oxygen-deprived, the walls of the capillaries degenerate and become brittle, and microaneurysms, dot- or sheet-like hemorrhages, and cotton-wool-like exudates appear on the retina at the back pole of the fundus, causing vision loss. If treatment is not started promptly, the damage will progress further. Due to the lack of oxygen, new blood vessels will form on the retina, which can lead to vitreous haemorrhage, proliferative retinopathy, tractional retinal detachment, secondary glaucoma, etc., and cause blindness. Lutein can significantly improve the resistance of blood vessels, restore the balance between osmotic pressure inside and outside the blood vessels, reduce the permeability of blood vessels, inhibit the leakage of substances in the blood vessels, ensure the integrity of the blood vessels in the eyes, and ensure an adequate blood supply to the eyes. It also prevents free radicals from binding to collagen in the eye, strengthens the collagen structure of the retina, thereby improving the treatment rate of various retinal diseases, such as diabetic retinopathy, retinitis pigmentosa, hemorrhagic and hypertensive retinopathy, and macular degeneration, and improving and restoring the loss of vision caused by these conditions.

1.3 Lutein separation and extraction

Lutein is a natural pigment that is widely found in vegetables, flowers, fruits and certain algae. It is the main component of plant pigments in corn, vegetables, fruits and flowers. Lutein was first extracted in 1831 by Heinrich Wilhelm Ferdinand Wackenroder from carrot roots. Later, Berzdlius extracted lutein from autumn yellow leaves in 1837. Subsequently, other researchers also extracted lutein from dark green vegetables such as kale, kale, spinach, etc., flowers such as marigolds, as well as seaweed and egg yolks. In recent years, with the increasing demand for lutein, researchers at home and abroad are striving to find extraction methods with higher yields. Currently, there are mainly the following methods for extracting lutein.

1.3.1 Organic solvent extraction method

Organic solvent extraction is by far the most widely used method for extracting lutein. Commonly used organic solvents include hexane, ethanol, acetone, ethyl acetate, petroleum ether, etc. The yellow pigment in marigolds is insoluble in water under neutral conditions, while its solubility in ethanol increases significantly. Therefore, But Jixing [1] used ethanol as a solvent for extraction under alkaline conditions. The extract was brownish yellow in color, and the brown solid was obtained by vacuum distillation, concentration, precipitation, and drying.

Zhou Yanfang et al. [2] used a Soxhlet extractor and reflux co-cooking method to extract the pigment from marigold particles, and the extraction yield of marigold yellow pigment could reach 22.6% after 7 h at a material-liquid ratio of 1:4. Song Hao et al. [3] studied the solubility of lutein in marigold in several organic pure solvents such as tetrahydrofuran, petroleum ether, hexane, acetone, and binary mixtures of these solvents and ethanol. The results showed that the appropriate two-component mixed solvent had a better lutein extraction effect than pure solvents. In another study, when extracting corn yellow pigment from corn yellowish pulp, a solvent oil with a hexane mass fraction of up to 74% to 80% was selected. According to the principle of liquid-solid extraction, the purpose of pigment leaching is achieved by molecular diffusion when there is a concentration difference between the liquid and solid phases, and by convective diffusion when an external force is applied by a pump cycle.

1.3.2 Microwave extraction method

At present, microwave extraction technology is being used more and more widely in people's production and lives, and has achieved good results, especially in the extraction of natural pigments. Microwave extraction makes use of its high efficiency and strong selectivity, as well as its advantages of being easy to operate, producing few by-products, high yield and easy purification of the product. Under the rapid vibration of 2.45 billion times per second generated by the magnetron, the molecules in the plant material collide and squeeze against each other, accelerating the leaching of the natural pigments. Its advantages lie not only in reducing equipment investment and operating costs, but also in meeting environmental protection requirements. Therefore, microwave extraction has broad application prospects in the extraction of natural pigments.

Li Jianying and Deng Yu [4] studied the extraction of lutein from plant sources—citrus peel and tea—using microwave heating. They explored the effects of factors such as microwave power, extraction solvent, material ratio, extraction time, extraction sequence, and sample particle size on the product extraction rate, and finally concluded that the main order of influence was: microwave power > material to liquid ratio > extraction time. Zhao Zhiguo and Zhang Hua [5] also used citrus peel as a raw material and extracted lutein by microwave heating and obtained the optimal conditions: solvent oil No. 6 as the extraction agent, microwave power of 800 W, extraction time of 25 min, and material ratio of 1/10. The lutein extraction rate from citrus peel was the highest, reaching 74.12%.

1.3.3 Supercritical CO2 extraction

Supercritical fluid technology is a new chemical separation technology that has developed over the past 20 years. It is increasingly being used in the extraction of natural products because of its non-toxic and harmless properties, strong solubility, low solvent residue and high product purity. It makes use of the influence of pressure and temperature on the solubility of critical fluids. It is carried out by contacting a mixture of solid or liquid to be separated with a supercritical fluid under high pressure, and then reducing the pressure and increasing the temperature to turn the supercritical fluid into a normal gas. This allows the various components to be selectively extracted in order of polarity, boiling point and relative molecular mass, thereby achieving the goal of separation and purification. A method for refining lutein by supercritical extraction has been disclosed, which comprises a preliminary extraction of marigold extract in an extraction kettle and a subsequent post-extraction, followed by the final product lutein. This invention not only removes odors and increases the lutein content to above 200 mg/kg, but also features a simplified production process, a short production cycle, and high production efficiency.

Li Gaofeng et al. [6] extracted lutein from marigold dried flower particles by supercritical CO2 extraction and concluded that the optimal process conditions were an extraction pressure of 45 MPa and a temperature of 50 °C; a separation I pressure of 8 MPa and a temperature of 55 °C, with the main extract collected in the separation I tank; and a separation II pressure of 4 MPa and a temperature of 20 °C, with the impurities collected in separation II. Under these conditions, the lutein extract has a high extraction rate. Liang Lin [7] used supercritical CO2 extraction technology to extract lutein from sea buckthorn pomace, and the optimal process conditions were determined to be a temperature of 48 °C, a pressure of 35 MPa, a separation pressure of 15 MPa, and an entrainment agent dosage of 9 mL.

1.3.4 Enzyme treatment

The enzyme method destroys the integrity of the cell structure, so that the substances inside the cells are more exposed during extraction, increasing the permeability of the oil. Since the plant cell wall is mainly composed of polysaccharides, cellulase and hemicellulase have the highest activity in degrading polysaccharides and produce the best results. However, in actual production, several enzymes including cellulase are often used together to achieve better results. Matoushek [8] studied the method of dissolving fresh marigold flowers in water (10%, w/v), treating with cellulase first, and then extracting with an organic solvent (chloroform or hexane). Compared with the enzyme-free control group, the yield was increased by 36%.

Delgado-Vargas and Paredes-Lopez [9] studied the aqueous enzymatic treatment of marigold flower powder, followed by extraction with a mixture of hexane-ethanol-acetone-toluene (10:6:7:7), which significantly increased the extraction rate of lutein. Enzymatic degradation of marigold flowers does not cause lutein isomerization, and the enzymatically treated marigold powder has the highest content of all-trans lutein, up to 25.1 g/kg dry weight [10]. However, due to the long reaction time of the enzymatic treatment method, the large amount of moisture in the enzymatic treatment process needs to be removed before solvent extraction, which limits the practical application of the above method.

BARZANAE et al. [11] proposed a method for carrying out an enzyme reaction and organic solvent extraction simultaneously, using a series of hydrolases to degrade cell wall components in a medium with mainly organic solvents and low moisture content. In terms of the selection of hydrolases, NAVARRETE-BOLANOS JL et al. [12-13] studied the effect of a non-commercial enzyme preparation on the extraction of lutein from marigold flowers. This enzyme was synthesized by an endophytic microorganism produced during the ensiling process, and had high cellulase activity and a good extraction effect. Li Xiuxia et al. [14] studied the ultrasonic-enzymatic assisted extraction process of lutein from corn protein powder, and determined that the optimal process parameters for enzymatic extraction of lutein from corn protein powder were an enzyme concentration of 7682 U/g, a substrate concentration of 818%, and an enzymatic hydrolysis time of 212 h. The yield of this process was 65 μg/g, which was consistent with the predicted results.

1.3.5 Membrane separation technology

Ceramic membrane microfiltration (MF) is used to refine and purify the extraction solution, and reverse osmosis (RO) membranes are used to concentrate the filtrate. This process uses membrane separation technology as the main method, replacing traditional alcohol purification and evaporation concentration. The process is simple, the pigment solution is basically operated at room temperature, which saves energy and ensures the quality of the pigment product. Therefore, from the perspective of both reducing costs and improving product quality, the use of membrane separation technology for the extraction of natural pigments is extremely valuable.

1.3.6 Lutein extraction by drying

A new type of rotary drum dryer has been developed abroad for drying and beating the petals of marigolds or marigolds, from which lutein can be extracted. When the beating ratio is different, the beating efficiency fluctuates between 70% and 90%. The amount of lutein depends on the drying time, but for the same drying time, the lutein extracted by drying at 70 °C is less than that extracted at 60 °C.

2 Application of lutein

Due to its bright color, strong coloring power, good antioxidant properties, safety and non-toxicity, and rich nutritional value, the natural pigment lutein is now being used more and more widely in many fields such as animal feed, food, health products, cosmetics, and tobacco.

2.1 Lutein in feed additives

2.1.1 Coloring

bamboo leaves, etc. [16] Adding a certain amount of lutein to chicken feed improves the color of the egg yolk and improves the quality of the egg yolk and white. Lutein can also give fish eggshells, skin, and muscles an egg yolk yellow, orange, or red color. Liang Xiangjun et al. [17] added lutein to the feed, which significantly improved the body color of the goldfish, increased the lutein content in the scales, skin, muscles and tail fins, and made the goldfish's body color more vibrant. The pigment commonly used in aquaculture feed is astaxanthin, a type of lutein. It was first recognized that astaxanthin can make the meat of salmon and trout pink. Similarly, astaxanthin is also commonly used as a coloring agent in shrimp feed.

2.1.2 Improves egg fertilization and hatchability

Studies have found that the circulatory system and vascular zone of the embryo develop faster in eggs with high lutein content. Lutein in the egg yolk also promotes the accumulation of large amounts of VA and glycogen in the embryo's liver, promotes the absorption of lipids in the embryo's liver, and improves egg fertilization and hatchability. In-depth research by foreign scholars has found that in certain waters, the reason adult salmon and trout cannot reproduce offspring is because their eggs and fry lack astaxanthin. The astaxanthin content of salmon and trout eggs is positively correlated with their hatching rate.

2.1.3 Improves immunity

Lutein can enhance the reproduction, survival and immune ability of livestock, fish and shrimp, and also protect lipids from oxidation. Foreign studies have found that lutein can stimulate egg-laying hens to produce antibody responses against bronchitis virus. Tian Heshan et al. [18] showed that adding lutein can improve the activity of antioxidant enzymes in the liver of chicks and reduce the content of lipid peroxide MDA.

2.2 Lutein in food additives

Lutein is non-toxic and safe, has excellent physiological effects, and meets the characteristics of food additives as being “natural”, “nutritious” and “multi-functional”. When added to food together with other beneficial complementary nutrients, it has a good nutritional and health-promoting effect. In the international market, the price of 1 g of lutein is equivalent to 1 g of gold, and it is known as “vegetable gold”. Adding a certain amount of lutein to food can prevent a series of diseases caused by the aging of organs in the human body, and has a good effect on preventing human aging, age-related macular degeneration, cataracts, etc.

However, lutein itself is not soluble in water, slightly soluble in oil, and very susceptible to oxidation. In addition, under some processing conditions, such as heating and light, it will oxidize and lose activity, so it cannot exert its health effects. Currently, lutein preparations developed on the market greatly improve the convenience of adding lutein and also maintain its activity. By directly using it in oil media such as cream and cooking oil, or using microcapsule embedding technology to embed and disperse lutein in plant oil, starch, gelatin and other matrices, and isolate it from light and air to improve stability. At present, this preparation has been widely used in beverages, dairy products, sweets, biscuits, ice cream, jam, and chewable tablets, opening up new ideas for the future development of a wide variety of eye-protecting foods.

2.3 Lutein in pharmaceuticals and health products

Lutein's protective effect on the retina: Lutein is the only carotenoid found in the human retina. It is selectively deposited in the macula and throughout the retina, and these yellow pigments effectively prevent oxidative reactions in the retina. Lutein-based macular pigments are effective in treating and preventing macular degeneration or damage to the retina, and are the only effective medicine.

Lutein has a significant therapeutic and preventive effect on cataracts. Lutein is related to the clarity of the human lens, and the intake of lutein and the lutein content in the blood are negatively correlated with the incidence of cataracts.

(1) Lutein can be deposited in the lens of the eye;

(2) Lutein has an inhibitory effect on the development of cataracts;

(3) High lutein intake can slow the development of cataracts.

In addition, lutein has certain anti-cancer effects. Lutein has an inhibitory effect on many types of cancer (such as breast cancer, prostate cancer, rectal cancer, colon cancer, skin cancer, etc.). Its independent effect can reduce the growth rate of cancer cells by 25%, inhibit the oxidation of cell membrane lipids and induce cell damage.

2.4 Lutein in cosmetics

Lutein can effectively prevent ultraviolet damage to human skin. As an antioxidant, it can inhibit the activity of active oxygen free radicals and prevent the damage to normal skin caused by active oxygen free radicals. Therefore, lutein monomers can be used to make a variety of skin care products and cosmetics to protect the health of the skin and prevent skin damage.

3 Prospects

Lutein research has a history of more than ten years. Although China has carried out relevant research work in the extraction, separation, analysis, detection, development and application of lutein, there is still a considerable gap compared with foreign countries. At present, the prices of lutein-containing health foods and nutritional supplements are relatively high in the international market, and the profit margins are very generous. Therefore, the development and research of high-purity lutein and the expansion of its application fields will become the focus of future work for researchers in China.

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