What Is Marigold Extract Lutein Good For?

Tagetes erecta L., also known as marigold, contains various chemical components such as carotenoids, flavonoids, polysaccharides, anthraquinones, amino acids, alkaloids, etc., and can be divided into two types: pigmented and ornamental [1]. The main component of marigold extract is lutein, a fat-soluble natural oxygenated carotenoid coloring agent that is insoluble in water but soluble in ethyl acetate, tetrahydrofuran, chloroform, etc. [2]. It has biological activities such as coloring, anti-inflammatory, improving immunity, improving the quality of meat and eggs, anti-cancer and antibacterial [3].

In the southern part of China, consumers prefer broiler products with yellow skin, believing that yellow skin is a sign of health, freshness and good quality. Therefore, the yellower the skin, the higher the market value [4]. Since poultry cannot synthesize pigments on their own, adding extra pigments to their diet can improve the color of their carcasses. Therefore, marigold lutein is often used as a coloring agent in poultry production, but at present, more research reports have been published on egg yolk coloring. The effects on poultry meat quality, anti-inflammatory, immunity, and absorption and metabolism need to be further studied. This paper reviews the extraction process, biological functions, and application of marigold lutein in poultry production, with the aim of providing a theoretical reference for the application and further development of marigold lutein in poultry diets.

1 Extraction process of marigold lutein

The main extract of marigold is lutein, which is easily affected by factors such as light, heat and pH. It is widely found in vegetables, flowers and fruits, but the lutein content in marigolds is the highest [5]. At present, common methods for extracting lutein include organic solvent extraction, microwave-assisted extraction, enzyme-assisted extraction, and ultrasound-assisted extraction. Among these methods, ultrasound-assisted extraction is commonly used in scientific research laboratories to extract natural plant ingredients. Compared with traditional extraction methods, the extraction rate and yield of these extraction processes have been significantly improved. However, due to the environmental factors that affect lutein and the defects in the extraction process technology, the extraction rate and yield are still limited. Several common extraction processes are summarized in Table 1.

2 Biological functions of marigold lutein

2.1 Coloring

Since poultry cannot synthesize pigments, they need to obtain additional pigments from the diet to meet consumer market demand [21]. Pigments can be divided into natural pigments and synthetic pigments according to their sources. Lutein is a natural pigment extracted mainly from the natural plant marigold, which has a good coloring effect on animals. Alay et al. [22] and Wei et al. [23] found that the egg yolk and skin color of marigold lutein group poultry was significantly higher than that of the group without added pigment. Lutein can be deposited in different tissues, and the deposition effect is also different. The general deposition order of pigments in poultry is tibia > skin > subcutaneous fat [24]. The application of lutein in aquaculture production plays a key role in solving the problem of body color in aquatic products or poultry.

2.2 Anti-inflammatory

Inflammation is a basic pathological process that occurs as a defense response when tissue damage is caused by harmful external stimuli. Lutein can inhibit the expression and secretion of pro-inflammatory cytokines and promote animal growth and development [25]. Meurer et al. [26] used interleukin-1β (1 μg/kg) to induce the recurrence of gastric ulcers in mice. They found that oral administration of 300 mg/kg lutein from marigold flowers significantly reduced the thickness of the gastric wall and the level of tumor necrosis factor in the recurrence model, promoted the healing of gastric ulcers, and reduced the area of gastric ulcers in mice.

Erhan et al. [27] showed that lutein can effectively treat and prevent oxidative damage and pro-inflammatory damage to vestibular and cochlear nerve tissue caused by acrolein. Comprehensive related studies have shown that lutein suppresses the secretion of pro-inflammatory cytokines by increasing the body's anti-inflammatory cytokine levels, thereby eliminating inflammation and enhancing the body's disease resistance.

2.3 Antioxidant

When there is an excessive accumulation of free radicals in the body, the redox system becomes imbalanced, causing cell damage, lipid peroxidation, and damage to proteins and endogenous lipids. Lutein can inhibit the increase in oxygen free radicals and increase the activity of superoxide dismutase (SOD) and the expression levels of superoxide dismutase 1 (SOD1) and superoxide dismutase 2 (SOD2) mRNA in mice after intraperitoneal injection of lutein, improving the antioxidant capacity of mice [28].

Lin et al. [29] showed that the addition of marigold powder to the aquaculture diet can significantly increase the activity of SOD, catalase (CAT), and glutathione peroxidase (GSH-Px) in aquatic animals, and can also reduce the content of malondialdehyde (MDA), a lipid peroxidation product, in serum, liver, pancreas, kidney, and spleen. Lutein exerts its biological effect by inactivating singlet oxygen through physical or chemical quenching [30]. It therefore inhibits the activity of oxygen free radicals, thereby protecting the body from damage to normal cells caused by oxygen free radicals. It is an excellent antioxidant for relieving oxidative stress.

2.4 Protecting eyesight

Lutein can help maintain eye health by scavenging active oxygen and filtering blue light, thereby preventing and treating certain eye diseases such as age-related macular degeneration (AMD), cataracts and retinitis pigmentosa [31]. Dietary supplementation with lutein may increase macular pigment density (MPOD) in patients with high myopia, and has potential development value. Richer et al. [32] found that after 12 months of taking 10 mg/d lutein, MPOD was increased and Snellen equivalent vision was improved by 5.4 letters, significantly improving the vision of AMD patients.

In addition, Ma et al. [33] used a randomized double-blind placebo-controlled method to study the effect of lutein intervention on the quality of life of 108 patients with early AMD. The results showed that lutein intervention can improve the visual acuity of patients with early AMD and significantly improve their near activity ability. Lutein is a component of macular pigment that has antioxidant and photoprotective properties. It is often used to protect the eyes from oxidative damage and degeneration and enhance visual function.

3 Marigold lutein in poultry production

3.1 Effect of marigold lutein on the antioxidant properties of poultry

Lutein can reduce lipid peroxidation levels and improve lipid oxidation stability. MDA is an oxidation product of lipids. Excessive levels can increase the amount of active oxygen in poultry and damage cells. GSH-Px, SOD, total antioxidant capacity (T-AOC) and CAT are the main indicators of the body's antioxidant status. When the content or activity of antioxidant enzymes in serum or tissue increases, it indicates that the body's antioxidant capacity has increased.

Chen Xiangyu et al. [34] demonstrated that adding 200 or 300 mg/kg marigold lutein to the diet of 56-week-old Taihang chickens significantly reduced the MDA content in the serum or liver of Taihang chickens and significantly increased the activities of GSH-Px, SOD and T-AOC activity. Li Li Ping et al. [35] found that adding different levels of marigold lutein to the basic diet of broilers significantly increased the T-AOC and SOD activity in the liver and leg muscles of 42-day-old broilers, while reducing the MDA content. Guo Junjie et al. [36] showed that adding lutein to the diet of 60-day-old yellow-breasted broilers under high temperature conditions (33±0.52) °C significantly increased T-AOC and GSH-Px activity in the breast muscle and reduced MDA content.

Jang et al. [37] compared the effects of two different sources of lutein on the antioxidant capacity of the liver in laying hens. They found that the addition of 40 mg/kg lutein to the basal diet of 24-week-old laying hens significantly increased SOD activity in the liver and improved the antioxidant capacity of the liver. The above studies show that adding marigold lutein to poultry diets can improve the antioxidant capacity of poultry by increasing the levels of T-AOC, SOD, CAT, GSH-Px, etc., effectively alleviating oxidative damage caused by oxidative stress in farming production.

3.2 Effect of marigold lutein on poultry coloration

Color is one of the sensory criteria for measuring the freshness of food and is also an important criterion for consumers when choosing food. The yellow color of poultry skin or egg yolk is mainly the result of lutein accumulation [38]. The color of poultry skin and egg yolk is mainly determined by the type and content of pigments. Kljak et al. [39] found that adding marigold lutein to the diet of laying hens can increase the lutein content in egg yolks and has a positive effect on improving egg yolk color. Adding lutein to the diets of laying hens of different breeds and ages can improve the lutein content of egg yolks and thus improve egg yolk color [40-41]. Grčevit et al. [42] showed that adding 2 g/kg lutein to the diets of 31-week-old laying hens significantly increased the lutein content of egg yolks and enhanced egg yolk color.

Rajput et al. [43] showed that adding 200 mg/kg lutein to the diet of 42-day-old Arbor Acres broilers significantly increased the skin yellow value of the breast muscle and leg muscles. A study by Jiang Yuanyuan et al. [44] showed that adding different doses and sources of pigments to the diet of 150-day-old Danzhou hens and feeding them until the 28th day significantly increased the yellow value of the Danzhou chicken back skin when 20 mg/kg carthamus red + 40 mg/kg carthamus yellow and 1,000 mg/kg lutein were added. Lü Yong et al. [45] found that adding different doses of natural lutein and a compound pigment to the basal diet during the medium-chicken stage (26–45 days) and large-chicken stage (46–75 days) significantly deepened the coloring effect of the shanks, feet, and abdominal skin of yellow-feathered broilers. The above research results show that adding marigold lutein to poultry diets can increase the lutein content in poultry skin and egg yolk, darken the skin and egg yolk color in different tissue parts of poultry, and improve poultry carcass coloration.

3.3 Effect of marigold lutein on poultry immune performance

The immune system is composed of immune tissues, organs, immune cells and immune active molecules. The immune organs of poultry mainly include the spleen, thymus and bursa of Fabricius. The bursa of Fabricius is a unique immune organ in poultry, which will gradually degenerate as the poultry grows older. The spleen is the largest peripheral immune organ in poultry, participating in the body's cellular and humoral immunity [46]. Numerous studies have shown that adding marigold lutein to poultry diets can not only improve the immune organ index of poultry, but also increase the content of immunoglobulin A (IgA), immunoglobulin M (IgM) and immunoglobulin G (IgG) in the serum, thereby enhancing their immune function [47-48]. Immunoglobulins can inhibit the reproduction of pathogens and protect the body against the invasion of pathogenic bacteria and viruses. They can reflect the body's disease resistance. When the content of immunoglobulins is elevated, it indicates that the body's immunity is enhanced, and vice versa.

Zeng Chenfeng et al. [49] showed that compared with the control group, the addition of marigold lutein to the diet of 21-week-old Roman gray laying hens significantly increased the serum IgG, IgA, and IgM levels to varying degrees. Yuan Na et al. [50] found that adding 0, 60, 120, or 240 mg/kg marigold lutein to the diet of 150-day-old Hy-Line brown-egg laying hens resulted in higher levels of Newcastle disease antibodies in the 120 mg/kg marigold lutein group than in the control group, which in turn increased the body's disease resistance. The above study proves that adding marigold lutein to the diet can enhance the immunity of poultry, thereby improving disease resistance and promoting healthy growth.

3.4 Effect of marigold lutein on the quality of poultry meat and eggs

Meat quality is often comprehensively assessed through various indicators such as meat color, tenderness, water-holding capacity, and pH [51]. Egg quality is generally measured using indicators such as Haugh units, yolk color, egg weight, egg shape index, shell strength and thickness. Wang et al. [52] found that adding marigold lutein to the diet of Arbor Acres broilers significantly reduced drip loss and shear force in the leg muscles of 40-day-old broilers and increased the redness value of the muscles. Meat color is a key indicator of freshness and is determined mainly by light reflection and oxidation [53]. The redness value can to some extent reflect the amount of myoglobin in the muscle, so the greater the redness value, the redder the meat color and the higher the meat quality score. In daily research, shear force values are often used to assess the tenderness of chicken meat. The greater the shear force value, the poorer the tenderness. Water-holding capacity is the ability of muscle tissue to retain water. The more fibers there are in the muscle, the stronger the water-holding capacity and the more delicate the meat [54].

Hu Weiheng et al. [55] and Xu Liang [56] showed that adding marigold lutein to the diets of laying hens of different breeds can significantly improve the Haugh unit and yolk color of eggs, the thickness of the eggshell, reduce the rate of broken soft-shelled eggs, and improve egg-laying performance, thereby improving egg quality. The Haugh unit represents the freshness and protein quality of eggs. The greater the Haugh unit value, the higher the concentration of protein and the fresher the egg. Wang Min et al. [57] showed that adding 0.10% dried marigold flowers (lutein) to the diet of 50-week-old Hy-Line brown laying hens can significantly improve the strength of the eggshell, but there is no significant change in the thickness of the eggshell, egg shape index and egg quality.

Xin Qingwu et al. [58] showed that adding 40 g/kg dried marigold flowers (lutein) to the diet of 35-week-old Hy-Line gray laying hens significantly increased the egg yolk color and shell weight of the fourth week eggs, as well as the egg weight, shell weight, yolk weight, egg yolk color and shell strength of the eighth week eggs. The above research results show that adding marigold lutein to the diet can improve the meat quality of poultry by reducing drip loss and shear force in the muscle, improving the tenderness and color of the chicken meat. The greater the thickness and strength of the eggshell, the lower the egg breakage rate and the higher the quality of the eggshell. Marigold lutein can improve the egg quality of poultry, which is important for the transportation of eggs.

4 Summary

In recent years, the safety of synthetic pigments has been questioned by consumers, and their use in livestock products has subsequently decreased. Research into the application of natural pigments in poultry has become an inevitable trend. Compared with traditional extraction processes, modern extraction techniques for natural pigments such as ultrasound-assisted extraction, supercritical fluid extraction, enzyme-assisted extraction and microwave-assisted extraction have the advantages of short extraction times, energy conservation and high efficiency, and have gradually replaced traditional methods. At the same time, adding marigold lutein to the diet can not only improve the color of poultry carcasses and egg yolks, enhance antioxidant properties and immunity, but also improve the quality of poultry meat and eggs.

At present, domestic and foreign research on marigold lutein mainly focuses on the deposition of egg yolk pigments in laying hens, and there is still much room for research on the immunity, intestinal flora and meat quality of broilers and other animals. In addition, further research is needed on the absorption and metabolic pathway mechanism of pigments, and the length of time that broiler carcasses retain their color after slaughter. This is important for solving the problem of uneven pigment distribution in tissues and reducing costs and increasing efficiency in the farming industry in the future, and can provide more comprehensive theoretical support for the future application of marigold xanthophyll in poultry and other animal production.

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