Pharmacological Effects of Marigold and the Current Status of Its Research Utilization
Marigold is an annual herbaceous plant of the genus Tagetes in the family Asteraceae, and it has other names such as smelly mallow, sato yomogi, and marigold lamp. It is harvested from summer to autumn, with thick, upright stems, leaves with glands on the edges, and a distinctive odor. The capitulum grows singly and ranges in color from yellow to orange. Marigold is native to Mexico, has few pests or diseases, and has a high survival ability. Marigold flowers can be used as a major plant source for extracting lutein, and humans can obtain lutein from food, which is effective in preventing age-related macular degeneration. Lutein also functions in preventing various chronic diseases, has anti-cancer properties, helps prevent cardiovascular diseases, and boosts immunity.
1.Antioxidant activity
Calendula flowers are a major raw material for lutein extraction. Lutein is a type of tetraterpenoid that contains abundant conjugated double bonds, giving it strong free radical scavenging ability and effectively preventing cell damage caused by oxygen free radicals. Some researchers have used chemiluminescence methods to analyze the scavenging effects of calendula lutein on peroxide, superoxide anion, hydroxyl radical, and lipid radicals, and found that lutein has strong scavenging effects on these free radicals. By combining in vitro antioxidant methods with an ethanol-induced oxidative damage model in mice, a study on the synergistic antioxidant activity of the two carotenoids, lutein and zeaxanthin, showed that a lutein-to-zeaxanthin ratio of 1:2 exhibited better synergistic antioxidant activity.
In recent years, both domestic and international studies have found that lutein contained in Calendula officinalis has the ability to inhibit tumor cells in cancers such as colorectal cancer, liver cancer, breast cancer, stomach cancer, and esophageal cancer. According to related research, the antitumor effects of lutein are primarily achieved through the inhibition of tumor cell proliferation and the induction of differentiation, the induction of apoptosis in tumor cells, immune regulation, and antioxidant activity. Research results indicate that lutein can suppress the proliferation of esophageal cancer EC9706 cells to a certain extent and induce apoptosis in EC9706 cells. Studies analyzing the inhibitory effects of lutein on the proliferation of human liver cancer HepG2 cells and the associated molecular mechanisms have found that lutein can inhibit the proliferation of HepG2 cells by affecting the transcriptional expression of AP-1, p53, and caspase-3 genes, as well as the expression of apoptosis-related proteins. Furthermore, two flavonoid compounds extracted and isolated from the stems and leaves of Calendula officinalis were found to inhibit the proliferation of human gastric cancer cells SGC7901 and human liver cancer cells SMMC7721, demonstrating anticancer and antistomach cancer activities in vitro.
3.Inhibit cardiovascular diseases
The accumulation of cholesterol and LDL (lipoproteins) in the human body is an important cause leading to atherosclerosis, which in turn contributes to cardiovascular diseases. Related epidemiological, in vitro, and animal model studies suggest that lutein from marigold leaves can reduce the occurrence of cardiovascular diseases by partially preventing the development of atherosclerosis. Research indicates that lutein can regulate the expression of Nrf-2 and NF-κB in brain vascular endothelial cells (bEND.3 cells), thereby inhibiting Aβ25-35-induced toxicity and improving mitochondrial membrane potential and cell viability. Animal studies using mice have demonstrated that lutein can improve atherosclerosis and hepatic steatosis in apoE-/- mice induced by a high-fat diet by regulating lipid metabolism and reducing oxidative stress. Studies reveal that lutein extracted from marigold can exert anti-atherosclerotic effects by modulating lipid metabolism, increasing plasma NO and cGMP levels, and reducing ET production. Moreover, lutein from marigold provides protective effects against visual disorders such as age-related macular degeneration and cataracts. Marigold extracts have been found to alleviate visual fatigue and improve symptoms including eye redness, pain, light sensitivity, blurred vision, and dryness. A hydroalcoholic extract of marigold helps reduce diabetic complications such as retinopathy, neuropathy, kidney disease, and cardiovascular disease, and therapeutic doses of marigold extract can also contribute to weight improvement.
4.Research on the Deep Processing and Utilization of Marigold Lutein Products
Marigold is currently one of the main raw materials industrially used for extracting and producing lutein. In addition to traditional solvent extraction methods, recent advancements in plant extraction technologies have led to the gradual application of enzyme methods, ultrasonic extraction, supercritical CO2 extraction, microwave-assisted extraction, and subcritical extraction technologies in the research and practical application of extracting and producing lutein from marigold.
Although marigold lutein has high physiological activity, lutein is a fat-soluble substance, and the presence of multiple conjugated double bonds in its molecular structure makes it prone to oxidative degradation under light, heat, and oxygen conditions, resulting in low stability and water solubility, which limits its use in deep processing. Recently, researchers both domestically and internationally have been actively developing studies to produce lutein microcapsules and lutein soft capsules using lutein as a raw material. The microcapsule technology aims to improve the stability and biological activity of encapsulated substances by encapsulating fat-soluble active substances such as lutein using substances like gelatin and gum arabic (wall materials) to form fine particles (microcapsules). One researcher selected gum arabic as the wall material and optimized the optimal formulation and process for producing lutein microcapsules through single-factor experiments and orthogonal experiments, resulting in a significant improvement in the stability and water solubility of the lutein microcapsule products. In one study, gelatin was used as the wall material to produce lutein enteric microcapsules using a single coacervation method, and the manufacturing process for the lutein enteric microcapsules was optimized through response surface experiments. The resulting lutein microcapsules were found to exhibit excellent enteric characteristics.
Softgel capsules are a new dosage form frequently used in the field of health functional foods. They have an attractive appearance, high bioavailability, good stability, and can effectively prevent the degradation of light- and heat-sensitive components of the target substance. Some scholars have selected medicinal soybean oil as the dispersion medium and added honey and soybean lecithin as suspension aids and wetting agents, obtaining the optimal formulation for lutein softgel capsules through meticulous experimentation. The results showed that the contents of the manufactured lutein softgel capsules were uniform and stable. According to research, by using lutein monomer, vitamin A, vitamin E, and other raw materials in a composite formulation, lutein softgel capsules with the function of relieving visual fatigue were developed and manufactured.
Lutein is a major bioactive substance contained in marigold, and it is also present in vegetables and fruits such as cabbage, corn, kiwi, and spinach. However, marigold has a high lutein content, is suitable for large-scale cultivation, and is cost-effective, making it the main industrial source for lutein production. Lutein is a type of carotenoid, and related studies have confirmed its clear effectiveness in preventing age-related eye diseases such as macular degeneration. In 1995, the U.S. Food and Drug Administration (FDA) reviewed the practicality and safety of lutein and approved it as a dietary supplement. In 2008, China included lutein derived from marigold in the list of new food ingredients, and currently, marigold lutein is widely used as a raw material for health functional foods and is utilized in the production of health supplements and dietary supplements.