Extraction of lutein ester from marigold petals and its clathration with β-cyclodextrin
Abstract
Lutein ester was extracted from marigold petals under hexane reflux at 60°C. For protection from oxidation, the as-obtained lutein ester was clathrated with β-cyclodextrin (β-CD) using two methods, viz. grinding lutein ester with β-CD in the presence of ethanol and through the mixing of an ethanol solution of lutein ester with an aqueous solution of β-CD. The results of DSC, IR, H1NMR analyses suggest successful clathration of lutein ester in β-CD. In terms of inclusion efficiency, the former is better than the latter to achieve clathration. We studied factors that can affect the stability of lutein ester such as light, air and temperature change, and the results confirm good stability of the clathrated lutein ester. The toxicity and pharmacokinetic tests on mice showed that the lutein-β-cyclodextrin complex is non-toxic and has an efficient release rate that matches body physiology
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Introduction
Lutein is a natural carotenoid widely exists in fruits and vegetables. It is known to be rich in marigold flowers (Tagetes erecta).[1] Carotenoids are fat-soluble vitamins and show high biological activity in fat. Lutein ester hydrolyses naturally in body to free lutein, and it is known that the absorption rate of lutein esters in fat is higher than that of lutein by 60%.[2-3]
Lutein is brilliantly yellow and is a natural pigment. Being a natural antioxidant and non-toxic, it is used to enhance nutritional value of food.[4] It is known to protect vision and reduce the incidence of cataract.[4-7] Furthermore, it can slow down the hardening of arteries and prevent age-related macular degeneration.[6,8] It is used to improve body immunity for anti-cancer and anti-radiation purposes as well as for skin nourishment and anti-ageing.[5-11] Lutein ester is widely used in industries such as medicine, health, food, tobacco, cosmetics, as well as animal and poultry feed.[11] As an approved food supplement by the U.S. food and drug administration, it has wide application, and is named “plant gold” because it has the price of gold.
β-Cyclodextrin (β-CD) is non-toxic[12] and rapidly hydrolyzed to glucose. Because of its unique “hydrophilic and hydrophobic” structure, it is used to Clathrate a wide variety of objects.[13-15] Once clathrated, a compound changes in bioavailability due to the change of solubility and dissolution rate.[15,16] For example, liquid medicines are clathrated to prevent volatile components from being lost. It is common to find medicines clathrated by β-CD for the purpose of stability enhancement, odor containment and reduction of ill side effects.[14-16] In this article, we describe the clathration of lutein ester using β-CD. To the best of our knowledge, this kind of lutein ester clathrate has never been reported before.
Conclusion
We demonstrated that the extraction yield of lutein ester from marigold petals can be 56.3% at 60°C by hexane solvent extraction. Through the simple grinding of lutein ester with β-CD in the presence of ethanol, there is efficient clathration of lutein ester in β-CD as confirmed by the results of DSC, IR and H1NMR analysis. It was observed that the clathrated lutein ester is more stable that the free counterpart in ambient environment. The results of toxicity test of mice indicate that the lutein-β-CD complex is non-toxic, and has a release rate of lutein agreeable to body physiology.