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Stevia rebaudiana Bertoni, known as the honey leaf plant, is native to South America and is known as a rich source of healthy, calorie-free sweet diterpene glycosides, including stevioside, steviol bioside, rhabdiosides A-E, and dalcoside-A. Among the sugar compounds of stevia, stevioside and rhabdioside A are found in larger amounts in the plant. Due to their unique characteristics, including sweetening power, 300 and 400 times that of sucrose, respectively, they are heat-resistant and stable in a wide range of acidic pH and without the harm caused by artificial sweeteners, they have been highly regarded by the food industry. However, the crude extract with bad smell, bitter taste and dark brown color is obtained from Stevia leaves, which requires the process of refining and decolorizing the extract to produce products with better taste and sweetness. Therefore, the purpose of this project is to extract sweet di-terpene glycosides from Stevia plant with a high purity and yield using a green, efficient and cost-effective method. In this research, extraction of syrupy extract from dry leaves of Stevia plant was done using deionized water in neutral pH range at 80 °C. Citric acid, calcium oxide, bentonite soil, and alumina were used to remove colored plant impurities such as chlorophyll, flavonoids, and other unwanted compounds. Also, ion exchange resins were used to remove metals and minerals. After further separation and purification steps, the resulting glycosides were identified by high performance liquid chromatography (HPLC) and compared with standard samples. The important point is that bentonite soil and alumina are among the minerals that can be recycled in this research, so that after absorbing the pigments, they can be reused by placing them in the oven at a temperature of 450 degrees Celsius and removing organic compounds, which is very economical. It is affordable. Based on HPLC analysis, the amount of four main sugars in stevia sugar molasses was determined in relation to each other, stevioside (62.5%), rhabdioside A (31.2%), rhabdioside C (5%) and dalcoside A (1.3%). The advantages of the used method include the use of water as a green and non-toxic solvent in all extraction stages, the use of cheap and available materials such as calcium oxide, alumina and bentonite clay for color removal, and food grade and recyclable ion exchange resins for removal minerals, extraction of sweet diterpene glycosides from stevia plant with good yield and purity, economical and in accordance with the goals of green chemistry.
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