Evaluation Of Cytotoxicity And Biological Activities In Steviol Glycosides Compounds

Steviol glycosides extracted from stevia are ent-kaurenoic acid/ester tetracyclic diterpenoids, possessing a wide range of biological activities, in addition to the low-calorie natural sweet quality. The main sweet composition is stevioside, consisting of two glucosidic linkages(alcohol glycoside bond in C13, β-1,2 glycosidic bonds in C13)and one ester linkage(C19). In this paper, different catalysts were used to hydrolysis the glucosidic linkages or ester linkage to prepare rubusodide, steviobioside, steviol and isosteviol. The eight kinds of steviol glycosides compounds were studied in four areas, cell cytotoxicity, the mechanism of anticancer, anti-inflammatory and antioxidant activity. The main conclusions are as follows:1 At the concentration of 250 μg/m L, stevioside, rebaudioside A, rebaudioside C, rubusodide and glycosylated stevioside had no cytotoxicity to 14 kinds of digestive system cells. Steviobioside had slight cytotoxicity to human intestinal cells T84, HCT-8, HCT 116 and hepatocyte cells Hep G2, Hep3 B. Except MHCC97-L and HCCLM3 cells, the cancer cells viability druged by steviol and isosteviol were less than 25%, and steviol and isosteviol had similar cytotoxicity with the traditional digestive anticancer drugs 5-FU, so in theory they can be used as anticancer drugs. 2 Steviol and isosteviol inhibited the growth of 9 kinds of digestive system cancer cells in a time and dose-dependent manner, the inhibition increaseing with the growth of concentration and time, and steviol and isosteviol were more evident than 5-FU, and isosteviol was better than steviol. The survey found that 48 h was the best time. Light microscope observation found that steviol and isosteviol could cause cells to density reduction, connection disappear, surrounding of cells detachment, translucent form of normal growth state lost, and with the increasing concentration, the density and extent of shrinkage were more evident. The IC50 of HCT-8 cells druged by steviol and isosteviol were 140.37 μg/m L、134.86 μg/m L, but the IC50 of T84 cells were 305.46 μg/m L、256.97 μg/m L, so steviol and isosteviol had a better selectivity. Steviol was the metabolite of steviol glycosides in the intestines. Steviol had lower inhibition effect to human intestinal epithelial cells T84,but higher to human ileo-caecal adenocarcinoma epithelial cells HCT-8 and human colorectal cells HCT 116. Therefore, we can take safety steviol glycosides to satisfy the taste in demand, when reaching the intestinal to steviol, to cure colon cancer and other intestinal diseases, playing a role in targeting drugs, while reducing the injury to the other cells and tissues, giving a better way to cure cancer. 3 Similar with the traditional digestive anticancer drugs 5-FU, steviol and isosteviol were also cell cycle arrested drugs to 7 kinds of cancer cells, but cells were arrested in different phases, and isosteviol was better than steviol. The difference in cell cycle arrested had a relationship with P53 gene. Steviol and isosteviol had no effect to the melting curves and effect on the relative viscosity of DNA. Hyperchromicity of UV-Vis absorption spectra showed that steviol and isosteviol cound combined with DNA in a way of groove binding,and isosteviol was better than steviol. 4 At the concentration of 250 μg/m L, stevioside, rebaudioside A, rebaudioside C, rubusodide and glycosylated stevioside had no cytotoxicity to Raw264.7 cells. At the concentration of 100 μg/m L, steviobioside, steviol and isosteviol had no cytotoxicity to Raw264.7 cells. With 1 μg/m L LPS stimulused Raw264.7 cells to establish inflammation model, steviol glycosides compound inhibited the mount of NO with increasing concentrations. The amount of NO was gradually reducing with the increasing concentrations of isosteviol, the reduction by about 4 μM at the concentrations of 100 μg/m L, while the inhibition of the others were lower. So isosteviol was a relatively better anti-inflammatory drug. 5 At the concentration of 5 mg/m L, the capacity on DPPH radical scavenging had no evident in stevioside, rebaudioside A, rebaudioside C, rubusodide and glycosylated stevioside, but steviobioside, steviol and isosteviol were relatively stronger capacity on DPPH radical scavenging. At the concentration of 20 mg/m L, the capacity on DPPH radical scavenging of steviobioside, steviol and isosteviol were 20.71%、21.16%、24.81%. Rubusodide was the strongest on ·OH radical scavenging. The capacity were 13.83% at the concentration of 20 mg/m L. But compared to 1 mg/m L VC scavenging DPPH radicals and ·OH radicals, steviol glycosides compounds were weaker in clearing the two free radical, but as additive with antioxidant activity, they were better to the body than single antioxidants.