Reaction coupling separation for isosteviol production from stevioside catalyzed by acidic ion-exchange resin.

Isosteviol, a prodrug used to be obtained via Wagner-Meerwein rearrangement from steviol with low yield and long reaction time. Herein, an in-situ separation-coupling-reaction is presented to prepare isosteviol from the natural sweetener stevioside. Simply with in-situ water-washing, the product containing 92.98% purity of isosteviol was obtained with a stevioside conversion of 97.23% from a packet bed reactor without further separation. Within the assayed inorganic acid, organic acids and acidic ionic liquids, the acidic ion-exchange resins provided higher product specificity towards isosteviol. Furthermore, comparing to 5-Fluorouracil, the product presented similar and even stronger inhibition on proliferation of the assayed human cancer cells in a time and dose-dependence by causing cell phase arrest. Isosteviol treatment caused G1 arrest on SGC-7901, HCT-8 and HCT-116 cells, S arrest on HepG2, Huh-7 and HepG3B cells, and G2 arrest on MGC-803 cells, respectively. Reaction coupling separation for isosteviol production catalyzed by acidic ion-exchange resin.

Steviol, a natural product inhibits proliferation of the gastrointestinal cancer cells intensively.

New anticancer agents with lower toxicity have been always urged because of drug resistance associated with overused chemotherapy agents. In this study, steviol, a colonic metabolite of natural sweetener and also a component in leaves of stevia rebaudiana bertoni, was found to possess intensive anticancer activity on the human gastrointestinal cancer cells. Steviol inhibited six human gastrointestinal cancer cells intensively as 5-fluorouracil did at 100 µg/mL. The inhibition mechanism follows mitochondrial apoptotic pathway that was evidenced by increase of Bax/Bcl-2 ratio, activation of p21 and p53; and caspase 3-independent mechanism was also involved. These results are consistent with the miRNA expression analysis. The most regulated miRNAs in the steviol treated gastrointestinal cancer cells were miR-203a-3p (log2 =1.32) and miR-6088 (log2 =-2.54) in HCT-116, miR-1268b (log2 =19.85) and miR-23c (log2 =-2.05) in MKN-45. In view of the metabolic characteristics of steviol and its cytotoxicity on the cancer cells, steviol could be a chemotherapy agent potentially for cancer treatment.

Production of a bioactive sweetener steviolbioside via specific hydrolyzing ester linkage of stevioside with a ß-galactosidase.

A ß-galactosidase from Kluyveromyces lactis was found to specifically catalyze hydrolysis of the glycosyl ester linkage of stevioside to yield steviolbioside, a rare sweetener that also exists in Stevia rebaudiana leaves. In a packed bed reactor, a reaction coupling separation was realized and a production yield of steviolbioside reached 90% in 6 h. The hydrolysis product steviolbioside presented higher cytoxicity on human normal cells (hepatocytes cell L02 and intestinal epithelial cell T84) than stevioside did. Comparing to the typical chemotherapy agent, 5-fluorouracil (5-FU), steviolbioside presents much lower cytotoxicity on all assayed human normal cells; it presented notable inhibition on human hepatocarcinoma cell Hep3B, human breast cancer cell MDA-MB-231 and human pancreatic cancer cell BxPC-3. The remarkable inhibition on MDA-MB-231 cells makes steviolbioside a potential remedy for human breast cancer, when steviolbioside is served as a natural sweetener.