Biological characterization of epigallocatechin gallate complex with different steviol glucosides

Steviol glucosides (SGs) such as rubusoside (Ru), stevioside (Ste), rebaudioside A (RebA) and stevioside glucosides (SG) are herbal tea sweeteners that enhance the solubility and stability of a number of pharmaceutically important compounds. The complex of epigallocatechin gallate (EGCG) with 10% (w/v) each Ru, Ste, RebA or SG enhanced the water solubility of EGCG over 15 times to 345, 312, 341, or 320 mg/mL, respectively. The 2,2-diphenyl-1-picrylhydrazyl radical scavenging (SC50) activities of EGCG, EGCG-Ru, EGCG-Ste, EGCG-RebA, and EGCG-SG in water were 5.88, 6.03, 6.52, 4.89, and 4.23 μg/mL, respectively. EGCGs complexed with different SGs maintained inhibitory activities against human intestinal maltase, human pancreatic α-amylase, and the growth of Streptococcus mutans, Helicobacter pylori, Salmonella typhimurium, Listeria monocytogenes, Staphylococcus aureus, and Clostridium difficile. In glucose tolerance test using C57BL/6 mice, plasma glucose levels in mice treated with EGCG or EGCG-Ste complex were decreased by 9.34%, which was 31.08% lower than those treated with maltose. The efficient and cost-effective EGCG-SGs production method might be applicable to produce water soluble bioactive nutraceuticals in large scale.