Development and validation of in vitro screening procedure for identifying herbals possessing sulfonylurea-like activity

An in vitro screening procedure for identifying herbals possessing sulfonyl-urea like activity has been developed and validated. The procedure consists of a combination of the membrane-based receptor binding assay and a cell-based insulin secretion assay. The receptor binding assay utilizes membranes prepared from Syrian hamster HIT-T15 insulinoma cells naturally expressing the SUR1 receptor. The interactions of herbals with SUR1 receptor is detected by measuring the inhibition of H3-glibenclamide binding to the receptor. If activity is found, it is further confirmed in the cell-based insulin secretion assay. The assay is based on the ability of cultures of HIT-T15 cells to increase insulin secretion in response to various stimulis. The conditions for both receptor binding and insulin secretion assays were optimized to allow for testing of crude herbal extracts.; The screening procedure was applied to a set of six herbs. American ginseng was identified as an herb most likely to possess sulfonylurea-like activity, which is in good correlation with previously reported data. The in vitro activity-guided fractionation of the crude American ginseng extract resulted in the isolation of an active principal. Its partial structure was elucidated by the combination of the wet chemistry, spectroscopic and chromatographic tests. This active principal appears to be a glycan, bearing most similarity to the hypoglycemic compounds isolated from Korean Ginseng (Panaxans A–J). Its molecular weight and monosaccharide composition, however, is quite different from other previously reported hypoglycemic principals of American ginseng (Quinquefolans A and B). Thus, apparent hypoglycemic properties of ginseng are due at least in part to interactions with sulfonylurea receptor resulting in induction of insulin secretion.; The developed and validated in vitro procedure that we report here may serve as a useful tool for identifying herbals exhibiting hypoglycemic activity through interactions with sulphonylurea receptor and isolation of the corresponding active principals. Such in turn may lead to development of the new, effective and safe therapeutic agents for treatment of Type II diabetes.