We developed a new method for evaluating the hypoglycemic effects of Rehmanniae Radix (RehR), an herbal medicine, by monitoring the decrease in the sugar level of hyperglycemic silkworms. Preparation of a test sample obtained from 5 g of RehR, and quantification of the hypoglycemic effects of the sample using the hyperglycemic silkworm model was completed within 2 days. We further applied the newly established protocol to RehR extracts, and found that three of six samples showed hypoglycemic activity against hyperglycemic silkworms, whereas the other three samples did not. These results suggest that the hyperglycemic silkworm model is a useful alternative animal model to evaluate the hypoglycemic effects of RehR.
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