Diabetes is a serious disease affecting many people throughout the world, and is expected to increase in the coming decades. Traditional medicine is used in many places around the globe, including the Dominican Republic, for the treatment of diabetes along with modern medicines. Fieldwork conducted in the Dominican community by the Institute of Economic Botany identified Costus species and Momordica charantia L. as being widely used for diabetes treatment, thus pointing to these plants for further investigation.

In an in vivo study, Costus spicatus Sw. tea or water were fed ad libitum to a C57BLKS/J mice (KS) db/db mouse model of obesity and type 2 diabetes mellitus (T2DM). The C. spicatus tea did not improve glucose or insulin tolerance, or moderate hyperglycemia or insulin sensitivity.

To analyze the hypoglycemic effect of Momordica charantia fruit, initial studies were conducted in vitro. Both an ethanol extract and saponin-rich fraction of fruit, along with the five isolated triterpene saponin compounds 3β,7β,25-trihydroxycucurbita-5,23(E)-dien-19-al, momordicine I, momordicine II, 3-hydroxycucurbita-5,24-dien-19-al-7,23-di- O-β-glucopyranoside, and kuguaglycoside G, were tested to assess their potential stimulation of insulin secretion. The saponin-rich fraction, along with mormordicin II and kuguaglycoside G, were active in the assay, suggesting saponins as the active hypoglycemic compounds in M. charantia .

To further characterize the antidiabetic activity of Momordica charantia, a saponin-rich fraction and ethanol extract of the fruit was gavaged daily to C57BL/6 mice fed a high-fat diet. Both treatments lowered fasting glucose and improved glucose tolerance after three weeks. Also, the ethanol-extract treated group had significantly less β-cell mass at the end of the study, pointing to improved β-cell function. The results of this study again suggest saponins in M. charantia as the therapeutic constituents.

In conclusion, the studies described aimed to investigate the efficacy of traditional medicine in a rigorous scientific setting and found that although Costus spicatus was not active, Momordica charantia displayed significant antidiabetic activity. Information about safety and efficacy of herbal medicine will continue to be important as these traditional treatments increase in use around the world for health conditions, including diabetes.