Diabetes mellitus, a chronic and the most common metabolic disease, affects 285 million people worldwide. The number of people getting affected is increasing every year, faster than the rate estimated by the World Health Organization. Diabetes occurs when the pancreas does not product enough insulin (Type I), or when the body cannot effectively use the insulin it produces (Type II). The most prevalent form of diabetes affecting 90 to 95 percent of diabetics worldwide is Type II.

Type II diabetes is presently treated using conventional drugs which act mainly by stimulating insulin absorption and its release from the pancreas or by blocking he enzymes that break down sugar, such as amylase and glucosidase. Most of these conventional drugs, however, have varied side-effects, thus a searcg for plant-derived insulin mimetrics and natural enzyme inhibitors from plant sources is being pursued.

This project aims to isolate, identify, and characterize molecules which mimic the action of insulin or bypass the insulin receptor and purify amylase and glucosidase inhibitors from Philippine medicinal plants with known anti-diabetic properties.

A total of 54 newly collected medicinal indigenous plants are currently being extracted for the screening of plant insulin mimetic propoerty. Most plant materials were collected from the screen house and some were gathered near the vicinity of the university including Mt. Pangasugan in Baybay City, Leyte. Plant samples wer subjected to aqueous and organic extraction to have comparison on whihc solvent will give the best activity. Four solvents namely: benzene, chloroform, acetone, and ethanol were used in organic extraction while sterile distilled water was used in aqueous extraction.

All plant samples were tested for their potential to block alylase and glucosidase. However, only a few showed good inhibitory activity during the assay. In glucosidase inhibitory assay, only 18 plant samples showed significant inhibition of more than 50 percent among other plant samples extracted. These are makahiya, basil, stevia, mahogany, sibucao, balbas pusa, rosy periwinkle, guava, buyo, dita, abgaw, tuba-tuba, kamias, celery, red alugbati, magsumpay, garlic, and gatas-gatas. These plant samples inhibit glucosidase in a dose-dependent manner; that is, inhibition increases as the concentration of sample increases.

Furthermore, in amylase inhibitory assay, only five plant samples showed significant inhibition of more than 50 percent against amylase. These include kamias, celery, abgaw, gatas-gatas and alugbati. The five samples also inhibit amylase in a dose dependent manner.

The evaluators chose the top three plant materials, namely, makahiya (Mimosa pudica, aqueous extract), basil (Ocimum tenuiflorum, aqueous extract) and kamias (Averrhoa bilimbi, acetone extract) to be used for further analysis. In this study, we used the Reverse Phase High Performance Liquid Chromatography to purify individual compounds from mixtures of compounds. Only the chosen plant materials were analyzed since they were the ones that gave the highest inhibitory activity. Several solvent systems were tested in order to have a good seperation and more peaks will b eluted.

Thirty individual cages made of steel plate were fabricated for in vivo experiment. Each cage is anough to accommodate eight heads of mice for one treatment group. Ordering of ICR strain mice were already done. Authentication was facilitated to ensure corrent identity of the mice.

In vivo assay will be done once target compounds are isolated and purified from the plant crude extracts. The amount needed for the assay must be computed before starting to avoid unfairness during the experiment. During the tests, supertyhpoon Yolanda totally destroyed the screen house where most of the plant materials were located. Power interruptions affected storage conditions of the cells, enzymes and other reagents essentials in the project. Some of the newly purchased laboratory equipment were exposed to the rain when the strong winds shattered the glass windows. Despite these events, the project managed to recover slowly and continue with its aim of discovering plant materials that can be used in the treatment of diabetes.

The discovery of plant-derived insulin mimetics may provide a breakthrough in the field of medicine. It would benefit not only people afflicted with diabetes mellitus but also individuals who are at risk of developing the disease. It is with optimism that once completed, the project will help curb the incidence of diabetes.

Written by: 
Dr. Edgardo E. Tulin
Visayas State University

Published by:
Department of Science and Technology-Science and Technology Information Institute (DOST-STII)