*7.1.5.1.1. Spontaneously developed diabetic rats*

An example is the diabetic Gato-Kakizaki rat which is a genetic lean model of type 2 diabetes originating from selective breeding over many generations of glucose-intolerant nondiabetic wistar rats [37]. One great advantage of these models is that they can be employed as model of atherosclerosis which represents the long-term complication of diabetes mellitus and tested against several natural products and is without the interference of side effects induced by chemical drugs [38]. Mutant strains obese diabetic mice are available such as the C57BL/Ksj-db/ db. With this model it is possible to test for effects of plant extracts on blood sugar, body weight, insulin production, and insulin resistance [38].

## *7.1.6. Genetically engineered diabetic mice*

 In this case, rodents may be produced to over- (transgenic) or under (knockout)-expressed proteins thought to play a key part in glucose metabolism [39]. Certainly, the high cost restricts their study in sophisticated protocols which explore mechanism of potential therapeutic agents that stimulate pancreatic β-cell death [40]. Insulin-dependent diabetes mellitus (IDDM) can be developed by inserting into the unique viral protein of mice which is then expressed as a self-antigen in the pancreatic islets of Langerhans. Another is lymphocytic choriomeningitis virus (LCMV)-induced IDDM mice [41]. This procedure is relatively new and rarely used because of the sophisticated techniques, cost, and equipment required.

 It suffices here to know that in the choice of assessing a compound, not all the available methods are chosen. Like in the case of the relaying researcher, the following were used to screen for an active compound especially at the stage of crude extract and the liquid-liquid partitioning fractions: normoglycemic animal model, oral glucose loading animal model, and alloxan model of DM. The choice for these three models was influenced by fund, availability, technical skill, and satisfaction of study requirement. At the stage of bioassaying (testing) the pure compound, the only model used was the definitive alloxan-induced DM [27].

After a successful bioassay of the pure compounds, that (pure compound) with the best activity is sent for structural elucidation through functional group analysis by nuclear magnetic resonance (NMR) spectroscopy and confirmed with gas chromatography and mass spectroscopy (GC MS) [27]. The readings are then read out by an experienced chemist. At this point the researcher would be fulfilled for such hard work to be graced by a chemical structure implicated for the bioactivity claimed.

It suffices here to note that there are some quests undertaken by the relaying researcher, not earlier mentioned in this chapter, such as lethal dose estimation (LD50) test of the extract; subacute toxicity; chronic toxicity study [10]; phytochemical analysis [25]; and peroxidatation test of the extract, that were necessary for a successful, question answering research (by providing parameters that aided the meaning/answers of the whole research quest).
