I.1.9.6 Extraction of plant
material
The choice of the extraction solvent depends mainly on the
polarity and hence the solubility of the bioactive compound(s) of interest.
Although water is generally used as an extractant in many traditional
protocols, organic solvents of varying polarities are often used (either alone
or in different combinations) in modern methods of extraction to exploit the
various solubilities of plant constituents. The polarity and chemical profiles
of most of the common extraction solvents have been determined (Eloff
et al., 1998) and are summarized in Table II.
Thus, if the polarity or the solubility of the compound(s) of
interest is known, information such as the one in the table below can be used
to select a suitable extractant solvent or a mixture of two or more solvents of
different polarity. Alternatively, a solvent such as acetone, which has the
capacity to extract both polar and non-polar substances, and has been
recommended by Eloff (1998) for the extraction of most polar
and non-polar compound.
If the polarity of the compounds of interest is not known, the
powdered plant material can be extracted simultaneously with a mixture of
different proportions of two or more solvents of different polarity.
Alternatively, the powdered plant material can be extracted sequentially with
solvent of different polarity in what is known as a sequential extraction
procedure (Bruneton, 1999).
The choice of the extraction procedure depends on the nature
of the source material and the compound to be isolated. Solvent extraction
procedures applied to plant natural products include but not limited to
maceration, percolation, soxhlet extraction, steam distillation and sequential
solvent extraction (Jones and Kinghorn, 2005).
Table II : Polarity and chemical
profiles of most of the common extraction solvents
I.1.10. Experimental diabetes
They are used for many decades. The can either be spontaneous
or provoked. This constitutes laboratory rodents and mammals. Small ruminants
are objects for many medical researches but are not used in diabetology because
their herbivoral metabolism is very different from that of omnivores.
Spontaneous model are rare in animals and the type of diabetes is not always
the same as the one found on man. Certain species of animals were created for
medical use.
Induced methods are obtained by administration of the toxic
agent on the endocrine pancreas or by pancreatectomy.
I.1.10.1. Chemical
induction model
· Diabetes induced by streptozotocin
Streptozotocin (STZ) is an antibiotic, anti-tumoral of
synthesis use in anticancerous chemotherapy in man. In animals, streptozotocin
selectively destroys the pancreatic insulin-secreting â-cells, leaving
less active cells. STZ diabetic mice are one of the animal models of human
insulin-dependent diabetes mellitus characterized by high fasting blood glucose
levels and drastic reduction in plasma insulin concentration (Jie
et al., 2007).
· Diabetes induced by alloxan
Alloxan is one of the usual substances used for the induction
of diabetes mellitus apart from streptozotocin. Alloxan has a destructive
effect on the beta cells of the pancreas (Vivek et al.,
2010). Alloxan causes a massive reduction in insulin
release by the destruction of â-cells of the islets of langerhans,
thereby inducing hyperglycemia. Insulin deficiency leads to various metabolic
alterations in the animals via increased blood glucose, increased cholesterol,
increased levels of alkaline phosphate and transaminases (Vivek et
al., 2010).
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