Biological Evaluation

BIOLOGICAL EVALUATION

The plant or extract can then be evaluated by various biological methods to determine pharmacological activity, potency, and toxicity. The biological evaluation would serve better than the physical and chemical evaluation for drugs that could not be satisfactorily assayed by these last two methods. Moreover, this is an important method, the crude drugs are considered important only because of their biological effects and this evaluation would conclude the effect. These methods are considered to be less precise, more time-consuming and more expensive. Bioassays should be as simple as possible, and attempts should be made to have access to a large number of different tests so that many biological properties can be screened. The bioassay methods are of three types they are, toxic, symptomatic and tissue or organ methods. Different animals are used in toxic and symptomatic method and isolated organ or tissue is used in the third method.

These assays are conducted by determining the amount of drug of known potency required to produce a definite effect on suitable test animals or organs under standard conditions. Reference standard are used in certain bioassay procedures to minimize errors.

Toxicity studies are performed in suitable animal models to decide the lethal dose and effective dose of crude drags. Mice are used to test the effects of various vaccines.

Oxytocic activity of vasopressin injection is tested on guinea pigs, and oxytocic injection is assayed on young domestic chickens by injecting into an exposed crural or brachial vein and noticing the changes in blood pressure. Pigeons are used to assay Digitalis glycosides by transfusing the drug through the alar vein to the blood stream and observing the lethal effects. Depressor activities and mydriatic effects of certain drugs are tested in cats and cat’s eye, respectively. Anthelmintic drugs are evaluated on worms.

The drugs that have an effect in eyes are assayed on rabbit’s eyes. Dogs are used to assay the drugs that exhibit cardiac and gastrointestinal activities. Effects of Ergot are carried out on cock’s comb or rabbit’s intestine or its uterus. Next to the animals, the studies are carried out in human beings also. In some instances, the effects that are observed from animal studies would be different when tested in humans. The tested biological activities include hepatoprotective activity, hypoglycaemic activity, antiinflammatory activity, antiulcer activity, immunomodulatory activity, etc.

Microbiological assays are carried out to determine the effects of drug in various microorganisms, and this is employed in the identification of antimicrobial drugs. The methods used in this type of assays are agar well-diffusion method, disc-diffusion method, and turbidimetric method. In other microbiological methods, the living bacteria yeast moulds are used for assaying vitamins.