Screening Methods for Drug Discovery from Plants

Abstract

Many early pharmacological studies with plant extracts involved injecting samples into rats or mice. The so-called hippocratic screening [1] was widely used. It typically involves administration of several different doses of test substance to small groups of animals and then observing behavior and looking for obvious symptoms at regular intervals for a period of up to 24 h. A systematic system for scoring observations relating to toxicity and to effects on the CNS has been developed as the Irwin test [2]. Such assays are expensive in terms of time and consumables, and they also require relatively large amounts of plant extract. They are more likely to be useful in assessing potential toxic effects than in revealing novel drug effects.Model organisms can be used instead of rodents. Nematode worms (Caenorhabditis elegans), fruit flies (Drosophila melanogaster), and zebrafish (Danio rerio) have all been used in drug discovery (see [3] for a review). Extracts of some traditionally used medicinal plants have been tested on nematodes for antioxidant activities and effects on aging [4][5][6]. Zebrafish embryos are attracting attention because they are vertebrates and many stages of their development can be readily visualized (e.g., [7][8][9]). They are suitable for screening plant extracts in 96-well microtiter plates [10]. Embryos can be exposed to test substances and observed for the development of unusual phenotypes, or disease models can be created in the embryos and samples tested for their ability to modify the expression of the disease (see [3] for examples of disease models in such organisms).

Phytochemical Composition and Bioactivity Assessment of Essential Oil of Cinnamomum bejolghota (Buch.-Ham.) Sweet from Xuan Son National Park, Vietnam

“…The standard liquid dilution method 15 was performed to determine the in vitro antimicrobial activity experiments on a 96-well microtiter plate as previous description 16 . The fungi were grown in the Sabouraud Dextrose Broth medium (SDB-Sigma).…”