**Author details**

as protein denaturation or reactivity, which would affect both the cell-free and cell-based assays. Another possibility is very low-affinity non-covalent binding to receptors, enzymes,

Cytotoxicity is one of the most important methods for biological evaluation as it has a series of advantages, along with the preferred and mandatory items. Given this information, the ability to accurately measure cytotoxicity can prove to be a very valuable tool in identifying compounds that might pose certain health risks in humans [3]. The cytotoxicity test is one of the most important indicators of the biological evaluation system *in vitro* to observe the cell growth, reproduction and morphological effects by chemicals, and with the progress of modern cell biology; experimental methods to evaluate cytotoxicity are also continuously being

Cytotoxicity studies are a useful initial step in determining the potential toxicity of a test substance, including plant extracts or biologically active compounds isolated from plants. Minimal to no toxicity is essential for the successful development of a pharmaceutical or cosmetic preparation and in this regard, cellular toxicity studies play a crucial role. The concept of basal cytotoxicity, where deleterious effects are noted on structures and functions common to all human cells, is relevant when considering the relationship between acute toxicity and cytotoxicity. The selectivity index is an important measure to identify substances with promising biological activity and negligible cytotoxicity. Various bioassays and a number of different cell lines have been used to assess cytotoxicity of chemicals. Regulations of cytotoxicity *in vitro*, countries have to make the relevant provisions of the corresponding cytotoxicity tests according to their actual situation [4]. With the continuous development of cytotoxicity tests, methods, such as detection of cell damage by morphological changes, determination of cell damage, measuring cell growth and metabolic properties, have appeared and have gradually been developed from qualitative evaluation to quantitative [5–8]. The ability to measure early indicators of toxicity is an essential part of drug discovery. *In vitro* cytotoxicity assays involving tissue specific cell cultures are considered as valuable predictors of human drug toxicity. However, there are no uniform cytotoxicity test methods and all these existing methods have particular problems. Measuring cell cytotoxicity also proves to be quite indispensable in the process of developing therapeutic anti-cancer drugs. By determining the cytotoxicity levels of cancer cells, anti-cancer medications can hinder the proliferation of target cells either by messing with their genetic material or by blocking the nutrients that the cells needs to survive. Additionally, understanding the mechanisms involved in cytotoxicity can likewise give researchers a more in-depth knowledge on the biological processes (both normal and abnor-

Identification of cytotoxic chemicals may be crucial in helping to explain target cells, and organ toxicity and species differences. Understanding the consequences of the induced natural

etc. that only occurs at very high concentrations [2].

mal) governing cell growth, cell proliferation, and death.

**1.1. Cytotoxicity**

4 Cytotoxicity

developed and improved [3].

**1.2. Cytotoxicity studies**

Tülay Aşkin Çelik

Address all correspondence to: tcelik@adu.edu.tr

Department of Biology, Art and Science Faculty, Adnan Menderes University, Central Campus, Aydin, Turkey
