Hello Lonneke Groothuis

The MTT (3-(4, 5-dimethylthiazolyl-2)-2, 5-diphenyltetrazolium bromide) assay is widely accepted as a simple and reproducible method for determining cell proliferation or cytotoxicity in vitro. In this study, we show that the flavonoids quercetin, rutin and luteolin but not apigenin can reduce MTT in the absence of live cells in the following order: quercetin >> rutin > luteolin > apigenin. Moreover, this reduction can be influenced by medium type and serum. The final concentrations of the flavonoids used were 200, 100, 50, 25 and 12.5 μg/mL. MTT reduction in Dulbecco’s Modified Eagle’s Medium (DMEM) is statistically higher than those in RPMI 1640 and F12 media, which are generally similar. Particularly for luteolin, MTT reduction is considerably higher with serum than without serum. In the case of quercetin at 50 μg/mL, a serum concentration of even only 0.01% is sufficient to significantly enhance MTT reduction versus that at 0% (P < 0.05). Serum at concentrations ranging from 0% to 5% also dose-dependently affects the pattern of formazan crystal formation. In the presence of 0.156–5% serum, the formazan crystals gradually change from being small, numerous and scattered to being large, few and clumpy. The authors hypothesize that flavonoid structure, nutrient concentration in the culture medium as well as serum components directly affect MTT reduction by flavonoids in the absence of cells

Please refer to the research article below for more information.

Article MTT Reduction by Flavonoids in the Absence of Cells: Influen...

Best Wishes.

Dear Lonneke Groothuis thank you for asking this interesting technical question. In addition to the expert answer provided by Malcolm Nobre please also have a look at the following potenially useful protocols:

MTT assay protocol

https://www.abcam.com/kits/mtt-assay-protocol

and

MTT Assay Protocol for Cell Viability and Proliferation

https://www.sigmaaldrich.com/DE/de/technical-documents/protocol/cell-culture-and-cell-culture-analysis/cell-counting-and-health-analysis/cell-proliferation-kit-i-mtt