Analysis of the interference of polyphenols and proanthocyanidins on the neutral red assay for cell viability.

Puksiri Sinchaiyakit, Robert W. Gracy, Wandee Wattanachaiyingcharoen, Surisak Prasarnpun, Maitree Suttajit


The neutral red uptake assay has been wildly used for screening cell viability. However, several natural polyol compounds such as polyphenolics and flavonoids have been observed to interfere with the neutral red assay and give false positive results. This study was designed to determine whether polyphenolic compounds and proanthocyanidins extracted from tamarind seed husk (TSH) affect cell viability. Two kinds of normal cells, retina ganglion cells (RGC-5) and hippocampal cells (HT-22), were used in the study. It was found that by using neutral red assay, the TSH extract increased normal cell viability to the maximum level of 2-folds higher than the control. The artifact was similarly shown in both serum-free and serum-added media which had no cell proliferation. Therefore, neutral red assay may not suitably used for the cell survival test especially in the presence of proanthocyanidins or materials containing polyphenols or proanthocyanidins.

Keywords: Polyphenol, proanthocyanidins, cell viability, neutral red assay.

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