Sze Mun Chan1,
Kong Soo Khoo2,
Nam Weng Sit1 
For correspondence:- Nam Sit Email: sitnw@utar.edu.my Tel:+6054688888
Received: 26 September 2014 Accepted: 27 August 2015 Published: 29 November 2015
Citation: Chan SM, Khoo KS, Sit NW. Interactions between plant extracts and eell viability indicators during cytotoxicity testing: Implications for ethnopharmacological studies. Trop J Pharm Res 2015; 14(11):1991-1998 doi: 10.4314/tjpr.v14i10.6
© 2015 The authors.
This is an Open Access article that uses a funding model which does not charge readers or their institutions for access and distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0) and the Budapest Open Access Initiative (http://www.budapestopenaccessinitiative.org/read), which permit unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited..
Purpose: To compare the cytotoxicity of six medicinal plants (Acmella ciliata, Amaranthus tricolor, Coriandrum sativum, Glebionis coronaria, Kyllinga brevifolia and Tradescantia zebrina) using 3-(4, 5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and neutral red uptake (NRU) assays.
Methods: Hexane, chloroform, ethyl acetate, ethanol, methanol and water extracts were obtained for each plant by sequential solvent extraction. Cytotoxicity was evaluated in triplicate, from 640 to 5 µg/mL, two-fold, serially on monkey kidney epithelial (Vero) cells.
Results: The hexane, chloroform and ethyl acetate extracts of the six plants were more toxic to the Vero cells compared to the ethanol, methanol and water extracts. Thirty one percent (11/36) and 75 % (27/36) of the extracts showed significant cytotoxicity (p < 0.05) in MTT and NRU assays, respectively. The 78, 52 and 7 % cytotoxicity levels detected in 27 extracts using the MTT assay were significantly (p < 0.05) underestimated at 640, 320 and 160 µg/mL, respectively, using NRU assay. Nine extracts from five plants exhibited significantly lower (p < 0.05) 50 % cytotoxic concentration (CC50) when NRU assay was employed compared to MTT assay. At 640 µg/mL, 10 of the 21 extracts were also found to react chemically with MTT, causing a 2.0 – 29.1-fold increase in the absorbance value (550 nm) compared to control.
Conclusion: The plant extracts of A. ciliata, A. tricolor, C. sativum, G. coronaria, K. brevifolia and T. zebrina show concentration- and extraction method-dependent cytotoxicity using MTT and NRU assays. NRU assay appears to be more sensitive and reliable than MTT assay for cell viability evaluation of the plant extracts.
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