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 (CC
50) 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.