Abstract
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. Keywords: Acmella ciliata , Amaranthus tricolor , Coriandrum sativum , Glebionis coronaria , Kyllinga brevifolia and Tradescantia zebrina , Extraction, Medicinal plant, Neutral red uptake assay, Vero cell
Highlights
Medicinal plants are prominent natural sources of phytochemicals, some of which have therapeutic values
Since the plant extracts for this study were obtained through sequential extraction method, the extracts were categorized as non-polar extracts, intermediate polar extract and polar extracts
Comparison of the extract concentrations between 320 μg/mL and 640 μg/mL revealed that the hexane and chloroform extracts of A. ciliata, hexane extract of C. sativum and hexane extract of G. coronaria were found to be toxic to the Vero cells (p < 0.05)
Summary
Medicinal plants are prominent natural sources of phytochemicals, some of which have therapeutic values. The presence of multiple components in a plant extract has increased the complexity of a screening assay involving cell culture technique. This demands a reliable indicator for the assessment of cell viability. This study was conducted to determine the cytotoxic effect of the extracts from six medicinal plants against Vero cells and to compare the reliability of MTT and NRU assays. Eight concentrations (640 to 5 μg/mL, 100 μL each) of the plant extracts, obtained by two-fold serial dilution in maintenance medium, was added into 96-well plates containing 4 × 104 Vero cells/well.
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