Effects of methanolic plant extracts on cell proliferation and HIF activity under hypoxic condition in vitro

Low oxygen tension is termed as hypoxia. Hypoxia will lead to transcription of hypoxia-inducible factor (HIF) and regulation of downstream gene expression. Underexpression or overexpression of HIF was found to be responsible for various diseases. Proper regulation of this transcriptional factor will aid in treatment of the related diseases. Nowadays, many different approaches are used to modulate HIF, including the usage of naturally-derived plant extracts. Plant extracts are widely accepted compared to other treatments as they are less harmful to the patient and are widely available. In this study, the cytotoxicity of eight different plant extracts under two different gaseous conditions, hypoxic and normoxic, were examined. We also examined the HIF activity shown by the cells under treatment of various concentrations of plant extracts. All eight plants were dried, blended, extracted using methanol, and evaporated to form crude plant extracts. MTT assay was performed by treating the cells with different concentrations of plant extracts and cell viability was determined. Meanwhile, HIF activity of the cells was evaluated by using single luciferase reporter assay. Relative cytotoxicity shown by the cells was different for each plant extract under the various concentration. Pereskia bleo, Orthosiphon aristatus, and Clinacanthus nutans showed high cell viability, 80% of cell viability, within the range of concentration tested. In contrast, Gynura procumbens, Hydrocotyle sibthorpiodies, Pereskia grandifolia, Strobilanthes cripus, and Melastoma malabathricum showed low cell viability. Most of the cells showed activation of HIF activity when treated with different concentrations of the plant extracts. When cells were treated with high concentrations of plant extracts, inhibition of HIF activity were seen and was correlated with low cell viability after treatment. The most notable part of the study was that more than 100% HIF activation was observed for Clinacanthus nutans. However, the cell viability remained high. This might indicate that Clinacanthus nutans is a promising candidate to activate HIF at a transcriptional level with minimal cytotoxicity.