Effects of Phyllanthus urinaria extract on HepG2 cell viability and oxidative phosphorylation by isolated rat liver mitochondria

Abstract

Ethnopharmacological relevance: Phyllanthus urinaria is widely used as anti-inflammatory, anti-diarrheal and hepatoprotective medicines in Asian countries such as India, China and Thailand. In Thailand, Phyllanthus urinaria is traditionally used as an adjuvant or alternative medicine for cancer patients, including liver cancer. However, there is limited scientific evidence supporting its use in cancer particularly hepatocellular carcinoma.

Aim of the study: To investigate the cytotoxic effect of Phyllanthus urinaria extract on human hepatocellular carcinoma HepG2 cells and the effect on oxidative phosphorylation by isolated rat liver mitochondria.

Materials and methods: HepG2 cells and isolated rat liver mitochondria were treated with the 50% methanolic extract of Phyllanthus urinaria. Cytotoxicity of the extract was assessed by trypan blue exclusion and MTT assay. Rates of oxygen consumption of isolated mitochondria were determined with a Clark oxygen electrode.

Results: It was found that the hydromethanolic extract induced cell death of HepG2 cells in a dose-dependent fashion. The IC(50) of Phyllanthus urinaria extract measured by trypan blue exclusion and MTT assay were 431+/-65 microg/ml and 445+/-62 microg/ml, respectively. Morphological changes of the cells were also observed. With isolated rat liver mitochondria, the extract slightly stimulated mitochondrial state 4 respiration but profoundly depressed state 3 respiration and respiratory control ratio.

Conclusions: The extract impairs energy metabolism by acting as inhibitor of oxidative phosphorylation and weak mitochondrial uncoupler. These mitochondrial effects may play a role in the cytotoxic action of Phyllanthus urinaria extract on HepG2 cells. These results provide preliminary experimental evidence supporting the use of Phyllanthus urinaria against hepatocellular carcinoma and open the possibility of considering this plant an adjunctive medicine for the treatment of this deadly disease.