Bulb extracts of Boophone disticha induce hepatotoxicity by perturbing growth, without significantly impacting cellular viability

Abstract

INTRODUCTION : Traditional remedies remain a prominent form of therapy in developing countries, such as South Africa. Boophone disticha, or the poison bulb, is used for the treatments of wounds. There is generally a lack of scientific evidence to support its safety or use. As hepatotoxicity is a major contributor to morbidity and mortality, and a leading factor in drug attrition during development, more emphasis should be placed on pre-clinical evaluation thereof. The aim of the study was to investigate the in vitro hepatotoxicity of an ethnomedicinal and organic extract of the bulbs. MATERIALS AND METHODS : Hot water (ethnomedicinal) and methanol (organic) extracts were prepared and assayed on HepG2 hepatocarcinoma cells to assess for effects on cell density (sulforhodamine B staining), mitochondrial membrane potential (JC-1 ratiometry), reactive oxygen species levels (H2-DCF-DA cleavage/activation), reduced glutathione levels (monocholorobimane adduct formation), fatty acid accumulation (nile red staining), lipid peroxidation (thiobarbituric acid reactive substances formation), caspase-3/7 activation (Ac-DEVD-AMC activation), adenosine triphosphate levels (chemiluminescence), cell viability (Annexin V-FITC/propidium iodide) and cellular kinetics (propidium iodide). RESULTS : Although cell density was reduced by both extracts (hot water extract IC50 = 51.39 μg/mL; methanol extract IC50 = 35.11 μg/mL), cell viability was not reduced to the same degree (6–10% after 24 h; ~ 2% at 72 h) after exposure to the IC50's. Furthermore, cellular kinetics was not significantly affected. Although mitochondria appeared to depolarize slightly, reactive oxygen species levels were reduced to below baseline. Reduced glutathione levels also decreased. Fatty acid levels increased, however, lipids did not peroxidise. Adenosine triphosphate levels increased, while caspase-3/7 activity was reduced to below baseline. DISCUSSION AND CONCLUSION : Extracts of B. disticha did not induce a loss of cell viability, however, notable reduction in cell density was apparent. While the methanol extract was more cytotoxic than the hot water extract, the latter still carries a risk should it be chronically used. Although cellular kinetics were not affected, it is proposed that extracts may shift cells into a quiescent phase of non-proliferation which the assay is not sensitive enough to detect. The antiproliferative effect is likely in response to altered redox status. However, mitochondrial depolarisation did not increase free radical levels, with no lipid peroxidation as consequence. Furthermore, a propensity for fatty acid accumulation was observed, which carries the risk of hepatosteatotic detriments. The antiproliferative effect may delay repair of hepatic injury, and thus reduce quality of life. Further emphasis should be placed on early investigation of herbal remedies for their effects on hepatocellular functioning.