Specific cytotoxicity of a novel arbutin derivative from myrothamnus flabellifolius against human leukemia cells

Abstract

Background: Myrothamnus flabellifolius is a South African medicinal plant which is known to be used traditionally in the treatment of cough, cold, gingivitis and kidney problems. Phytochemicals from the leaves of this plant contain anti-oxidant and anti-inflammatory compounds. In a previous study, the methanolic extract from the leaves and stems of this plant showed anti-cancer activity against human leukemia cells (HL-60) without affecting the normal lymphocytes (TK6). Materials and Methods: For this, the methanolic extract was fractionated by HPLC into thirty fractions. The fractions were tested against HL-60, TK-6 and the fraction that showed selective death of leukemia cells were further fractionated. Compounds in this fraction were identified using mass spectrometry and nuclear magnetic resonance. Results: Thirteen fractions were selected and tested against HL-60 and TK6. Out of the 13 tested only one was the most active fraction and therefore, it was selected for further fractionation using HPLC. Using mass spectrometry and nuclear magnetic resonance, a novel arbutin derivative (compound 1) [(3R,6S)-3,4,5-Trihydroxy-6-(p-hydroxyphenoxy)tetrahydro-2H-pyran-2-yl]methyl 2-(E)-methyl-4-(2-methyl-3-vinyl-2-cyclohexen-1-yl)-2-butenoate was isolated from the active fraction. This compound has selective in vitro cytotoxic activity with IC50 0.53 μM against HL-60 with negligible effects on TK6. Conclusion: The data from this study has led in establishing a novel arbutin derivative to be specifically cytotoxic to acute myeloid leukemia cells. This compound can be chemically modified and developed as a potential anti-leukemia drug.