In vitro inhibition of human leukemia THP-1 cells by Origanum syriacum L. and Thymus vulgaris L. extracts

Abstract

Background: Natural products including, traditional medicinal plants have emerged as a tempting alternative to conventional chemotherapeutic protocols of leukemia because of their minimum side effects and less documented drug resistance. Methods. Ethanol extracts were prepared from Thymus vulgaris L. and Origanum syriacum L. plants and investigated against the THP-1 leukemia cell line and freshly isolated peripheral blood mononuclear cells (PBMCs). The 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide (MTT) assay and the lactate dehydrogenase (LDH) assay were respectively used to determine the cellular viability and cytotoxicity in response to treatment with increasing extract concentrations. Results: Both extracts exhibited a concentration dependent reduction in viability of the THP-1 cells (IC50 = 2.126 mg/mL for O. syriacum, and 0.1569 mg/mL for T. vulgaris). O. syriacum was more potent against the PBMCs (IC50 = 0.4247 mg/mL), while T. vulgaris was moderately selective (IC50 = 0.3345 mg/mL with PBMCs and SI = 2.1). Only in O. syriacum the reduction in cells viability was caused by cytotoxic effect against leukemic cells (LC50 = of 9.646 mg/mL). Conclusion: T. vulgaris and O. syriacum are both antileukemic in vitro. T. vulgaris represents a potential selective cytostatic and safe target for future anticancer agents' development. O. syriacum on the other hand is cytotoxic against the leukemia cell line THP-1.