Screening Of Some Selected Ethiopian Medicinal Plants For Cytotoxic And Antiviral Activities

Abstract

Cancer and viral diseases are an increasing worldwide health concern. There is an increasing evidence for the potential of natural products-derived compounds in cancer and viral diseases prevention and therapy. Approximately 60% of drugs currently used for cancer treatment have been isolated from natural products and the plant kingdom has been the most significant source. In this regard, plants extracts and activity-monitored isolation of compounds from three endemic medicinal plants of Ethiopia, Millettia ferrguinea ssp. ferrguinea, Aloe pirottea and Aloe sinana, were screened in-vitro for anticancer and antiviral activities. Chromatographic (vacumm liquid chromatography on silica gel, TLC and UV light) separation of the extracts from the chloroform fraction of Millettia ferrguinea seed led to the identification of eight isoflavones compounds, of which, one is new (10CH-05-II]. The structural elucidation of the compounds was performed using spectroscopic: NMR and ESIMS. The methanol extract, solvent fractions, isolated compounds and mixtures were evaluated in vitro for anticancer activities against human non-small cell lung cancer A549, ovarian cancer A2780, pancreatic cancer MIA-Paca-2 and stomach cancer SNU-638 cell lines using a sulforhodamine B (SRB) assay method to determine the percentage of growth inhibition and IC50 values. The extracts/solvent fractions of plants showed cytotoxic effect in the four cancer cell lines tested with different degrees of potency in a dose-dependent manner. The percentage growth inhibition was found to be increasing with increasing concentration of test compounds. The MeOH extract, n-Hxf and CHf of M. ferrguinea seed showed potent cytotoxic activity in the four cancer cell lines with IC50 values ranging from -0.07-13.66 µg/ml. All fractions of A. sinana root, all fractions except n-butanol fractions of A. pirottea root and CHF of A. sinana latex exhibited strong to moderate cytotoxic activity in A549, A2780 and SNU638 cell lines with IC50 values ranging from 6.32 - 29.87 µg/ml, and weak or no cytotoxic activity in MIA-PaCa-2 cell line. Extract/solvent fractions of M. ferrguinea seed were almost 1.5 to 8 times higher than that of reference standard anticancer drug etoposide in killing A549, A2780, MIA-PaCa-2 and SNU-638 cell lines. The cytotoxic activity profile of the plant extracts and etoposide decreased in the following order: M. ferrguinea seed > etoposide > A. sinana root > A. pirottea root > A. sinana leaf latex. The sensitivity of cancer cells to the extract/fractions decreases in the following order: SNU-638 > A2780 > A549 > MIPPaCa-2. 7 The isolated compounds and mixtures, except 10CH-02, showed high cells growth inhibitory activity with IC50 value ranging from < 0.1 to 0.34 µg/ml (0.89 - < 0.12 µM) which are more potent than reference standard anticancer drug etoposide (0.58 µM for A2780 and 1.48 µM for PAN-2) against A2780 and PANC-2. Compound 10CH-03 exhibited strongest cell growth inhibitory activity (IC50 = 1.38 µM) against MIA-PaCa-2 which is more potent than etoposide (IC50 = 1.48 µM). The methanol extract and solvent fractions were evaluated in vitro for anticancer activities against human influenza A and B viruses, picornaviruses and dengue virus using a viral cytopathic effect (CPE) inhibitory method for influenza A and B viruses and picornaviruses, and an immunofluorescence assay (IFA) for dengue virus. Among the 18 samples, 14 samples from three species showed strong antiviral activity with 50% - complete cell protection against influenza viruses induced CPE CHF of A. pirottea and A. sinana latex, and EAf of A. sinana root exhibited higher anti-influenza A and B activity than reference anti-influenza reagents RBV and AMT. In antipicorna virus assay, 4 samples from M. ferrguinea and root of A. sinana significantly inhibited EV-68 and EV-71(H) viral induced CPE with 65 % - 109% of cells did not show viral cytopathic effect. In anti-dengue virus assay, 13 from three species exhibited complete inhibition of DENV2, while 11 exhibited potent inhibition effect based on CPE or cell death from DENV-2 with cell viability ranging from 50 % - 98.0 %. Among the purified compounds; 10CH-01 and 10CH-02, and mixtures; 10CHf, 10CH-06 and 10CH-7 exhibited potent antiviral activity in EV-68 with SI values ranging from 6.3 - > 111, compounds 10CH-03 and 10CH-05 in EV-71 (BrCr) with SI values of 5.3 and 3.6, respectively, and A10CH-02 in HRV-A21 and HRV-A71 with SI values of > 12.5. In the US NCI plant screening program, A. sinana root and leave latex, A. pirottea root and M. ferrgunia seed extracts and isolates have potent cytotoxic activity in the four cancer cell lines and antiviral activity in influenza A and B viruses, picornaviruses and DENV-2, and our findings suggest that these extracts are promising for continued research and containing significant components that may be effectively utilized as broad spectrum anticancer and antiviral agents, and applied to development of a novel herbal medicine.