Telomerase inhibitory effects and anti-proliferative properties of onion and other natural spices against cancer cells

The objectives of current study were to find the potential telomerase inhibitors from spices and to investigate their anticancer properties. The in vitro inhibitory effects of 28 spices against telomerase activity of HL-60 cells were systematically studied using polymerase chain reaction (PCR) based telomeric repeat amplification protocol, the PCR products were determined using native polyacrylamide gel electrophoresis. Telomerase inhibitory activity was evaluated by comparing DNA ladders. Telomerase inhibitory samples were further tested for anti-proliferation effects against gastric cancer cells SNU-1 using MTT assay. Hexane extract of onion, hexane extract of chili, ethyl acetate extract of chili, water extract of chili, and water extract of parsley exhibited strong telomerase inhibiting activity at the concentration of 10 μg/mL. Further anti-proliferation study indicated that hexane and ethyl acetate extracts of onion and ethyl acetate extract of chili at the concentration of 10 μg/mL showed 51.9%, 43.7% and 22.2% inhibitory rate against gastric cancer cells SNU-1, respectively; while the water extracts of chili and parsley did not show cancer cell proliferation inhibitory effect. The hexane extract of onion exhibited both telomerase inhibitory effect and cancer cell proliferation inhibitory effect with IC50 value at 14.18 μg/mL. Onion deserves to be further studied, it has a potential to be developed into an anticancer agent targeted on telomerase.