Abstract / Summary
Tea tree oil (TTO) presents many biological and pharmacological activities in animals and humans. In this study, six TTO preparations (TTO A–F) with different terpinen-4-ol and isoterpinene contents were screened for cytotoxicity against B16F10 melanoma cells in vitro; the two most active preparations (TTO B and TTO E) were subsequently evaluated by intratumoral injection (0.1 mL of 10% TTO once daily for 7 days; five mice per group) in a syngeneic B16F10 tumor model in C57BL/6 mice, and the mechanistic analyses focused on TTO E. The results showed that 0.0125–0.1% TTOs exhibited dose-dependent cytotoxic effects in B16F10 cells, with TTO E exhibiting a stronger inhibitory effect than the others. Intratumoral injection of TTO E significantly suppressed the growth of B16F10 syngeneic tumors, with reductions in tumor volume of 69.1% and in tumor weight of 61.2% on day 14 compared with the PBS control. Apoptosis and cleavage of caspase-3/-9 in B16F10 cells in vitro and in their syngeneic tumors in mice were significantly induced by TTO E. These data indicate that TTO E shows antitumor activity towards B16F10 cells in vitro and in a syngeneic mouse model in vivo through an apoptosis-associated mechanism; this merits further preclinical evaluation.