Preparation of Nanoemulsions of Mentha piperita Essential Oil and Investigation of Their Cytotoxic Effect on Human Breast Cancer Lines

Breast cancer is the most common cancer among women worldwide. Common disadvantages of chemotherapy, such as drug resistance, nausea, and vomiting, have encouraged researchers to use herbal remedies. In this study, constituents of Mentha piperita essential oil were identified using GC-MS analysis with five major ingredients of menthol (31.0%), menthone (22.1%), camphane (7.0%), menthofuran (6.0%), and iso-menthone (5.8%). The essential oil anticancer activity was evaluated at various incubation periods (24, 48, and 72 h) against three human breast cancer cell lines. After that, nanoemulsions of M. piperita were prepared, and long- and short-time stability tests were also performed. The anticancer effect of the best nanoemulsion with a mean droplet size of 136 ± 2 nm (PDI 0.3 and SPAN 0.8) was significantly better than that of non-formulated essential oil. Interestingly, the obtained effect from nanoemulsion with an exposure time of 24 h was significantly better than essential oil even within 72-h exposure time. M. piperita possesses an antiemetic effect, and by preparation of its nanoemulsion dosage form, its anticancer effect was also improved. Therefore, this green nanoemulsion could be used as an anticancer agent for further investigation.