**6. Unsatisfactory EOs results for BC**

Some EOs used in research were not able to have satisfactory in vitro anticancer effects on MCF7 as EO from *Sideritis perfoliata*, *Satureja thymbra*, *Salvia officinalis*, *Laurus nobilis*, *Pistacia palaestina* [111], *Nepeta cataria* L. [112], *Nectandra leucantha* [113], *Laurus nobilis* L, *Origanum syriacum* L, *Origanum vulgare* L, *Salvia triloba* L. [37], *Salvia officinalis* [114], grapefruit (*Citrus paradisi*), ginger (*Zingiber officinale*) [83], and *Anemopsis californica* [115].

*Origanum vulgare* EO, composed mostly of 4-terpineol, induced cell proliferation of MCF7, although at the concentration of 50 mg/mL opposite effect was found, but still with minor effect when compared to the result in other cancer cells [116]. *Aloysia citriodora, Boswellia sacra, Boswellia serrata, Cistus ladanifer, Citrus × aurantium, Citrus limon, Citrus sinensis, Cymbopogon citratus, Foeniculum vulgar, Illicium verum, Satureja montana, Syzygium aromaticum, Thymus capitatus, and Thymus vulgaris* presented minor effects in MCF7, T47D, and MDA-MB-231 [94].

EO of *Semenovia suffruticosa* grown in Kerman, Iran, induced cell death in MCF7, but it also had the same effect on normal cell line [117]. EO from the leaves of *Solanum macranthum* did not show anticancer properties in Hs578T [90].

This information is helpful to elucidate some effects of EOs that are used by the population. Some EOs may not have any effect for BC or can even help stimulate BC cells or have toxic action. Due to this, it is important to determinate if they are safe for common use. Furthermore, it is worth mentioning that the results show unsatisfactory effects in regard to concentrations used, which does not prevent the use of these EOs in other researches with different outcomes.

## **7. Conclusions**

Sesquiterpenes and monoterpenes are part of the main components of essential oils, some of them already being isolated and with actions described, although it is important to establish the force of the use of multiple compounds together.

A large number of essential oils from different plants have been described in the literature with promising in vitro effect in a variety of breast cancer cells and even

with in vivo effects in murine model; it is important to continue this research and take it to the next level with clinical trials.

The articles found in the literature and their results encourage the use of essential oils. The importance of plant research and the production of these oils demonstrated the difference they can make as a supporting anticancer agent or as a reducer of the side effects of breast cancer, which shows its power in the fight against breast cancer.
