Mexican oregano (Lippia graveolens) is a culinary herb in the verbena family with strong antioxidant and anti-inflammatory properties. It contains a variety of volatile oils, including thymol and carvacrol, which give the herb its characteristic scent and flavor. The phenolic acid and flavonoid contents of Mexican oregano can vary substantially depending on where it is grown.
Mexican oregano is native to the southwestern U.S., Mexico, and Central America. It's volatile oil components give it a flavor similar to the Mediterranean-derived common oregano (although stronger, it is at the same time less bitter and less minty). Although similar in both flavor and appearance, Mexican oregano is not part of the same plant family as oregano, which is in the mint family.

Breast cancer-related effects of eating Mexican oregano

Mexican oregano has a greater proportion of chemopreventive compounds than oregano. It has more of the phenolic compounds thymol and carvacrol. Mexican oregano also has higher apigenin, luteolin, naringenin and quercetin contents than oregano. Some varieties are reported to have significant rosmarinic acid content.

Apigenin

Apigenin has been shown to exhibit potent growth-inhibitory effects in HER2+ breast cancer cells. Apigenin has also been shown to inhibit the growth of patient-derived triple negative (ER-/PR-/HER2-) organoids and sensitize breast cancer cells to Adriamycin (doxorubicin) and Taxol (paclitaxel) chemotherapy. In addition, apigenin has been shown to lessen Adriamycin-induced kidney damage without reducing its cytotoxic effects against tumor cells in a mouse model of breast cancer.

Carvacrol

Carvacrol has been demonstrated to reduce proliferation and viability of both ER+/PR+ and triple negative breast cancer cells. Combining carvacrol with thymol (both abundant in Mexican oregano) results in synergistic anticancer activities in both types of cells.
Carvacrol has been reported to enhance the treatment effects of tamoxifen. It has also been shown to show strong synergistic anticancer effects when combined with Adriamycin in ER+/PR+ cells. In addition, it has been found to inhibit Adriamycin-resistant triple negative cell proliferation in a concentration-dependent manner. Carvacrol also has been reported to act as a cisplatin sensitizer in treating triple negative disease.

Luteolin

Luteolin has been reported to inhibit angiogenesis (new blood vessel formation) and aromatase activity (in which androgens are converted into estrogens) in the laboratory. Luteolin has also been found to suppress triple negative breast cancer cell proliferation and metastasis and to reduce ER+/PR+ cell viability in a dose- and time-dependent manner. In addition, luteolin has been found to inhibit the growth, proliferation and migration of HER2+ breast cancer cells, as well as blocking their acquisition of stem cell-like properties. Luteolin has also been reported to increase the anticancer effects of Taxol.

Naringenin

While grapefruit is the most abundant source of naringenin, it is also found in Mexican oregano. Naringenin has been shown to inhibit metastasis in a mouse model of breast cancer. Naringenin also has cytotoxic activity against both ER+/PR+ and triple negative breast cancer cells.
Naringenin has been found to inhibit the proliferation of ER+/PR+ breast cancer cells by impairing glucose uptake. In addition, naringenin has been shown to inhibit ER+ breast cancer cell growth and migration in the presence of estradiol (E2). However, one study reported that ER+/PR+ breast cancer cells treated with naringenin experienced upregulation of genes associated with estrogen signaling and epithelial-to-mesenchymal transition, strongly suggesting it should not be taken as a supplement.
Naringenin has also been shown to act as an HER2 inhibitor, with antiproliferative, pro-apoptotic and other anticancer activities against HER2+ breast cancer cells.
Combining the chemotherapy drug Adriamycin with naringenin and the anti-diabetes drug metformin in a mouse model of triple negative breast cancer resulted in lower tumor volume and weight compared to treatment with Adriamycin alone in one study. A 2025 study reported that naringenin induced apoptosis (programmed cell death) in tamoxifen-resistant breast cancer cells.

Quercetin

Quercetin is a phytoestrogen flavonol found in a variety of fruits and vegetables. Most foods with significant quercetin content have been found to be associated with reduced breast cancer risk. A major Italian population study reported that the risk of breast cancer was reduced for increasing intake of flavonols such as the quercetin found in Mexican oregano.
Quercetin has been shown to increase the effectiveness of both Adriamycin (doxorubicin) and Taxol (paclitaxel) chemotherapy in multidrug resistant ER+/PR+ breast cancer cells, in part by eliminating cancer stem cells. In addition, quercetin has been reported to increase the sensitivity of ER+/PR+ cells to 5-fluorouracil (5-FU), thereby increasing its treatment effects. Quercetin has also been found to inhibit the migration and adhesion of triple negative breast cancer cells and to significantly inhibit tumor progression in a mouse model of triple negative breast cancer. Finally, quercetin also acts as an iron chelator, which can help reduce iron's breast cancer-promoting effects in some women.

Thymol

Thymol has been demonstrated to inhibit the growth of both ER+/PR+ and triple negative breast cancer cells. It has been reported to induce apoptosis, halt the cell division cycle (i.e., cause cell cycle arrest), and inhibit metastasis by modulating critical signaling pathways.
As noted above, combining thymol with carvacrol (both abundant in Mexican oregano) results in synergistic anticancer actions in both ER+/PR+ and triple negative breast cancer cells.

Additional comments

Approximately 40 species of herbaceous plants with oregano's characteristic scent and flavor are commonly called "oregano" in Mexico. Most commercialized are Lippia palmeri and Hedeoma patens, in addition to Lippia graveolens. However, among the three, Lippia graveolens has been demonstrated to have the most powerful anticancer activities.
Oregano can successfully be replaced by Mexican oregano in many recipes. We would recommend substituting Mexican oregano, which is sold in dried form, but it should be purchased organic.
Based on the available evidence, the amounts of Mexican oregano normally used as a herb or spice in food are safe, however Mexican oregano oil in medicinal amounts has not been adequately studied and has not been proven safe.

Sources of information provided in this webpage

The information above, which is updated continually as new research becomes available, has been developed based solely on the results of academic studies. Clicking on any of the underlined terms will take you to its tag or webpage, which contain more extensive information.
Below are links to 20 recent studies concerning this food and its components. For a more complete list, including less recent studies, please click on Mexican oregano.