This work was carried out in collaboration between all authors. Authors NC and MM have participated equitably in the study and consequently shared the first place. Author MEM carried out the toxicity tests, participated in the project design and drafted the manuscript. Author NC participated in the project design, carried out the plant collection and participated in the toxicity tests. Author MEM conceived the study and participated in the design and coordination of the project and drafted the manuscript. Author SG carried out in the chemical analysis of plant extracts. Author SA participated in the conception and design of the study and review of the final manuscript. Author LB participated in the conception and design of the study, and supervised the toxicity tests. Author MEH participated in the design and coordination of the project and review of the final manuscript. All authors read and approved the final manuscript.

The toxicity of the aqueous extract of Origanum majorana was tested (5 and 10 g/kg) in albino mice. No symptoms of toxicity or mortality were observed. The mice survived being active and healthy during all 14 days of observation. In addition, the weight measurement of the left and right kidneys, heart, and liver shows no significant difference between the control, 5 g/kg, and 10 g/kg. All extracts (aqueous, petroleum ether, dichloromethane, ethyl acetate, methanolic, and depleted aqueous extracts) of Origanum majorana tested against both types of cancer cells showed a more pronounced cytotoxic effect against breast cell line MDA-MB-231 than colon cells line HT-29 cells. The most marked effect is that of the ethyl acetate extract with IC50 30.90 ± 1.39 and 50.11 ± 1.44 (µg/ml), respectively. HPLC analysis of extracts from Origanum majorana showed that this plant contained polyphenols and flavonoids, which may be responsible for the biological activities found.