**4. Biological activity of essential oils**

One of the most important research lines of the CENIVAM Project is related to the study of different biological activities of essential oils. Bioactivity assays against *Trypanosoma cruzi* (epimastigotes and amastigotes), *Leishmania chagasi* (promastigotes and amastigotes), Vero cell assays, and THP cells were carried out at the Research Center for Tropical Illnesses, CINTROP. About 48% of the essential oils examined were active against *T*. *cruzi*. The essential oils were also tested against *L*. *chagasi* (promastigotes and amastigotes) and 19% were active [28, 29]. The virucidal activity of some essential oils was studied at the CINTROP, against the dengue (serotype 2) [30–33], and yellow fever [31, 34] viruses. Of the essential oils tested, respectively, 83 and 66% were active against this type of virus, constituting this result in a very interesting contribution, especially considering that there is not much data in the literature on the activity of essential oils against this type of virus. The essential oils of two chemotypes of *Lippia origanoides* (Fam. Verbenaceae) were in vitro potent agents against dengue and yellow fever viruses, which warrant the future study of the mechanism of their antiviral action.

Different CENIVAM groups, among them, in the Research Center for Biomolecules, CIBIMOL [35, 36], Environmental and Computational Chemistry of the University of Cartagena [37, 38], Chemistry and Biology of the Universidad del Norte, in Barranquilla [39] measured the antioxidant activity of essential oils by different techniques, e.g., lipid oxidation, measurement of secondary end products of lipoxidation, thiobarbituric acid reactive substances (TBARS) test, and free radical trapping tests (2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid, ABTS + and 2,2-diphenyl-1-picrylhydrazyl, DPPH). Grosso modo, about 40% of the analyzed samples were active in different tests of antioxidant activity.

The study of the cytotoxic activity (acute toxicity, LC50) of the essential oils was carried out by several groups. Cecilia Mesa et al. examined the activity against *Candida krusei* and *Aspergillus*  *fumigatus* [40]. *Lippia origanoides* and *L*. *alba* have several chemotypes, and these have been the subject of detailed study to check that their cytotoxicity does not prevent their use in some topical pharmaceutical applications [41, 42]. The group of Environmental and Computational Chemistry has used the *Artemia franciscana* assay to test for acute toxicity [43]. More than 30% of all samples analyzed in these trials did not have any degree of toxicity. In the same group, anti-quorum sensing activities, teratogenic and antigenotoxic effects, and the insect repellent activity of essential oils were studied [44, 45].

Insect repellency is an interesting biological activity that leads to rather soon implementation of essential oils as active ingredients of commercial products. Olivero et al. have examined the potential application of essential oils to repel insects of importance to food storage [46–49]. Another application of insect repellence is the prevention of diseases for which *Aedes aegypti* is the vector [50–52]. More than 50% of the tested essential oils and pure terpenes proved to be good insect repellents (56 and 80%, respectively).

The assays of the anti-genotoxic and chemopreventive activity carried out at the CIBIMOL-UIS group demonstrated a DNA protective effect of the essential oils of several chemotypes of *Lippia alba* and *Lippia origanoides* (Fam. Verbenaceae) [53–56].

Several bacterial strains have been employed in assays of essential oil antibacterial activity [57, 58]. Due to their carvacrol and thymol content, *L*. *origanoides* oils have shown important antibacterial activity [59]. Antimycobacterial activity, which is of interest in tuberculosis research, has received special attention by CENIVAM researchers [60, 61]. It has been determined in oils from the state of Santander [62].
