The leaf essential oils of seven Ocimum basilicum L. accessions were analyzed by a combination of GC and GC/MS. They were tested for cytotoxicity using brine shrimp lethality test and for their ability to inhibit the enzymatic activity of the glycossomal glyceraldehyde-3-phosphate dehydrogenase (GAPDH) from Trypanosoma cruzi and adenine phosphoribosyltransferase (APRT) from Leishmania tarentolae. The oils showed significant activity (LC50 < 90 μg/mL) in the Brine shrimp lethality test. However, all samples did not show relevant inhibitory activity against GAPDH and APRT.