Antimicrobial, Antioxidant, and Cytotoxic Activities of Ocimum forskolei and Teucrium yemense (Lamiaceae) Essential Oils.

and (Lamiaceae) are used in traditional medicine in Yemen. The chemical composition, antimicrobial, antioxidant and cytotoxic activities of the essential oils isolated from the leaves of Benth. (EOOF) and two different populations of Deflers., one collected from Dhamar province (EOTY-d), and another collected from Taiz (EOTY-t) were investigated. The antimicrobial activities of the oils were evaluated against several microorganisms with the disc diffusion test or the broth microdilution test. The essential oils were screened for cytotoxic activity against human tumor cells. EOOF and EOTY-d were screened for free-radical-inhibitory activity using the DPPH radical scavenging assay. Sixty-four compounds were identified in (EOOF) representing 100% of the oil content with -fenchol (31.1%), fenchone (12.2%), τ-cadinol (12.2%), and methyl ()-cinnamate (5.1%) as the major compounds. In EOTY-d, 67 compounds were identified, which made up 91% of the total oil. The most abundant constituents were ()-caryophyllene (11.2%), α-humulene (4.0.%), γ-selinene (5.5%), 7--α-selinene (20.1%), and caryophyllene oxide (20.1%), while the major compounds in EOTY-t were α-pinene (6.6%), ()-caryophyllene (19.1%) α-humulene (6.4%), δ-cadinene (6.5%), caryophyllene oxide (4.3%), α-cadinol (9.5%), and shyobunol (4.6%). The most sensitive microorganisms for EOOF were , , and with inhibition zones of 34, 16, and 24 mm and MIC values of, 4.3 mg/mL, 4.3 mg/mL, and 8.6 mg/mL, respectively. EOTY-t showed antimicrobial activity against , , , and with MIC values of 0.156, 0.156, 0.313 and 0.313 mg/mL, respectively. Neither essential oil showed remarkable radical inhibition (IC = 31.55 and 31.41 μL/mL). EOTY-d was active against HT-29 human colorectal adenocarcinoma cell lines with IC = 43.7 μg/mL. Consistent with this, EOTY-t was active against both MCF-7 and MDA-MB-231 human breast adenocarcinoma cells. The antimicrobial activity of essential oil against and is consistent with its traditional use in Yemeni traditional medicine to treat skin infections. Both and show wide variations in their respective essential oil compositions; there remains a need to investigate both species botanically, genetically, and phytochemically more comprehensively.