The Toxicity of Essential Oils From Three Origanum Species Against Head Louse, Pediculus humanus capitis.

PURPOSE: Pediculosis caused by human head louse, Pediculus humanus capitis De Geer (Anoplura: Pediculidae) is a public health problem with a high prevalence, especially among children in school age. Different chemical pediculicides (insecticides) are used against lice but the repeated application of these pediculicides for the treatment of P. humanus capitis infestation in the past decades has resulted in the development of resistance. The plant essential oils have been used as alternative sources of lice treatment agents. Pediculicidal activity of the essential oils of three Origanum species (O. onites, O. majorana and O. minutiflorum) against P. humanus capitis adults was examined in this study. METHODS: Essential oils from aerial parts of three Origanum species were obtained by hydrodistillation using a Clevenger-type apparatus. P. humanus capitis specimens used were obtained from infested children by combing method at primary schools. Adult lice were exposed to three dilutions (1%, 0.5% and 0.1% w/v) of tested oils for 5 min using the adult immersion test. RESULTS: According to the results, all Origanum essential oils at 1% concentration have been shown to significantly decrease the rate of limb, bowel and abdomen movements, producing more than 90% mortality after 12 h. CONCLUSION: Our results indicated that Origanum essential oils can be used for the development of new pediculicides against head louse.

Acaricidal activity of Origanum bilgeri P.H. Davis (Lamiaceae) essential oil and its major component, carvacrol against adults Rhipicephalus turanicus (Acari: Ixodidae).

The acaricidal activity of an essential oil obtained from aerial parts of Origanum bilgeri P.H. Davis (Lamiaceae), an endemic species in Turkey, and its major constituents, carvacrol was evaluated against unfed adults Rhipicephalus turanicus Pomerantzev (Acari: Ixodidae) collected from Kepez, Antalya. The composition of the essential oil was analyzed by GC/MS. The major compound identified in the oil was carvacrol (93.02%). Generally, tick mortalities to the O. bilgeri distillate and carvacrol increased with concentrations. O. bilgeri oil produced >83% mortality at 48h at a concentration of 0.8% and mortality was higher than 63% at a carvacrol concentration of 0.4%. Our results have shown that O. bilgeri essential oil and its major component, carvacrol, may have potential as acaricidal agents against R. turanicus.

Extraction of the essential oil from endemic Origanum bilgeri P.H.Davis with two different methods: comparison of the oil composition and antibacterial activity.

The antibacterial activity and chemical composition of the essential oils (EOs) isolated from Origanum bilgeri P.H.Davis by two different extraction methods, i.e., hydrodistillation (HD) and solvent-free microwave extraction (SFME), were examined. This endemic Origanum species had shown very good antibacterial activity. The composition of the O. bilgeri EOs obtained by SFME and HD was investigated by GC/MS analysis. The main components of the oils obtained by both methods were carvacrol (90.20-84.30%), p-cymene (3.40-5.85%), γ-terpinene (0.47-1.20%), and thymol (0.69-1.08%). The EO isolation by SFME offered many important advantages, including a higher extraction yield, a shorter extraction time, and a higher content of the active component carvacrol. The carvacrol-rich oils obtained by both HD and SFME showed a good antibacterial activity. The largest inhibition zones were observed for the O. bilgeri EO obtained by SFME. Our study suggests that O. bilgeri EO has the potential to be used as preventative against bacterial contamination in many foods, instead of the common synthetic antimicrobial products.

Larvicidal activity of some Labiatae (Lamiaceae) plant extracts from Turkey.

Ethanol extracts of the aerial parts from five Labiatae (Lamiaceae) species, obtained from Antalya, Turkey, were tested for larvicidal activity against the house mosquito Culex pipiens L. (Diptera: Culicidae) under laboratory conditions. Third and fourth instar mortality from six concentrations (5, 10, 25, 50, 100 and 200 ppm) of each plant extract were compared against the organophosphorus insecticide, temephos which is currently used for larval control. All plant extracts showed high larvicidal activity in 24 h exposure tests. Teucrium divaricatum Sieber was the most toxic, followed by Mentha longifolia (L.) Huds., Melissa officinalis L., Salvia sclarea L. and Mentha pulegium L. with LC(50) values of 18.6, 26.8, 39.1, 62.7 and 81.0 ppm, respectively. This study is the first to report on the larvicidal activity of ethanol extracts of these five plant species against C. pipiens.