|LETTER TO EDITOR
|Year : 2020 | Volume
| Issue : 2 | Page : 165-167
Pediculicidal activity assessment of four essential oil terpenoids using filter contact and immersion bioassays
Kerdalidec Candy, Mohammad Akhoundi, Arezki Izri
Department of Parasitology-Mycology, Avicenne Hospital (AP-HP), Bobigny, France
|Date of Submission||30-Jun-2019|
|Date of Decision||15-Jun-2020|
|Date of Acceptance||20-Jun-2020|
|Date of Web Publication||23-Jan-2021|
Department of Parasitology-Mycology, Avicenne Hospital (AP-HP), 125, Route De Stalingrad, 93009 Bobigny Cedex
|How to cite this article:|
Candy K, Akhoundi M, Izri A. Pediculicidal activity assessment of four essential oil terpenoids using filter contact and immersion bioassays. Trop Parasitol 2020;10:165-7
Head louse infestation is one of the most common human parasitic infestations worldwide. It is caused by an obligatory ectoparasite, namely Pediculus humanus capitis (De Geer, 1767). Head louse infestation occurs in particular among school infants and may cause clinical and psychological disorders such as skin irritation, secondary infection by scratching, and distress. In recent years, the louse infestation reports are on the rise across some countries particularly in North and South America, Australia, Europe, and Asia.
Several chemical-based pediculicides with various formulations (e.g., shampoo and lotion) have been applied for the treatment of head louse infestation. In spite of various preparations, multiple cases of resistance in head lice have been reported from different regions of the world. Repeated reports of resistance in head lice have led to look for substitute remedies. Therefore, plant essential oils have been suggested as an alternative to control lice.
Essential oils are blends of different volatile low-molecular-weight metabolites extracted from plants through steam distillation. Essential oils usually contain two or three major terpene or terpenoid components. Several essential oils such as Eucalyptus (Eucalyptus spp.), clove (Eugenia caryophyllata), lavender (Lavender spp.), geranium (Pelargonium spp.), anise (Illicium verum), tea tree (Melaleuca alternifolia), and ylang-ylang (Cananga odorata) have been evaluated and incorporated into medical products for treating head louse infestation., The in vitro pediculicidal efficacy is often attributed to the major components of essential oils such as 1,8-cineole, eugenol, linalool, citronellol, geraniol, anethole, and terpinen-4-ol.,
The main goal of this pilot study is to evaluate the pediculicidal efficacy of four terpenoides including geraniol, linalool, terpinen-4-ol (terpineol), and β-caryophyllene, demonstrated to be effective on head lice using filter contact and immersion bioassays. For this purpose, adult head lice were collected manually by dry combing the hair of the infested patients aged 7–59 years who were referred to the parasitology department of Avicenne Hospital in Paris in spring 2017. The obtained lice were kept in a Petri dish in laboratory ambient temperature (25°C ± 2°C, 30%–50% relative humidity) for further experiments. Based on the patients' statement, they had not been treated with any anti-louse products during the last 3 months. The alive and noninjured adults (evaluated under binocular stereo microscope) were subjected to two bioassay experiments separately using filter contact and immersion to evaluate the effect of four essential oil constituent terpenoids on the head louse survival. Therefore, the pure terpenoids including geraniol (C10H18O), linalool (C10H18O), β-caryophyllene (C15H24), and terpinen-4-ol (C10H18O) were purchased from Sigma Aldrich (L'isle d'Abeau Chesnes, France) and served for in vivo bioassays.
| Filter Paper|| |
A volume of 0.5 mL of each pure terpenoid was spread evenly across the surface of a filter paper (Whatman no. 1; 8.5 cm in diameter) that was placed at the bottom of a Petri dish (5 cm in diameter). Then, thirty head lice were put in contact with the impregnated filter paper within the Petri dish covered by its lid and kept in ambient temperature for 30 min.
| Immersion|| |
Thirty intact lice were dipped into a Petri dish containing 0.5 mL of each pure terpenoid for 30 min. Then, the Petri dish was covered with its lid and sealed using Parafilm® membrane (American National Can, Chicago, IL, USA) to prevent compound evaporation.
Furthermore, a couple of negative controls including sterile water were added to the filter paper and immersion bioassays. After 30-min exposure time, the processed lice were washed with a neutral shampoo, Neutrapharm™ (Laboratoire Gilbert, Hérouville Saint-Clair, France), rinsed under tap water, and dried with an absorbent paper. At the end of each experiment, the lice were examined for activity under a binocular magnifier at 15, 30, 60, 120, and 180 min post experiment. The specimens with no vital signs (e.g., movements of antennae, internal gut, and legs, with/without external stimulation) were considered as dead.
In total, 300 intact head lice were collected from the infested patients, divided equally, and subjected separately for immersion and filter contact bioassays. Based on the results of immersion bioassay, all head lice exposed to geraniol, linalool, and terpinen-4-ol were dead at 180 min post experiment. Concerning β-caryophyllene, only a single louse remained alive at the end of the experiment (29/30, 97%). For filter contact, geraniol and linalool terpenoids demonstrated high pediculicidal activity with 100% mortality. Terpinen-4-ol and β-caryophyllene were ineffective on 2 and 12 specimens and remained alive at the end of bioassay. All the thirty head lice exposed to sterile water were alive at 180 min post experiment [Figure 1].
|Figure 1: Immersion (a) and filter contact (b) bioassays of four terpenoids on head lice at different experimental times|
Click here to view
Essential oils are known to be effective in killing head lice. This effectiveness correlates commonly to the major components (terpenoid) of the essential oils. Because of difficulty in the interpretation of the pediculicidal activity of essential oils due to their numerous components, in this study, we have evaluated the pediculicidal activity of four terpenoids including linalool derived from Lavandula angustifolia; terpinen-4-ol from M. alternifolia; geraniol from Pelargonium spp. and Monarda fistulosa; and β-caryophyllene from C. odorata and E. caryophyllata.
Based on our findings, geraniol, linalool, and terpinen-4-ol have demonstrated to be highly effective in immersion and filter contact bioassays. In an investigation conducted to evaluate the toxic effects of Eucalyptus globulus leaf oil-derived monoterpenoids and Eucalyptus leaf oil terpenoids (β-eudesmol and geranyl acetate) on the eggs and female head lice, linalool demonstrated high fumigant activity. Gonzalez-Audino et al. reported high knockdown and mortality effect of geraniol on adults (60%) as well as third-stage nymphs in immersion method. In addition, linalool showed >50% mortality. Priestley et al. reported more effectiveness of linalool than geraniol in direct contact with impregnated paper. Toloza et al. studied the fumigant activity of monoterpenoids on adults and found that linalool has better knockdown effect than geraniol. Our findings are in accordance with those results reported by Gonzalez-Audino et al., Gallardo et al., and Priestley et al. This effectiveness is supposed to be due to the mono-oxygenated structure of mentioned molecules. Some differences in the results of the mentioned investigations may probably be due to different methodologies used for bioassays. In addition, β-caryophyllene is a sesquiterpene which has been found effective in immersion and not in filter contact bioassay.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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