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  • Toxicity of basil oil constituents and related compounds and the efficacy of spray formulations to Dermatophagoides farinae (Acari: Pyroglyphidae).

Toxicity of basil oil constituents and related compounds and the efficacy of spray formulations to Dermatophagoides farinae (Acari: Pyroglyphidae).

Journal of medical entomology (2014-06-06)
Haribalan Perumalsamy, Jae Yeon Kim, Jun-Ran Kim, Kum Na Ra Hwang, Young-Joon Ahn
ABSTRACT

Pyroglyphid house dust mites are the most common cause of allergic symptoms in humans. An assessment was made of the toxicity of basil, Ocimum basilicum L, essential oil, 11 basil oil constituents, seven structurally related compounds, and another 22 previously known basil oil constituents to adult American house dust mites, Dermatophagoides farinae Hughes. The efficacy of four experimental spray formulations containing basil oil (1, 2, 3, and 4% sprays) was also assessed. Results were compared with those of two conventional acaricides benzyl benzoate and N,N-diethyl-3-methylbenzamide. The active principles of basil oil were determined to be citral, alpha-terpineol, and linalool. Citral (24 h LC50, 1.13 microg/cm2) and menthol (1.69 microg/cm2) were the most toxic compounds, followed by methyl eugenol (5.78 microg/cm2). These compounds exhibited toxicity greater than benzyl benzoate (LC50, 8.41 microg/cm2) and N,N-diethyl-3-methylbenzamide (37.67 microg/cm2). Potent toxicity was also observed with eugenol, menthone, spathulenol, alpha-terpineol, nerolidol, zerumbone, and nerol (LC50, 12.52-21.44 microg/cm2). Interestingly, the sesquiterpenoid alpha-humulene, lacking only the carbonyl group present in zerumbone, was significantly less effective than zerumbone, indicating that the alpha,beta-unsaturated carbonyl group of zerumbone is a prerequisite component for toxicity. These compounds were consistently more toxic in closed versus open containers, indicating that their mode of delivery was largely a result of vapor action. Basil oil applied as 3 and 4% sprays provided 97 and 100% mortality against the mites, respectively, whereas permethrin (cis:trans, 25:75) 2.5 g/liter spray treatment resulted in 17% mortality. Our results indicate that practical dust mite control in indoor environments can be achieved by basil oil spray formulations (3 and 4% sprays) as potential contact-action fumigants.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Benzyl benzoate, tested according to Ph. Eur.
Sigma-Aldrich
Benzyl benzoate, ≥99%, FCC, FG
Sigma-Aldrich
Benzyl benzoate, natural, ≥99%, FG
Supelco
DEET, PESTANAL®, analytical standard
Sigma-Aldrich
Benzyl benzoate, meets USP testing specifications
Sigma-Aldrich
Benzyl benzoate, ReagentPlus®, ≥99.0%
Supelco
Benzyl benzoate, Pharmaceutical Secondary Standard; Certified Reference Material
USP
Benzyl benzoate, United States Pharmacopeia (USP) Reference Standard
Supelco
Benzyl benzoate, analytical standard
Sigma-Aldrich
N,N-Diethyl-3-methylbenzamide, 97%