Identification of electrophysiologically-active compounds for the malaria mosquito, Anopheles gambiae, in human sweat extracts.
Human sweat samples were chemically fractionated into acid and non-acid components. The most abundant volatile compounds present in the fractions were identified by linked gas chromatography mass spectrometry. The acid fractions were found to be composed of a range of twenty aliphatic and three aromatic carboxylic acids ranging, on average, from 0.02 to 20 micrograms per ml of sweat sampled. Non-acid fractions were found to contain: 6-methyl-5-hepten-2-one, 1-octen-3-ol, decanal, benzyl alcohol, dimethylsulphone, phenylethanol, phenol and 4-methylphenol, collectively amounting to 0.1 and 3 micrograms per ml of sweat. The major component of sweat was found to be L-lactic acid which constituted from 1 to 5 mg/ml. Using the intact antennae of the anthropophilic malaria vector mosquito Anopheles gambiae Giles, the peripheral olfactory activities of compounds identified in the sweat fractions were investigated by electroantennography (EAG). Short-chain saturated carboxylic acids, methanoic, ethanoic, propanoic, butanoic, pentanoic and hexanoic acids were found to elicit significantly larger EAG responses than longer chain saturated carboxylic acids from female An.gambiae. For a given dose the largest amplitude EAG response was elicited by methanoic acid. Pentanoic acid elicited larger EAG responses than either butanoic or hexanoic acids. Two non-acidic compounds, 1-octen-3-ol and 4-methylphenol, were found to elicit significant dose-dependent EAG responses from female An.gambiae. 1-Octen-3-ol elicited larger EAG responses than 4-methylphenol for a given dose, but both compounds elicited smaller EAG responses than the same dose of C1-C6 straight-chain aliphatic carboxylic acids. The possible behavioural significance of the EAG-active compounds identified in human sweat samples is discussed.
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Natural Resources Institute, Chatham Maritime, Kent, U.K.
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D000328:Adult; D000818:Animals; D000852:Anopheles / Q000502:physiology*; D003408:Cresols; D004305:Dose-Response Relationship, Drug; D004594:Electrophysiology; D005260:Female; D008401:Gas Chromatography-Mass Spectrometry; D006801:Humans; D019344:Lactic Acid; D000442:Octanols; D013542:Sweat / Q000737:chemistry*
D003408:Cresols; D000442:Octanols; C032538:4-cresol; D019344:Lactic Acid; C038844:1-octen-3-ol