Isolation and identification of mosquito (Aedes aegypti) biting- deterrent compounds from the native American ethnobotanical remedy plant Hierochloë odorata (Sweetgrass)

Authors: Cantrell, Charles; JONES, A. MAXWELL - University Of Guelph; ALI, ABBAS - University Of Mississippi

Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/15/2016
Publication Date: 10/15/2016
Publication URL: http://handle.nal.usda.gov/10113/5581284
Citation: Cantrell, C.L., Jones, A.P., Ali, A. 2016. Isolation and identification of mosquito (Aedes aegypti) biting- deterrent compounds from the native American ethnobotanical remedy plant Hierochloë odorata (Sweetgrass). Journal of Agricultural and Food Chemistry. 64:8352-8358. doi:10.1021/acs.jafc.6b01668.

Interpretive Summary: Hierochloë odorata (L.) P. Beauv. (Poaceae), commonly known as sweetgrass, has documented use as an insect repellent by the Flatheads of Montana and Blackfoot of Alberta. Both the Flatheads of Montana and Blackfoot of Alberta would use braided plant material in a sachet in clothing or burn them from one end as incense, air/clothing freshener, and insect repellent. This study evaluated the insect repellent properties of this plant using an in vitro mosquito feeding bioassay-directed approach to identify the compound(s) responsible for the observed activities. Evaluation of crude extracts produced from H. odorata revealed that the hydrodistillate had the highest level of mosquito biting deterrence. Fractionation of this extract followed by re-evaluation for mosquito biting deterrence produced many active fractions which were evaluated by spectroscopic techniques and determined to contain phytol, coumarin, and 2-methoxy-4-vinylphenol. Phytol and coumarin were both determined to be responsible for the Aedes aegypti biting deterrency.

Technical Abstract: Ethnopharmacological relevance: Hierochloë odorata (L.) P. Beauv. (Poaceae), commonly known as sweetgrass, has documented use as an insect repellent by the Flatheads of Montana and Blackfoot of Alberta. Both the Flatheads of Montana and Blackfoot of Alberta would use braided plant material in a sachet in clothing or burn them from one end as incense, air/clothing freshener, and insect repellent. This study evaluated the insect repellent properties of this plant using an in vitro mosquito Aedes aegypti feeding bioassay-directed approach to identify the compound(s) responsible for the observed activities. Material and methods: The aerial parts of H. odorata were extracted with hexane, methylene chloride, ethanol, and via hydrodistillation. Bioactive essential oil from the hydrodistillation was fractionated using silica gel column chromatography (CC) providing twelve fractions. The most active fractions were investigated using chromatographic (CC, GC with retention indices) and spectroscopic techniques (MS, 1H and 13C NMR). Aedes aegypti biting deterrence of these fractions and pure compounds was compared to DEET using a K&D bioassay. Results: Evaluation of crude extracts produced from H. odorata revealed that the hydrodistillate had the highest level of mosquito biting deterrence. Fractionation of this extract followed by re-evaluation for mosquito biting deterrence produced many active fractions which were evaluated by spectroscopic techniques and determined to contain phytol, coumarin, and 2-methoxy-4-vinylphenol. Phytol and coumarin were both determined to be responsible for the Aedes aegypti biting deterrency. Conclusions: The mosquito repelling folk remedy plant H. odorata has been investigated using an Ae. aegypti biting deterrent bioassay-guided fractionation approach leading to the isolation and identification of phytol and coumarin as the constituents responsible for the biting deterrency. Scientific evidence reported here validates its traditional use as a biting insect deterrent.