Essential oils of clove (Syzygium aromaticum) (CAS No. 8000-34-8/84961-50-2), cinnamon (Cinnamomum sp.) (product code PO128351, Batch No. 990133) and citronella (Cymbopogon sp.) (Batch No. 0000065697) were purchased from the Union Science Co., Ltd. (Chiang Mai, Thailand). The dried fruit of cardamon (Amomum krervanh) was purchased from a herbal store in Chiang Mai and was extracted using a hydro-distillation method [33 (link)]. Their chemical compositions are shown in Table 1. Liquid paraffin (Labchem, Ajax Finechem Pty Ltd.), canola and sunflower oil, coconut oil (Naturel, Lam Soon (Thailand) Public Company Limited) and rice bran oil (King, Thai Edible Oil Co., Ltd.) were used to test for suitable solvents for the essential oils.
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