Appetite-enhancing effects of inhaling cinnamon, clove, and fennel essential oils containing phenylpropanoid analogues.

Cinnamon, clove, and fennel are commonly used as spices and herbal medicines, and one of their medicinal uses is as aromatic stomachics. We investigated the effect on appetite in mice of inhaling volatile compounds contained in essential oils extracted from herbal medicines used as aromatic stomachics. The appetite-enhancing effects of cinnamon and fennel essential oils were similar to those of their main components trans-cinnamaldehyde and trans-anethole, respectively. The appetite-enhancing effects of clove essential oil were observed over a wide range of doses (4.5 × 10 to 4.5 × 10 mg/cage), even though the active compounds showed effects within a narrow range of doses (eugenol: 4.5 × 10 to 2.5 × 10 mg/cage; eugenol acetate: 1.1 × 10 to 4.5 × 10 mg/cage). The increase in appetite at doses that differed by tenfold in mice administered clove oil was due to synergistic effects between eugenol and eugenol acetate in clove oil. Thus, loss of appetite could be treated more effectively using essential oil containing both eugenol and eugenol acetate compared with the active compounds administered separately. Administering essential oils, such as cinnamon and clove, could improve loss of appetite without strict dosage adjustment.