Sesquiterpenes. I. Nootkatone, A New Grapefruit Flavor Constituent


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    One of the laboratories of the Western Utilization Research and Development Division, Agricultural Research Service, U. S. Department of Agriculture.

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The bicyclic conjugated sesquiterpene ketone, nootkatone, has been found in grapefruit peel oil and in peel-oil-free grapefruit juice. The flavor intensity of grapefruit oil appears to be related to the relative abundance of nootkatone. A combination of gas-liquid chromatography and thin-layer chromatography revealed the presence of this ketone, which was identified by its infrared spectrum and the melting point of its 2,4-dinitrophenylhydrazone derivative. Traces of nootkatone were found also in bergamot, lemon, lime, orange, and tangerine oils.