Accumulation of the sesquiterpenes nootkatone and valencene by callus cultures of Citrus paradisi, Citrus limonia and Citrus aurantium.

The production of the sesquiterpenes nootkatone and valencene by callus cultures of Citrus species is described. The levels of these compounds were examined by gas chromatography-mass spectrometry and their yields were compared with the amounts found in mature fruits. A simultaneous increase and decrease in the levels of nootkatone and valencene, respectively, were observed with the aging of callus cultures of Citrus paradisi. These results suggest that valencene might be a possible precursor of nootkatone in this species. The high level of nootkatone detected in 9-month-old callus cultures of Citrus paradisi might be associated with the corresponding cell morphological changes observed.