Studies in the biosynthesis of [6]-gingerol, pungent principle of ginger (Zingiber officinale)

The biosynthesis of [6]-gingerol has been investigated by the administration of labelled precursors to whole Zingiber officinale plants and to rhizome sections. The results show that phenylalanine is elaborated to ferulic acid which then condenses, in an unusual version of the ‘biological Claisen’ reaction, with malonate and hexanoate to yield [6]-dehydrogingerdione (11). Hexanoate is incorporated intact as shown by the location of label and the constancy of isotope ratios. Dihydroferulate is accepted, but loss of tritium shows it to be first dehydrogenated. Dione (11) is reduced in two steps to [6]-gingerol; in the preferred path, CO reduction precedes CC reduction, with (12) as intermediate, although dione (13) is also converted.