Hemigossypol, a constituent in developing glanded cottonseed (Gossypium hirsutum)

Gossypol is a dimeric sesquiterpenoid first identified in cottonseed, but found in various tissues in the cotton plant including the seed. From its first discovery, it was assumed that hemigossypol was the biosynthetic precursor of gossypol. Previous studies established that peroxidase (either from horseradish or from cottonseed) converts hemigossypol to gossypol. However, hemigossypol has never been identified in healthy cottonseed. In a temporal study using HPLC and LC-MS, hemigossypol was identified in the developing cotton embryo. It was shown to concomitantly accumulate until 40 days postanthesis (dpa) with gossypol and with transcripts of δ-cadinene synthase and 8-hydroxy-δ-cadinene synthase, genes involved in the biosynthesis of hemigossypol and gossypol. After 40 dpa, hemigossypol and its biosynthetic gene transcript levels declined, whereas the gossypol level remained almost unchanged until the bolls were open. These results provide further evidence to support the previous findings that establish hemigossypol as the biosynthetic precursor of gossypol.