Labdane-type diterpenoids from hairy root cultures of Coleus forskohlii, possible intermediates in the biosynthesis of forskolin

Significant attention has been devoted to studying hairy root cultures as a promising strategy for production of various valuable secondary metabolites. These offer many advantages, such as high growth rate, genetic stability and being hormone-free. In this study, a detailed phytochemical investigation of the secondary metabolites of Coleus forskohlii hairy root cultures was undertaken and which resulted in the isolation of 22 compounds, including four forskolin derivatives and a monoterpene. Their structures were elucidated by extensive spectroscopic analyses. These compounds could be classified into four groups viz.: labdane-type diterpenes, monoterpenes, triterpenes and phenylpropanoid dimers. Apart from one compound, all labdane type diterpenes are oxygenated at C-11 as in forskolin and a scheme showing their biosynthetic relationships is proposed.