Clerodane diterpene


Clerodane diterpenes, sometimes referred to as clerodane diterpenoids, are a large group of secondary metabolites that have been isolated from several hundreds of different plant species, as well as fungi, bacteria and marine sponges. They are bicyclic terpenes that contain 20 carbons and a decalin core.

Classification

The clerodane diterpenes are classified into four groups trans-cis, trans-trans, cis-cis, and cis-trans based on the relative stereochemistry at the decalin junction and the relative stereochemistry of the substituents at C-8 and C-9. The absolute stereochemistry of the clerodanes is classified as neo or ent-neo. The neo-clerodanes share the same absolute stereochemistry as clerodin. Approximately 25% of clerodanes have the 5:10 cis ring junction. The remaining 75% have a trans 5:10 ring junction.

Biosynthesis

They are structurally related to the bicyclic labdane diterpenes. Its biosynthesis in plants takes place in the chloroplasts. Some forms can be useful intermediates in organic synthesis. Some clerodanes like clerodin from the leaves of Clerodendrum infortunatum have anthelminthic properties, others like ajugarins are repellent to herbivore predators or have a very bitter taste, such as gymnocolin.
Some examples for clerodanes are ajugarins I to V extracted from bugleweeds like Ajuga remota, Ajuga ciliata, Ajuga decumbens, common skullcap, and germanders, cascarillin from Croton eleuteria, columbins from Jateorhiza columba, Jateorhiza palmata and guduchi, gymnocolin from Gymnocolea inflata, hardwickiic acid from Hardwickia species. Neo-clerodane diterpenes can have hallucinogenic properties such as salvinorin A, a trans-neoclerodane diterpene from Salvia divinorum''.