Clerodanes

Clerodanes are a large class of diterpenoids defined by their clerodane skeleton, a bicyclic decalin core derived from geranylgeranyl pyrophosphate. They typically comprise 20 carbon atoms with various oxygenated substituents and occur as normal and enantiomeric forms. The core structure consists of two fused six-member rings in a decalin arrangement, often with trans fusion and a side chain that carries additional functional groups. The diversity of clerodanes arises from oxidative tailoring that generates lactones, furan rings, epoxides, ketones, and hydroxylations at multiple positions.

Biosynthesis begins with geranylgeranyl pyrophosphate, which undergoes cyclization enzymes to form the clerodane framework, followed by oxidative enzymes that introduce oxygenations and ring closures. The result is a broad array of clerodane diterpenoids, with substantial stereochemical variation and the occasional rearranged or transposed core leading to many diastereomers.

Occurrence and significance: Clerodane diterpenoids have been found in a wide range of plants, especially within families such as Lamiaceae, Moraceae, and Asteraceae, and have also been reported in certain fungi and insect-associated sources. They are frequently used as chemotaxonomic markers in phytochemical studies.

Biological activity and applications: Clerodanes exhibit diverse bioactivities, including insect antifeedant and repellent properties, antimicrobial and antifungal effects, anti-inflammatory activity, and cytotoxic or enzyme-inhibitory activities. Because of this, clerodane derivatives are of interest in natural product research and drug discovery as potential lead compounds.