The major diterpenoids of the genus Arctopus (Apiaceae) with notes on their chemotaxonomic and medicinal significance

The main diterpenoids in the roots of Arctopus (Apiaceae, tribe Saniculeae) have been identified for the first time. The major compounds are manool, ent-trachyloban-19-oic acid and a kauren-19-oic acid, while methyl-16β-hydroxy-. ent-kaur-11-en-19-oate is a minor diterpene. Comparative studies of non-polar extracts by means of LC-MS showed that the isolated main compounds are present in all three species of Arctopus. The study also revealed that the diterpenoid pattern in Arctopus is very similar to that of the genus Alepidea. The tuberous roots of Arctopus and the rhizomes and roots of Alepidea are important traditional medicines in South Africa, used mainly for infections and respiratory ailments. Their efficacy is ascribed to antimicrobial and anti-inflammatory activity. The known biological activities of the isolated diterpenes provide a scientific rationale for the traditional uses. The chemical similarity in diterpenoids also supports the idea that the two genera are closely related, despite their conspicuous morphological differences.