Myrsinane-Type Diterpenes: A Comprehensive Review on Structural Diversity, Chemistry and Biological Activities

Euphorbia species are important sources of polycyclic and macrocyclic diterpenes, which have been the focus of natural-product-based drug research due to their relevant biological properties, including anticancer, multidrug resistance reversal, antiviral, and anti-inflammatory activities. Premyrsinane, cyclomyrsinane, and myrsinane diterpenes are generally and collectively designated as myrsinane-type diterpenes. These compounds are derived from the macrocyclic lathyrane structure and are characterized by having highly oxygenated rearranged polycyclic systems. This review aims to describe and summarize the distribution and diversity of 220 myrsinane-type diterpenes isolated in the last four decades from about 20 Euphorbia species. Some myrsinane diterpenes obtained from Jatropha curcas are also described. Discussion on their plausible biosynthetic pathways is presented, as well as isolation procedures and structural elucidation using nuclear magnetic resonance spectroscopy. Furthermore, the most important biological activities are highlighted, which include cytotoxic and immunomodulatory activities, the modulation of efflux pumps, the neuroprotective effects, and the inhibition of enzymes such as urease, HIV-1 reverse transcriptase, and prolyl endopeptidase, among other biological effects.