Studies of pentacyclic triterpenoids structures and antidiabetic properties of Myrianthus genus

In a continuation of studies on the lipophilic extracts from wood, foliage, and bark from Betula alleghaniensis Britt., we have more recently undertaken studies on the extracts from the root bark of Myrianthus arboreus P. Beauv. These species belonging to Betulaceae and Cecropiaceae, families, are important trees growing in temperate and tropical hardwood forests of North America and Central Africa, respectively. Various tissues from these species represent important source of various triterpenoids, including pentacyclic triterpenes of ursane, lupane, and oleanane type from Betulaceae and ursane and oleanane type triterpenes from Cecropiaceae. However, the search for new triterpene molecules is continuing as they have diverse biological activities and therefore represent promising targets for the medicinal applications in numerous disorders. The first part of this review will provide an overview of the extraction techniques and/or isolation and characterization of these phytochemicals. Some comparisons between the triterpenes determined in these two very different and geographically distant species are proposed. A special focus is placed on the triterpenes and their derivative products reported, for the first time, in M. arboreus lipophilic extracts. The most important compounds identified in B. alleghaniensis foliage extracts are triterpene squalene and pentacyclic triterpenes α-amyrin (ursane skeleton), β-amyrin (oleanane skeleton). Most interesting, four Δ12 ursene-type pentacyclic triterpenes containing the trans-feruloyl moiety were isolated from a M. arboreus root bark hexane extract after its bioassay-guided fractionation. The several chemical classes of triterpenoids present in these two lipophilic extracts are explored and the analytical techniques employed for their quantification discussed. The second part will focus on the biological properties attributed to each chemical class of phytochemicals discussed in this chapter. A detailed update of the antidiabetic effects of M. arboreus extracts is presented.