Occurrence and spatial distribution of maytansinoids in Putterlickia pyracantha, an unexplored resource of anticancer compounds.

Maytansinoids possess remarkable antibiotic activities along with high cytotoxicity, many of which are currently used (or in clinical trials) in the treatment of breast cancer. Celastraceous plants and their associated microorganisms serve as an important resource of maytansinoids. Here, we report the occurrence and structural elucidation of several maytansinoids in Putterlickia pyracantha plants bioprospected in South Africa. In addition to maytansine, which is already known to be present in this species, we show the presence of maytanprine, maytanbutine, maytanvaline, normaytancyprine and an abundant maytansine precursor in different tissues using high-resolution mass spectrometry. Furthermore, we identified two new hydroxylated maytansinoids by HRMS(2) analyses. We also employed MALDI-imaging-HRMS to study the spatial distribution and localization of the maytansinoids within the different plant tissues. On the one hand, the fragmentation pathways of the maytansinoids we report herein using HRMS(n) will allow quick identification of these compounds in the future without isolating from the natural resources. On the other hand, MALDI-imaging-HRMS revealed insights into the plausible ecological roles and biosynthetic pathways of these compounds in P. pyracantha plants.