Expedient preparative isolation and tandem mass spectrometric characterization of C-seco triterpenoids from Neem oil

• MPLC based isolation of eight C-seco triterpenoids of salannin type from Neem oil.
• Expedient preparative isolation protocol to furnish pure triterpenoids.
• ESI(+)-quadrupole/orbitrap-MS/MS characterization of C-seco triterpenoids.
• Elucidation of fragmentation pathway of isolated and semi-synthesized triterpenoids.
• MS/MS identification of studied triterpenoids in Neem bark and stem extract.

C-seco triterpenoids are widely bioactive class of natural products with high structural complexity and diversity. The preparative isolation of these molecules with high purity is greatly desirable, although restricted due to the complexity of natural extracts. In this article we have demonstrated a Medium Pressure Liquid Chromatography (MPLC) based protocol for the isolation of eight major C-seco triterpenoids of salannin skeleton from Neem (Azadirachta indica) oil. Successive application of normal phase pre-packed silica-gel columns for the fractionation followed by reverse phase in automated MPLC system expedited the process and furnished highly pure metabolites. Furthermore, eight isolated triterpenoids along with five semi-synthesized derivatives were characterized using ultra performance liquid chromatography–electrospray ionization-quadrupole/orbitrap-MS/MS spectrometry as a rapid and sensitive identification technique. The structure–fragment relationships were established on the basis of plausible mechanistic pathway for the generation of daughter ions. The MS/MS spectral information of the triterpenoids was further utilized for the identification of studied molecules in the complex extract of stem and bark tissues from Neem.