Characterization and fragmentation mechanism of 3-aminospirostane alkaloids from roots of Solanum paniculatum L. with hepatoprotective activity.

Rationale Solanum paniculatum L., popularly known as jurubeba, has traditionally been used in Brazilian folk medicine for liver diseases. However, there is a lack of knowledge about the chemical characterization of 3-aminospirostane alkaloids, an important class related to pharmacological activities. This work aimed to characterize the alkaloids using liquid chromatography with tandem mass spectrometry (LC/MS/MS) supported by molecular networking and theoretical calculations as well as to evaluate the contribution to hepatoprotective activity. Methods S. paniculatum roots were collected and macerated with MeOH/H2O (8:2) obtaining the crude extract (SP-CE). From this, partition using EtOAc with pH variation yielded the alkaloidic fraction (SP-AF). Both were evaluated in an acute liver injury model (100 and 200 mg/kg), after intraperitoneal administration of carbon tetrachloride (CCl4) in mice. AST (aspartate transaminase) and ALT (alanine transaminase) serum levels were investigated, as well as the histopathological characteristics. The SP-CE and SP-AF were analyzed by LC/MS/MS, using quadrupole/time-of-flight and ion-trap systems. The alkaloids annotated by the GNPS molecular network had their structures defined using gas-phase ionization and fragmentation reaction supported by theoretical calculations. Results The SP-CE and SP-AF decreased the ALT serum levels compared with the negative control. The group treated with the SP-CE (at the highest dose) demonstrated a significant decrease of ALT. Hepatic cell degeneration decrease was observed mainly at the highest dose of the treatment. Detailed electrospray ionization MS/MS data allowed us to identify alkaloids not previously reported, to propose their gas-phase reactions and to redefine the initial open ring fragmentation mechanism of the steroidal alkaloids with the jurubidine moiety. Conclusions The results allowed us to identify seven steroidal alkaloids from jurubeba and redefine the initial mechanism of fragmentation. A significant hepatoprotective effect was also demonstrated, corroborating its traditional use.