Rapid identification of stigmastane-type steroid saponins from Vernonia amygdalina leaf based on α-glucosidase inhibiting activity and molecular networking.

Steroid saponins are secondary metabolites with multiple medicinal values that are found in large quantities in natural medicines, especially Vernonia amygdalina, a famous nature medicine for the treatment of tonsillitis, diabetes, pneumonia. The current study was designed to combine molecular networking (MN) with diagnostic ions for rapid identification of Δ7,9(11) stigmastane-type saponins which were the α-glucosidase inhibitory active substances in V. amygdalina. First, the α-glucosidase inhibitory activities of five Δ7,9(11) stigmastane-type steroid saponins that were previously isolated were screened, which indicated that the Δ7,9(11) stigmastane-type steroid saponin was one of the active constituents responsible for ameliorating diabetes. Furthermore, a strategy was proposed to identify stigmastane-type steroid saponins and verify the plausibility of derived fragmentation pathways by applying MN, MolNetEnhancer and unsupervised substructure annotation (MS2LDA). Based on this strategy, other seven Δ7,9(11) stigmastane-type steroid saponins were identified from this plant. Our research provide scientific evidence for the antidiabetic potential of the steroid saponin-rich extract of V. amygdalina leaf.

Stigmastane-type steroid saponins from the leaves of Vernonia amygdalina Del.

Vernoramyosides A-F (1-6), six new Δ7,9(11) stigmastane-type steroid saponins, along with four known analogues (7-10) were isolated from the leaves of Vernonia amygdalina Delile (Compositae). Their structures were determined by the combination of NMR, ECD and HR-ESI-MS data. These compounds all possessed highly oxidized side chain and a γ-lactam or α,ß-unsaturated five-membered lactone ring. All isolates were screened for their activities in reversing resistance in MCF/DOX cells.

MS diagnostic model and rapid distinguishing of bioactive limonoids in fruits of Melia toosendan using solid-phase extraction coupled with LC-MS/MS.

INTRODUCTION: Melia toosendan Sieb. et Zucc. has been used as a Chinese folk medicine for roundworm treatment since ancient times. Many diverse limonoids have been isolated from Meliaceae plants, but it remains difficult to isolate and identify other limonoids because of their small natural concentrations. OBJECTIVE: This study was performed to overcome the difficulties associated with fast and accurate identification of limonoids and establish a reliable and sensitive method for the analysis of minor limonoids in M. toosendan fruits. METHODS: An efficient strategy for enrichment, detection, and identification of minor limonoids from M. toosendan fruits using solid-phase extraction with high-performance liquid chromatography-quadrupole time-of-flight tandem mass spectrometry (SPE-HPLC-Q-TOF-MS/MS) was developed herein. RESULTS: Characteristic fragmentations and fragmentation ions containing trichilin-, nimbin-, and vilasinin-class limonoid skeletons were initially studied, and characteristic diagnostic ions involved retro Diels-Alder (RDA) reactions or homolytic cleavages, which were used to identify minor limonoids. In total, 13 limonoids, including four new ones, were identified. CONCLUSION: This is the first report on the analysis of M. toosendan fruits to identify limonoids. This novel analysis method may stimulate further research regarding the identification of limonoids in other plant species.