Spirostanol-Type Saponins From Allium Macrostemonis Bulbus Alleviate Chronic Unpredictable Mild Stress–Induced Depression-Like Behavior in Mice

Major depressive disorder is a chronic, recurrent, and potentially life-threatening mental disorder that severely impacts both psychological and physiological health. Allii Macrostemonis Bulbus (AMB), a traditional Chinese medicinal and edible plant, is believed to be beneficial for mood regulation. Recent preclinical studies have demonstrated its total saponins’ antidepressant effects, though the specific active substances and pathways remain unclear.We first established an in vitro model of hippocampal neuronal injury in mice induced by Glu and conducted preliminary screening of different polarity fractions of AMB’s total saponins, identifying spirostanol-type saponins (AMBN-90) with antidepressant potential. We then analyzed the components and used network pharmacology to predict the targets and pathways of AMBN-90’s antidepressant effects. Next, we established an in vivo mouse model of depression induced by chronic unpredictable mild stress and treated it with AMBN-90 for 6 weeks. Behavioral tests, hippocampal HE staining, and monoamine level measurements in the hippocampus were used to verify AMBN-90’s antidepressant effects. Subsequently, Western blotting and molecular docking methods were employed to preliminarily reveal AMBN-90’s potential antidepressant mechanisms. Results showed that AMBN-90 exhibited significant neuroprotective activity in vitro. In vivo, AMBN-90 significantly improved weight loss and depression-like behaviors in mice exposed to chronic unpredictable mild stress, ameliorated hippocampal neuronal damage, and significantly increased levels of 5-HT, DA, and NE in the hippocampus. It also elevated brain-derived neurotrophic factor levels and reduced neuronal apoptosis by activating the PKA–CREB–BDNF pathway. Molecular docking showed that components of AMBN-90 have superior affinity for the upstream proteins of the pathway, C-type G protein–coupled receptors (GPCRs). Our findings suggest that steroidal saponins in AMB may be developed as functional foods and drugs for alleviating depression.