## 2 Materials and Methods
### Instrumentation and Conditions  
HPLC-QQQ/MS analysis was performed on an Agilent 1100 series HPLC system (Agilent, Palo Alto, CA, USA) coupled with an API 3000 triple quadrupole mass spectrometer (Applied Biosystems, Warrington, UK), with a Turbo-assisted ion spray (ESI) ionization source in a positive ionization mode. Chromatographic separation was conducted on an Agilent Eclipse XDB-C18 (4.6 mm \(\times\) 100 mm \(\times\) 3.5 \(\upmu\)m). The column temperature was maintained at 22 \({}^{\circ}\)C. The mobile phase consisted of water containing 0.1% formic acid (A) and methanol (B). Gradient elution was used, starting with 70% B, increasing to 100% B within 5 min, holding for 3 min with 90% B, decreasing B to 70% within 0.1 min, and re-equilibration at 70% B for 2.9 min. A flow rate of 350 \(\upmu\)L/min was applied, and a volume of 10 \(\upmu\)L was injected.  
Detection was performed with an ionizing voltage of +4500 V. Ion source temperature was set at 350 \({}^{\circ}\)C, with ultrahigh-purity nitrogen as curtain gas (7 psi). Nebulizer gas was 8 psi. Other mass-dependent parameters, such as declustering potential (DP), entrance potential (EP), focusing potential (FP), and collision energy (CE) for each compound, were determined in positive mode using standard solutions. Multiple reaction monitoring (MRM) was carried out using nitrogen as collision gas (2 psi) and with a dwell time of 200 ms for each transition. Erinacine A was detected by monitoring the transitions \(m/z\) 443.200 \(\rightarrow\) 301.200, 283.200. The data were analyzed using Analyst 1.4.2 software (Applied Biosystems, Concord, ON, Canada) and Graphpad (Prism 8.0.0.).  
UPLC-QTOF/MS analysis was performed on an Agilent 1290 Infinity II UPLC system (Agilent, Palo Alto, CA, USA), coupled with an Agilent 6546 quadrupole time-of-flight mass spectrometry (Agilent, Palo Alto, CA, USA). Chromatographic separation was conducted on a Phenomener Kineetxe(r) C18 LC Column (3 mm \(\times\) 100 mm \(\times\) 1.7 \(\upmu\)m). The column temperature was maintained at 40 \({}^{\circ}\)C. The mobile phase A consisted of water containing 0.1% (\(v/v\)) formic acid in positive mode, 0.1% (\(v/v\)) formic acid, and 10 mM CH\({}_{3}\)COONH\({}_{4}\) in negative mode. The mobile phase B was acetonitrile. Gradient elution was used, starting with 5% B and holding for 0.5 min, increasing to 50% B within 5.5 min, increasing to 100% B within 10 min, and holding for 6 min. A flow rate of 400 \(\upmu\)L/min was applied, and a volume of 2 \(\upmu\)L was injected.  
Agilent 6546 quadrupole time-of-flight mass spectrometry was equipped with an electrospray ionization (ESI) source. The data acquisition was under the control of Mass Hunter workstation software. The typical operating source conditions in positive and negative ion ESI mode were optimized as follows: ion spray voltage (ESI\({}^{+}\)/ESI\({}^{-}\)) were 4000 V/3000 V; the gas temperature was 320 \({}^{\circ}\)C; drying gas flow rate was 8 L/min; nebulizer pressure was 45 psi; sheath gas temperature was 350 \({}^{\circ}\)C; sheath gas flow rate was 12 L/min; the collision energy was 10, 20, 40, and 60 V. Metabolites were identified using Agilent MassHunter Biotransformation software (version B.04.00) (Santa Clara, CA, USA). Chromatograms and mass spectra of the parent and identified metabolites were extracted using Agilent MassHunter Qualitative Analysis software (version B.05.00) (Santa Clara, CA, USA).