## 2 Materials and Methods
### Volatile Compositions Using HS-SPME-GC-MS  
The assessment of volatile metabolite components within _V. kulingiana_ leaves was performed utilizing the Headspace Solid-Phase Microextraction (HS-SPME) technique coupled with an Agilent 8890 gas chromatograph (GC) and an Agilent 7000D mass spectrometer (MS) (Agilent, Palo Alto, CA, USA) in triplicates. Briefly, the samples were meticulously ground to obtain a fine powder immersed in liquid nitrogen. Subsequently, 500 mg of the obtained powder was promptly transferred into a 20 mL headspace vial containing a saturated NaCl solution to impede enzymatic reactions. Before the SPME analysis, each vial was subjected to a temperature of 60 \({}^{\circ}\)C for 5 min. Following this, a 120 \(\upmu\)m DVB/CWR/PDMS fiber (Agilent) was introduced into the sample's headspace, where it remained for 15 min at 60 \({}^{\circ}\)C. Upon the completion of sampling, the desorption of volatile organic compounds (VOCs) from the fiber coating occurred within the injection port of the GC apparatus at a temperature of 250 \({}^{\circ}\)C for 5 min in splitless mode. The VOCs were separated in a DB-5 MS capillary column (30 m \(\times\) 0.25 mm \(\times\) 0.25 \(\upmu\)m). Helium was used as the carrier gas at a 1.2 mL/min linear velocity. The injector temperature was maintained at 250 \({}^{\circ}\)C, while the detector was set at 280 \({}^{\circ}\)C. The oven temperature was programmed as follows: it was initiated at 40 \({}^{\circ}\)C (held for 3.5 min), ramped up at 10 \({}^{\circ}\)C/min to 100 \({}^{\circ}\)C, further increased at 7 \({}^{\circ}\)C/min to 180 \({}^{\circ}\)C, and finally raised to 25 \({}^{\circ}\)C/min to 280 \({}^{\circ}\)C, where it was held for 5 min. Mass spectra were recorded using electron ionization (EI) in ionization mode at 70 eV. The quadrupole mass detector, ion source, and transfer line temperatures were adjusted to 150 \({}^{\circ}\)C, 230 \({}^{\circ}\)C, and 280 \({}^{\circ}\)C, respectively. The VOCs were identified using a widely targeted volatilomics (WTV) method recently described by [PERSON] et al. (2018). The features were characterized by comparing the deconvoluted spectra and Kovats' retention index (RI) with those in the NIST 17 library and by comparing the determined RT and qualitative ions with those in the MWGCSIM1.0 library. The RI deviation was maintained within \(\pm\)20. Two to three qualitative ions were selected for each compound. These ions were then detected separately for each group, adhering to the sequence of peak appearance. A compound was determined if the retention \begin{table}
\begin{tabular}{c c c} \hline \hline \multicolumn{2}{c}{**Test Items**} & \multicolumn{2}{c}{**Determination Methods**} \\ \hline \multirow{4}{*}{Macronutrient} & Energy & GB/Z 21922-2008 [(20)] \\  & Protein & GB 5009.5-2016 method 1 [(21)] \\  & Fat & GB 5009.6-2016 method 2 [(22)] \\  & Dietary fiber & GB 5009.88-2014 [(23)] \\  & Starch & GB 5009.9-2016 method 2 [(24)] \\ \hline \multicolumn{2}{c}{Trace elements} & GB 5009.268-2016 method 2 [(25)] \\ \hline \multirow{4}{*}{Vitamins} & Vitamin A & GB 5009.82-2016 method 1 [(26)] \\  & Vitamin B1 & GB 5009.84-2016 method 2 [(27)] \\  & Vitamin B2 & GB 5009.85-2016 method 1 [(28)] \\  & Vitamin C & GB 5009.86-2016 method 2 [(29)] \\  & Vitamin E & GB 5009.82-2016 method 1 [(26)] \\ \hline \multicolumn{2}{c}{Total flavonoids} & ISO 20759:2017 (Annex C) [(30)] \\ \hline \hline \end{tabular} The determined methods mostly followed the Standardization Technical Guidance Document of the People’s Republic of China and International Organization for Standardization.  
\end{table} 
Table 1: Determination of nutritional components in _V. kulingiana_. times of the detected peaks aligned with the standard reference and all the selected ions were present in the mass spectra of the samples after background subtraction [31]. The relative abundance of the annotated VOCs is expressed as a percentage of the peak area in the total ion chromatograms.