3.1.1. General Experimental Procedures

UV and IR spectra were recorded on a Varian Cary 50 UV-Vis and Varian 640-IR FT-IR spectrophotometer, respectively. Optical rotations were measured on a Rudolph Autopol® IV automatic polarimeter. NMR spectra were determined on a Bruker 500 MHz NMR spectrometer at 500 MHz for 1H and 125 MHz for 13C-NMR (internal standard: TMS). Negative-ion mode ESI-Q-Orbitrap MS were obtained on a Thermo UltiMate 3000 UHPLC instrument (Thermo, Waltham, MA, USA).

Column chromatographies (CC) were performed on macroporous resin D101 (Haiguang Chemical Co., Ltd., Tianjin, China), silica gel (48–75 μm, Qingdao Haiyang Chemical Co., Ltd., Qingdao, China), ODS (40–63 μm, YMC Co., Ltd., Tokyo, Japan), and Sephadex LH-20 (Ge Healthcare Bio-Sciences, Uppsala, Sweden). Preparative high performance liquid chromatography (pHPLC) column, Cosmosil 5C18-MS-II (20 mm i.d. × 250 mm, Nakalai Tesque, Inc., Tokyo, Japan) were used to separate the constituents.

#### 3.1.2. Plant Material

The fresh aerial parts of *Allium mongolicum* Regel were collected from Alxa League, Inner Mongolia Autonomous Region, China, and identified by Dr. Li Tianxiang (The Hall of TCM Specimens, Tianjin University of TCM, China). The voucher specimen was deposited at the Academy of Traditional Chinese Medicine of Tianjin University of TCM.

#### 3.1.3. Extraction and Isolation

See supporting information.

#### 3.1.4. Acid Hydrolysis of 1, 3, 4 and 6

Solution of **1**, **3**, **4** and **6** (each 2.0 mg) in 5% aqueous H2SO4-1,4-dioxane were heated under reflux for 1 h, respectively. After cooling, the reaction mixture was neutralized with Amberlite IRA-400 (OH<sup>−</sup> form), removed by filtration, subjected to ODS CC (H2O), and the H2O eluate was reacted with l-cysteine methyl ester hydrochloride in pyridine and *N*,*O*-bis(trimethylsilyl)trifluoroacetamide (BSTFA), successively. Finally, the reaction product was elucidated by GC analysis (GC conditions, column: Agilent Technologies INC Catalog 19,091 J-413 HP-5, 30 m × 0.320 mm (i.d.) capillary column; column temperature: 230 ◦C; carrier gas: N2), and d-glucuronic acid and d-glucose hydrolysates were identified from **1**, **3**, and **6**; d-glucuronic acid, d-glucose, as well as l-rhamnose hydrolysates were detected from **4** by comparing it retention times (*t*R: d-glucuronic acid, 23.3 min; d-glucose, 19.6 min; l-rhamnose, 11.4 min) with those of their authentic samples treated in the same way.

#### 3.1.5. Acid Hydrolysis of **2**, **5** and **7**–**10**

The solution of compounds **2**, **5** and **7**–**10** (each 1.5 mg) in 1 M HCl (1.0 mL) was heated under reflux for 3 h. After cooling, the reaction mixture was neutralized with Amberlite IRA-400 (OH− form), then analyzed by HLPC [column, Kaseisorb LC NH2-60-5, 4.6 mm i.d. × 250 mm (Tokyo Kasei Co., Ltd., Tokyo, Japan); mobile phase, CH3CN-H2O (75:25, *v*/*v*; flow rate, 1.0 mL/min)]. As a result, d-glucose was detected from the aqueous phase of **2**, **5** and **7**–**10** by comparison of its retention time and optical rotation with those of the authentic sample, d-glucose (*t*<sup>R</sup> 12.5 min, positive), respectively.
