*3.2. Plant Material*

The plants of *S. hookeriana* were collected from Hezhang Country, Guizhou Province of China, in July 2015 and identified by Prof. JunHua Zhao*,* Guiyang College of Traditional Chinese Medicine. A voucher specimen (No. 150708) was deposited at College of Pharmacy, Guiyang College of Traditional Chinese Medicine.

## *3.3. Extraction and Isolation*

The powdered stems and roots of *S. hookeriana* (14.5 Kg) were extracted ultrasonically with MeOH for three times. The combined extracts were concentrated and then partitioned between EtOAc and 1% aq. H2SO4. The acid-soluble fraction was alkalinized with aq. Na2CO3 to pH 9 and followed by exhaustive extraction with CH2Cl2 to afford crude alkaloids (156 g). The crude alkaloids were roughly separated by CC (SiO2; CH2Cl2/MeOH/Et2NH, 100:0:0→10:1:0→5:1:1) to give five fractions: *Frs. A-E*. *Fr. A* (32 g) was passed through CC [SiO2; petroleum ether (PE)/CH2Cl2/Et2NH 50:1:1→10:1:1, then cyclohexane/acetone/Et2NH 20:1:1] to afford **3** (150 mg), **4** (800 mg). *Fr. B* (24 g) was subjected to CC (PE/CH2Cl2/ Et2NH, 50:1:1→20:1:1, then CH2Cl2/MeOH 20:1) to yield **1** (60 mg) and **2** (40 mg).
