*2.2. Biological Evaluation*

Compounds **1**–**11** were tested for their inhibitory e ffects against α-glucosidase, and antioxidant activity. As seen in Table 4, the results indicated that compounds **1**, **8** and **9** showed significant inhibitory effects against α-glucosidase with IC50 values of 17.1, 26.7 and 15.7 μM, respectively, which were better than the positive controls acarbose (610.2 μM) and 1-deoxynojirimycin (71.5 μM). Beyond that, all of the compounds were tested for their antioxidant activity based on DPPH· (2, 2-diphenyl-1-picrylhydrazyl radical) scavenging. The results showed the antioxidant activity of **8** was 89% at the concentration of 100 μM and compound **8** possessed more potent capacity than positive control ascorbic acid in scavenging DPPH· with an EC50 value of 16.3 μM. Compounds **1**, **4** and **6** also exhibited weak DPPH· scavenging activity with respective EC50 values of 77.8, 85.8 and 59.1 μM.


**Table 4.** The α-glucosidase inhibitory and antioxidant activities of compounds **1**–**11**.


## **3. Experimental Section**

#### *3.1. General Experimental Procedures*

UV data were measured on a UV-Vis-NIR spectrophotometer (Perkin Elmer, Waltham, UK). IR spectrum data were recorded using a Bruker Vector spectrophotometer 22. Melting points

were tested on a Fisher-Johns hot-stage apparatus which were uncorrected. Optical rotations were recorded using an MCP300 (Anton Paar, Shanghai, China). HRESIMS data were conducted on an Ion Mobility-Q-TOF High-Resolution LC-MS (Synapt G2-Si, Waters). The ECD experiment data were measured with J-810 spectropolarimeter (JASCO, Tokyo, Japan). The NMR spectra were recorded on Bruker Avance spectrometer (Bruker, Beijing, China) (Compounds **1** and **3**: 500 MHz for 1H and 125 MHz for 13C, respectively; compounds **2** and **4**: 400 MHz for 1H and 100 MHz for 13C). Column chromatography (CC) was carried out on silica gel (200–300 mesh, Marine Chemical Factory, Qingdao, China) and sephadex LH-20 (Amersham Pharmacia, Piscataway, NJ, USA).
