*Article* **Secondary Metabolites with** α**-Glucosidase Inhibitory Activity from the Mangrove Fungus** *Mycosphaerella* **sp. SYSU-DZG01**

#### **Pei Qiu 1, Zhaoming Liu 1,2, Yan Chen 1, Runlin Cai 1, Guangying Chen 3,\* and Zhigang She 1,4,\***


Received: 29 July 2019; Accepted: 18 August 2019; Published: 20 August 2019

**Abstract:** Four new metabolites, asperchalasine I (**1**), dibefurin B (**2**) and two epicoccine derivatives (**3** and **4**), together with seven known compounds (**5**–**11**) were isolated from a mangrove fungus *Mycosphaerella* sp. SYSU-DZG01. The structures of compounds **1**–**4** were established from extensive spectroscopic data and HRESIMS analysis. The absolute configuration of **1** was deduced by comparison of ECD data with that of a known structure. The stereostructures of **2**–**4** were further confirmed by single-crystal X-ray diffraction. Compounds **1**, **8** and **9** exhibited significant α-glucosidase inhibitory activity with IC50 values of 17.1, 26.7 and 15.7 μM, respectively. Compounds **1**, **4**, **6** and **8** showed antioxidant activity by scavenging DPPH· with EC50 values ranging from 16.3 to 85.8 μM.

**Keywords:** secondary metabolites; *Mycosphaerella* sp.; asperchalasine; α-glucosidase
