*Article* **Immunosuppressive Cytochalasins from the Mangrove Endophytic Fungus** *Phomopsis asparagi* **DHS-48**

**Zhao Feng †, Xuexia Zhang †, Jingwan Wu, Chengwen Wei, Ting Feng, Dongdong Zhou, Zhenchang Wen and Jing Xu \***

† These authors contributed equally to this work.

**Abstract:** Three new cytochalasins, phomoparagins A-C (**1**–**3**), along with five known analogs (**4**–**8**), were isolated from *Phomopsis asparagi* DHS-48, a mangrove-derived endophytic fungus. Their structures, including their absolute configurations, were elucidated using a combination of detailed HRESIMS, NMR, and ECD techniques. Notably, **1** possessed an unprecedented 5/6/5/8/5-fused pentacyclic skeleton. These compounds were tested for their inhibitory activity against concanavalin A (ConA)/lipopolysaccharide (LPS)-induced spleen lymphocyte proliferation and calcineurin (CN) enzyme. Several metabolites (**2** and **4**–**6**) exhibited fascinating inhibitory activities with a relatively low toxicity. Furthermore, **2** was demonstrated to inhibit ConA-stimulated activation of NFAT1 dephosphorylation and block NFAT1 translocation in vitro, subsequently inhibiting the transcription of interleukin-2 (IL-2). Our results provide evidence that **2** may, at least partially, suppress the activation of spleen lymphocytes via the CN/NFAT signaling pathway, highlighting that it could serve as an effective immunosuppressant that is noncytotoxic and natural.

**Keywords:** mangrove endophytic fungi; *Phomopsis* sp.; cytochalasins; immunosuppressive activity; CaN/NFAT signaling pathway
