*Article* **New Chlorinated Metabolites and Antiproliferative Polyketone from the Mangrove Sediments-Derived Fungus** *Mollisia* **sp. SCSIO41409**

**Jian Cai 1,2,†, Xueni Wang 1,3,†, Xia Gan 3,4, Qian Zhou 3, Xiaowei Luo 4, Bin Yang 1,2, Yonghong Liu 1,2, Disna Ratnasekera 5,\* and Xuefeng Zhou 1,2,\***


**Abstract:** Two new chlorinated metabolites, 8-chlorine-5-hydroxy-2,3-dimethyl-7-methoxychromone (**1**) and 3,4-dichloro-1*H*-pyrrole-2,5-dione (**3**), and eight known compounds (**2** and **4**–**9**) were isolated from the mangrove sediments-derived fungus *Mollisia* sp. SCSIO41409. Their structures were elucidated by physicochemical properties and extensive spectroscopic analysis. The absolute configuration of stemphone C (**4**) was established for the first time by the X-ray crystallographic analysis. Compounds **3** and **4** showed different intensity of antimicrobial activities against several pathogenic fungi and bacteria, and antiproliferative activities against two human prostate cancer cell lines (IC50 values 2.77 to 9.60 μM). Further, stemphone C (**4**) showed a reducing PC-3 cell colony formation, inducing apoptosis and blocking the cell cycle at S-phase in a dose-dependent manner; thus, it could be considered as a potential antiproliferative agen<sup>t</sup> and a promising anti-prostate cancer lead compound.

**Keywords:** mangrove sediments-fungus;*Mollisia* sp.; chlorinated metabolites; prostate cancer; antimicrobial
