A new prenylated indole alkaloid, named paraherquamide J (1), together with four known compounds (2–5), were isolated from the mangrove rhizosphere soil-derived fungus Penicillium janthinellum HK1-6. The planar structure and relative configuration of 1 were determined by detailed analysis of the spectroscopic data especially the NOESY spectrum. The absolute configuration of 1 was determined by ECD spectra. Compound 2 was first isolated as a natural product and named as paraherquamide K. All isolated metabolites were evaluated for their antibacterial, topoisomerase I (topo I) inhibitory activities and lethality towards brine shrimp Artemia salina. © 2019, © 2019 Informa UK Limited, trading as Taylor & Francis Group.