A Bornean red algal population of Laurencia simlis Nam et Saito was analyzed for its secondary metabolite composition. Seven compounds were identified: ent -1(10)-aristolen-9β-ol (1), (+)-aristolone (2), axinysone B (3), 9-aristolen-1α-ol (4), 2,3,5,6-tetrabromoindole (5), 1-methyl-2,3,5,6-tetrabromoindole (6), and 1-methyl-2,3,5-tribromoindole (7). Compound 1 was identified as a new optical isomer of 1(10)-aristolen-9β-ol. Compounds 1, 4 and 5 exhibited good antibacterial activity against antibiotic resistant clinical bacteria and cytotoxic effects against selected cancer cell lines.