Sumardi, Basyuni M, Wati R. 2018. Antimicrobial activity of polyisoprenoids of sixteen mangrove species from North Sumatra, Indonesia. Biodiversitas 19: 1243-1248. Mangroves including those that are distributed in the coast of North Sumatra containpolyisoprenoid with varying levels of polyprenol and dolichol constituents. Differences in polyisoprenoid levels were closely related tothe salinity of sea but the information about their biological activities is scarce. The present study aimed to describe the biologicalactivities, antimicrobial, antioxidant, and antifungal effects of polyisoprenoid extracts from sixteen mangrove species of North Sumatra,Indonesia. Polyisoprenoids were isolated from mangrove leaves and tested for their antimicrobial activity against Escherichia coli,Staphylococcus aureus, and Candida albicans. Meanwhile, their antioxidant activity was represented by their capacity in scavengingDPPH (2,2-diphenyl-1-picrylhydrazyl) free-radical agents. The most predominant polyisoprenoids found in sixteen mangrove leafextracts was dolichols (75%). Polyprenols-dominant species, Acacia auriculiformis, Hibiscus tiliaceus, Pongamia pinnata, and Ricinuscommunis, and dolichols-dominant species, Avicennia lanata, Av. marina, Av. officinalis, Barringtonia asiatica, Bruguieragymnorrhiza, Calophyllum inophyllum, Nypa fruticans, and Pandanus odoratissimus, inhibited the growth of E. coli and S. aureus.However, the antioxidant activity of those sixteen mangrove species was of a weak category. Surprisingly, all other mangrovespolyisoprenoid extracts did not inhibit C. albicans growth. This study suggested that polyisoprenoids in mangroves have potentialantibacterial properties to be developed further.