Free radicals are reactive oxygen that have unpaired electrons looking for partners by binding to electron molecules in the vicinity. Free radicals can cause several degenerative diseases such as diabetes, atherosclerosis, Parkinson's disease, Alzheimer's disease. The content of secondary metabolites in mangroves has the potential to prevent various diseases. Several methods commonly used to estimate the presence of antioxidants in plants include DPPH (2,2-diphenyl-1-picrylhydrazyl), FRAP (ferrous reducing antioxidant power), and ABTS (2,2-azinobis-3-ethylbenzothiazole-6-sulfonic acid). The results of recent studies showed that some mangrove plants have antioxidant activity including: Rhyzophora mucronata, Nypa fruticans, Avicennia marina, Sonneratia alba, Acanthus ilicifolius L, Acrostichum aureum dan Scaevola taccada. Mangrove plants that have the highest IC50 value were found in leaves (methanol extract). The antioxidant activity of mangrove plants is caused by the presence of secondary metabolites contained in the extract such as flavonoids, phenolics, saponins, and tannins.