The effect of boiling on antioxidant activity, total phenolic content (TPC) and total flavonoid content (TFC) in the ethanol extracts from Plectranthus amboinicus leaves were studied. The dried leaves were boiled in water for 0 (control), 30, 60, 90 and 120 minutes, then extracted with ethanol to produce ethanol extracts. The ethanol extracts were subjected to three antioxidant assays, i.e., 2, 2-diphenyl-1-picrylhydrazyl (DPPH), 2, 2'-azino-bis (3-ethylbenzothiazoline-6sulphonic acid) (ABTS) and ferric reducing antioxidant power (FRAP). TPC and TFC in extracts were determined by Folin-Ciocalteu assay and aluminium chloride colorimetric assay, respectively. The results of DPPH, ABTS and FRAP assays indicated that the antioxidant of extracts were significantly (p < 0.05) more potent than the control and also increased when the boiling time was increased. Furthermore, TPC and TFC in extracts from boiled samples were significantly (p < 0.05) higher than the control and correlated with antioxidant activity. This study revealed that boiling of P. amboinicus leaves were increased its antioxidant activity, TPC and TFC as determine in ethanol extracts, and suggested that boiling can be used as a method for enhancing antioxidant activity of P. amboinicus.

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