Abstract: Antioxidant activity of Guava leaf was determined at ambient temperature by means of a 2,2-diphenyl-1-picrylhydryzyl (DPPH•) colorimetry with detection scheme at 515 nm. The activity was evaluated by the decrease inabsorbance as the result of DPPH• color change from purple to yellow. The higher the sample concentration used, the higherthe free radical-scavenging effect. The results showed that ascorbic acid was substantial powerful antioxidant than theextracts from guava leaf. The parameter EC50 and the time needed to reach the steady state to EC50 concentration (TEC50) affectedthe antiradical capacity of the sample. The antiradical efficiency (AE) has been shown to be a more adequate parameter toselect antioxidants than the widely used EC50. This study revealed that guava leaf extracts are an effective potential source ofnatural antioxidants.

Key words: antioxidant capacity, radical-scavenging activity, DPPH free radical, colorimetry, guava, polyphenols