The application of response surface methodology to the production of phenolic extracts of lemon grass, galangal, holy basil and rosemary

The effects of independent variables (ethanol:water ratio, temperature and time) on the extraction yield and antioxidant properties of phenolic extracts from lemon grass, galangal, holy basil and rosemary were studied. The extraction solvent ratio of ethanol to water was found to have a significant (P < 0.05) influence on extraction yield, reducing power and total phenolic content, but not on the antioxidant activity of all herb and spice samples, while extraction temperature had only minor effects. Extraction time had a significant (P < 0.05) effect only on the reducing power of holy basil extracts. The optimum extraction conditions, i.e. extraction solvent ratio of ethanol to water, extraction temperature and extraction time for maximum total phenolic content, were 3:1 at 25 degrees C for 30 min for lemon grass, 3:1 at 75 degrees C for 90 min for galangal and holy basil and 3:1 at 75 degrees C for 30 min for rosemary.