Improvement in the anti-inflammatory activity of guava (Psidium guajava L.) leaf extracts through optimization of extraction conditions

Our objective was to improve the anti-inflammatory activity of guava leaf extract through optimization of extraction conditions by using response surface methodology. Central composite design was used to evaluate the effect of three independent variables - extraction temperature (X1), ethanol concentration (X2), and extraction time (X3) - on the response variables, i.e. LPS-induced prostaglandin E2 (PGE2) and NO production in RAW 264.7 cells. Analysis of variance showed that the predicted quadratic models were significant and suitable for the responses. From the superimposed four-dimensional response surface plots, the optimum ranges, which minimized PGE2 and NO production simultaneously, were X1 = 38-56 °C, X2 = 42-68%, and X3 = 3.2-6.6 h. When the extraction was performed at selected points within these optimal ranges, the experimental values were in close agreement with the predicted values. These results, when applied to industrial extraction processes, may help improve the anti-inflammatory effect of guava leaf extracts.