RESULTS AND DISCUSSION
1. Modeling of the extraction process from rice husk. In order to optimize the extraction process with reference to the extraction of phenolic, flavonoid, anthocyanin and antioxidant components from rice husk using Ultrasound Assisted Extraction (UAE) as well as Microwave Assisted Extraction (MAE), Independent variables and their levels employed in a box behken design was developed as represented as well as experimental design of the five factors and four variable Box Behken design in Table 1 and 2. The values of total phenols, flavonoid, anthocyanin’s and antioxidant activities of rice husk extracts at various experimental conditions are also presented in Table 3. Analysis of variance showing the linear, quadratic interaction…show more content… 1) were constructed according to equation 4. Extraction process variables significantly effected the extraction of total phenols from the rice husk. The total phenolic contents increased slowly with the increase of ethanol concentration at fixed solvent solute ratio and nearly reached a peak at higher concentration of ethanol. Similarly, the increase in solvent solute ratio at fixed ethanol concentration led to a gradual increase in the total phenolic content. (Fig. 1)
3. Effect of process variables on extraction of flavonoid Multiple regression analysis was performed on the experimental data, and the coefficients of the model were evaluated for significance. The values of the coefficients for total flavonoid as presented in Table 4 were used for a final predictive equation neglecting the non-significant cross-terms as given below eq. (5)
Y=1.38-0.16X_1-0.29X_2+0.24X_3+0.71X_4-0.12X_5+0.14X_1^2+0.003958X_2^2…show more content… The effect of extraction time was highly significant at P≤0.05 on the extraction of antioxidant, and it was consistent with the findings of higher yields of antioxidant from rice husk when extraction was done for a longer time. Antioxidant activity increased with the increase of ethanol concentration reached at 88.61 % at a fixed sonication temperature while Antioxidant activity decrease significantly with the increase of sonication temperature at a fixed ethanol concentration (Fig. 9). Antioxidant activity with the increase of ethanol concentration at fixed solvent solute ratio and a similar increase in antioxidant activity with the increase of solvent solute ratio at a constant ethanol concentration (Fig.10). In table 3 The R2, adjusted R2 values of the model are 0.77, 0.59