3. Result and discussion
In the present study, the relationship between the response
functions and the process variables were identified by three-factor
inscribed central composite design. Further, the extraction condi-
tions of total polyphenol content and antioxidant activities were
optimised. Polyphenols were extracted by subjecting the plant
material to acid hydrolysis (2 M HCl) in order to release the bound
molecules from their complex matrix, and then selectively sepa-
rated with hydroalcohol, an all-purpose solvent for preliminary
extraction of chemical constituents from plants (Harborne, 1984).
Table 2 shows the results of the predicted and experimentally
measured responses for the 20 runs according to the experimental
design. The yield of the TPC ranged from 3.01 to 7.23 mg GAE/g on
dry weight basis and the maximum yield was obtained for the 15th
run under the experimental conditions of X1 = 50%; X2 = 45.5 °C;
X3 = 30 mL/g. In terms of antioxidant activity, the DPPH and ABTS
radical scavenging ability ranged from 49.3% to 83.7% to 52.2–
83.3%, respectively. The lowest activity was observed for the 9th
run with the following conditions of X1 = 16.3%; X2 = 48.5 °C;
X3 = 30 mL/g where as the highest activity was obtained for 9th
and 20th runs, respectively for DPPH and ABTS radical scavenging
ability. Based on these data, the extraction process was optimised
for obtaining desirable responses at maximum.