Optimization of Graptophyllum pictum leaves extraction using a simplex centroid design focused on extracting flavonoids with antioxidant activity

Abstract

Graptophyllum pictum (L.) Griff, which is called “daun ungu” in Indonesia, is a medicinal plant that contained flavonoids with antioxidant activity. The different extractor solvents (water, acetone, methanol, and ethanol) and their combinations were studied using a simplex centroid design through the Design Expert 13.0 program. From the optimized crude extract, it was investigated for total flavonoid content (TFC) using the colorimetric method (AlCl3), as well as the antioxidant activity using 2,2-diphenyl-1-picryl hydrazyl (DPPH) and ferric reducing antioxidant power (FRAP) methods. The optimum condition was obtained at a desirability value of 0.745 with a water solvent system at a proportion of 1.00 (100%) which resulted in a TFC of 10.464 mg QE/g DW, the antioxidant activity of DPPH 2.179 μmol TE/g DW, and FRAP 22.009 μmol TE/g DW. The method was verified and analyzed based on the percentage of residual standard error, which resulted in <5% so that the predicted and actual results were not significantly different. These results indicate that the simplex centroid design can optimize flavonoid compounds with potent antioxidant activity from G. pictum leaves.