Optimization of phenolic and flavonoid content from Graptophyllum pictum (L.) Griff. leaf under maceration extraction methods using response surface methodology and its antioxidant activity

Graptophyllum pictum (L.) Griff. is a plant with many pharmacological effects and contains secondary metabolites which are phenolic and flavonoid compounds. This study aims to determine the optimum phenolic and flavonoid extraction conditions using a Box-Behnken design (BBD) and the correlation of optimized extract with antioxidant activity. The experimental design was conducted based on 3 factors and 3 levels: solvent concentration (X1; 50, 70, and 90% ethanol in water), extraction time (X2; 1, 2, and 3 days), and solid-to-liquid ratio (X3; 1: 5 – 1: 15). The phenolic and flavonoid compounds of the optimized extract were identified using LC-HRMS. Meanwhile, the antioxidant activity of the optimized extract was determined using DPPH radical scavenging activity. Statistical analysis results suggest that the model used is quadratic (p-value < 0.05) for the entire response. The R2 was obtained at a high figure of 97.96%, 98.59%, and 91.13%, respectively. The optimum yield, TPC, and TFC with the application of response surface methodology were obtained at 68.33% (X1), 2.10 days (X2), and 1: 10.36 (X3) and the experiment value of yield, TPC, and TFC was 48.712 ± 2.896 g, 99.937 ± 3.672 mg GAE/ g, and 37.562 ± 2.984 mg QE/ g, respectively. The optimized extract's phytochemical compounds included phenolics of p-coumaric acid, ferulic acid, cinnamic acid, and anacardic acid. Moreover, the optimized extract has the strongest antioxidant activity in radical DPPH inhibition with a dependent concentration manner. In summary, this method was successfully applied to optimize yield, TPC, and TPC in G. pictum leaves following the highest antioxidant activity. The optimized extraction method is reproducible and could be applied in the pharmaceutical industry to develop a product containing G. pictum extract.