Optimal extraction of <i>Chenopodium formosanum</i> leaves using the response surface method

Chenopodium formosanum (CF) is a species endemic to Taiwan that is rich in both nutrients and antioxidants. Although the seeds of CF have long been considered valuable sources of antioxidants, no studies have yet examined the levels of antioxidant in CF leaves or these leaves’ optimal extraction methods. In this study, Response Surface Methodology (RSM) was applied to determine the optimal conditions for promoting total phenolic content (TPC), total flavonoid content (TFC), di(phenyl)-(2,4,6-trinitrophenyl)iminoazanium (DPPH) radical scavenging, 2,2’-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) radical scavenging, and ferric reducing ability of plasma (FRAP). Results showed that the concentration of ethanol had a major effect on TPC, DPPH radical scavenging, ABTS radical scavenging, and FRAP, whereas temperature had a major effect on TFC. The final optimized results for 100 mL ethanol solution to extract 1 g CF leaves determined using RSM were 141.26 µg gallic acid equivalents/mL for TPC, 158.09 µg quercetin equivalents/mL for TFC, 92.85% for DPPH radical scavenging, 50.49% for ABTS radical scavenging, and 26.85 µg vitamin C equivalents/mL for FRAP. RSM employed in this study revealed that CF leaves, similar to CF seeds, are a potent source of antioxidants.