Total flavonoid content (TFC) was determined using the AlCl3
colorimetric method (Do et al., 2014). Briefly, 2.0 mL of properly
diluted extract solution was mixed with 2.0 mL of 2% (m/v)
AlCl3 6H2O. Ten minutes later, the absorbance was measured at
430 nm against a blank. Quercetin (2.0–12.0 μg/mL) was used as
standard, the results were expressed as mg of quercetin equivalents
per gram of dried sweet potato leaf material (mg QE/g DM).