Abstract:

The objective of this study was to establish the optimal conditions for microwave-assisted extraction of total
flavonoids from seed shell of Juglans mandshurica. The extraction yield and total reducing power of total flavonoids
were investigated as a function of independent variables including ethanol concentration, solid-to-liquid ratio, microwave
output power and irradiation time by fitting a regression model. These variables were ranked in decreasing order of
importance as solid-to-liquid ratio, ethanol concentration, microwave output power and irradiation time. The optimized
extraction conditions were found to be 55% ethanol as the extraction solvent with a solid-to-liquid ratio of 1:34 (g/mL) and
microwave irradiation for 13 min with an output power of 640 W. The average extraction yield of total flavonoids obtained
from validation experiments was 9.59 mg/g with RSD of 1.98% (n = 3), and the experimental data could be fitted with
the developed regression model very well. Within 7 h, the total flavonoid content and total reducing power of the extract
obtained remained substantially.

Key words: Juglans mandshurica, seed shell, total flavonoids, microwave-assisted extraction, response surface methodology