Organic Solvent Extraction. To determine the
amount of anthraquinones remaining in the plant materials
after each subcritical water extraction, solvent
extraction with ethanol was carried out. The root residue
was taken out of the extractor and placed into a 125 mL
Erlenmeyer flask, containing 20 mL of ethyl alcohol. It
was then allowed to release the products into the solvent
overnight. The solution was then replaced with 20 mL
of fresh ethanol daily for 3 days. The concentration of
the total ethanol extract was then measured by means
of a spectrophotometer.