Supercritical fluid extraction of piceid, resveratrol and emodin from Japanese knotweed

In the present study, the use of supercritical fluid extraction was investigated for selected compounds from the plant Japanese knotweed (Polygonum cuspidatum Siebold & Zucc.). The effects of parameters such as type of modifier, pressure, temperature and time on the extraction efficiency of piceid, resveratrol and emodin were studied. The optimal conditions were found as follows: modifier acetonitrile, 40 MPa, 100 °C and 45 min. SFE results were compared with those obtained by conventional Soxhlet extraction carried out for 4 h. The extracts obtained using these two techniques were analysed by liquid chromatography coupled with UV detection. LiChrospher® 100, RP-18 column (125 mm × 4 mm, 5 μm) coupled with gradient elution acetonitrile in acidified water was used for the separation of compounds at flow rate 0.5 mL min−1. Detection was carried out at 306 nm. Limits of detection were 21, 8 and 52 μg L−1 for piceid, resveratrol and emodin, respectively. The linear range was 0.5–10 mg L−1 for piceid and resveratrol, and 1–50 mg L−1 for emodin with correlation coefficients above 0.9981. Based on the comparison of both methods extracted amount of piceid by Soxhlet extraction is approximately 10 times higher than by SFE method, while the extraction yield of emodin by Soxhlet extraction in approx. 2.5 times lower than by SFE. The advantage of SFE over Soxhlet extraction method is more than 5 times shorter extraction time period.