Ultrasound-assisted subcritical water extraction of proanthocyanidins from defatted grape seed and its antioxidant activity

OBJECTIVE: To optimize the the ultrasound-assisted subcritical water extraction (USWE) parameters of proanthocyanidins from defatted grape seed, study antioxidant activity of proanthocyanidins and compare the effects of USWE and other extraction techniques. METHOD: The 2 L equipment of USWE was designed and used to extract the proanthocyanidins. The factors including extraction temperature, extraction time and extraction pressure were studied. The best extraction condition was found through the response surface design. Antioxidant activity of proanthocyanidins was studied by its DPPH free radical and NaNO2 scavenging action. RESULT: The USWE parameters were extraction temperature 145 degrees C, extraction time 18 min, extraction pressure 14 MPa and the extraction yield (EY) was 4.05% under this extraction condition. The proanthocyanidins extracted under this optimized extraction condition had better scavenging action on DPPH free radical and NaNO2. As compared with the conventional soxhlet's extraction and heat reflux extraction, the USWE cost less extraction time, and possessed high efficiency and so on. CONCLUSION: The extraction technology of USWE is highly feasible to extract proanthocyanidins from defatted grape seed.