A Comparative Evaluation of the Antioxidant Ability of Polygonum cuspidatum Extracts with That of Resveratrol Itself

In this article, the resveratrol content and antioxidant activity of extracts obtained from Japanese knotweed (Polygonum cuspidatum Siebold & Zucc.) were evaluated. The extracts were prepared by pressurized liquid extraction (PLE), maceration, ultrasound-assisted solvent extraction (UASE), and sea sand disruption method (SSDM) using different extractants (methanol, methanol–water mixture, and water). The following methods were used to study antioxidant properties: ABTS (2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid), FRAP (ferric reducing antioxidant power), DPPH (2,2′-diphenyl-1-picrylhydrazyl), and CUPRAC (cupric ion reducing antioxidant capacity). It was proven that the resveratrol content depends not only on the extraction technique used but also on the solvent and extraction temperature. High resveratrol content was obtained by maceration and PLE using a mixture of methanol and water as the extraction solvent. Among the extracts tested, these were the ones showed the greatest antioxidant properties. However, it was confirmed that not only resveratrol but also other components of the extracts are responsible for the antioxidant properties. It was therefore shown that not only resveratrol, most commonly associated with Japanese knotweed, but also other ingredients affect the biological activity of this valuable-for-health plant.