Polygonum hydropiper Leaves have More Medicinal Value than Stems: Based on Chemical Composition and Antioxidant Activity

Background: Polygonum hydropiper, a traditional Chinese herbal medicine, contains abundant volatile components and effective ingredients such as flavonoids, exerting antiinflammatory, antioxidant and antibacterial effects. The pharmacologically active components are differentially distributed in different parts of P. hydropiper. Leaf loss commonly occurs during the processing of medicinal and edible products. Methods: In the present study, the total flavonoid content and DPPH antioxidant activity of the stems and leaves of P. hydropiper were compared and analyzed. A method for determining the content of six antioxidant-active components in P. hydropiper stems and leaves was established based on highperformance liquid chromatography. Simultaneously, the contents of volatile compounds in stems and leaves were determined using gas chromatography–mass spectrometry, and the compositional differences between stem and leaf extracts of P. hydropiper were analyzed. : This study aims to develop and validate an analytical method based on combined HPLC and GC-MS analysis of the constituents of P. hydropiper, and to compare the differences in constituents in different tissues of P. hydropiper using the method. Results: The average total flavonoid content in the leaves of the eight batches of P. hydropiper was 0.4 mg/mL, while the average total flavonoid content in the stems was 0.3 mg/mL. The average DPPH scavenging rate of the leaves in the eight batches of P. hydropiper was 99.35%, while the average DPPH scavenging rate of the stems was 98.88%. According to the results of the HPLC assay, the content of flavonoids is significantly higher in leaves than in stems. Kaempferol was not detected in stem samples from various batches. The highest percentage of terpenoids was found in the leaves by GC-MS assay. Conclusion: The medicinal components were concentrated in the leaves of P. hydropiper, which could contribute to cost savings, increase production efficiency, and promote the development of the P. hydropiper industry.