Isolation and Characterization of Secondary Metabolites from Endemic and Edible Polygonum sivasicum with In Vitro Antioxidant and Cytotoxic Activities.

Polygonum sivasicum Kit Tan and Yildiz, one of the eight endemic Polygonum species in Türkiye, belongs to the Polygonaceae family. Preliminary phytochemical investigation of methanol and hexane extracts of P. sivasicum resulted in four compounds, namely, annphenone (1), hyperoside (2), daucosterol (3), and β-sitosterol (4). Their structures were elucidated by 1D-, 2D-NMR, and HRESIMS analyses. This study signifies the first isolation of annphenone from the Polygonum genus. Antioxidant capabilities of different extracts of P. sivasicum were carried out using DPPH·, ABTS·+, CUPRAC, metal chelating, and β-carotene linoleic acid bleaching assays, and their effectiveness was quantified through IC50 values. Furthermore, 27 phenolic compounds were identified using LC-HRESIMS from methanol extract, which has the highest antioxidant activity among the P. sivasicum extracts. The major phenolic constituents identified were hyperoside (4535.0 μg/g extract), rutin (4387.4 μg/g extract), and chlorogenic acid (3306.6 μg/g extract). GC-MS analysis determined palmitic acid, α-linolenic acid, and 8,11-octadecadieonic acid as major fatty acids in the hexane extract. The cell viability profile of P. sivasicum methanol extract and its isolates hyperoside, annphenone, and daucosterol was evaluated on fibroblast (CCD-1079Sk), breast carcinoma (MCF-7) and lung carcinoma (A549) cell lines. Annphenone exhibited IC50 values of 0.25 ± 0.01 mg/mL against the A549 cell line and 0.36 ± 0.02 mg/mL against the MCF-7 cell line. The selective cytotoxicity observed for daucosterol against the A549 cell line, with a high selectivity index of 1.44, underscores its potential as a promising candidate for drug development. The study establishes a framework integrating phytochemical profiling with biological assays to identify therapeutic agents from endemic plants.