Semih BULUT, Ahmet KAHRAMAN, Ayşenur IŞIK, Mustafa Abdullah YILMAZ
Turkish Journal of Medical Sciences - 2026;56(4):1296-1307
Background/aim: Rubia species (Rubiaceae) are recognized as medicinal and industrial plants exhibiting diverse biological activities. This study was conducted to evaluate the antioxidant, antidiabetic, and antiobesity potential of extracts prepared from Rubia davisiana Ehrend. (an endemic species), R. peregrina L., and R. rotundifolia Banks & Sol., which grow naturally in Türkiye. Materials and methods: The antioxidant activity of 80% ethanol extracts prepared from the aerial parts was evaluated using 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonate) (ABTS) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assays, ferric reducing power, metal chelating capacity, and total antioxidant capacity assays. Inhibition assays for alpha-glucosidase and alpha-amylase were performed to evaluate antidiabetic activity, whereas a pancreatic lipase inhibition assay was conducted to assess antiobesity activity. Additionally, the quantitative chemical composition of the extracts was determined using liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis. Results: The total phenolic content of the extracts ranged from 52.15 to 66.77 mg GAE/g extract. All extracts exhibited strong DPPH radical scavenging activity at concentrations of 1 and 2 mg/mL. ABTS radical scavenging activity and ferric reducing power increased in a concentration-dependent manner. Among the tested extracts, R. rotundifolia exhibited the highest total antioxidant capacity (147.35 mg ascorbic acid equivalent [AAE]/g extract). R. rotundifolia extract demonstrated stronger alpha-amylase inhibitory activity than the other extracts at all tested concentrations. At a concentration of 2 mg/mL, R. rotundifolia extract exhibited 74.70% inhibition of alpha-glucosidase activity. LC-MS/MS analysis revealed that the aerial parts of R. rotundifolia were rich in quinic acid and chlorogenic acid. Conclusion: The antidiabetic and antiobesity activities of extracts obtained from all studied species were evaluated for the first time. In conclusion, the alpha-glucosidase inhibitory and antioxidant activities of the extract prepared from the aerial parts of R. rotundifolia were more pronounced. Further studies are warranted to investigate fractionation processes and bioactivity-guided isolation of active constituents.
