Centaurea lycaonica is a local endemic species from the Centaurea L. genus. The Centaurea species has a wide range of usage in treating diseases in folk medicine. There are limited biological activity studies on this species in the literature. This study investigated enzyme inhibition and antimicrobial activity, antioxidant effect, and chemical content of extract and fractions of C. lycaonica. Enzyme inhibition activity was tested by α-amylase, α-glucosidase, and tyrosinase enzyme inhibition methods and antimicrobial activity by the microdilution method. The antioxidant activity was investigated using DPPH^•, ABTS^•+, and FRAP tests. The chemical content was determined by LC-MS/MS. The methanol extract showed the highest activity for α-glucosidase and α-amylase, even surpassing the positive control acarbose, with IC₅₀ values of 56.333 ± 0.986 and 172.800 ± 0.816 μg/mL, respectively. Additionally, the ethyl acetate fraction also exhibited high activity for α-amylase with an IC₅₀ value of 204.067 ± 1.739 μg/mL and tyrosinase with an IC₅₀ value of 213.900 ± 1.553 μg/mL. Moreover, this extract and fraction were found to have the highest total phenolic and flavonoid contents and antioxidant activity. Additionally, LC-MS/MS analyses of active extract and fraction revealed mainly the presence of phenolic compounds and flavonoids. In silico molecular docking and molecular dynamics simulation studies of determining compounds apigenin and myristoleic acid, common in CLM and CLE extracts and active against α-glucosidase and α-amylase, were performed. In conclusion, methanol extract and ethyl acetate fraction showed potential enzyme inhibition and antioxidant activity as a natural agent. Molecular modeling studies corroborate the findings of in vitro activity analyses.

Diabetes mellitus (DM) is one of the globally worst killer diseases. In this study, the in vitro and in vivo antidiabetic activity and antioxidant capacity were determined and the phytochemical analyses were carried out on flower extract and sub-extracts of Rhaponticoides iconiensis. The in vitro antidiabetic activity was tested with α-amylase and α-glucosidase enzyme inhibition methods and an in vivo OGTT test in healthy and alloxan-induced rats. Although, the antioxidant activity was investigated with DPPH^●, ABTS^●+ and FRAP tests, the phytochemical composition analysis was carried out by LC-MS/MS. The highest α-glucosidase and α-amylase activity even from positive control acarbose were found in the ethyl acetate sub-extract of R. iconiensis (IC₅₀ = 11.737 ± 0.823 µg/mL and 84.247 ± 0.721 µg/mL, respectively). This sub-extract also was active according to the results of in vivo tests. Moreover, the highest antioxidant activity on DPPH^● (IC₅₀ = 0.126 ± 0.002 mg/mL), FRAP (at a concentration of 1 mg/mL equivalent to 3112.052 ± 2.023 mmol Fe²⁺) and ABTS^+● (at a concentration of 0.5 mg/mL equivalent to 0.608 ± 0.005 µM Trolox) tests. In addition, LC-MS/MS analyses of the active sub-extract revealed mainly the presence of patuletin, patuletin 3,7-diglucoside, naringin and 3,4-dicaffeoylquinic acid detected in the active sub-extract. In silico molecular docking and dynamics simulations studies were performed on these compounds with α-amylase and α-glucosidase enzymes for protein–ligand interactions and stability.

Context: Eryngium kotschyi is one of the species of Eryngium genus and was endemic to Turkey. It was known, that traditionally uses of this plant in the South-Western part of Turkey for the treatment of various diseases. Aims: To evaluate the antioxidant capacities of methanol extract and ethyl acetate, n-butanol and water sub-extracts as well as to determine the phytochemical composition and to quantify the major antioxidant compounds in the active sub-extract. Methods: Besides the total phenolic compounds and total flavonoid compounds, the antioxidant capacity of E. kotschyi was evaluated by DPPH●, ABTS+● and FRAP methods and qualitative and quantitative determination of phytochemical constituents in active sub-extract by LC-MS/MS. Results: The highest total phenolic (173.710 ± 1.088 mg gallic acid equivalent/gextract) and total flavonoid content (86.978 ± 0.650 mg catechin equivalent/gextract) was found in ethyl acetate sub-extract of E. kotschyi (EKE) and this sub-extract showed the highest antioxidant capacity on DPPH● (IC50 = 0.264 ± 0.040 mg/mL), ABTS+● (at a concentration of 0.125 mg/mL equivalent to 0.497 µM Trolox) and FRAP (at a concentration of 1 mg/mL equivalent to 1476 ± 5.292 mmol Fe2+) tests. Preliminary examination of the mass spectrums revealed the presence of 24 phytochemical compounds in this sub-extract and 7 of them was quantified. According to quantitative analyses the main compounds of EKE sub-extract were rosmarinic acid (490.820 ± 0.703 µg/mgextract), chlorogenic acid (80.405 ± 0.170 µg/mgextract), isorhamnetin 3-O-rutinoside (72.280 ± 0.33 µg/mgextract), rutin (63.020 ± 0.052 µg/mgextract) and caffeic acid (55.153 ± 0.523 µg/mgextract). Conclusions: The data suggest that EKE possess utilizable antioxidant properties in vitro. The antioxidant capacity of this sub-extract could be due to high content of phenolic and flavonoid contents.