## 4 Discussion  
Plants produce and store a diverse range of phytoconstituents in variable amounts, necessitating the use of a variety of analytical procedures to assess them [34]. _C. Druguieriana_ \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Compound** & **Retention Time (min)** & \begin{tabular}{c} **Range** \\ **(\(\mathbf{\mu}\)/mL)** \\ \end{tabular} & \begin{tabular}{c} **Linearity** \\ **(\(\mathbf{\mu}\)/mL)** \\ \end{tabular} & \
\begin{tabular}{c} **LOD** \\ **(\(\mathbf{\mu}\)/mL)** \\ \end{tabular} &
\begin{tabular}{c} **LOQ** \\ **(\(\mathbf{\mu}\)g/mL)** \\ \end{tabular} \\ \hline Chlorogenic acid & 10.25 \(\pm\) 0.03 & 0.20–25.00 & 0.998 & 0.171 & 0.518 \\ \hline luteolin 7-O-glucoside & 13.88 \(\pm\) 0.05 & 0.20–25.00 & 0.997 & 0.159 & 0.481 \\ \hline Kaempfer & 22.37 \(\pm\) 0.04 & 0.20–25.00 & 0.997 & 0.161 & 0.483 \\ \hline Isorhamnetin & 26.18 \(\pm\) 0.03 & 0.20–25.00 & 0.998 & 0.175 & 0.544 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Calibration parameters and sensitivity data for the polyphenols using the proposed HPLC method. Figure 8: HPLC chromatograms of (**A**) standard phenolic compounds and (**B**) _Centaurea bruguieriana_ ethyl acetate extract (inserts show chromatographic UV spectra of the main phenolic compounds). is a medicinally significant plant that contains a variety of volatile components along with nonvolatile constituents. In the investigation of unknown plant components, GC-MS plays a crucial role. Plant materials are often complex, making GC-MS an excellent choice for their examination due to its high sensitivity and selectivity. Compounds are ionized and their mass numbers are measured using GC-MS. This adds to the structure of these profiles by providing more information [35]. A total of 20 compounds were identified in the extract. The findings indicated that there was a presence of 3 methyl 8-oxooctanoate (17.6%) and 1,10-di-epi-cubenol (13.4%) as the major compounds in the chloroform extract of _C. pruguieriana_. Flavonoid composition has long been known in the Asteraceae family. Apigenin, luteolin, and their glucosides, particularly 7-glycosides, are the most frequent flavonoids. Polyphenols, especially flavonoids, have sparked a lot of interest due to their widespread distribution in plants, biological (including antioxidant) activity, and physiological impacts [36]. Therefore, in our study, in the group of phenolic compounds, chlorogenic acid, luteolin 7-O-glucose, kaempfer and isorhamtein were specifically identified and quantified in the ethyl acetate fraction. For the first time, quantitative study of these two chemicals was carried out in this species. The phytochemical chlorogenic acid is well-known and well-described. Chlorogenic acid is an ester of caffeic and quinic acids with a broad range of antioxidant, anti-inflammatory, anti-HIV, anti-HBV, mutagenesis suppression, and carcinogenesis properties in vivo and in vitro [37; 38; 39; 40; 41; 42]. Luteolin 7-O-glucose also has pharmacological effects, such as reducing superoxide production in neutrophils [43]. In lipopolysaccharide-induced macrophage RAW 264 cells, the protein expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase (COX) was inhibited by the action of luteolin [44]. Therefore, the presence of different phenolic compounds such as chlorogenic acid, luteolin 7-O-glucose, kaempfer, and isorhamnetin could be responsible for the antioxidant activity. Similarly, [PERSON] et al. found [45] a significant association between phenolic acid concentration and antioxidant activity in _C. cyanus_ plant sections (edible flowers and non-edible portions); however, this class of phenolic compounds was not found in our investigation. [PERSON] et al. [46] reported that the n-butanol extracts of _C. ghareocrophula_ exhibited higher antioxidant activity than other extracts. They were likewise more abundant in total phenolics and flavonoids.