Characterization and Quantification of Luteolin-Metal Complexes in Aqueous Extract of Lonicerae Japonicae Flos and Huangshan Wild Chrysanthemum

Abstract

Luteolin is a flavonoid compound widely found in vegetables, fruits, and medicinal plants. In this study, the reaction conditions for luteolin and five metal ions (Ca2+, Mg2+, Zn2+, Fe3+, and Cu2+) to form complexes in hot water were optimized, which was at a molar ratio of 1 : 1 for luteolin and metal ions at 90°C in a volume of 20 mL for 2 h, and the ability of luteolin to form complexes with Cu2+ was the strongest. The DPPH scavenging test showed that luteolin exerted a dose-dependent effect on the clearance of free radicals; luteolin-Cu2+ complexes and luteolin-Fe3+ complexes accentuated the clearance of free radicals. Furthermore, we used high performance liquid chromatography (HPLC) to analyze luteolin in samples from two medicinal plants, obtained from the dissolution of aqueous extracts in two different solvents. The results showed that the peak areas for luteolin in the samples dissolved in 20% formic acid-methanol were significantly larger than those from the samples dissolved in methanol alone, with increases in the peak area being 135.6% (Lonicerae Japonicae Flos), and 161.16% (Huangshan wild chrysanthemum). The aforementioned results indicate that complexes formed from organic compounds and metal ions are present in the decoction of a plant.

Cerium–Luteolin Nanocomplexes in Managing Inflammation-Related Diseases by Antioxidant and Immunoregulation

“…Luteolin, as a flavonoid, can complex with metal ions to assemble into nanostructured materials. 21 The transmission electron microscope (TEM) image of CeLutNCs revealed their irregular spherical shape with an average diameter of 60 nm, and elemental mapping demonstrated the copresence and distribution of C, O, and Ce elements (Figure 1b). The powder X-ray diffraction (XRD) pattern in Figure 1c showed that the CeLutNCs were amorphous without the detection of crystallized Ce-containing phases.…”

“…In this study, CeLutNCs were obtained by mixing Ce­(NO 3 ) 3 with a luteolin ethanol solution in the presence of polyethylene glycol (PEG) 8000 at room temperature (Figure a). Luteolin, as a flavonoid, can complex with metal ions to assemble into nanostructured materials . The transmission electron microscope (TEM) image of CeLutNCs revealed their irregular spherical shape with an average diameter of 60 nm, and elemental mapping demonstrated the copresence and distribution of C, O, and Ce elements (Figure b).…”

Application of Luteolin in Neoplasms and Nonneoplastic Diseases

“…For instance, as flavonoids have chelating properties, their antioxidant activity is determined by the concentration of copper (Cu), cadmium (Cd), and iron (Fe) in cells. It has been proven that under low Fe 3+ concentrations, luteolin acts as an antioxidant agent, whereas increased concentration stimulates its pro-oxidant activity [25,26]. The understanding of the mechanisms by which luteolin can behave in certain ways is incomplete and thus requires further examination.…”