Quercetin is a flavanol, which is widely distributed in green apple, onion, green tea, and
lemon. Due to strong antioxidant properties, quercetin has the potential for applications in the
promotion of health and prevention against inflammations, cancer, viral deceases caused by free
radicals [1]. Scavenging activity of the quercetin against superoxide anion and hydrogen
peroxide, as well as capability to prevent the generation of reactive oxygen species, makes the
investigation of the quercetin extraction and its optimization undoubtedly considerable field of
studying.
During this research, have been studied parameters such as several raw material origin (dry
red onion skins, red onion pulp), volume of the extractant, temperature (20o and 40oC), and type
of the extractant (ethanol and acetone).
Quercetin was extracted by maceration during the period of 24 hours, in absence of light.
The quercetin was identified by thin-layer chromatography and ultraviolet–visible spectroscopy
(UV-VIS). The spectroscopic investigation confirm the characteristic peaks of quercetin (365-
380 nm). For the determination of total content of polyphenolic compounds, Folin-Ciocalteu
method was applied [2].
The research results revealed that the optimized conditions for quercetin extraction were
25oC, ethanol used as extractant, dry onion skins as raw material, and the ratio 1:10 for raw
material to extractant(136 mg Quercetin per 100 g of raw material).
The precentage of antioxidant activity (AA,%) of the quercetin was determined after
interaction with cation radical ABTS+• and estimated by decrease in absorbance after one minute
at 754nm. The process of the quercetin functionalization with DNA was studied, by means of the
UV-VIS and infrared spectra. Modification and shifting of functional groups peaks in the UVVIS
readouts presumes the formation of other compound between DNA and quercetin.
After the formation of DNA-functionalized quercetin, AA (89.1 %) has not been decreased
significantly compared to AA (91.2 %) of pure quercetin solution with the same concentration.
Therefore, new quercetin polymer complex can contribute to inhibiting of free radicals because
of its high scavenging activity and prolongation of the life span of antioxidant properties. For
investigation of quercetin coupled with DNA polymer, physical properties have been studied by
means of optical properties and spectroscopy methods. Although the films barely showed
luminescence properties, on the pictures of the films magnified 1000 times the formations of
clusters have been observed. This fact confirms, earlier made assumptions, that the new DNAquercetin
formation was obtained.
Acknowledgements. This research was financially supported by bilateral project Romania
(ANCS) Nr. - Moldova (ASM) Nr.13.820.15.11/RoA.
1. K. Raj Narayana, et. al., Indian Journal of Pharmacology, 2001, 33, p.2-16
2. Andressa Blainski et.al., Molecules, 2013, 18, p.6852-6865.