Preparation of Isoquercetin From Toona sinensis by Liquid-Liquid-Refining Extraction And Consecutive Counter-Current Chromatography

A high-speed counter-current chromatographic (HSCCC) method using ethyl acetate-water as solvent system was established to separate isoquercetin from Toona sinensis. In an HSCCC single separation, the sample sizes of ethanol extract were optimized from 203 to 1200 mg. The results showed that the yield of the target compound increased from 4 to 26 mg, and the corresponding purity decreased from 93.30 to 81.82%. To further improve the yield and purity, liquid-liquid-refining extraction was introduced to pretreat the ethanol extract and enrich the target compound. The ethanol extract was extracted with n-hexane-ethyl acetate-method-water (1:5:1:5, v/v) and ethyl acetate-water in turn to remove the low-polarity and high-polarity impurities and obtain the crude sample. Under the similar conditions, 85.25 mg of the target compound with the purity of 95.12% was separated from 240 mg of the crude sample. Subsequently, a consecutive HSCCC was developed to obtain 257 mg of the target compound from 720 mg of crude sample, which was equivalent to 14.4 g of ethanol extract. This method improved the purity of the target compound, but more importantly, the sample size can reach 12 times of the maximum sample size of the ethanol extract in a single run.

Evaluation of Factors Affecting Tree and Shrub Bark's Antioxidant Status

The importance of using the barks of trees and shrubs as powerful natural antioxidants suggests the necessity to evaluate the effect of different environmental factors on bark extracts’ quality. The determination of total antioxidant activity (AOA) and polyphenol content (TP) in the bark of 58 tree and shrub species from 7 regions differing in mean annual temperature, insolation, humidity, salinity level, and altitude was performed. The above stress factors positively affected bark AOA but did not have a statistically significant effect on TP. The bark of trees grown in the seashore proximity was characterized by significantly higher AOA than samples gathered in other areas, similarly to the trees grown at high altitude. The bark antioxidant status of 18 species was described for the first time. New sources of powerful antioxidants were represented by the ornamental shrubs Cornus sanguinea and Cornus alba, which showed the highest AOA (169−171 mg GAE g−1 d.w.). Among the typical halophytes, Calligonum and Tamarix had high AOA (172 and 85 mg GAE g−1 d.w.), while in the bark of tamarisk, an Se accumulator, an Se concentration of about 900 µg kg−1 d.w. was recorded. A significant positive correlation was found between leaves and bark AOA in the Karadag Nature Reserve’s deciduous trees (r = 0.898, p < 0.01). The relationship between bark AOA and TP was highly significant (r = 0.809; p < 0.001) for all samples except the mountainous ones. The results of the present research revealed new opportunities in successive bark utilization.

Potential of isoquercitrin as antisickling agent: a multi-spectroscopic, thermophoresis and molecular modeling approach

Sickle cell disease is an inherited disease caused by point mutation in hemoglobin (β-globin gene). Under oxygen saturation, sickle hemoglobin form polymers, leading to rigid erythrocytes. The transition of the blood vessels is altered and initiated by the adhesion of erythrocytes, neutrophils and endothelial cells. Sickle Hemoglobin (HbS) polymerization is a major cause in red blood cells (RBC), promoting sickling and destruction of RBCs. Isoquercitrin, a medicinal bioactive compound found in various medicinal plants, has multiple health benefits. The present study examines the potential of isoquercitrin as an anti-sickle agent, showing a significant decrease in the rate of polymerization as well as sickling of RBCs. Isoquercitrin-induced graded alteration in absorbance and fluorescence of HbS, confirmed their interaction. A negative value of ΔG° strongly suggests that it is a spontaneous exothermic reaction induced by entropy. Negative ΔH° and positive ΔS° predicted that hydrogen and hydrophobic binding forces interfered with a hydrophobic microenvironment of β6Val leading to polymerization inhibition of HbS. HbS-Isoquercitrin complex exhibits helical structural changes leading to destabilization of the HbS polymer as confirmed by CD spectroscopy. MST and DSC results indicate greater changes in thermophoretic mobility and thermal stability of sickle hemoglobin in the presence of isoquercitrin, respectively. These findings were also supported by molecular simulation studies using DOCK6 and GROMACS. Hence, we can conclude that isoquercitrin interacts with HbS through hydrogen bonding, which leads to polymerization inhibition. Consequently, isoquercitrin could potentially be used as a medication for the treatment of sickle cell disease.Communicated by Ramaswamy H. Sarma.