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In order to study the different effects of ginsenosides with similar structures, research on interactions between ginsenoside Rg1, Re and lysozyme was carried out by electrospray ionization mass spectrometry (ESI-MS) and molecular docking. The 1:1 and 2:1 noncovalent complexes of ginsenosides and lysozyme were observed in the mass spectra and the dissociation constants for them were directly calculated based on peak intensities of lysozyme and its noncovalent complexes with ginsenosides. The results showed that the 1:1 complex of ginsenoside Rg1 and lysozyme was more stable than that of ginsenoside Re and lysozyme. As the acidity increased, the stabilities of the 1:1 complexes of Rg1, Re and lysozyme both decreased. Interestingly, as the acidity increased, the stability of the 2:1 complex of Rg1 and lysozyme increased while that of Re decreased. From the result of molecular docking, ginsenosides interacted with the active sites of lysozyme. And the stability of the complexes could be affected by the conformation changes of lysozyme as acidity increased., (Copyright © 2010 Elsevier B.V. All rights reserved.)

Even though the degradation of ginsenosides has been thoroughly studied in animals and in vitro using acids, enzymes, and intestinal bacteria, a new degradation method is established for obtaining the ginsenosides Rg(3), Rh(2) and their aglycon 20(S)-protopanaxadiol. This method is based on the microwave irradiation degradation of the major ginsenosides from the Panax quinquefolium L. coupled with foam floatation. The results indicated that ginsenosides Rg(3), Rh(2) and aglycon are not naturally present in Panax quinquefolium L., but are the products obtained simultaneously in the microwave irradiation degradation process. The yield of Rg(3) is 7.69 mg/g and 250 times as high as that obtained from red ginseng, and the transformation rate of total ginsenosides to aglycon is 78.11%. It is important to stress that a new degradation medium, N,N-dimethylformamide, was discovered and, when the medium was used, the transformation rate of total ginsenosides to aglycon was 20.20%. The proposed method is simple, efficient, time saving and a noteworthy improvement on the traditional degradation methods such as acidic hydrolysis, alkaline degradation, enzymatic conversion or microbial degradation.

In order to evaluate the essence of the interactions of ginsenosides and proteins which are composed by alpha-amino acids, electrospray ionization mass spectrometry was employed to study the noncovalent interactions between ginsenosides (Rb(2), Rb(3), Re, Rg(1) and Rh(1)) and 18 kinds of alpha-amino acids (Asp, Glu, Asn, Phe, Gln, Thr, Ser, Met, Trp, Val, Gly, Ile, Ala, Leu, Pro, His, Lys and Arg). The 1:1 and 2:1 noncovalent complexes of ginsenosides and amino acids were observed in the mass spectra. The dissociation constants for the noncovalent complexes were directly calculated based on peak intensities of ginsenosides and the noncovalent complexes in the mass spectra. Based on the dissociation constants, it can be concluded that the acidic and the basic amino acids, Asp, Glu, Lys and Arg, bound to ginsenosides more strongly than other amino acids. The experimental results were verified by theoretical calculations of parameters of noncovalent interaction between ginsenoside Re and Arg which served as a representative example. Two kinds of binding forms, "head-tail" ("H-T") and "head-head" ("H-H"), were proposed to explain the interaction between ginsenosides and amino acids. And the interaction in "H-T" form was stronger than that in "H-H" form.

The noncovalent complexes of cytochrome c and ginsenoside were studied by electrospray ionization mass spectrometry (ESI-MS). Ginsenoside Rb2 and Re were bound to cytochrome c to form several complexes with different stoichiometric relation. The 1:1 and 1:2 complexes of cytochrome c to ginsenoside were considered and the dissociation constants were obtained according to the intensities of cytochrome c and complexes when the concentrations of cytochrome c and ginsenoside have been known. Competition experiment was performed to validate the result. The K(D) values obtained with different reactive systems were consistent with each other.

Abstract: The contents of 12 ginsenosides (Rg1, Re, F11, Rf, Rg2, Rh1, Rb1, Rc, Rb2, Rb3, Rd, Rh2) in different parts and ages of Panax quinquefolius L. (American ginseng) were quantified by high pressure microwave-assisted extraction (HPMAE) high-performance liquid chromatography coupled with evaporative light scattering detection (HPLC-ELSD). The analytical method was established and analytical performances were evaluated. The chemical marker of American ginseng F11 was detected, and Rf which is the chemical marker of Asian ginseng was not found. Rare ginsenoside Rh1, Rg2 and Rh2 were also studied in this experiment. The total contents of these 12 ginsenosides in the different parts of 5-year-old American ginseng follow this order: leaf>root-hair>rhizome>root>stem. Therefore, compared with the other parts of American ginseng, the leaf is a better available source of ginsenosides. The contents of ginsenosides in root and leaf also change with age. [Copyright &y& Elsevier]