Structural characterization of trace stilbene glycosides in Lysidice brevicalyx Wei using liquid chromatography/diode-array detection/electrospray ionization tandem mass spectrometry.

J Chromatogr B Analyt Technol Biomed Life Sci. 2009 Oct 20;

Authors: Hu Y, Qu J, Liu Y, Yu S, Li J, Zhang J, Du D

The mass fragmentation patterns of stilbene glycosides isolated from the genus Lysidice were investigated by negative ion electrospray ionization tandem mass spectrometry, and the influence of collision energy on their fragmentation behavior is discussed. It is found that the presence of the Y(0)(-) and B(0)(-) ions in the MS(2) spectra is characteristic for 1-->6 linked diglycosyl stilbenes, while the Y(0)(-), Y(1)(-), and Z(1)(-) ions are representative ions of 1-->2 linked diglycosyl stilbenes. These results indicate that ESI-MS(n) in the negative ion mode can be used to differentiate 1-->6 and 1-->2 linked diglycosyl stilbenes. Based on the fragmentation rules, 9 new trace constituents were identified or tentatively characterized in a fraction of Lysidice brevicalyx by using HPLC/HRMS and HPLC-DAD/ESI-MS(n). The results of the present study can assist in on-line structural identification of analogous constituents and targeted isolation of novel compounds from crude plant extracts.

BOTTOM LINE: In this case an endangered plant whose bark has known antioxidant activity was evaluated. It turns out that some constituents of it show antioxidant activity at concentrations of 10⁻⁴ and 10⁻⁵ mol/L. What does this mean?? It means ULTRA-TINY amounts of it show antioxidant activity, but are limited to SOME of the constituents or parts. The whole plant is not antioxidant. This goes against some naturopathic holism principles, but otherwise we may find consuming 99% of something does no good (or even harm) and 1% leads to the effect we want. This highly specific technology will allow us to figure that out. Then it will be up to us what extracts or parts we wish to consume rather than doing it blindly.