Biopolym. Cell. 2001; 17(3):256-258.
Short Communications
Cooperative intramolecular H-bonds in quercetine: MNDO/H quantum chemical investigation
1Potyahaylo A. L., 2Pylypchuk L. B., 1Hovorun D. M.
  1. Institute of Molecular Biology and Genetics, NAS of Ukraine
    150, Akademika Zabolotnoho Str., Kyiv, Ukraine, 03680
  2. P. L. Shupik National medical academy of post-graduate education
    9, Dorohozhytska Str., Kyiv, Ukraine, 04112


For the first time four anticooperative intramolecular H-bonds have been determined by the semiempirical quantum chemical method MNDO/H in eight low-energy (in the energy range ΔE ≤ 1 kcal/mol) conformations of quercetine, a molecule with the wide spectrum of biological activity. Two of these H-bonds are bifurcated ones (C5OH...OC4 and C3OH...OC4) in a heterocycle, one (C6'H...OC3) – between a hetero- and a phenyl cycles, and one (C3'OH...OC4' or C4OH..OC3', depending on conformation) – in a phenyl ring. The H-bonds energies are 8.8, 2.9, 2.8 and 1.4 kcal/mol , respectively. The H-bonds parameters are conformationally insensitive. The effect of their anticooperativity, mutual weakening, reaches –1.1 kcal/mol A possibility of experimental (by vibrational spectroscopy) confirmation of the existence of these intramolecular H-bonds is discussed as well as the reasons of a propeller-like orientation of planar hetero- and phenyl cycles, which is the intrinsic characteristic of all low-energy quercetine con­formations.


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