Hydrogen bonding and drug designs Term Paper Example | Topics and Well Written Essays - 1250 words

Hydrogen bonding and drug designs - Term Paper Example Hydrogen bonding and drug designs The extent of solubility of a solute depends on its hydrophilic nature. A molecule is more soluble if it can form numerous hydrogen bonds with its water solvent.1 Hydrophobic interactions between hydrophobic regions of the binding site of a ligand and its lipophilic surfaces are important predictors of its interactions in a biological system, which may affect water solubility to such an extent that may even result in unfavorable pharmacokinetic properties.2 It is thus evident that the number of hydrogen bonds made by a drug is an important determinant of its solubility, and ultimately, its bioavailability and effectiveness in a living system. This paper reviews three studies on the hydrogen bonding properties of drugs in an attempt to investigate the utility of hydrogen bonding studies in drug solubility prediction and drug design. Methodology The aim of this paper is to investigate the effects of hydrogen bonding on the molecular properties of drugs dissolved in water. Additionally, other aspects of the role of hydrogen bonding in drug design will also be dealt with. For the purpose of this review, studies relevant to the aims of this paper were searched via Google Scholar. Three most relevant studies were chosen based on the correlation of their subject of study and the aims of this paper. Results The first study assessed the impact of hydrogen bonding on molecular properties, namely Infrared (IR) and Raman spectra, of three drug molecules (caffeine, aspirin, and ibuprofen) dissolved in water.... ssolved in water.3 The second study investigated various computational and experimental models for the prediction of aqueous drug solubility.4 The third study presented a theoretical calculation of the strength of hydrogen bonding of drug molecules. The findings of these studies are systematically reviewed here. As the first study3 investigated changes in spectra upon dissolution of drugs in water, a frequency calculation was done for three drug molecules (caffeine, aspirin, and ibuprofen) in both gas phase and aqueous solution. IR and Raman spectra of the molecules were analyzed to investigate the influence of both long and short-range interactions on spectral intensity and vibrational frequency. The investigated frequencies were divided into three regions, namely – high, middle and low frequencies. Four different calculations were carried out. The first two calculations began with gas phase geometry optimization followed by calculation of IR and Raman frequencies in the gas phase (GS) and in PCM (Polarized continuum model) using water as solvent. The last two calculations were also done in two stages – geometry optimization with the water molecules located where they are assumed to form hydrogen bonds, followed by calculation of IR and Raman frequencies with and without polarized dielectric continuum. The structures of the three drug molecules with hydrogen-bonded water are shown in figures 1, 2 & 3. Figure 1 — Structure of aspirin hydrogen bonded to water molecules Figure 2 — Structure of caffeine hydrogen bonded to water molecules Figure 3 — Structure of Ibuprofen hydrogen bonded to water molecules In case of caffeine, there was a very small IR absorbance in the high frequency region except for peaks of higher absorbance indicating presence of OH bonds in