Water proton NMR relaxation revisited: Ultrahighly diluted aqueous solutions beyond Avogadro’s limit prepared by iterative centesimal dilution under shaking cannot be considered as pure solvent

Abstract

• Ultramolecular dilutions prepared according to homeopathic pharmacopoeia differ from solvent and from simply diluted samples. • Evidence for an unexpected gradual increase of correlation times of water with dilution in ultrahighly diluted solutions. • Evidence for solute-induced nanostructures in aqueous high dilutions growing with dilution. • Nanostructures result from nucleation between the solute, nanobubbles and elements coming from the medium during preparation. • Nanostructures in ultrahigh dilutions, even ultramolecular, enhance leaching processes in glass containers. The biological activity of ultrahigh dilutions (HDs) as used in homeopathy, especially those beyond Avogadro's limit, is still controversial and an intriguing problem for scientists. Homeopathic remedies are mostly prepared by iterative centesimal dilution under vigorous shaking, called dynamization. Cn corresponds to a dilution factor of 10 -2n , and C12 (10 -24 ) to the theoretical limit of molecular presence. Since the 1990 s, NMR relaxation of water protons has emerged as a potent tool for investigating HDs. This article reviews studies of high methodological quality by five independent teams over more than two decades. They demonstrate an increase in T1 and T1/T2, with a decrease in T2, although less constant, in dynamized aqueous HDs. No variation was observed in the similarly treated solvent controls. The phenomenon seems to be common, regardless of solute, dissolved oxygen, material used (glass or plastic), method of shaking, frequency from 0.02 to 600 MHz. Strikingly, the changes in relaxation times increased gradually with dilution, even in the C12-C30 ultramolecular range and they totally vanished after a heating–cooling cycle directly applied on the sealed NMR tubes. The results were interpreted in terms of increasing correlation times of water, greater than 10 −8 s, resulting from the formation of growing solute-induced nanostructures involving nanobubbles and various elements coming from the medium, the atmosphere and the container. Another unexpected result was that HDs were able to enhance some leaching processes in glass containers.