Experimental parameters that influence the resolution of ¹H-NMR phenol OH signals are critically evaluated with emphasis on the effects of pH, temperature and nature of the solvents. Extremely sharp peaks (Δν_1/2 ≤ 2 Hz) can be obtained under optimized experimental conditions which allow the application of ¹H-¹³C HMBC-NMR experiments to reveal long range coupling constants of hydroxyl protons and, thus, to provide unequivocal assignment of the OH signals even in cases of complex polyphenol natural products. Intramolecular and intermolecular hydrogen bonds have a very significant effect on ¹H OH chemical shifts which cover a region from 4.5 up to 19 ppm. Solvent effects on –OH proton chemical shifts, temperature coefficients (Δδ/ΔT), OH diffusion coefficients, and ⁿJ(¹³C, O¹H) coupling constants are evaluated as indicators of hydrogen bonding and solvation state of phenol –OH groups. Accurate ¹H chemical shifts of the OH groups can be calculated using a combination of DFT and discrete solute-solvent hydrogen bond interaction at relatively inexpensive levels of theory, namely, DFT/B3LYP/6-311++G (2d,p). Excellent correlations between experimental ¹H chemical shifts and those calculated at the ab initio level can provide a method of primary interest in order to obtain structural and conformational description of solute-solvent interactions at a molecular level. The use of the high resolution phenol hydroxyl group ¹H-NMR spectral region provides a general method for the analysis of complex plant extracts without the need for the isolation of the individual components.

Although the increasing prevalence of thyroid nodular disease (TND) has been partially attributed to the more frequent usage of improved diagnostics, environmental factors, such as exposures to thyroid-disrupting chemicals may contribute to TND and altered thyroid function. We investigated the association between exposures to bisphenol A (BPA), its chlorinated derivatives (ClxBPA), and bisphenol F (BPF) with TND and thyroid measures in adult women. A case-control study in Cyprus and Romania (n = 212) was conducted, where cases were those with thyroid nodules (diameter >3mm), and controls without nodules. Serum TSH and free thyroxine and urinary levels of BPA, BPF and ClxBPA were measured using immunoassays and tandem mass spectrometry, respectively. The association between exposures to BPA compounds and TND, adjusting for age, BMI, thyroid hormones and urinary iodine was assessed using logistic regression. Linear regression was used to explore associations between urinary BPA, BPF and ClxBPA and serum thyroid hormones. With the exception of a chlorinated BPA compound (30%), the rest of bisphenols were quantified in 100% of urine samples. A positive and significant (p<0.05) association was observed between urinary BPA and serum TSH that remained after adjusting for urinary creatinine, age, BMI, study site and disease status; there was no significant association between BPF or ClxBPA with TSH. None of the BPA compounds were associated with higher odds of TND. Our study found associations of urinary BPA with TSH but not with BPF or ClxBPA. A larger study would be justified.

Correlations between hydrogen bonds and solvent effects on phenol –OH proton shieldings, temperature coefficients (Δδ/ΔT) and effects on OH diffusion coefficients for numerous phenolic acids, flavonols, flavones, and oleuropein derivatives of biological interest were investigated in several organic solvents and were shown to serve as reliable indicators of hydrogen bonding and solvation state of –OH groups. The temperature coefficients span a range of −0.5 to −12.3 ppb K⁻¹. Shielding differences of 2.0 to 2.9 ppm at 298 K were observed for solvent exposed OH groups between DMSO-d₆ and CD₃CN which should be compared with a shielding range of ∼7 ppm. This demonstrates that the solvation state of hydroxyl protons is a key factor in determining the value of the chemical shift. For –OH protons showing temperature gradients more positive than −2.5 ppb K⁻¹, shielding changes between DMSO-d₆ and CD₃CN below 0.6 ppm, and diffusion coefficients significantly different from those of traces of H₂O, there is an intramolecular hydrogen bond predictivity value of 100%. The C-3 OH protons of flavonols show very significant negative temperature coefficients and shielding changes between DMSO-d₆ and CD₃CN of ∼2.3 ppm, which indicate the absence of persistent intramolecular hydrogen bonds, contrary to numerous X-ray structures.

Type 1 diabetes (T1D), an autoimmune inflammatory disorder, develops as a consequence of pancreatic β-cell destruction and results in hyperglycaemia. Since current T1D therapy mainly involves insulin replacement, the aim of the present study was to evaluate the therapeutic potential ofOriganum vulgareL. ssp.hirtum(Greek oregano) leaf extract rich in biophenols for the treatment of T1D. The phytochemical profile of methanolic oregano extract (MOE) and aqueous oregano extract (AOE) was determined by liquid chromatography/electrospray ion-trap tandem MS (LC/DAD/ESI-MSn), while their main compounds were quantified by HPLC with diode array detection. After establishing their potentin vitroantioxidant activity, the extracts were administered to C57BL/6 mice treated with multiple low doses of streptozotocin for diabetes induction. While prophylactic AOE therapy had no impact on diabetes induction, MOE reduced diabetes incidence and preserved normal insulin secretion. In addition, MOE scavenged reactive oxygen and nitrogen species and, therefore, alleviated the need for the up-regulation of antioxidant enzymes. MOE treatment specifically attenuated the pro-inflammatory response mediated by T helper 17 cells and enhanced anti-inflammatory T helper 2 and T regulatory cells through the impact on specific signalling pathways and transcription factors. Importantly, MOE preserved β-cells fromin vitroapoptosis via blockade of caspase 3. Finally, rosmarinic acid, a predominant compound in MOE, exhibited only partial protection from diabetes induction. In conclusion, acting as an antioxidant, immunomodulator and in an anti-apoptotic manner, MOE protected mice from diabetes development. Seemingly, there is more than one compound responsible for the beneficial effect of MOE.