Polyphenols have been the subject of numerous research over the past years, being referred as the nutraceuticals of modern life. The healthy properties of these compounds have been associated to a natural chemoprevention of 21st century major diseases such as cancer and neurodegenerative diseases (e.g. Parkinson's and Alzheimer's). This association led to an increased consumption of foodstuffs rich in these compounds such as red wine. Related to the ingestion of polyphenols are the herein revised sensorial properties (astringency and bitterness) which are not still pleasant. This review intends to be an outline both at a sensory as a molecular level of the mechanisms underlying astringency and bitterness of polyphenols. Up-to-date knowledge of this matter is discussed in detail.

Astringency and bitterness are organoleptic properties widely linked to tannin compounds. Due to their significance to food chemistry, the food industry, and to human nutrition and health, these tannins’ taste properties have been a line of worldwide research. In recent years, significant advances have been made in understanding the molecular perception of astringency pointing to the contribution of different oral key players. Regarding bitterness, several polyphenols have been identified has new agonists of these receptors. This review summarizes the last data about the knowledge of these taste properties perceived by tannins. Ultimately, tannins’ astringency and bitterness are hand-in-hand taste properties, and future studies should be adapted to understand how the proper perception of one taste could affect the perception of the other one.

BackgroundThe aim of this study was to evaluate the effect of uneventful phacoemulsification on the morphology and thickness of the macula, the submacular choroid, and the peripapillary choroid.MethodsIn 14 eyes from 14 patients, retinal macular thickness, choroidal submacular thickness, and choroidal peripapillary thickness were measured preoperatively and at one week and one month after phacoemulsification using enhanced depth imaging spectral domain optical coherence tomography. Changes in thickness of the different ocular tissues were evaluated.ResultsThere was a statistically significant increase in mean retinal macular thickness at one month. In horizontal scans, the mean increase was +8.67±6.75 μm (P<0.001), and in vertical scans, the mean increase was +8.80±7.07 μm (P=0.001). However, there were no significant changes in choroidal morphology in the submacular and peripapillary areas one month after surgery. In vertical scans, there was a nonsignificant increase in choroidal thickness (+4.21±20.2 μm; P=0.47) whilst in horizontal scans a nonsignificant decrease was recorded (−9.11±39.59 μm; P=0.41). In peripapillary scans, a nonsignificant increase in mean choroidal thickness was registered (+3.25±11.80 μm; P=0.36).ConclusionUncomplicated phacoemulsification induces nonpathologic increases in retinal macular thickness probably due to the inflammatory insult of the surgery; however these changes are not accompanied by significant changes in choroidal thickness. In the posterior segment, the morphologic response to the inflammatory insult of phacoemulsification is mainly observed at the retinal level, and seems to be independent of choroidal thickness changes.

Polysaccharides are described to inhibit aggregation between food polyphenols and salivary proteins (SP) and may hence lead to astringency modulation. In this work, the effect of two wine polysaccharides (arabinogalactan proteins-AGPs and rhamnogalacturonan II- RGII) on SP-polyphenol interaction was evaluated. In general, both polysaccharides were effective to inhibit or reduce SP-polyphenol interaction and aggregation. They can act by two different mechanisms (ternary or competitive) depending on the SP-tannin pair. In the case of salivary P-B peptide, AGPs and RGII seem to act by a ternary mechanism, in which they surround this complex, enhancing its solubility. Concerning acidic proline-rich proteins (aPRPs), it was possible to observe both mechanisms, depending on the tannin and the polysaccharide involved. Overall, this work point out for a specific property of wine polysaccharides important to modulate this and other beverages and food astringency perception.

Purpose: To report the clinical outcomes of intravitreal aflibercept therapy in eyes with refractory and recurrent neovascular age-related macular degeneration (AMD) switched from intravitreal bevacizumab or ranibizumab. Methods: This is a retrospective review of eyes with neovascular AMD switched to intravitreal aflibercept with at least 1 year of follow-up after the switch. All patients had had a minimum of 3 injections of bevacizumab or ranibizumab before the switch. Aflibercept was used in patients considered refractory to bevacizumab (group 1) and in recurrent patients on therapy with ranibizumab due to an institutional policy decision (group 2). Changes in best-corrected visual acuity, fluid on optical coherence tomography (OCT), central retinal thickness (CRT) and the frequency of injections were compared. Results: Eighty-five eyes of 69 patients were analyzed, 39 eyes in group 1 and 46 in group 2. The mean follow-up time was 31.6 months prior to the switch and 14.7 months on treatment with aflibercept. One year after the switch, there was a nonsignificant mean decrease of 2 letters in visual acuity in both groups (group 1: from 58.2 to 55.8 letters, p = 0.086; group 2: from 56.4 to 54.5 letters, p = 0.168), but the mean number of injections per month was significantly lower (from 0.76 to 0.57, p < 0.001). With the switch, 90.6% of the patients showed anatomic improvement with a reduction of fluid on OCT, and both groups presented significant improvement in CRT (group 1: 65.3 µm, p = 0.051; group 2: 91.0 µm, p < 0.001). Conclusion: Aflibercept appears to be a valuable tool for the management of patients with poor responses to other anti-vascular endothelial growth factor drugs. These patients could have anatomic improvement, and the injection intervals could be extended.

The general accepted mechanism for astringency arises from the interaction between tannins and salivary proteins (SP) resulting in (in)soluble aggregates. By HPLC analysis, it was observed that repeated sips of procyanidins (PC) solution practically depleted aPRPs (∼14%) and statherin (∼2%), and significantly reduced the amount of gPRPs. On the other hand, bPRPs were not significantly affected. In the analysis performed after the last exposure to PC solution, it was seen a significant recovering of the chromatographic peaks corresponding especially to aPRPs (∼74%) and statherin (∼80%). In vitro interaction between SP and PC results in the decrease of the chromatographic peaks of aPRPs and statherin, suggesting that these proteins were involved in the formation of a significant quantity of insoluble complexes. In general, the results suggest that the different families of SP can be involved in different stages of the development of astringency sensation.

Purpose To analyze and compare choroidal thickness between keratoconus (KC) patients and age-matched non-KC subjects. Methods A cross-sectional, case-control study. One hundred and thirty-four keratoconic eyes and 78 control eyes, from individuals aged from 12 to 30 years old, were studied. Patients with KC followed in Corneal Department of Centro Hospitalar São João, Porto, Portugal, were identified and consecutively included between December 2017 and February 2018. A spectral-domain optical coherence tomography (OCT) using depth enhanced imaging was performed, and choroidal thickness in the center of the fovea and at 500 μm intervals along a horizontal section was measured and compared. Results The statistical analysis showed that keratoconic eyes present a thicker choroid in every measured location (p < 0.05). Mean subfoveal choroidal thickness (SFCT) values obtained were 375.86 ± 89.29 and 322.91 ± 85.14 in keratoconus and control groups, respectively (p < 0.001). In a multivariate analysis, SFCT was significantly associated with spherical equivalent (p=0.004) and the presence of keratoconus (p < 0.001), but not with age (p=0.167), gender (p=0.579), or best-corrected visual acuity (p=0.178). In a “fixed model,” keratoconus patients were found to have a 67.55 μm (95% CI 36.61–98.49) thicker subfoveal choroid compared to controls. Conclusion Keratoconus patients seem to have a thicker choroid than healthy individuals. The exact pathophysiological mechanism resulting in a thicker choroid in KC patients is not known, but it could possibly be associated with inflammatory choroidal mechanisms.

The choroid may be subclinically involved in autoimmune diseases. However, the choroidal response seems to differ depending on the autoimmune disease. Infiltrative mechanisms specific for lupus may justify the thickened choroid found in these patients.