Novel edible coating based on shellac and tannic acid for prolonging postharvest shelf life and improving overall quality of mango

This study aimed to investigate the combined effects of a coating based on shellac and the active agent tannic acid (TA) on the storability and physiological variations of mangoes stored at room temperature. Results showed that TA-shellac prolonged shelf life and improved overall quality of mangoes to a higher extent compared with controls, which was reflected in the extension of shelf life for approximately 10 days, maintaining of tissue firmness and weight loss, slowing down of respiration rate, improvement of physical properties and chemical qualities, suppression of browning, reduction of lipid peroxidation, preservation of aromatic volatiles, and regulation of the related enzymes activities. Addition of TA to shellac coating also improved the antifungal effect of the formulation. The results suggest that a synergistic effect took place between TA and shellac, which demonstrates the high potential for shelf life extension and quality improvement of mangoes of this formulation.

Thermosensitive and pH-responsive tannin-containing hydroxypropyl chitin hydrogel with long-lasting antibacterial activity for wound healing

Polysaccharide hydrogels have been widely used as wound dressings because of their biocompatibility and ability to provide moist environment for wound healing. However, bacterial infection often delays the healing process. Herein, a novel thermosensitive and pH-sensitive hydroxypropyl chitin/tannic acid/ferric ion (HPCH/TA/Fe) composite hydrogel was fabricated by a simple assembly. The pre-cooled hydrogel precursor solution can be injected onto the irregular wound area and gel rapidly at physiological temperature. The TA not only acted as a crosslinker to enhance mechanical properties of the hydrogel, but also as an antibacterial agent which could be sustainably released in response to the acidic environment. The composite hydrogel showed excellent broad-spectrum antibacterial activity up to 7 days with negligible cytotoxicity. Moreover, the hydrogel can inhibit bacterial infection and accelerate the wound healing process without scars in the mouse experiment. These results indicate the potential application of this composite hydrogel for the infected wound healing.

Resveratrol dimer trans-ε-viniferin prevents rotaviral diarrhea in mice by inhibition of the intestinal calcium-activated chloride channel

We previously identified, by a natural-product screen, resveratrol oligomers as inhibitors of the cystic fibrosis transmembrane conductance regulator (CFTR) chloride channel. Here, we report the resveratrol dimer trans-ε-viniferin (TV) and tetramer r-2-viniferin (RV) as inhibitors of the intestinal calcium-activated chloride channel (CaCC) and demonstrate their antisecretory efficacy in a neonatal mouse model of rotaviral diarrhea. Short-circuit measurements show inhibition of CaCC current in the human colonic cell line HT-29 by TV and RV with IC₅₀∼1 and 20μM, respectively. TV primarily inhibited the physiologically relevant, long-term CaCC current following agonist stimulation, without effect on cytoplasmic Ca²⁺ signaling. TV and RV inhibited short-circuit current in mouse colon as well. In a neonatal mouse model of rotaviral secretory diarrhea produced by oral inoculation with rotavirus, 2μg TV or 11μg RV inhibited secretory diarrhea by >50%, without effect on the rotaviral infection. Our results support the antisecretory efficacy of non-toxic, natural-product resveratrol oligomers for diarrheas produced by CaCC activation. Because these compounds also inhibit the CFTR chloride channel, they may be useful for antisecretory therapy of a wide range of diarrheas.

Correlation of lithium bioaccessibility from tea (Camellia sinensis L.) with tea type and consumption habits

In this study, the total contents, leachability into tea infusions, and bioaccessibility of lithium from black, Earl Grey, and green teas were evaluated by inductively coupled plasma mass spectrometry. Leachabilities were evaluated after infusion for 2, 5, or 10min. Bioaccessibility was determined in vitro under simulated stomach and intestinal digestion conditions. Addition of lemon juice, sugar, or milk for consumption, and calcium, tannic acid, and citric acid as additives were evaluated to determine if they affected bioaccessibility of lithium from black tea. The bioaccessible lithium contributed to 0.01%, 0.02%, and 0.03% of the recommended dietary allowances of lithium for black, Earl Grey, and green tea samples, respectively. These contributions may increase up to 4.4 times or decrease up to seven times with certain additives.

Fabrication and characterization of electrospun gelatin nanofibers crosslinked with oxidized phenolic compounds

In this study, the ability of oxidized phenolic compounds of tannic, gallic, ferulic and caffeic acids to crosslink gelatin (G) was investigated. The electrospun crosslinked gelatin nanofibers were assessed in terms of gelatin solution properties, fiber morphology, thermal properties, FTIR spectra, XRD pattern and antioxidant activity. Tannic acid showed the most crosslinking activity towards gelatin (13.3 vs 7.44, 4.65, and 3.45% for caffeic, gallic and ferulic, respectively). Crosslinking enhanced roughly electrical conductivity of gelatin solution while the surface tension and viscosity reduced. According to scanning electron microscopy (SEM) results, the fibrous structure of crosslinked gelatin nanofibers didn't change while their diameter increased to the highest value of 280nm for gelatin-tannic. Gelatin-gallic sample showed the highest total phenolic content (86.3mg gallic acid equivalent/g) and antioxidant activity (86.5%). Surprisingly, from differential scanning calorimetry (DSC) curves, it was found that crosslinking led to the reduction of thermal stability of gelatin nanofibers.