Casein phosphopeptides (CPPs) have been demonstrated to be calcium chelators. Unfortunately, few studies have been reported on the effects of CPPs on the mechanism of the uptake and absorption of Ca²⁺ and bone metabolism. In this study, a monomeric peptide fraction isolated by RP-HPLC (F6-1) that possessed high calcium transport capacity in Caco-2 cell monolayers was separated and characterized. The effects of F6-1 on the absorption mechanisms of Ca²⁺ in a Caco-2 monolayer model and bone metabolism in rats were investigated. F6-1 was isolated by preparative and analytical RP-HPLC. Results for calcium transport suggested that the rates of Ca²⁺ transportation by F6-1 were approximately 2.57, 2.87 and 2.38 times higher than those in the control group at 30, 60 and 120 min, respectively. Results of ultraviolet (UV) spectroscopy indicated that the intensity of UV absorption changed because of the binding of Ca²⁺ to F6-1. Analysis of transepithelial electrical resistance (TEER) and the expression of TRPV6 in Caco-2 cells showed that F6-1 was likely to influence the transcellular pathway of intestinal absorption of Ca²⁺ rather than the paracellular pathway. Furthermore, the F6-1 group (1% Ca, 0.03% F6-1) exhibited increases in serum Ca²⁺ levels, femur length and femur Ca and decreases in serum alkaline phosphatase (ALP) levels and urinary pyridinoline content in a Sprague-Dawley rat model, which implied that F6-1 was beneficial for bone calcification. Overall, our results suggested that F6-1 enhanced the transport of Ca²⁺ in Caco-2 cells by affecting the transcellular pathway by upregulating the expression of TRPV6. F6-1 also improved bone formation and prevented bone resorption to benefit bone health in rats, which provided a basis for using F6-1 in calcium supplements or functional foods.

Brazilian green propolis is a complex mixture of natural compounds that is difficult to analyze and standardize; as a result, controlling its quality is challenging. In this study, we used the positive and negative modes of ultra-performance liquid chromatography coupled with electrospray ionization quadrupole time of flight mass spectrometry in conjunction with high-performance liquid chromatography for the identification and characterization of seven phenolic acid compounds in Brazilian green propolis. The optimal operating conditions for the electrospray ionization source were capillary voltage of 3500 V and drying and sheath gas temperatures of 320 °C and 350 °C, respectively. Drying and sheath gas flows were set to 8 L/min and 11 L/min, respectively. Brazilian green propolis was separated using the HPLC method, with chromatograms for samples and standards measured at 310 nm. UPLC-ESI-QTOF-MS was used to identify the following phenolic compounds: Chlorogenic acid, caffeic acid, isochlorogenic acid A, isochlorogenic acid B, isochlorogenic acid C, caffeic acid phenethyl ester (CAPE), and artepillin C. Using a methodologically validated HPLC method, the seven identified phenolic acids were then quantified among different Brazilian green propolis. Results indicated that there were no significant differences in the content of a given phenolic acid across different Brazilian green propolis samples, owing to the same plant resin sources for each sample. Isochlorogenic acid B had the lowest content (0.08 ± 0.04) across all tested Brazilian green propolis samples, while the artepillin C levels were the highest (2.48 ± 0.94). The total phenolic acid content across Brazilian green propolis samples ranged from 2.14–9.32%. Notably, artepillin C quantification is an important factor in determining the quality index of Brazilian green propolis; importantly, it has potential as a chemical marker for the development of better quality control methods for Brazilian green propolis.

A comparative study between Chinese propolis and Brazilian green propolis showed that they have a distinct chemome but similar antioxidant and anti-inflammatory potential.

Casein phosphopeptides (CPPs) are a series of peptides containing serine phosphate, which prevents calcium precipitation in the small intestine, so that it can be absorbed. Calcium metabolism studies have been typically carried out using traditional metabolic balance tests. Non-radioactive stable isotopes have rarely been used to examine the in vivo absorption and metabolism of calcium in animal models due to their high cost and the difficulty in their accurate detection. However, they have recently attracted intense research attention. In this study, we developed InertSep ME-1 using a chelating resin to effectively separate ⁴²Ca from spectral-interference in the process of ICP-MS detection. The method effectively removes interfering ions like potassium and sodium and greatly improves the accurate detection of the calcium ion isotope. We also investigated the absorption, distribution, and metabolism of different CPPs through both in vitro cell experiments and in vivo animal experiments. The results indicate that CPPs strongly promote calcium absorption, especially the P5 active monomer component. The results of our in vivo studies show that the calcium isotope can be absorbed from the small intestine into the blood. Then, one part is transported to various organs through tissue fluids while another part is excreted into the urine through the kidneys. In general, our results reveal that CPPs promote the absorption of calcium significantly and positively affect calcium metabolism.

Background: The emergence and dissemination of antibiotic resistance represents a significant and ever-increasing global threat to human, animal, and environmental health. The explosive proliferation of resistance has ultimately been seen in all clinically used antibiotics. Infections caused by antibiotic-resistant bacteria have been associated with an estimated 4,950,000 deaths annually, with extremely limited therapeutic options and only a few new antibiotics under development. To combat this silent pandemic, a better understanding of the molecular mechanisms of antibiotic resistance is immensely needed, which not only helps to improve the efficacy of current drugs in clinical use but also design new antimicrobial agents that are less susceptible to resistance. Results: The past few years have witnessed a number of new advances in revealing the molecular mechanisms of AMR. Following five sophisticated mechanisms (efflux pump, antibiotics inactivation by enzymes, alteration of membrane permeability, target modification, and target protection), the roles of various novel proteins/enzymes in the acquisition of antibiotic resistance are constantly being described. They are widely used by clinical bacterial strains, playing a key role in the emergence of resistance. Conclusion: While most of these have so far received less attention, expanding our understanding of these emerging resistance mechanisms is of crucial importance to combat the antibiotic resistance crisis in the world. This review summarizes recent advances in our knowledge of emerging resistance mechanisms in bacteria, providing an update on the current antibiotic resistance threats and encouraging researchers to develop critical strategies for overcoming the resistance.