The Metabolism and Potential Bioactivity of Chlorophyll and Metallo‐chlorophyll Derivatives in the Gastrointestinal Tract

Orange carbon dots based smart sensing platforms for rapid, visual, quantitative identification of sodium copper chlorophyllin

A highly affordable, sensitive and portable detection platform for the quantitative identification of sodium copper chlorophyllin (SCC) in food and environment is a crucial need. Even though many carbon dots (CDs) based sensors have been developed, few reports on using CDs as optical probes for SCC detection have been published so far. In this paper, orange luminescent CDs (OLCDs) were prepared via solvothermal method, which have high fluorescence quantum yield (27.20 %) and excellent photostability. OLCDs can detect SCC via inner filter effect (IFE), with fast response, high selectivity, outstanding sensitivity and superior anti-interference ability. Benefiting from the remarkable properties of OLCDs, a portable sensing platform was triumphantly constructed, which facilitated the in situ, real-time quantitative determination of SCC in diverse actual samples, by catching the fluorescence change of OLCDs-based paper sensors via smartphone RGB colorimetric analysis. This first CDs-based smart sensing system displays great potential for quantification of SCC in various fields.

Chlorophyll a and novel synthetic derivatives alleviate atopic dermatitis by suppressing Th2 cell differentiation via IL-4 receptor modulation

Atopic dermatitis (AD) treatment has largely relied on non-specific broad immunosuppressants despite their long-term toxicities until the approval of dupilumab, which blocks IL-4 signaling to target Th2 cell responses. Here, we report the discovery of compound 4aa, a novel compound derived from the structure of chlorophyll a, and the efficacy of chlorophyll a to alleviate AD symptoms by oral administration in human AD patients. 4aa downregulated GATA3 and IL-4 in differentiating Th2 cells by potently blocking IL-4 receptor dimerization. In the murine model, oral administration of 4aa reduced the clinical severity of symptoms and scratching behavior by 76% and 72%, respectively. Notably, the elevated serum levels of Th2 cytokines reduced to levels similar to those in the normal group after oral administration of 4aa. Additionally, the toxicological studies showed favorable safety profiles and good tolerance. In conclusion, 4aa may be applied for novel therapeutic developments for patients with AD.

Evidence of increases of phytol and chlorophyllide by enzymatic dephytylation of chlorophylls in smoothie made from spinach leaves

Phytol is a diterpene alcohol found abundantly in nature as the phytyl side chain of chlorophylls. Free form of phytol and its metabolites have been attracting attention because they have a potential to improve the lipid and glucose metabolism. On the other hand, phytol is unfavorable for those who suffering from Refsum's disease. However, there is little information on the phytol contents in leafy vegetables rich in chlorophylls. This study indicated that raw spinach leaves contain phytol of 0.4-1.5 mg/100 g fresh weight. Furthermore, crude enzyme extracted from the leaves showed the enzyme activities involved in dephytylation of chlorophyll derivatives and they were high at mild alkaline pH and around 45°C, and lowered at 55°C or above. Under the optimum pH and temperature for such enzymes determined in the model reaction using the crude enzyme, phytol content in the smoothie made from raw spinach leaves increased with an increase of chlorophyllide, another reaction product. Comparison between the increased amounts of phytol and chlorophyllide showed that the enzymatic dephytylation of chlorophylls was critically responsible for the increase of phytol in the smoothie. PRACTICAL APPLICATION: Phytol, which is released by the enzymes related to chlorophyll metabolism in plants, has been investigated because of its potential abilities to improve the lipid metabolism and blood glucose level. In contrast to such health benefits, they are known to be toxic for patients suffering from Refsum's disease. This research for the first time reports the phytol content in raw spinach leaves and that phytol can be increased in the smoothie made from spinach leaves by the action of endogenous enzymes on chlorophyll derivatives under a certain condition. These results help control phytol content in the smoothies.

Fat-soluble vitamin and phytochemical metabolites: Production, gastrointestinal absorption, and health effects

Consumption of diets rich in fruits and vegetables, which provide some fat-soluble vitamins and many phytochemicals, is associated with a lower risk of developing certain degenerative diseases. It is well accepted that not only the parent compounds, but also their derivatives formed upon enzymatic or nonenzymatic transformations, can produce protective biological effects. These derivatives can be formed during food storage, processing, or cooking. They can also be formed in the lumen of the upper digestive tract during digestion, or via metabolism by microbiota in the colon. This review compiles the known metabolites of fat-soluble vitamins and fat-soluble phytochemicals (FSV and FSP) that have been identified in food and in the human digestive tract, or could potentially be present based on the known reactivity of the parent compounds in normal or pathological conditions, or following surgical interventions of the digestive tract or consumption of xenobiotics known to impair lipid absorption. It also covers the very limited data available on the bioavailability (absorption, intestinal mucosa metabolism) and summarizes their effects on health. Notably, despite great interest in identifying bioactive derivatives of FSV and FSP, studying their absorption, and probing their putative health effects, much research remains to be conducted to understand and capitalize on the potential of these molecules to preserve health.

Influence of food composition on chlorophyll bioaccessibility

Chlorophylls are ingested and effectively absorbed by our organism daily, but the effect of food composition on its bioaccessibility is unknown. Therefore, the present research analyses the chlorophyll bioaccessibility of ten commercial foods (guacamole, virgin olive oil, tortellini, basil hummus, creamed spinach, vegetable pasta, green tea chocolate, avocado and kiwi juices, and pesto sauce), selected based on their different nutritional (fat, fiber, protein, and carbohydrates) and chlorophyll composition and content. The most unexpected result was to correlate chlorophyll degradation during in vitro digestion with the salt content of the digested food. Surprisingly, independently of the foods' nutritional composition or the chlorophyll content, the chlorophyll profile after in vitro digestion was formed by 90% pheophytins and 10% chlorophylls and pheophorbides. Such a pattern can only be modified when the ingested food contains a high proportion of pheophorbides (˃20%) that prevailed up to the mixed micelles.

Could chlorophyllins improve the safety profile of beta-d-N4-hydroxycytidine versus N-hydroxycytidine, the active ingredient of the SARS-CoV-2 antiviral molnupiravir?

Could natural plant pigment (chlorophyll) derivatives (chlorophyllins) improve the safety of the antiviral Molnupiravir, used to treat COVID-19 disease?

Molnupiravir, a specific SARS-CoV-2 antiviral, may cause adverse genetic changes and thereby create potential host cell damage (through genotoxicity and DNA stressors). In our opinion, this side effect of treatment could be reduced if the antiviral was taken as a combined therapy with chlorophyllins. Specifically, we hypothesise that chlorophyllins might improve the overall effectiveness of molnupiravir, typically used to treat patients suffering from COVID-19. Chlorophyllins, antioxidants derived from natural plant chlorophyll, are safe, effective and non-toxic antioxidants that could combat possible genotoxic flow-on effects of molnupiravir. In addition, as they possess antiviral properties, treatment with chlorophyllins may enhance the overall antiviral effect via a mechanism different to molnupiravir.

Structural and functional comparison of magnesium transporters throughout evolution

Magnesium (Mg²⁺) is the most prevalent divalent intracellular cation. As co-factor in many enzymatic reactions, Mg²⁺ is essential for protein synthesis, energy production, and DNA stability. Disturbances in intracellular Mg²⁺ concentrations, therefore, unequivocally result in delayed cell growth and metabolic defects. To maintain physiological Mg²⁺ levels, all organisms rely on balanced Mg²⁺ influx and efflux via Mg²⁺ channels and transporters. This review compares the structure and the function of prokaryotic Mg²⁺ transporters and their eukaryotic counterparts. In prokaryotes, cellular Mg²⁺ homeostasis is orchestrated via the CorA, MgtA/B, MgtE, and CorB/C Mg²⁺ transporters. For CorA, MgtE, and CorB/C, the motifs that form the selectivity pore are conserved during evolution. These findings suggest that CNNM proteins, the vertebrate orthologues of CorB/C, also have Mg²⁺ transport capacity. Whereas CorA and CorB/C proteins share the gross quaternary structure and functional properties with their respective orthologues, the MgtE channel only shares the selectivity pore with SLC41 Na⁺/Mg²⁺ transporters. In eukaryotes, TRPM6 and TRPM7 Mg²⁺ channels provide an additional Mg²⁺ transport mechanism, consisting of a fusion of channel with a kinase. The unique features these TRP channels allow the integration of hormonal, cellular, and transcriptional regulatory pathways that determine their Mg²⁺ transport capacity. Our review demonstrates that understanding the structure and function of prokaryotic magnesiotropic proteins aids in our basic understanding of Mg²⁺ transport.

Porphyra tenera Protects against PM2.5-Induced Cognitive Dysfunction with the Regulation of Gut Function

To evaluate the biological effects of Porphyra tenera (P. tenera), we tried to confirm the possibility that the intake of P. tenera could modulate cognitive and intestinal functions in PM_2.5-induced cognitive decline mice. P. tenera attenuated PM_2.5-induced learning and memory impairment through antioxidant and anti-inflammatory effects by regulating the mitochondrial function and TLR-initiated NF-κB signaling. In addition, P. tenera effectively alleviated Aβ production/tau phosphorylation by inhibiting the JNK phosphorylation. Also, the bioactive constituents of P. tenera determined the sulfated galactan, mycosporine-like amino acids (MAAs), and chlorophyll derivatives. Moreover, the bioactive compounds of P. tenera by gut fermentation protected against gut dysbiosis and intestinal tight junction damage with a decrease in inflammatory response and short-chain fatty acid production. Based on these results, our findings suggest that P. tenera with sulfated galactan and MAAs is a potential material for cognitive function improvement.

The physicochemical properties and the release of sodium caseinate/ polysaccharide gum chlorophyll multiple-layer particles by rotary side-spray fluid bed technology

Multiple-layer coating technology has widely applied to the quality modification of bioactive ingredients nowadays. This research used a rotary side-spray fluid bed to manufacture chlorophyll multiple-layer particles to adjust control release characteristics. The chlorophyll extracts were coated with sodium alginate (A1) and sodium caseinate (CA1) as the primary layer on sugar spheres and the product yield was 96.98 and 96.71%, respectively. The content of chlorophyll a and b (μg/g) were 41.04 and 13.20 in A1, 47.40 and 13.68 in CA1. The Fourier-transform infrared spectroscopy confirmed the bonding change and increase stability. The CA1 was coated with sodium alginate (CA-A), sodium carboxymethylcellulose (CA-C) and xanthan gum (CA-X) as the secondary layer, which can increase coated integrity, shell strength and thermal stability. The simulated gastrointestinal fluid showed 30.11% release in the stomach and 94.27% in the intestine, which improved release control characteristics. Increased retention rate and color stability in the storage test.

A multi-responsive Au NCs@PMLE/Ca2+ antitumor hydrogel formed in situ on the interior/surface of tumors for PT imaging-guided synergistic PTT/O2-enhanced PDT effects

At present, although phototherapy and related imaging have proven to be promising cancer diagnosis and treatment strategies, the free diffusion of photosensitizers into normal tissues can cause side effects, and the efficiency of photodynamic therapy (PDT) can also be limited by the tumor hypoxic microenvironment. Herein, we designed and prepared a new cancer nanoplatform containing Au nanoclusters (NCs)@Premna microphylla leaf extract (PMLE) with both responsiveness to near-infrared (NIR) laser irradiation and tumor microenvironment (TME) by facile redox and coordination reactions. Then, the Au NCs@PMLE/Ca²⁺ hydrogel was constructed in situ inside and on the surface of tumors for locoregional antitumor activity under 808 nm laser irradiation. The Au NCs@PMLE nanoplatform showed distinguished performance in killing cancer cells and alleviating tumor hypoxia by enhancing the temperature of the tumor sites and producing reactive oxygen species (ROS) under NIR irradiation as well as catalyzing hydrogen peroxide (H₂O₂) decomposition in TME for oxygen (O₂) generation via catalase in PMLE. The ultra-small size of about 3 nm of the Au NCs in this nanoplatform was obtained using the biological molecules present in PMLE as reductants and coordination agents simultaneously, which also demonstrated the outstanding capability of photothermal (PT) imaging and photothermal therapy (PTT) towards tumors. Furthermore, the Au NCs@PMLE/Ca²⁺ hydrogel formed in situ through natural PMLE and intrinsic Ca²⁺ in TME could not only improve the biocompatibility of the nanoplatform and stability of Au NCs but was also highly concentrated around the tumor thus enhancing the therapeutic efficiency and inhibiting its migration to normal tissues, decreasing the side effects. The results of the experiments confirmed that the Au NCs@PMLE/Ca²⁺ hydrogel possessed PT imaging-guided NIR laser/TME-responsive synergetic cancer PTT/O₂-enhanced PDT and remarkable locoregional antitumor effect for cancer therapy. This work may open a new versatile route for multi-responsive localized cancer therapeutic nanoplatforms.

Bioaccessibility and intestinal cell uptake of carotenoids and chlorophylls differ in powdered spinach by the ingredient form as measured using in vitro gastrointestinal digestion and anaerobic fecal fermentation models

Insights into food matrix factors impacting bioavailability of bioactive carotenoids and chlorophylls from fruits and vegetable ingredients are essential to understanding their ability to promote health. The stability and bioaccessibility of carotenoids and chlorophylls were assessed from dehydrated, spray-dried, freeze-dried and fresh spinach ingredient forms using in vitro models simulating upper gastrointestinal (GI) digestion and lower GI anaerobic fecal fermentation. Intestinal transport of bioaccessible bioactives from both upper and lower GI compartments was assessed using the Caco-2 human intestinal cell model. Differences in carotenoid and chlorophyll contents were observed between ingredient forms and these influenced bioaccessibility. Lower carotenoid and chlorophyll contents in spray dried spinach resulted in the lowest total bioaccessible content among all spinach treatments (5.8 ± 0.2 μmoles per g DW carotenoid and chlorophyll). The total bioaccessible content was statistically similar between freeze-dried (12.5 ± 0.6 μmoles per g DW), dehydrated (12.5 ± 3.2 μmoles per g DW), and fresh spinach (14.2 ± 1.2 μmoles per g DW). Post anaerobic fermentation, cellular accumulation of carotenoids was higher (17.57-19.52 vs. 5.11-8.56%), while that of chlorophylls was lower (3.05-5.27 vs. 5.25-6.44%), compared to those observed following upper GI digestion. Collectively, these data suggest that spinach forms created by various drying technologies deliver similar levels of bioaccessible spinach bioactives and that the lower GI tract may serve as a site for significant absorption fostered by interactions with gut microbial communities that liberate additional bioactives from the spinach matrix.

Chlorophylls: A Personal Snapshot

Chlorophylls provide the basis for photosynthesis and thereby most life on Earth. Besides their involvement in primary charge separation in the reaction center, they serve as light-harvesting and light-sensing pigments, they also have additional functions, e.g., in inter-system electron transfer. Chlorophylls also have a wealth of applications in basic science, medicine, as colorants and, possibly, in optoelectronics. Considering that there has been more than 200 years of chlorophyll research, one would think that all has been said on these pigments. However, the opposite is true: ongoing research evidenced in this Special Issue brings together current work on chlorophylls and on their carotenoid counterparts. These introductory notes give a very brief and in part personal account of the history of chlorophyll research and applications, before concluding with a snapshot of this year’s publications.

Chlorophyllides: Preparation, Purification, and Application

Chlorophyllides can be found in photosynthetic organisms. Generally, chlorophyllides have a-, b-, c-, d-, and f-type derivatives, and all chlorophyllides have a tetrapyrrole structure with a Mg ion at the center and a fifth isocyclic pentanone. Chlorophyllide a can be synthesized from protochlorophyllide a, divinyl chlorophyllide a, or chlorophyll. In addition, chlorophyllide a can be transformed into chlorophyllide b, chlorophyllide d, or chlorophyllide f. Chlorophyllide c can be synthesized from protochlorophyllide a or divinyl protochlorophyllide a. Chlorophyllides have been extensively used in food, medicine, and pharmaceutical applications. Furthermore, chlorophyllides exhibit many biological activities, such as anti-growth, antimicrobial, antiviral, antipathogenic, and antiproliferative activity. The photosensitivity of chlorophyllides that is applied in mercury electrodes and sensors were discussed. This article is the first detailed review dedicated specifically to chlorophyllides. Thus, this review aims to describe the definition of chlorophyllides, biosynthetic routes of chlorophyllides, purification of chlorophyllides, and applications of chlorophyllides.

Light-Activated Biomedical Applications of Chlorophyll Derivatives

Tetrapyrroles are the basis of essential physiological functions in most living organisms. These compounds represent the basic scaffold of porphyrins, chlorophylls, and bacteriochlorophylls, among others. Chlorophyll derivatives, obtained by the natural or artificial degradation of chlorophylls, present unique properties, holding great potential in the scientific and medical fields. Indeed, they can act as cancer-preventing agents, antimutagens, apoptosis inducers, efficient antioxidants, as well as antimicrobial and immunomodulatory molecules. Moreover, thanks to their peculiar optical properties, they can be exploited as photosensitizers for photodynamic therapy and as vision enhancers. Most of these molecules, however, are highly hydrophobic and poorly soluble in biological fluids, and may display undesired toxicity due to accumulation in healthy tissues. The advent of nanomedicine has prompted the development of nanoparticles acting as carriers for chlorophyll derivatives, facilitating their targeted administration with demonstrated applicability in diagnosis and therapy. In this review, the chemical and physical properties of chlorophyll derivatives that justify their usage in the biomedical field, with particular regard to light-activated dynamics are described. Their role as antioxidants and photoactive agents are discussed, introducing the most recent nanomedical applications and focusing on inorganic and organic nanocarriers exploited in vitro and in vivo.