Arbutin alleviates intestinal colitis by regulating neutrophil extracellular traps formation and microbiota composition

BACKGROUND

Ulcerative colitis (UC) is a chronic recurrent intestinal disease lacking effective treatments. β-arbutin, a glycoside extracted from the Arctostaphylos uva-ursi leaves, that can regulate many pathological processes. However, the effects of β-arbutin on UC remain unknown.

PURPOSE

In this study, we investigated the role of β-arbutin in relieving colitis and explored its potential mechanisms in a mouse model of dextran sulfate sodium (DSS)-induced colitis.

METHODS

In C75BL/6 J mice, DSS was used to induce colitis and concomitantly β-arbutin (50 and 100 mg/kg) was taken orally to evaluate its curative effect by evaluating disease activity index (DAI) score, colon length and histopathology. Alcian blue periodic acid schiff (AB-PAS) staining, immunohistochemistry (IHC), immunofluorescence (IF) and TdT-mediated dUTP Nick-End Labeling (Tunel) staining were used to assess intestinal barrier function. Flow cytometry, double-IF and western blotting (WB) were performed to verify the regulatory mechanism of β-arbutin on neutrophil extracellular traps (NETs) in vivo and in vitro. NETs depletion experiments were used to demonstrate the role of NETs in UC. Subsequently, the 16S rRNA gene sequencing was used to analyze the intestinal microflora of mouse.

RESULTS

Our results showed that β-arbutin can protect mice from DSS-induced colitis characterized by a lower DAI score and intestinal pathological damage. β-arbutin reduced inflammatory factors secretion, notably regulated neutrophil functions, and inhibited NETs formation in an ErK-dependent pathway, contributing to the resistance to colitis as demonstrated by in vivo and in vitro experiments. Meanwhile, remodeled the intestinal flora structure and increased the diversity and richness of intestinal microbiota, especially the abundance of probiotics and butyric acid-producing bacteria. It further promoted the protective effect in the resistance of colitis.

CONCLUSION

β-arbutin promoted the maintenance of intestinal homeostasis by inhibiting NETs formation, maintaining mucosal-barrier integrity, and shaping gut-microbiota composition, thereby alleviating DSS-induced colitis. This study provided a scientific basis for the rational use of β-arbutin in preventing colitis and other related diseases.

Metabolomic analysis and bioactivities of Arbutus unedo leaves harvested across the seasons in different natural habitats of Sardinia (Italy)

BACKGROUND

Arbutus unedo L. is a wild tree of Mediterranean regions used as food and in traditional medicine and important for afforestation programs. There is no detailed information available on the variation of A. unedo leaves metabolome across the seasons. The leaves were analyzed by Proton nuclear magnetic resonance (1 H NMR)-based metabolomics, comparing samples harvested across the seasons and in ten different natural habitats of Sardinia (Italy).

RESULTS

Multivariate analysis showed the impact of seasonal variation on the metabolome: glucose and quinic acid increased in summer, while in spring sucrose was accumulated. β-Arbutin, the main known active principle of A. unedo, generally reached the highest concentration in autumn. In winter, O-β-methylglucose, γ-aminobutyric acid (GABA), flavonols (quercetin-3-O-α-rhamnoside, myricetin-3-O-α-rhamnoside, kaempferol-3-O-α-rhamnoside), catechin, and gallocatechin increased. Characteristic metabolomic features were found also for samples collected in different locations. For instance, trees growing at the highest altitude and exposed to lower temperatures produced less flavonols and catechins. The only sample collected on trees growing on limestones, dolomites, and dolomitic limestones type of soil showed generally the highest content of arbutin. The highest phenolics content was found during spring, while samples collected on flowering branches in winter were the ones with the highest flavonoid content. The antioxidant activity was also variated, ranging from 1.3 to 10.1 mg of Trolox equivalents (TE)/mL of extract, and it was positively correlated to both total phenolics and flavonoid content. Winter samples showed the lowest antibacterial activity, while summer and autumn ones exhibited the highest activity (IC50 values ranging from 17.3 to 42.3 µg/mL against Staphylococcal species).

CONCLUSION

This work provides 1 H-NMR fingerprinting of A. unedo leaves, elucidating the main metabolites and their variations during seasons. On the basis of arbutin content, autumn could be considered the balsamic period of this taxon. Samples collected in this season were also the most active ones as antibacterial. Moreover, an interesting metabolomic profile enriched in catechins and flavonols was observed in leaves collected in winter on flowering branches which were endowed with high antioxidant potential.

Inhibitory Activities of Samples on Tyrosinases Were Affected by Enzyme Species and Sample Addition Methods

The inhibition of tyrosinase (TYR) activity is an effective measure to inhibit melanin synthesis. At present, there are many methods with discrepant details that study the TYR inhibitory activity of samples. Under the same experimental conditions, this paper systematically studies whether enzyme species and sample addition methods are the key factors that determine the TYR inhibitory activity of samples. TYRs extracted from B16F10 cells, apple and mushroom, called BTYR, ATYR and MTYR, respectively, were selected to implement this study. Results showed that TYR inhibitory activities of samples were obviously affected by the above two factors. It was necessary to select the appropriate enzyme according to the problems to be explained. It was speculated that indirectly inhibitory activity reflected the comprehensive effects of samples on TYR catalytic activity and intracellular TYR synthesis pathway, while directly inhibitory activity reflected the effects of samples on TYR catalytic activity. Additionally, kojic acid could be used as a positive control for both B16F10 cells and MTYR models. The TYR inhibitory activity of β-arbutin was complicated and fickle, while that of epigallocatechin gallate (EGCG) was universal and stable, which is to say, EGCG always inhibited TYR activity in a dose-dependent manner. In conclusion, the TYR inhibitory activities of samples were affected by enzyme species and sample addition methods. Compared with the unstable β-arbutin, EGCG was more valuable for clinical research.

Effects of Itxasol© Components on Gene Expression in Bacteria Related to Infections of the Urinary Tract and to the Inflammation Process

Urinary tract infections (UTIs) represent a health problem of the first magnitude since they affect large segments of the population, cause increased mortality and comorbidity, and have a high incidence of relapse. Therefore, UTIs cause a major socioeconomic concern. Current antibiotic treatments have various limitations such as the appearance of resistance to antibiotics, nephrotoxicity, and side effects such as gastrointestinal problems including microbiota alterations that contribute to increasing antibiotic resistance. In this context, Itxasol© has emerged, approved as an adjuvant for the treatment of UTIs. Designed with biomimetic principles, it is composed of arbutin, umbelliferon, and N-acetyl cysteine. In this work, we review the activities of these three compounds concerning the changes they produce in the expression of bacterial genes and those related to inflammation as well as assess how they are capable of affecting the DNA of bacteria and fungi.

α-Glucosidic hydroquinone derivatives from Viburnum erosum

Six undescribed compounds (1-6) were isolated from the leaves of Viburnum erosum along with four known compounds 7-10. The structures were determined by NMR and MS spectroscopic analyses, and their absolute configurations were established by chemical and spectroscopic methods. Compounds 1-6 were α-glucosidic hydroquinone derivatives with different linear monoterpenoid structures. Compounds 1-10 were also evaluated for their tyrosinase inhibitory activities, and 10 showed potent inhibition of tyrosinase enzyme with IC₅₀ value of 37.9 μM compared to 47.6 μM of the positive control (β-arbutin).

Capsaicin reverses the inhibitory effect of licochalcone A/β-Arbutin on tyrosinase expression in b16 mouse melanoma cells

Introduction:

Melanin is synthesized by melanocytes, which are located in the basal layer of the skin. After synthesis, melanin is further deposited on the surface of the skin to form black spots or chloasma. Tyrosinase is a rate-limiting enzyme that plays an important role in melanogenesis. Currently, there are many drugs that inhibit tyrosinase expression to further reduce melanogenesis. Nevertheless, some of these could reverse the pharmacological effect of other drugs, when used simultaneously.

Materials and Methods:

B16 mouse melanoma cells were treated with the tyrosinase inhibitors licochalcone A and β-arbutin, alone or in combination with capsaicin, an alkaloid found in peppers. Cytotoxicity, melanin content, and tyrosinase activity and expression were determined.

Results:

Licochalcone A/β-arbutin inhibited tyrosinase expression and further hindered melanin synthesis when applied individually to B16 mouse melanoma cells. However, licochalcone A/β-arbutin combined with 50 μmol/L capsaicin enhanced the expression of tyrosinase in these cells and further increased melanin content.

Conclusion:

Our data implied that capsaicin could reverse the inhibitory effect of licochalcone A/β-arbutin on tyrosinase expression in B16 mouse melanoma cells.

SUMMARY

B16 mouse melanoma cells were treated with the tyrosinase inhibitors licochalcone A and β-arbutin, alone or in combination with capsaicin, an alkaloid found in peppers. Cytotoxicity, melanin content, and tyrosinase activity and expression were determined. Licochalcone A/β-arbutin inhibited tyrosinase expression and further hindered melanin synthesis when applied individually to B16 mouse melanoma cells. However, licochalcone A/β-arbutin combined with 50 μmol/L capsaicin enhanced the expression of tyrosinase in these cells and further increased melanin content. Our research implied that capsaicin could reverse the inhibitory effect of licochalcone A/β-arbutin on tyrosinase expression in B16 mouse melanoma cells.

Abbreviations used: B16: B16 mouse melanoma cells; L-DOPA: 3, 4-L-dihydroxyphenylalanine; TYR: Tyrosinase; USP: United States Pharmacopeia; FBS: Fetal bovine serum; EDTA: Ethylenediaminetetraacetic acid; DMSO: Dimethyl sulfoxide; RPMI: Roswell Park Memorial Institute; MTT3: 4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide, NaOH: Sodium hydroxide; PBS: Phosphate-buffered saline; RIPA: Radio-immunoprecipitation assay; PMSF: Phenylmethanesulfonyl fluoride or phenylmethylsulfonyl fluoride; SDS: Sodium dodecyl sulfate, sodium salt; PVDF: Polyvinylidene fluoride; ECL: Enhanced chemiluminescence.

Reassessment of the polar fraction of Stachys alopecuros (L.) Benth. subsp. divulsa (Ten.) Grande (Lamiaceae) from the Monti Sibillini National Park: A potential source of bioactive compounds

BACKGROUND

The phytochemical analysis of Stachys alopecuros subsp. divulsa, an endemic Italian species, has been recently reported and has showed the presence of 8-O-acetylharpagide (2), harpagide (3), allobetonicoside (4), and 4¢-O-galactopyranosyl-teuhircoside (5). In this paper, an in deep study of its glycosidic fraction with the aim to widen the knowledge on its secondary metabolites content is reported.

MATERIALS AND METHODS

Chromatographic techniques were used for the isolation of constituents while spectroscopic and spectrometric techniques were applied for the structures elucidation.

RESULTS

Besides the known constituents, all of them reconfirmed, ajugoside (1), reptoside (6) and 6-O-acetyl-ajugol (7) were also identified among the iridoids while the phenolic components resulted to be chlorogenic acid (8), b-arbutin (9), verbascoside (10), and stachysoside A (11), instead.

CONCLUSION

The iridoid pattern of S. alopecuros subsp. divulsa has been expanded with the identification of not previously reported compounds as well as for the phenolic fraction. Except for the reconfirmed verbascoside (10), the other phenolic compounds were recognized for the first time in the studied species. The complete NMR assignment of compound (1) by means of bidimensional techniques is reported, and both the chemotaxonomic and pharmacological relevance of the isolated compounds is largely discussed.

Opinion of the Scientific Committee on Consumer Safety (SCCS)--Opinion on the safety of the use of β-arbutin in cosmetic products

CONCLUSION OF THE OPINION

The SCCS considers the use of β-arbutin to be safe for consumers in cosmetic products in a concentration up to 7% in face creams provided that the contamination of hydroquinone in the cosmetic formulations remain below 1 ppm. A potential combined use of β-arbutin and other hydroquinone releasing substances in cosmetic products has not been evaluated in this Opinion.

Comparative studies on the chemical and enzymatic stability of alpha- and beta-arbutin

OBJECTIVE

The aim of this study was to establish a comparative analysis of the chemical and enzymatic stability of α- and β-arbutins as potential sources of the substance of concern hydroquinone (HQ). The study was performed using an array of techniques including HPLC-PDA, nuclear magnetic resonance (NMR) and optical rotation (OR). Both arbutins are emerging as popular and effective skin whiteners, acting as tyrosinase inhibitors in a fashion similar to the popular whitening agent HQ. Due to their structural similarity to the regulated agent HQ, both arbutins may be regarded as potential sources of the active aglycone after chemical or metabolic conversion.

METHODS

Various cosmetic formulations including creams, sera, gels and lotions were analysed by HPLC-PDA for their arbutin and HQ content in freshly opened and aged samples stored for 16 months. Solutions of pure compounds were also aged and periodically checked for degradation products using 1D and 2D NMR experiments and OR measurements. The metabolic stability was investigated using pear peels as a biological model.

RESULTS

Both arbutins were found to be stable in water and methanol solutions in the absence of buffer or stabilizers. Their stability in cosmetic formulations, however, was found to depend on the type of formulation and pH. Both compounds were unstable under strong hydrolytic conditions, with consequent release of HQ. Enzymatic instability of both arbutins was also observed, although no formation of HQ was observed under the chosen experimental conditions.

CONCLUSION

Both arbutins were found to possess similar stability profiles, and to be more prone to in vivo rather than in chemico degradation, although no HQ was found after enzymatic hydrolysis. Also, no epimerization was observed in any of the tested conditions. Diverse experimental approaches can be applied to analyse the chemical and enzymatic stability of arbutins in regard to the potential release of HQ in different types of preparations. These result showed the potential use of NMR and OR as complementary investigative tools for the stability and safety assessment of arbutin along with more established HPLC methods.

A double-blind, placebo-controlled randomized trial of Serratulae quinquefoliae folium, a new source of β-arbutin, in selected skin hyperpigmentations

BACKGROUND

Arbutin is one of the most effective lightening substances. Serratula quinquefolia is a new source of its β-anomer. The HPLC method showed that the solid content of this compound in the dried plant raw material accounts for 6.86%. The leaves of Serratula quinquefolia do not contain hydroquinone.

AIMS

To assess the efficacy of the aqueous extract from' leaf of five-leaf serratula as a skin-lightening agent.

PATIENTS/METHODS

We did a randomized, placebo-controlled, double-blind trial. The study involved 102 women aged 26-55, with two kinds of hyperpigmentary diseases: melasma and lentigo solaris. Patients were randomly assigned to one of the treatment groups: a study group (N = 54) or a control group (N = 48). The study group applied the cream with the aqueous extract from leaf of five-leaf serratula containing 2.51% of arbutin. The cream was applied twice a day on the discolored side for 8 weeks.

RESULTS

The experimental data showed that the cream with the extract causes decreased level of melanin in the skin pigmentation spot. Clinical effect in the form of lightening and evening skin tone on the discolored side was observed in 75.86% of the female patients with melasma and 56.00 % of the female patients with lentigo solaris.

CONCLUSIONS

The cream with the aqueous extract from leaf of five-leaf serratula proved to be an effective and safe preparation for lightening skin discolorations (66.67 % of the female patients in the study group).