Arbutin and decrease of potentially toxic substances generated in human blood neutrophils

Effects of Strawberry Tree (Arbutus unedo L.) Aqueous Leaf Extract and Arbutin on PK-15 and HepG2 Cells

The antioxidant properties of the leaves of the Mediterranean strawberry tree (Arbutus unedo L.) are mainly attributed to the main bioactive compound, the phenolic glycoside arbutin. In this study, the safety profile of strawberry tree aqueous leaf extract (STE) and arbutin at the DNA level was assessed in vitro using porcine PK-15 kidney cells and HepG2 cells derived from human hepatomas. To examine the effects on cell viability and DNA damage, cells were treated for 24 h with STE or arbutin at three concentrations presumed to be non-toxic (400, 200, and 11.4 µg/mL). Assessments were performed using the MTS viability assay, dual acridine orange/ethidium bromide fluorescent staining, and alkaline comet assay. Results showed that the highest concentration (400 µg/mL) of both tested compounds had no significant cytotoxic effects on either PK-15 or HepG2 cells. Apoptosis was the predominant type of cell death and the total amount of DNA damage in treated cells was within acceptable limits. These results on the in vitro cytocompatibility of arbutin and STE with PK-15 and HepG2 cells could serve to make more reliable judgements about safe levels of arbutin in cosmetic products and functional foods, given the increased popularity of the compound in recent years.

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.

Investigation of Possible Positive Effects of Arbutin Application in Experimental Colitis Model

BACKGROUND/AIMS

 This study aimed to investigate the possible positive effects of arbutin in a trinitrobenzene sulfonic acid (TNBS)- induced experimental colitis model, to compare it with mesalazine, which is used in treating inflammatory bowel disease and to observe the effect of its concomitant use.

MATERIALS AND METHODS

 Forty Wistar albino species male rats were randomized into 5 groups as control, colitis, colitis+arbutin (Arb), colitis+mesalazine (Mes), and colitis+mesalazine+arbutin (M+A). Proinflammatory cytokines [interleukin (IL)-6, IL-1β, tumor necrosis factor alpha (TNF-α)] and oxidant/antioxidant parameters [malondialdehyde (MDA), superoxide dismutase inhibition (SOD) inhibition, myeloperoxidase (MPO), and catalase, glutathione peroxidase (GPx)] were processed from the samples. Histopathological evaluation evaluated goblet cell reduction, cellular infiltration, and mucosal loss.

RESULTS

 When the treatment groups and the TNBS group were compared, statistical significance was achieved in MDA, MPO, SOD inhibition, GPx values, IL-6, IL-1β and TNF-α levels. Histopathological evaluation revealed a statistically significant decrease in the mucosal loss value in the group where mesalazine and arbutin were used together compared to the TNBS group.

CONCLUSION

 Our study's results elaborated that using arbutin alone or in combination with mesalazine produced positive effects in colitis-induced rats.

The protective effect of arbutin against potassium bromate-induced oxidative damage in the rat brain

This study aimed to investigate the protective effects of arbutin (ARB) against brain injury induced in rats with potassium bromate (KBrO₃ ). The rats were divided into four groups as Group 1: Control (0.9% NaCl ml/kg/day p.), Group 2: KBrO₃ (100 mg/kg (gavage), Group 3: ARB (50 mg/kg/day p.), and Group 4: KBrO₃  + ARB (100 mg/kg (gavage) + 50 mg/kg/day p.). At the end of the fifth day of the study, the rats in all groups were killed, and their brain tissues were collected. In the collected brain tissues, malondialdehyde (MDA), superoxide dismutase (SOD), and catalase (CAT) levels were measured, and routine histopathological examinations were made. The MDA levels in the group that was exposed to KBrO₃ were significantly higher than those in the control group (p ˂ 0.001). In comparison to the KBrO₃ group, the MDA levels in the KBrO₃  + ARB group were significantly lower (p ˂ 0.001). It was observed that SOD and CAT enzyme activity levels were significantly lower in the KBrO₃ group compared to the control group (p ˂ 0.001), while these levels were significantly higher in the KBrO₃  + ARB group than in the KBrO₃ group (p ˂ 0.001). Additionally, the group that was subjected to KBrO₃ toxicity, as well as ARB administration, had much lower levels of histopathologic signs than the group that was subjected to KBrO₃ toxicity only. Consequently, it was found that KBrO₃ exposure led to injury in the brain tissues of the rats, and using ARB was effective in preventing this injury.

Arbutin: Occurrence in Plants, and Its Potential as an Anticancer Agent

Arbutin, a hydroquinone glucoside, has been detected in ca. 50 plant families, especially in the plants of the Asteraceae, Ericaceae, Proteaceae and Rosaceae families. It is one of the most widely used natural skin-whitening agents. In addition to its skin whitening property, arbutin possesses other therapeutically relevant biological properties, e.g., antioxidant, antimicrobial and anti-inflammatory, as well as anticancer potential. This review presents, for the first time, a comprehensive overview of the distribution of arbutin in the plant kingdom and critically appraises its therapeutic potential as an anticancer agent based on the literature published until the end of August 2022, accessed via several databases, e.g., Web of Science, Science Direct, Dictionary of Natural Products, PubMed and Google Scholar. The keywords used in the search were arbutin, cancer, anticancer, distribution and hydroquinone. Published outputs suggest that arbutin has potential anticancer properties against bladder, bone, brain, breast, cervix, colon, liver, prostate and skin cancers and a low level of acute or chronic toxicity.

Arbutin attenuates ethanol-induced acute hepatic injury by the modulation of oxidative stress and Nrf-2/HO-1 signaling pathway

Alcoholic liver disease (ALD) is a pervasive ailment due to the excessive consumption of alcohol and there is no operative drug for its treatment. The current exploration was intended to examine the hepatoprotective efficacy of arbutin against ethanol-provoked liver injury in rats via the modulation of the Nrf-2/HO-1 signaling cascade. Wistar rats were challenged with the 3 g/kg/day (40% v/v) of ethanol for 4 weeks to provoke the ALD and concomitantly supplemented with 40 mg/kg of arbutin. The liver function markers enzymes, inflammatory cytokines, and oxidative stress markers levels were scrutinized by using the respective assay kits. The mRNA expression of Nrf-2/HO-1 signaling proteins was studied by reverse-transcription polymerase chain reaction. The histological alterations of liver tissues were examined. HepG2 cells were used for the in vitro studies. The levels of oxidative stress markers and liver marker enzymes were examined by using kits. Reactive oxygen species (ROS) and apoptotic cell death was detected by using fluorescent staining. There were no major differences in the body weight and liver weight of experimental animals. Arbutin treatment appreciably reduced the liver marker enzymes, upregulated superoxide dismutase, glutathione peroxidase, total antioxidant capacity, and the hydroxyl scavenging ability, and diminished the tumor necrosis factor-α and interleukin-6 levels in the serum of ethanol provoked animals. Arbutin triggered Nrf-2/HO-1 signaling cascade liver tissues of ethanol-provoked animals. Histological findings proved the preventing effects of arbutin. Arbutin did not demonstrate toxicity to the HepG2 cells. It reduced the aspartate aminotransferase and alanine aminotransferase, ROS, apoptotic cell death, lipid peroxidation and improved the antioxidants' levels in the ethanol-challenged HepG2 cells. In conclusion, our findings unveiled the hepatoprotective efficacy of arbutin against ethanol-provoked liver injury in rats. It could be a promising agent to treat alcoholic liver disease in the future.

A comprehensive review of the therapeutic potential of α-arbutin

Cosmetic dermatology preparations such as bleaching agents are ingredients with skin-related biological activities for increasing and improving skin beauty. The possibility of controlling skin hyperpigmentation disorders is one of the most important research goals in cosmetic preparations. Recently, cosmetics containing herbal and botanical ingredients have attracted many interests for consumers of cosmetic products because these preparations are found safer than other preparations with synthetic components. However, high-quality trial studies in larger samples are needed to confirm safety and clinical efficacy of phytotherapeutic agents with high therapeutic index. Arbutin (p-hydroxyphenyl-β-d-glucopyranoside) is a bioactive hydrophilic polyphenol with two isomers including alpha-arbutin (4-hydroxyphenyl-α-glucopyranoside) and β-arbutin (4-hydroxyphenyl-β-glucopyranoside). It is used as a medicinal plant in phytopharmacy. Studies have shown that alpha-arbutin is 10 times more effective than natural arbutin. A comparison of IC50 values showed that α-arbutin (with concentration 2.0 mM) has a more potent inhibitory activity on human tyrosinase against natural arbutin (with higher concentration than 30 mM). A review of recent studies showed that arbutin could be beneficial in treatment of various diseases such as hyperpigmentation disorders, types of cancers, central nervous system disorders, osteoporosis, diabetes, etc. This study was designed to describe the therapeutic efficiencies of arbutin.

Arbutin Improves Functional Recovery and Attenuates Glial Activation in Lysolecethin-Induced Demyelination Model in Rat Optic Chiasm

Neuroinflammation, glial activation, and oxidative injury are the main pathological mechanisms of demyelination in multiple sclerosis (MS). Arbutin, a natural polyphenol compound, possesses antioxidant, anti-inflammatory, and neuroprotective properties whose therapeutic potential has not been studied in the experimental animal models of MS. In the present study, the efficiency of arbutin on lysolecthin (LPC)-induced local demyelination model was investigated. Demyelination was induced by micro-injection of 2 μl LPC (1%) into the rat optic chiasm and the treated group received daily injection of arbutin (50 mg/kg, i.p) during 2 weeks. Visual-evoked potential (VEP) recordings were used to functionally assess the visual pathway. Gene expression analysis was done to evaluate the arbutin effect on the inflammatory, stress oxidative-related mediators, and myelin markers. The myelin-specific staining was performed to assess demyelination and GFAP staining as an astrocyte marker. We found that arbutin significantly reduced P1-latency of VEPs waves and demyelination at 7 and 14 days post-demyelination. Arbutin decreased inflammatory cytokines (IL-1B, IL-17, TNF-α) and iNOS mRNA expression level. In addition, the expression level of anti-inflammatory cytokine (IL-10) and antioxidant mediators (Nrf-2 and HO-1) was enhanced by arbutin treatment. Arbutin increased MBP and Olig2 expression levels in demyelination context. Finally, arbutin attenuated GFAP as an astrocyte marker. Finally, this study demonstrates that arbutin improves functional recovery and myelin repair in the demyelinated optic chiasm through attenuation of inflammation, astrocyte activation, and oxidative stress. These findings might open new promising avenues for treating demyelinating disorders such as multiple sclerosis. Graphical abstract.

The Effect of Arbutin on The Expression of Tumor Suppressor P53, BAX/BCL-2 Ratio and Oxidative Stress Induced by Tert-Butyl Hydroperoxide in Fibroblast and LNcap Cell Lines

Objective

Arbutin (p-hydroxyphenyl-β-D-glucopyranoside) possesses beneficial functions including antioxidant, antiinflammatory, and anti-tumoral activities. Due to the important role of oxidative stress and apoptosis in the successful treatment of cancer, understanding mechanisms that lead to apoptosis in cancer cells, is essential. The purpose of the current study was to evaluate the effect of arbutin on tert-butyl hydroperoxide (t-BHP)-induced oxidative stress and the related mechanisms in fibroblast and Lymph Node Carcinoma of the Prostate (LNCaP) cells.

Materials and Methods

In this experimental study, the LNCaP and fibroblast cell lines were pre-treated with arbutin (50, 250 and 1000 μM). After 24 hours, t-BHP (30 and 35 μM) was added to the cells. Viability was measured (at 24 and 48 hours) using MTT assay. The antioxidant effect of arbutin was measured by FRAP assay. The mRNA expression of P53 and BAX/BCL-2 ratio were measured using quantitative polymerase chain reaction (PCR). The percentage of apoptotic or necrotic cells was determined using a double staining annexin V fluorescein isothiocyanate (FITC) apoptosis detection kit.

Results

Arbutin pre-treatment increased the total antioxidative power and cell viability in the MTT assay and reduced BAX/BCL-2 ratio, P53 mRNA expression and necrosis in fibroblasts exposed to the oxidative agent (P<0.001). In addition, our results showed that arbutin can decrease cell viability, induce apoptosis and increase BAX/BCL-2 ratio in LNCaP cells at some specific concentrations (P<0.001).

Conclusion

Arbutin as a potential functional β-D-glucopyranoside has strong ability to selectively protect fibroblasts against t-BHP-induced cell damage and induce apoptosis in LNCaP cells.

In vitro safety assessment of the strawberry tree (Arbutus unedo L.) water leaf extract and arbutin in human peripheral blood lymphocytes

Strawberry tree (Arbutus unedo L.) leaves have long been used in the traditional medicine of the Mediterranean region. One of their most bioactive constituents is the glycoside arbutin, whose presence makes A. unedo suitable as a potential substitute for bearberry [Arctostaphylos uva ursi (L.) Spreng] leaves, an herbal preparation widely used for treating urinary tract infections. The safety and biocompatibility of strawberry tree water leaf extract have not yet been documented well. This study estimated arbutin content in strawberry tree water leaf extract (STE) using high performance liquid chromatography. Furthermore, we performed an in vitro safety assessment of the 24 h exposure to three presumably non-toxic concentrations of standardized STE and arbutin in human peripheral blood lymphocytes using the apoptosis/necrosis assay, the alkaline comet assay, and the cytokinesis-block micronucleus cytome assay. The STE was also tested for total antioxidant capacity and lipid peroxidation. At a concentration corresponding to the maximum allowable daily intake of arbutin, the tested extract was not cytotoxic, had a negligible potential for causing primary DNA damage and even hindered micronuclei formation in lymphocytes. It also showed a valuable antioxidant capacity, and did not exert marked lipid peroxidation. These promising results represent a solid frame for further development of STE-based herbal preparations. Although arbutin generally had a low DNA damaging potential, the slowing down of lymphocyte proliferation observed after 24 h of exposure points to a cytostatic effect, which merits further research.

The effects of strawberry tree water leaf extract, arbutin and hydroquinone on haematological parameters and levels of primary DNA damage in white blood cells of rats

ETHNOPHARMACOLOGICAL RELEVANCE

Strawberry tree (Arbutus unedo L., Ericaceae) leaves represent a potent source of biologically active compounds and have been used for a long to relieve symptoms of various health impairments and diseases. Two major compounds related to their beneficial activities in animals and humans are arbutin and hydroquinone.

AIM OF THE STUDY

To establish potential benefit/risk ratio associated with daily oral administration of strawberry tree water leaf extract, arbutin and hydroquinone in doses expected to be non-toxic.

MATERIALS AND METHODS

We performed a 14-day and a 28-day study on male and female Lewis rats and evaluated main haematological parameters and the effects of treatments on the levels of primary DNA damage in white blood cells (WBC) using the alkaline comet assay.

RESULTS

Our findings suggest no significant changes in the haematological parameters following prolonged exposure to strawberry tree water leaf extract, arbutin, and hydroquinone. However, hydroquinone causes increased, and extract as well as arbutin decreased WBC count in male rats compared to control after 14 days of treatment. DNA damage measured in WBC of rats treated with all compounds was below 10% of the DNA in the comet tail, which indicates low genotoxicity. The genotoxic potential of strawberry water leaf extract was within acceptable limits and reflected effects of a complex chemical composition upon DNA. We also observed slight gender- and exposure time- related differences in primary DNA damage in the leucocytes of control and treated rats.

CONCLUSIONS

Future studies should investigate which doses of strawberry tree water leaf extract would be most promising for the potential use as a substitute for bearberry leaves for treatment of urinary infection.

On the pharmacology of oxidative burst of human neutrophils

The effect of three therapeutically used drugs and five polyphenolic compounds on the mechanism of oxidative burst was compared in whole blood and isolated neutrophils at cellular and molecular level. In 10 microM concentration, the compounds investigated decreased the oxidative burst of whole blood in the rank order of potency: N-feruloylserotonin (N-f-5HT) > curcumin (CUR) > quercetin (QUER) > arbutin (ARB) > resveratrol (RES) > dithiaden (DIT) > carvedilol (CARV) > brompheniramine (BPA). The ratio between the percentage inhibition of extracellular versus intracellular chemiluminescence (CL) followed the rank order QUER > N-f-5HT > RES > CUR > DIT and is indicative of the positive effect of the compounds tested against oxidative burst of neutrophils, demonstrating suppression of reactive oxygen species extracellularly with minimal alteration of intracellular reactive oxygen species (ROS). Activation of protein kinase C was significantly decreased by DIT, CUR, QUER and N-f-5HT. CARV, DIT, QUER and ARB reduced activated neutrophil myeloperoxidase release more significantly compared with the effect on superoxide anion generation. All compounds tested increased the activity of caspase-3 in cell-free system. It is suggested that other regulatory mechanisms than protein kinase C might participate in the inhibition of neutrophil activation with the compounds tested. Different mechanisms are concerned in controlling the assembly of NADPH oxidase and the regulatory role of calcium ions is suggested. Compounds decreasing the amount of extracellular ROS generation, yet affecting but minimally intracellular ROS generation, are promising for further investigation in vivo.