Improving physicochemical characteristics and cytotoxicity of baicalin esters by liposome encapsulation.

The instability of ester bonds, low water solubility, and increased cytotoxicity of flavonoid glycoside esters significantly limit their application in the food industry. Therefore, the present study attempted to resolve these issues through liposome encapsulation. The results showed that baicalin butyl ester (BEC4) and octyl ester (BEC8) have higher encapsulation and loading efficiencies and lower leakage rate from liposomes than baicalin. FTIR results revealed the location of BEC4 and BEC8 in the hydrophobic layer of liposomes, which was different from baicalin. Additionally, liposome encapsulation improved the water solubility and stability of BEC4 and BEC8 in the digestive system and PBS but significantly reduced their cytotoxicity. Furthermore, the release rate of BEC4 and BEC8 from liposomes was lower than that of baicalin during gastrointestinal digestion. These results indicate that liposome encapsulation alleviated the negative effects of fatty chain introduction into flavonoid glycosides.

Efficient regioselective enzymatic acylation of troxerutin: difference characterization of in vitro cellular uptake and cytotoxicity.

In this study, we developed a multi-site acylation strategy to improve the lipophilicity and cellular uptake of troxerutin, a natural flavonoid with many health-promoting bioactivities. By clarifying the acylation properties of troxerutin catalyzed by lipases from different sources, a series of troxerutin ester derivatives acylated at different sites was synthesized, including troxerutin dipropyl (TDP), tripropyl (TTP), tetrapropyl (TEP), dibutyl (TDB), monohexyl (TMH), monooctyl (TMO) and monodecyl (TMD) esters. Interestingly, the troxerutin esters acylated at multiple sites with shorter fatty chains (TDP, TTP and TEP) had similar lipophilicity to the mono-acylated esters bearing longer fatty chains (TMH, TMO and TMD, respectively) and meanwhile demonstrated surprisingly lower cytotoxicity than that of the long fatty-chain mono-esters. In particular, the multi-acylated esters with shorter fatty chains showed remarkably higher cellular uptake than the mono-esters with long fatty chains. In vitro gastrointestinal digestion suggested that the multi-acylated esters of troxerutin were more resistant to gastrointestinal degradation than the mono-esters. These results indicated that multi-site acylation with short fatty chains could be an effective alternative to introducing one-site mono-acylation for the modification of troxerutin and other flavonoid compounds.

Microbial-Driven Synthesis and Hydrolysis of Neohesperidin Dihydrochalcone: Biotransformation Process and Feasibility Investigation.

A novel yeast-mediated hydrogenation was developed for the synthesis of neohesperidin dihydrochalcone (NHDC) in high yields (over 83%). Moreover, whole-cell catalytic hydrolysis was also designed to hydrolyze NHDC into potential sweeteners, hesperetin dihydrochalcone-7-O-glucoside (HDC-G) and hesperetin dihydrochalcone (HDC). The biohydrogenation was further combined with whole-cell hydrolysis to achieve a one-pot two-step biosynthesis, utilizing yeast to hydrogenate C═C in the structure, while Aspergillus niger cells hydrolyze glycosides. The conversion of NHDC and the proportion of hydrolysis products could be controlled by adjusting the catalysts, the components of the reaction system, and the addition of glucose. Furthermore, yeast-mediated biotransformation demonstrated superior reaction stability and enhanced safety and employed more cost-effective catalysts compared to the traditional chemical hydrogenation of NHDC synthesis. This research not only provides a new route for NHDC production but also offers a safe and flexible one-pot cascade biosynthetic platform for the production of high-value compounds from citrus processing wastes.

Study of high-pressure thermophysical properties of orthocarbonate Sr3CO5 using deep learning molecular dynamics simulations.

The exploration of the physical attributes of the recently discovered orthocarbonate Sr3CO5 is significant for comprehending the carbon cycle and storage mechanisms within the Earth's interior. In this study, first-principles calculations are initially used to examine the structural phase transitions of Sr3CO5 polymorphs within the range of lower mantle pressures. The results suggest that Sr3CO5 with the Cmcm phase exhibits a minimal enthalpy between 8.3 and 30.3 GPa. As the pressure exceeds 30.3 GPa, the Cmcm phase undergoes a transition to the I4/mcm phase, while the experimentally observed Pnma phase remains metastable under our studied pressure. Furthermore, the structural data of SrO, SrCO3, and Sr3CO5 polymorphs are utilized to develop a deep learning potential model suitable for the Sr-C-O system, and the pressure-volume relationship and elastic constants calculated using the potential model are in line with the available results. Subsequently, the elastic properties of Cmcm and I4/mcm phases in Sr3CO5 at high temperature and pressure are calculated using the molecular dynamics method. The results indicate that the I4/mcm phase exhibits higher temperature sensitivity in terms of elastic moduli and wave velocities compared to the Cmcm phase. Finally, the thermodynamic properties of the Cmcm and I4/mcm phases are predicted in the range of 0-2000 K and 10-120 GPa, revealing that the heat capacity and bulk thermal expansion coefficient of both phases increase with temperature, with the constant volume heat capacity gradually approaching the Dulong-Petit limit as the temperature rises.

The Ponto-Geniculo-Occipital (PGO) Waves in Dreaming: An Overview.

Rapid eye movement (REM) sleep is the main sleep correlate of dreaming. Ponto-geniculo-occipital (PGO) waves are a signature of REM sleep. They represent the physiological mechanism of REM sleep that specifically limits the processing of external information. PGO waves look just like a message sent from the pons to the lateral geniculate nucleus of the visual thalamus, the occipital cortex, and other areas of the brain. The dedicated visual pathway of PGO waves can be interpreted by the brain as visual information, leading to the visual hallucinosis of dreams. PGO waves are considered to be both a reflection of REM sleep brain activity and causal to dreams due to their stimulation of the cortex. In this review, we summarize the role of PGO waves in potential neural circuits of two major theories, i.e., (1) dreams are generated by the activation of neural activity in the brainstem; (2) PGO waves signaling to the cortex. In addition, the potential physiological functions during REM sleep dreams, such as memory consolidation, unlearning, and brain development and plasticity and mood regulation, are discussed. It is hoped that our review will support and encourage research into the phenomenon of human PGO waves and their possible functions in dreaming.

T cell receptor ß repertoires in patients with COVID-19 reveal disease severity signatures.

Background: The immune responses to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are crucial in maintaining a delicate balance between protective effects and harmful pathological reactions that drive the progression of coronavirus disease 2019 (COVID-19). T cells play a significant role in adaptive antiviral immune responses, making it valuable to investigate the heterogeneity and diversity of SARS-CoV-2-specific T cell responses in COVID-19 patients with varying disease severity. Methods: In this study, we employed high-throughput T cell receptor (TCR) ß repertoire sequencing to analyze TCR profiles in the peripheral blood of 192 patients with COVID-19, including those with moderate, severe, or critical symptoms, and compared them with 81 healthy controls. We specifically focused on SARS-CoV-2-associated TCR clonotypes. Results: We observed a decrease in the diversity of TCR clonotypes in COVID-19 patients compared to healthy controls. However, the overall abundance of dominant clones increased with disease severity. Additionally, we identified significant differences in the genomic rearrangement of variable (V), joining (J), and VJ pairings between the patient groups. Furthermore, the SARS-CoV-2-associated TCRs we identified enabled accurate differentiation between COVID-19 patients and healthy controls (AUC > 0.98) and distinguished those with moderate symptoms from those with more severe forms of the disease (AUC > 0.8). These findings suggest that TCR repertoires can serve as informative biomarkers for monitoring COVID-19 progression. Conclusions: Our study provides valuable insights into TCR repertoire signatures that can be utilized to assess host immunity to COVID-19. These findings have important implications for the use of TCR ß repertoires in monitoring disease development and indicating disease severity.

Time in range as a useful marker for evaluating retinal functional changes in diabetic retinopathy patients.

AIM: To elucidate the relationship between macular sensitivity and time in range (TIR) obtained from continuous glucose monitoring (CGM) measures in diabetic patients with or without diabetic retinopathy (DR). METHODS: This was a cross-sectional study including 100 eyes of non-DR patients and 60 eyes of DR patients. An advanced microperimetry was used to quantitate the retinal mean sensitivity (MS) and fixation stability in central macula. TIR of 3.9-10.0 mmol/L was evaluated with CGM. Pearson coefficient analysis and multiple linear regression analysis were used to assess the correlation between TIR and retinal sensitivity. RESULTS: In a comparison of non-DR patients, significant differences (P<0.05) were found in HbA1c, TIR, coefficient of variation (CV), standard deviation of blood glucose (SDBG) and mean amplitude of glucose excursion (MAGE) values in DR patients. Besides, those DR patients had significantly poor best-corrected visual acuity (BCVA, logMAR, P=0.001). In terms of microperimetry parameters, retinal mean sensitivity (MS) and the percentages of fixation points located within 2° and 4° diameter circles were significantly decreased in the DR group (P<0.001, P<0.001, P=0.02, respectively). The bivariate contour ellipse area (BCEA) encompassing 68.2%, 95.4%, 99.6% of fixation points were all significantly increased in the DR group (P=0.01, P=0.006, P=0.01, respectively). Correlation analysis showed that MS were significantly correlated with HbA1c (P=0.01). TIR was positively correlated with MS (r=0.23, P=0.01). SDBG was negatively correlated with MS (r=-0.24, P=0.01) but there was no correlation between CV and MAGE with MS (P>0.05). A multivariable linear regression analysis was performed to prove that TIR and SDBG were both independent risk factors for MS reduction in the DR group. CONCLUSION: TIR is correlated with retinal MS reduction in DR patients, suggesting a useful option for evaluating DR progression.

A G-triplex and G-quadruplex concatemer-enhanced fluorescence probe coupled with hybridization chain reaction for ultrasensitive aptasensing of ochratoxin A.

Ochratoxin A (OTA), a typical mycotoxin contaminant found in various agricultural products and foods, poses a serious threat to human health. In this study, an aptasensor based on a novel fluorescence probe comprising a G-rich DNA sequence (G43) and thioflavin T (ThT) was designed via hybridization chain reaction (HCR) for the ultrasensitive detection of OTA. G43 is a concatemer of G-quadruplex and G-triplex (a G-quadruplex-like structure with one G-quartet removed), which can drastically enhance the fluorescence intensity of ThT. For this strategy to work, the OTA aptamer is pro-locked in a hairpin structure, denoted "hairpin-locked aptamer" (HL-Apt). OTA binds to HL-Apt, opens the hairpin structure, releases the trigger sequence, and initiates the HCR reaction to form a long DNA duplex and numerous side chains. The side chains combine entirely with the complementary DNA and liberate the pro-locked G43 DNA, dramatically enhancing the intensity of the ThT fluorescence signal. The fluorescence intensity correlates linearly with the OTA concentration between 0.02 and 2.00 ng mL-1, and the method has a detection limit of 0.008 ng mL-1. The developed aptasensor was used to detect OTA in foodstuffs with satisfactory results.

Realist evaluation of a transdisciplinary mealtime management service for autistic children.

LAY ABSTRACT: Mealtimes and eating can be difficult for autistic children. A service where different professions work together is required to address the varied and complex mealtime difficulties of autistic children. Little is known about what is needed for such services to be effective. We interviewed six caregivers of autistic children who were engaged in a mealtime service and 10 therapists who are involved in delivering the service to understand their perspectives on the factors that were driving the effectiveness of the mealtime service. We found that different health professionals from different disciplines working together, focusing on adapting intervention to the child and family and managing expectations of the caregiver were important in contributing to outcomes of the mealtime service. The findings of this study can be used to inform the development of more effective interventions and services to support the well-being and development of autistic children.

Reliability and validity of the Chinese version of adverse childhood experiences international questionnaire in parents of preschool children / 北京大学学报(医学版)

OBJECTIVE@#To test the reliability and validity of the Chinese version of adverse childhood experiences international questionnaire (ACE-IQ) in Chinese parents of preschool children.@*METHODS@#The parents of preschool children in 6 kindergartens in Tongzhou District of Beijing were selected by stratified random cluster sampling, and the Chinese version of ACE-IQ after translation and adaptation was used for survey online. The collected data were randomly divided into two parts. One part of the data (n=602) was used for exploratory factor analysis (EFA), to screen items and evaluate structural validity, and then form the final Chinese version of ACE-IQ. The other part of the data (n=700) was used for confirmatory factor analysis (CFA), criterion validity analysis and reliability analysis. At the same time, experts investigation method was used to evaluate the content validity of the final Chinese version of ACE-IQ.@*RESULTS@#After deleting four items of collective violence, the Chinese version of ACE-IQ with twenty-five items indicated good structural, criterion and content validity. Analysis results showed that the Chinese version of ACE-IQ presented a seven-factor model dimension, namely emotional neglect, physical neglect, family dysfunction, family violence, emotional and physical abuse, sexual abuse and violence outside the home, and the total score of the binary version of ACE-IQ Chinese version was positively correlated with the total score of childhood trauma questionaire-28 item short form (CTQ-SF, r=0.354, P < 0.001) and the center for epidemiological studies depression scale (CES-D, r=0.313, P < 0.001) respectively. Results from five experts showed that the item-level content validity index (I-CVI) of 25 items was between 0.80 and 1.00, and the average of all I-CVIs on the scale (S-CVI/Ave) of the scale was 0.984. At the same time, the internal consistency (Cronbach's α coefficient) of the whole scale was 0.818, and the split-half reliability (Spearman-Brown coefficient) was 0.621, which demonstrated good reliability.@*CONCLUSION@#This study has formed a Chinese version of ACE-IQ with 25 items and 7 dimensions, which has good reliability and validity among the parents of preschool children in China. It can be used as an evaluation instrument for measuring the minimum threshold of the adverse childhood experiences in the parents of preschool children in the cultural background of China.

A novel mutation in RS1 and clinical manifestations in a Chinese twin family with congenital retinoschisis.

Purpose: We aim to analyze the clinical and genetic features in a Chinese family with congenital retinoschisis by whole-exome sequencing and comprehensive clinical examination. Methods: Six members were recruited from a Chinese family. Three of them were diagnosed as congenital retinoschisis, including two twin siblings. All subjects received a full eye examination. Whole-exome sequencing (WES) and Sanger sequencing were performed on two twin probands and all participants, respectively. Results: A novel splice site mutation RS1.c.53-1G>A was identified in a Chinese congenital retinoschisis family. The mean onset age was 16.7 ± 2.4 years old. The average BCVA in patients was 0.37 ± 0.05. A typical spoke-wheel pattern was observed in all affected eyes. OCT examination results showed fovea schisis and schisis cavities were located in the inner nuclear layer in 100% eyes (6/6). ERG b/a ratio was decreased markedly, but was still more than 1 in the four eyes that were available. Conclusion: The present study discovered a new pathogenic splice cite variant of RS1 in congenital retinoschisis, which expands the mutational spectrum. In contrast to previous research, the phenotype of patients with the same mutation within one family was highly similar. Early molecular testing is crucial for early diagnosis, clinical management, and genetic counseling of patients with congenital retinoschisis.

Stereotaxic atlas of the infant rat brain at postnatal days 7-13.

Recently, researchers have paid progressively more attention to the study of neural development in infant rats. However, due to the lack of complete intracerebral localization information, such as clear nuclear cluster boundaries, identified main brain structures, and reliable stereotaxic coordinates, it is difficult and restricted to apply technical neuroscience to infant rat's brain. The present study was undertaken to refine the atlas of infant rats. As such, we established a stereotaxic atlas of the infant rat's brain at postnatal days 7-13. Furthermore, dye calibration surgery was performed in P7-P13 infant rats by injecting Methylene blue, and sections were incubated in Nissl solutions. From the panoramic images of the brain sections, atlases were made. Our article has provided the appearance and measurements of P7-P13 Sprague-Dawley rat pups. Whereas the atlas contains a series of about 530 coronal brain section images from olfactory bulbs to the brainstem, a list of abbreviations of the main brain structures, and reliable stereotaxic coordinates, which were demonstrated by vertical and oblique injections with fluorescent dye DiI. The present findings demonstrated that our study of P7-P13 atlases has reasonable nucleus boundaries and accurate and good repeatability of stereotaxic coordinates, which can make up for the shortage of postnatal rat brain atlas currently in the field.

Comparative transcriptomics to reveal the mechanism of enhanced catalytic activities of Aspergillus niger whole-cells cultured with different inducers in hydrolysis of citrus flavonoids.

A new Aspergillus niger whole-cell catalyst was cultured for the cascade hydrolysis of hesperidin (HES) to produce high-value hesperetin-7-O-glucoside (HG) and hesperetin with high conversion (above 90%). Moreover, the inducers used were shown to be useful for cell growth and to induce cells to produce specific enzymes. Remarkably, the type of inducers determined whether the cells can hydrolyze HES. The product composition was also controllable by adjusting different inducers. Transcriptome analysis suggested that both naringin-vs-blank group and saccharose-vs-blank group had obviously difference in gene expression. The naringin-vs-blank group was mainly up-regulated differentially expressed genes (DEGs), while saccharose-vs-blank group was mainly down-regulated DEGs. The Gene Ontology (GO) analysis showed that whether naringin or saccharose was added as an inducer would greatly affect the catalytic activity of cells. Furthermore, 3 genes related to rhamnosidase, 14 genes related to glucosidase and 5 genes related to hydrolase activity were found. These genes were not only involved in rhamnosidase and glucosidase activities, but also spliceosome and the sucrose and starch metabolic pathways. The quantitative real-time polymerase chain reaction (qRT-PCR) analysis indicated that the results of transcriptome sequencing were reliable. This study gave a new approach to hydrolyze HES, and new perspectives to understand the mechanisms associated with the hydrolysis of whole-cell catalyst.

Effects of two polysaccharides from Lepidium meyenii (maca) on intestinal immunity and inflammation in vitro.

In our previous studies, two polysaccharides (MC-1 and MC-2) were identified in the roots of maca (Lepidium meyenii). In this study, the effects of these two polysaccharides on intestinal immunity and inflammation were assessed using intestinal epithelial cells, i.e., Caco-2 cells. The levels of cytokines and tight junction proteins were measured using ELISA and qPCR, respectively. The results showed that MC-1 and MC-2 were difficult to be absorbed in the Caco-2 cell monolayer, but promoted the secretion of IL-8, IL-10, IL-12, and INF-γ in the Caco-2 cells, and the secretion of TNF-α, IL-6, and NO in macrophages (RAW264.7 cells) via the Caco-2 cell monolayer. Additionally, both polysaccharides inhibited damage induced by lipopolysaccharides to the densification of the Caco-2 monolayer membrane by regulating the expressions of TLR4, ZO-1, and occludin. Furthermore, the secretion of inflammatory factors such as TNF-α, IL-8, and INF-γ was inhibited, and the secretion of the anti-inflammatory factor, IL-10, increased. The results indicated that MC-1 and MC-2 can activate intestinal immunity and alleviate intestinal inflammation in vitro.

In vitro absorption and lipid-lowering activity of baicalin esters synthesized by whole-cell catalyzed esterification.

Baicalin, a phenolic glycoside with good lipid-lowering activity, has poor intestinal absorption due to low lipophilicity. In this study, six ester derivatives of baicalin, named BECn (n = 2, 3, 4, 6, 8, and 10) based on their fatty chain lengths, were synthesized by whole-cell catalyzed esterification to improve lipophilicity, and the intestinal absorption and lipid-lowering activity of the synthesized esters were investigated using cell models in vitro. BEC2, BEC3, and BEC4 exhibited higher Papp values than baicalin in Caco-2 cell monolayers. The lipid-lowering activity of the three esters was stronger than baicalin in the cell models of hepatic steatosis, adipocytes and foam macrophages, and was attributed to their higher intracellular accumulation and stronger direct activation of the carnitine palmitoyltransferase 1A. Moreover, these esters were easily hydrolyzed by carboxylesterase and were unstable at pH 7.4, which significantly weakened their absorption and lipid-lowering activity. This study laid the foundation for industrial production and practical application of BAI esters.

Analysis of the etiology and clinical characteristics of infants with moderate-severe visual impairment / 国际眼科杂志(Guoji Yanke Zazhi)

AIM: To explore the etiology classification and clinical characteristics of infants with moderate-severe visual impairment aged 0-2 years old, and preliminarily formulate a set of process for grass-roots health-care institutions to carry out the screening and management of children visual impairment.METHODS: There were 245 cases of children aged 0-2 years with moderate-severe visual impairment who were admitted to the Children Eye Care Specialist Clinic in Nanjing Maternal and Child Health Hospital from January 2009 to December 2020 were retrospectively analyzed. A complete profile of visual development was established, including age, sex, medical history, vision, eye position and movement, anterior segment examination, fundus examination, refractive examination under cycloplegia with 1% atropine ophthalmic gel, if necessary, some special eye examinations such as fundus photography, eye A/B ultrasound and visual electrophysiology were received.RESULTS: The average visit age of 245 cases of infants was 1.82±0.79 years, including refraction error of 128 cases(52.2%), among them, 100 cases(40.8%)were high refraction error; 79 cases(32.2%)were eye diseases, most of which were congenital cataract(33 cases); and 38 cases(15.5%)were cerebral visual impairment(CVI)(15.5%).CONCLUSION: It is necessary to proceed classified managements according to the etiology and clinical characteristics of infant visual impairment to find early and diagnose and treat multidisciplinary,including drawing up screening plans for remediable eye diseases, carrying out necessary refractive correction and training children to use residual visual function.

Efficient Enzymatic Synthesis of Lipophilic Phenolic Glycoside Azelaic Acid Esters and Their Depigmenting Activity.

In this paper, an enzymatic route for synthesizing phenolic glycoside azelaic acid esters was successfully set up via lipase-catalyzed esterification and transesterification. Among the lipases tested, Candida antarctica lipase B (Novozyme 435) showed the highest activity in catalyzing esterification and Thermomyces lanuginosus (Lipozyme TLIM) gave the highest substrate conversion in catalyzing transesterification for the synthesis of ester. The addition of 4A molecular sieves into the reaction system is found to be an effective method for in situ absorption of the byproduct water and methanol, with which the substrate conversions of the enzymatic esterification and transesterification were 98.7 and 95.1%, respectively. Also, the main product ratios in transesterification were above 99.0% with lipozyme TLIM as a catalyst because the hydrolysis reaction was hindered. The results of the physical and biological properties indicate that all esters had higher Clog p values than their parent compounds. Also, the esters showed higher intracellular tyrosinase inhibitory and depigmentating activities than phenolic glycosides, azelaic acid (AA), and their physical mixtures due to their higher membrane penetration and tyrosinase inhibitory effects. In particular, piceid 6″-O-azelaic acid ester (PIA) showed the strongest inhibitory effect against melanin production. Its inhibitory rate was 77.4% at a concentration of 0.25 mM, about 4.2 times higher than that of arbutin (18.5%).

Highly efficient whole-cell biosynthesis and cytotoxicity of esculin esters.

Esculin is a polyphenol with multiple bioactivities and poor lipophilicity. Therefore, a whole-cell catalytic strategy for esculin acylation was developed to improve its lipophilicity. A total of 12 strains were tested, among which Pseudomonas stutzeri exhibited the highest catalytic activity and mono-acylated regioselectivity. The conversion reached the highest level of 92.7 % at 24 h under the optimal conditions, when vinyl acetate was used as an acyl donor. The catalytic ability of P. stutzeri remained above 60 % after three cycles. Subsequently, five esculin esters with different lengths of fatty chains were synthesized and structurally identified. Of them, esculin-6'-O-octanoate, esculin-6'-O-laurate, and esculin-6'-O-myristate exhibited cytotoxicity on LO2 cells by inducing apoptosis and necrosis. The cytotoxicity of these three esters may attribute to their membrane-disrupting properties. This study provides a novel whole-cell biocatalytic strategy for the acylation of esculin and insight for application of esculin esters as a food additive or drug.

Debittering effect of partially purified proteases from soybean seedlings on soybean protein isolate hydrolysate produced by alcalase.

To explore the potential application of proteases from soybean seedlings in the debittering of soybean protein hydrolysates, soybean seeds were germinated from 1 to 10 days. It was found that the sixth day seedlings exhibited highest proteases activity (130 U/g). After partial purification, the activity of proteases (PSP) from the sixth day seedlings further increased to 2675 U/g. In addition, PSP exhibited maximum activity at 50 â„ƒ and pH 5.5, and mainly comprised of two proteins with the molecular weight of 64.57 and 25.12 kDa respectively. PSP could decrease the bitterness score of the soybean protein isolate hydrolysate (SPIH) produced by Alcalase 2.4L from 3.45 to 0 in 3 h. Meanwhile, the degree of hydrolysis of SPIH slightly increased from 11.87% to 15.61% without reducing the antioxidant activity. This study may provide a solution to the contradiction between removing the bitterness of soybean protein hydrolysates and maintaining the bioactivity.

Antityrosinase Mechanism and Antimelanogenic Effect of Arbutin Esters Synthesis Catalyzed by Whole-Cell Biocatalyst.

Tyrosinase is a key enzyme responsible for enzymatic browning of fruits and vegetables and skin disorders due to overproduction of melanin. Arbutin is an inhibitor of tyrosinase; however, its high polarity and weak transdermal absorption capacity limit its applications. In this paper, a green solvent system was developed to successfully synthesize arbutin esters with improved liposolubilities (Clog P values = 0.27-5.03). Among the obtained esters, arbutin undecenoate (AU) showed the strongest tyrosinase-inhibiting activity (15.6%), which was 9.0 times higher than that of arbutin. An enzyme kinetics study indicated that AU was a competitive inhibitor with reversible inhibition. The esters inhibited tyrosinase by making the secondary structure of tyrosinase looser and less stable; moreover, the interactions between tyrosinase and AU driven by metal interactions and hydrogen bonds also offered a mechanism for inhibition of AU on tyrosinase. In addition, AU (100 µM) reduced the melanin content of B16 mouse melanoma cells to 61.3% of the control group.