Engineering Yarrowia lipolytica for Enhanced Production of Arbutin

Determination of arbutin in vitro and in vivo by LC-MS/MS: Pre-clinical evaluation of natural product arbutin for its early medicinal properties

ETHNOPHARMACOLOGICAL RELEVANCE

Arbutin is a naturally occurring glucoside extracted from plants, known for its antioxidant and tyrosinase inhibiting properties. It is widely used in cosmetic and pharmaceutical industries. With in-depth study of arbutin, its application in disease treatment is expanding, presenting promising development prospects. However, reports on the metabolic stability, plasma protein binding rate, and pharmacokinetic properties of arbutin are scarce.

AIM OF THE STUDY

The aim of this study is to enrich the data of metabolic stability and pharmacokinetics of arbutin through the early pre-clinical evaluation, thereby providing some experimental basis for advancing arbutin into clinical research.

MATERIALS AND METHODS

We developed an efficient and rapid liquid chromatography-tandem mass spectrometry (LC-MS/MS) assay for determining arbutin in plasma. We investigated the metabolic and pharmacokinetic properties of arbutin through in vitro metabolism assay, cytochrome enzymes P450 (CYP450) inhibition studies, plasma protein binding rate analysis, Caco-2 cell permeability tests, and rat pharmacokinetics to understand its in vivo performance.

RESULTS

In vitro studies show that arbutin is stable, albeit with some species differences. It exhibits low plasma protein binding (35.35 ± 11.03% ∼ 40.25 ± 2.47%), low lipophilicity, low permeability, short half-life (0.42 ± 0.30 h) and high oral bioavailability (65 ± 11.6%). Arbutin is primarily found in the liver and kidneys and is eliminated in the urine. It does not significantly inhibit CYP450 up to 10 μM, suggesting a low potential for drug interactions. Futhermore, preliminary toxicological experiments indicate arbutin's safety, supporting its potential as a therapeutic agent.

CONCLUSION

This study provides a comprehensive analysis the drug metabolism and pharmacokinetics (DMPK) of arbutin, enriching our understanding of its metabolism stability and pharmacokinetics properties, It establishes a foundation for further structural optimization, pharmacological studies, and the clinical development of arbutin.

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.

Application of modern synthetic biology technology in aromatic amino acids and derived compounds biosynthesis

Aromatic amino acids (AAA) and derived compounds have enormous commercial value with extensive applications in the food, chemical and pharmaceutical fields. Microbial production of AAA and derived compounds is a promising prospect for its environmental friendliness and sustainability. However, low yield and production efficiency remain major challenges for realizing industrial production. With the advancement of synthetic biology, microbial production of AAA and derived compounds has been significantly facilitated. In this review, a comprehensive overview on the current progresses, challenges and corresponding solutions for AAA and derived compounds biosynthesis is provided. The most cutting-edge developments of synthetic biology technology in AAA and derived compounds biosynthesis, including CRISPR-based system, genetically encoded biosensors and synthetic genetic circuits, were highlighted. Finally, future prospects of modern strategies conducive to the biosynthesis of AAA and derived compounds are discussed. This review offers guidance on constructing microbial cell factory for aromatic compound using synthetic biology technology.

De novo biosynthesis of β-arbutin in Corynebacterium glutamicum via pathway engineering and process optimization

BACKGROUND

β-Arbutin, a hydroquinone glucoside found in pears, bearberry leaves, and various plants, exhibits antioxidant, anti-inflammatory, antimicrobial, and anticancer effects. β-Arbutin has wide applications in the pharmaceutical and cosmetic industries. However, the limited availability of high-performance strains limits the biobased production of β-arbutin.

RESULTS

This study established the β-arbutin biosynthetic pathway in C. glutamicum ATCC13032 by introducing codon-optimized ubiC, MNX1, and AS. Additionally, the production titer of β-arbutin was increased by further inactivation of csm and trpE to impede the competitive metabolic pathway. Further modification of the upstream metabolic pathway and supplementation of UDP-glucose resulted in the final engineered strain, C. glutamicum AR11, which achieved a β-arbutin production titer of 7.94 g/L in the optimized fermentation medium.

CONCLUSIONS

This study represents the first successful instance of de novo β-arbutin production in C. glutamicum, offering a chassis cell for β-arbutin biosynthesis.

Systems metabolic engineering of Escherichia coli for high-yield production of Para-hydroxybenzoic acid

Para-hydroxybenzoic acid (PHBA) is extensively used as an additive in the food and cosmetics industries, significantly enhancing product shelf life and stability. While microbial fermentation offers an environment-friendly and sustainable method for producing PHBA, the titer and productivity are limited due to product toxicity and complex metabolic flux distributions. Here, we initially redesigned a L-phenylalanine-producing Escherichia coli by employing rational metabolic engineering strategies, resulting in the production of PHBA reached the highest reported level of 14.17 g/L. Subsequently, a novel accelerated evolution system was devised comprising deaminase, the alpha subunit of RNA polymerase, an uracil-DNA glycosylase inhibitor, and the PHBA-responsive promoter PyhcN. This system enabled us to obtain a mutant strain exhibiting a 47% increase in the half-inhibitory concentration (IC50) for PHBA within 15 days. Finally, the evolved strain achieved a production of 21.35 g/L PHBA in a 5-L fermenter, with a yield of 0.19 g/g glucose and a productivity rate of 0.44 g/L/h. This engineered strain emerges as a promising candidate for industrial production of PHBA through an eco-friendly approach.

Enhancing Gastrodin Production in Yarrowia lipolytica by Metabolic Engineering

Gastrodin, 4-hydroxybenzyl alcohol-4-O-β-D-glucopyranoside, has been widely used in the treatment of neurogenic and cardiovascular diseases. Currently, gastrodin biosynthesis is being achieved in model microorganisms. However, the production levels are insufficient for industrial applications. In this study, we successfully engineered a Yarrowia lipolytica strain to overproduce gastrodin through metabolic engineering. Initially, the engineered strain expressing the heterologous gastrodin biosynthetic pathway, which comprises chorismate lyase, carboxylic acid reductase, phosphopantetheinyl transferase, endogenous alcohol dehydrogenases, and a UDP-glucosyltransferase, produced 1.05 g/L gastrodin from glucose in a shaking flask. Then, the production was further enhanced to 6.68 g/L with a productivity of 2.23 g/L/day by overexpressing the key node DAHP synthases of the shikimate pathway and alleviating the native tryptophan and phenylalanine biosynthetic pathways. Finally, the best strain, Gd07, produced 13.22 g/L gastrodin in a 5 L fermenter. This represents the highest reported production of gastrodin in an engineered microorganism to date, marking the first successful de novo production of gastrodin using Y. lipolytica.

Metabolic Engineering of Pseudomonas putida KT2440 for De Novo Biosynthesis of Vanillic Acid

Vanillic acid (VA), as a plant-derived phenolic acid compound, has widespread applications and good market prospects. However, the traditional production process cannot meet market demand. In this study, Pseudomonas putida KT2440 was used for de novo biosynthesis of VA. Multiple metabolic engineering strategies were applied to construct these P. putida-based cell factories, including the introduction of a Hs-OMTopt, engineering the cofactor S-adenosylmethionine supply pathway through the overexpression of metX and metH, reforming solubility of Hs-OMTopt, increasing a second copy of Hs-OMTopt, and the optimization of the fermentation medium. The resulting strain, XCS17, de novo biosynthesized 5.4 g/L VA from glucose in a fed-batch fermentation system; this is the highest VA production titer reported up to recently. This study showed that P. putida KT2440 is a robust platform for achieving the effective production of phenolic acids.

Sustainable bio-manufacturing of D-arabitol through combinatorial engineering of Zygosaccharomyces rouxii, bioprocess optimization and downstream separation

Biosynthesis of D-arabitol, a high value-added platform chemical, from renewable carbon sources provides a sustainable and eco-friendly alternative to the chemical industry. Here, a robust brewing yeast, Zygosaccharomyces rouxii, capable of naturally producing D-arabitol was rewired through genome sequencing-based metabolic engineering. The recombinant Z. rouxii obtained by reinforcing the native D-xylulose pathway, improving reductive power of the rate-limiting step, and inhibiting the shunt pathway, produced 73.61% higher D-arabitol than the parent strain. Subsequently, optimization of the fermentation medium composition for the engineered strain provided 137.36 g/L D-arabitol, with a productivity of 0.64 g/L/h in a fed-batch experiment. Finally, the downstream separation of D-arabitol from the complex fermentation broth using an ethanol precipitation method provided a purity of 96.53%. This study highlights the importance of D-xylulose pathway modification in D-arabitol biosynthesis, and pave a complete and efficient way for the sustainable manufacturing of this value-added compound from biosynthesis to preparation.

Biosynthetic pathway of prescription bergenin from Bergenia purpurascens and Ardisia japonica

Bergenin is a typical carbon glycoside and the primary active ingredient in antitussive drugs widely prescribed for central cough inhibition in China. The bergenin extraction industry relies on the medicinal plant species Bergenia purpurascens and Ardisia japonica as their resources. However, the bergenin biosynthetic pathway in plants remains elusive. In this study, we functionally characterized a shikimate dehydrogenase (SDH), two O-methyltransferases (OMTs), and a C-glycosyltransferase (CGT) involved in bergenin synthesis through bioinformatics analysis, heterologous expression, and enzymatic characterization. We found that BpSDH2 catalyzes the two-step dehydrogenation process of shikimic acid to form gallic acid (GA). BpOMT1 and AjOMT1 facilitate the methylation reaction at the 4-OH position of GA, resulting in the formation of 4-O-methyl gallic acid (4-O-Me-GA). AjCGT1 transfers a glucose moiety to C-2 to generate 2-Glucosyl-4-O-methyl gallic acid (2-Glucosyl-4-O-Me-GA). Bergenin production ultimately occurs in acidic conditions or via dehydration catalyzed by plant dehydratases following a ring-closure reaction. This study for the first time uncovered the biosynthetic pathway of bergenin, paving the way to rational production of bergenin in cell factories via synthetic biology strategies.

High-yield production of β-arbutin by identifying and eliminating byproducts formation

β-Arbutin is a plant-derived glycoside and widely used in cosmetic and pharmaceutical industries because of its safe and effective skin-lightening property as well as anti-oxidant, anti-microbial, and anti-inflammatory activities. In recent years, microbial fermentation has become a highly promising method for the production of β-arbutin. However, this method suffers from low titer and low yield, which has become the bottleneck for its widely industrial application. In this study, we used β-arbutin to demonstrate methods for improving yields for industrial-scale production in Escherichia coli. First, the supply of precursors phosphoenolpyruvate and uridine diphosphate glucose was improved, leading to a 4.6-fold increase in β-arbutin production in shaking flasks. The engineered strain produced 36.12 g/L β-arbutin with a yield of 0.11 g/g glucose in a 3-L bioreactor. Next, based on the substrate and product's structural similarity, an endogenous O-acetyltransferase was identified as responsible for 6-O-acetylarbutin formation for the first time. Eliminating the formation of byproducts, including 6-O-acetylarbutin, tyrosine, and acetate, resulted in an engineered strain producing 43.79 g/L β-arbutin with a yield of 0.22 g/g glucose in fed-batch fermentation. Thus, the yield increased twofold by eliminating byproducts formation. To the best of our knowledge, this is the highest titer and yield of β-arbutin ever reported, paving the way for the industrial production of β-arbutin. This study demonstrated a systematic strategy to alleviate undesirable byproduct accumulation and improve the titer and yield of target products. KEY POINTS: • A systematic strategy to improve titer and yield was showed • Genes responsible for 6-O-acetylarbutin formation were firstly identified • 43.79 g/L β-arbutin was produced in bioreactor, which is the highest titer so far.

Cinnamic acid and p-coumaric acid are metabolized to 4-hydroxybenzoic acid by Yarrowia lipolytica

Yarrowia lipolytica has been explored as a potential production host for flavonoid synthesis due to its high tolerance to aromatic acids and ability to supply malonyl-CoA. However, little is known about its ability to consume the precursors cinnamic and p-coumaric acid. In this study, we demonstrate that Y. lipolytica can consume these precursors through multiple pathways that are partially dependent on the cultivation medium. By monitoring the aromatic acid concentrations over time, we found that cinnamic acid is converted to p-coumaric acid. We identified potential proteins with a trans-cinnamate 4-monooxygenase activity in Y. lipolytica and constructed a collection of 15 knock-out strains to identify the genes responsible for the reaction. We identified YALI1_B28430g as the gene encoding for a protein that converts cinnamic acid to p-coumaric acid (designated as TCM1). By comparing different media compositions we found that complex media components (casamino acids and yeast extract) induce this pathway. Additionally, we discover the conversion of p-coumaric acid to 4-hydroxybenzoic acid. Our findings provide new insight into the metabolic capabilities of Y. lipolytica and hold great potential for the future development of improved strains for flavonoid production.

Highly Efficient Biosynthesis of Protocatechuic Acid via Recombinant Pseudomonas putida KT2440

Owing to their physiological activities, plant-derived phenolic acids, such as protocatechuic acid (PCA), have extensive applications and market prospects. However, traditional production processes present numerous challenges and cannot meet increasing market demands. Hence, we aimed to biosynthesize PCA by constructing an efficient microbial factory via metabolic engineering of Pseudomonas putida KT2440. Glucose metabolism was engineered by deleting the genes for gluconate 2-dehydrogenase to enhance PCA biosynthesis. To increase the biosynthetic metabolic flux, one extra copy of the genes aroG^opt, aroQ, and aroB was inserted into the genome. The resultant strain, KGVA04, produced 7.2 g/L PCA. By inserting the degradation tags GSD and DAS to decrease the amount of shikimate dehydrogenase, PCA biosynthesis was increased to 13.2 g/L in shake-flask fermentation and 38.8 g/L in fed-batch fermentation. To the best of our knowledge, this was the first use of degradation tags to adjust the amount of a key enzyme at the protein level in P. putida KT2440, evidencing the remarkable potential of this method for naturally producing phenolic acids.

Metabolic engineering for the high-yield production of polydatin in Yarrowia lipolytica

Polydatin, a glycosylated derivative of resveratrol, has better structural stability and biological activity than resveratrol. Polydatin is the extract of Polygonum cuspidatum, which has various pharmacological effects. Owing to its Crabtree-negative characteristics and high supply of malonyl-CoA, Yarrowia lipolytica was selected to produce polydatin. Initially, the resveratrol synthetic pathway was established in Y. lipolytica. By enhancing the shikimate pathway flow, redirecting carbon metabolism, and increasing the copies of key genes, a resveratrol yield of 487.77 mg/L was obtained. In addition, by blocking the degradation of polydatin, its accumulation was successfully achieved. Finally, by optimizing the glucose concentration and supplementing with two nutritional marker genes, a high polydatin yield of 6.88 g/L was obtained in Y. lipolytica, which is the highest titer of polydatin produced in a microbial host to date. Overall, this study demonstrates that Y. lipolytica has great potential for glycoside synthesis.

Bio-Based Valorization of Lignin-Derived Phenolic Compounds: A Review

Lignins are the most abundant biopolymers that consist of aromatic units. Lignins are obtained by fractionation of lignocellulose in the form of "technical lignins". The depolymerization (conversion) of lignin and the treatment of depolymerized lignin are challenging processes due to the complexity and resistance of lignins. Progress toward mild work-up of lignins has been discussed in numerous reviews. The next step in the valorization of lignin is the conversion of lignin-based monomers, which are limited in number, into a wider range of bulk and fine chemicals. These reactions may need chemicals, catalysts, solvents, or energy from fossil resources. This is counterintuitive to green, sustainable chemistry. Therefore, in this review, we focus on biocatalyzed reactions of lignin monomers, e.g., vanillin, vanillic acid, syringaldehyde, guaiacols, (iso)eugenol, ferulic acid, p-coumaric acid, and alkylphenols. For each monomer, its production from lignin or lignocellulose is summarized, and, mainly, its biotransformations that provide useful chemicals are discussed. The technological maturity of these processes is characterized based on, e.g., scale, volumetric productivities, or isolated yields. The biocatalyzed reactions are compared with their chemically catalyzed counterparts if the latter are available.

Engineered production of bioactive polyphenolic O-glycosides

Polyphenolic compounds (such as quercetin and resveratrol) possess potential medicinal values due to their various bioactivities, but poor water solubility hinders their health benefits to humankind. Glycosylation is a well-known post-modification method to biosynthesize natural product glycosides with improved hydrophilicity. Glycosylation has profound effects on decreasing toxicity, increasing bioavailability and stability, together with changing bioactivity of polyphenolic compounds. Therefore, polyphenolic glycosides can be used as food additives, therapeutics, and nutraceuticals. Engineered biosynthesis provides an environmentally friendly and cost-effective approach to generate polyphenolic glycosides through the use of various glycosyltransferases (GTs) and sugar biosynthetic enzymes. GTs transfer the sugar moieties from nucleotide-activated diphosphate sugar (NDP-sugar) donors to sugar acceptors such as polyphenolic compounds. In this review, we systematically review and summarize the representative polyphenolic O-glycosides with various bioactivities and their engineered biosynthesis in microbes with different biotechnological strategies. We also review the major routes towards NDP-sugar formation in microbes, which is significant for producing unusual or novel glycosides. Finally, we discuss the trends in NDP-sugar based glycosylation research to promote the development of prodrugs that positively impact human health and wellness.

One-pot biosynthesis of gastrodin using UDP-glycosyltransferase itUGT2 with an in situ UDP-glucose recycling system

Gastrodin, the major effective ingredient in Tianma (Gastrodia elata), is a p-hydroxybenzoic acid derivative with various activities. Gastrodin has been widely investigated for food and medical applications. The last biosynthetic step for gastrodin is UDP-glycosyltransferase (UGT)-mediated glycosylation with UDP-glucose (UDPG) as glycosyl donor. In this study, we performed a one-pot reaction both in vitro and in vivo to synthesize gastrodin from p-hydroxybenzyl alcohol (pHBA) by coupling UDP-glucosyltransferase from Indigofera tinctoria (itUGT2) to sucrose synthase from Glycine max (GmSuSy) for regeneration of UDPG. The in vitro results showed that itUGT2 transferred a glucosyl group to pHBA to generate gastrodin. After 37 UDPG regeneration cycles with 2.5% (molar ratio) UDP, the pHBA conversion reached 93% at 8 h. Furthermore, a recombinant strain with itUGT2 and GmSuSy genes was constructed. Through optimizing the incubation conditions, a 95% pHBA conversion rate (220 mg/L gastrodin titer) was achieved in vivo without addition of UDPG, which was 2.6-fold higher than that without GmSuSy. This in situ system for gastrodin biosynthesis provides a highly efficient strategy for both in vitro gastrodin synthesis and in vivo biosynthesis of gastrodin in E. coli with UDPG regeneration.

Establishing a growth-coupled mechanism for high-yield production of β-arbutin from glycerol in Escherichia coli

Biodiesel production has increased significantly in recent years, leading to an increase in the production of crude glycerol. In this study, a novel growth-coupled erythrose 4-phosphate (E4P) formation strategy that can be used to produce high levels of β-arbutin using engineered Escherichia coli and glycerol as the carbon source was developed. In the strategy, E4P formation was coupled with cell growth, and a growth-driving force made the E4P formation efficient. By applying this strategy, efficient microbial synthesis of β-arbutin was achieved, with 7.91 g/L β-arbutin produced in shaking flask, and 28.1 g/L produced in a fed batch fermentation with a yield of 0.20 g/g glycerol and a productivity of 0.39 g/L/h. This is the highest β-arbutin production through microbial fermentation ever reported to date. This study may have significant implications in the large-scale production of β-arbutin as well as other aromatic compounds of importance.

Arbutin improves gut development and serum lipids via Lactobacillus intestinalis

Arbutin has been widely studied in whitening, anti-inflammatory, and antioxidant. However, the interaction between arbutin and intestinal microbes has been rarely studied. Thus, mice were treated with arbutin concentrations of 0, 0.1, 0.2, 0.4, and 1 mg/ml. We found that arbutin promoted gut development such as villus length, villus areas, and villus length/crypt depth (L/D). Total cholesterol (TC), high-density lipoprotein (HDL), and low-density lipoprotein (LDL) were significantly reduced by low concentrations of arbutin. Importantly, we analyzed the microbial composition in the control and 0.4 mg/ml arbutin group and found that the abundance of Lactobacillus intestinalis (L. intestinalis) was highest and enhanced in arbutin. Further, mice were fed with oral antibiotics and antibiotics + 0.4 mg/ml arbutin and then we transplanted fecal microbes from oral 0.4 mg/ml arbutin mice to mice pretreated with antibiotics. Our results showed that arbutin improves gut development, such as villus width, villus length, L/D, and villus areas. In addition, L. intestinalis monocolonization was carried out after a week of oral antibiotics and increased villus length, crypt depth, and villus areas. Finally, in vitro arbutin and L. intestinalis co-culture showed that arbutin promoted the growth and proliferation of L. intestinalis. Taken together, our results suggest that arbutin improves gut development and health of L. intestinalis. Future studies are needed to explore the function and mechanism of L. intestinalis affecting gut development.

Recent Progress on Feasible Strategies for Arbutin Production

Arbutin is a hydroquinone glucoside and a natural product present in various plants. Arbutin potently inhibits melanin formation. This property has been exploited in whitening cosmetics and pharmaceuticals. Arbutin production relies mainly on chemical synthesis. The multi-step and complicated process can compromise product purity. With the increasing awareness of sustainable development, the current research direction prioritizes environment-friendly, biobased arbutin production. In this review, current strategies for arbutin production are critically reviewed, with a focus on plant extraction, chemical synthesis, biotransformation, and microbial fermentation. Furthermore, the bottlenecks and perspectives for future direction on arbutin biosynthesis are discussed.

Antioxidant Activity of Natural Hydroquinones

Secondary metabolites derived from hydroquinone are quite rare in nature despite the original simplicity of its structure, especially when compared to other derivatives with which it shares biosynthetic pathways. However, its presence in a prenylated form is somewhat relevant, especially in the marine environment, where it is found in different algae and invertebrates. Sometimes, more complex molecules have also been identified, as in the case of polycyclic diterpenes, such as those possessing an abietane skeleton. In every case, the presence of the dihydroxy group in the para position gives them antioxidant capacity, through its transformation into para-quinones.This review focuses on natural hydroquinones with antioxidant properties referenced in the last fifteen years. This activity, which has been generally demonstrated in vitro, should lead to relevant pharmacological properties, through its interaction with enzymes, transcription factors and other proteins, which may be particularly relevant for the prevention of degenerative diseases of the central nervous system, or also in cancer and metabolic or immune diseases. As a conclusion, this review has updated the pharmacological potential of hydroquinone derivatives, despite the fact that only a small number of molecules are known as active principles in established medicinal plants. The highlights of the present review are as follows: (a) sesquiterpenoid zonarol and analogs, whose activity is based on the stimulation of the Nrf2/ARE pathway, have a neuroprotective effect; (b) the research on pestalotioquinol and analogs (aromatic ene-ynes) in the pharmacology of atherosclerosis is of great value, due to their agonistic interaction with LXRα; and (c) prenylhydroquinones with a selective effect on tyrosine nitration or protein carbonylation may be of interest in the control of post-translational protein modifications, which usually appear in chronic inflammatory diseases.

Discovery and Characterization of Phenolic Compounds in Bearberry (Arctostaphylos uva-ursi) Leaves Using Liquid Chromatography-Ion Mobility-High-Resolution Mass Spectrometry

The characterization and quantification of phenolic compounds in bearberry leaves were performed using hyphenated ion mobility spectroscopy (IMS) and a quadrupole time-of-flight mass spectrometer. A higher identification confidence level was obtained by comparing the measured collision cross section (^TWCCS_N2) with predicted values using a machine learning algorithm. A total of 88 compounds were identified, including 14 arbutin derivatives, 33 hydrolyzable tannins, 6 flavanols, 26 flavonols, 9 saccharide derivatives, and glycosidic compounds. Those most reliably reproduced in all samples were quantified against respective standards. Arbutin (47-107 mg/g), 1,2,3,4,6-pentagalloylglucose (6.6-12.9 mg/g), and quercetin 3-galactoside/quercetin 3-glucoside (2.7-5.7 mg/g) were the most abundant phenolic components in the leaves. Quinic acid and ellagic acid were also detected at relatively high concentrations. The antioxidant activity of the most abundant compounds was evaluated. A critical view of the advantages and limitations of traveling wave IMS and CCS for the discovery of natural products is given.

Arbutin as a Skin Depigmenting Agent with Antimelanogenic and Antioxidant Properties

Arbutin is a compound of hydroquinone and D-glucose, and it has been over 30 years since there have been serious studies on the skin lightening action of this substance. In the meantime, there have been debates and validation studies about the mechanism of action of this substance as well as its skin lightening efficacy and safety. Several analogs or derivatives of arbutin have been developed and studied for their melanin synthesis inhibitory action. Formulations have been developed to improve the stability, transdermal delivery, and release of arbutin, and device usage to promote skin absorption has been developed. Substances that inhibit melanin synthesis synergistically with arbutin have been explored. The skin lightening efficacy of arbutin alone or in combination with other active ingredients has been clinically evaluated. Combined therapy with arbutin and laser could give enhanced depigmenting efficacy. The use of arbutin causes dermatitis rarely, and caution is recommended for the use of arbutin-containing products, especially from the viewpoint that hydroquinone may be generated during product use. Studies on the antioxidant properties of arbutin are emerging, and these antioxidant properties are proposed to contribute to the skin depigmenting action of arbutin. It is hoped that this review will help to understand the pros and cons of arbutin as a cosmetic ingredient, and will lead to future research directions for developing advanced skin lightening and protecting cosmetic products.

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.

Yeast-Based Biosynthesis of Natural Products From Xylose

Xylose is the second most abundant sugar in lignocellulosic hydrolysates. Transformation of xylose into valuable chemicals, such as plant natural products, is a feasible and sustainable route to industrializing biorefinery of biomass materials. Yeast strains, including Saccharomyces cerevisiae, Scheffersomyces stipitis, and Yarrowia lipolytica, display some paramount advantages in expressing heterologous enzymes and pathways from various sources and have been engineered extensively to produce natural products. In this review, we summarize the advances in the development of metabolically engineered yeasts to produce natural products from xylose, including aromatics, terpenoids, and flavonoids. The state-of-the-art metabolic engineering strategies and representative examples are reviewed. Future challenges and perspectives are also discussed on yeast engineering for commercial production of natural products using xylose as feedstocks.

Metabolically engineering of Yarrowia lipolytica for the biosynthesis of naringenin from a mixture of glucose and xylose

Xylose-inducible modules simultaneously expressing xylose utilization and naringenin biosynthesis pathways were developed in Yarrowia lipolytica to produce naringenin from a mixture of glucose and xylose. The naringenin synthetic pathway was constructed using a constitutive expression to yield 239.1 ± 5.1 mg/L naringenin. Furthermore, the introduction of an inducible pathway realized the dual function of xylose as a substrate and synthetic inducer, which coupled the xylose utilization with naringenin biosynthesis and increased production. Interestingly, the simultaneous enhancement of xylose reductase and xylose transporter expression along with that of xylitol dehydrogenase and xylulokinase can further improve the xylose utilization ability of Y. lipolytica. As expected, xylose-inducible synthesis of naringenin could achieved a titer of 715.3 ± 12.8 mg/L through the shake-flask cultivation level. Therefore, xylose-induced activation of both the xylose utilization and product biosynthesis pathway is considered to be an effective strategy for the biosynthesis of xylose-derived chemicals in yeast.

De novo production of resveratrol from glycerol by engineering different metabolic pathways in Yarrowia lipolytica

Resveratrol is a polyphenol with multiple applications in pharma, cosmetics and food. The aim of this study was to construct Yarrowia lipolytica strains able to produce resveratrol. For this purpose, resveratrol-biosynthesis genes from bacteria and plants were expressed in this host. Since resveratrol can be produced either via tyrosine or phenylaniline, both pathways were tested, first with a single copy and then with two copies. The phenylalanine pathway resulted in slightly higher production in glucose media, although when the media was supplemented with amino acids, the best production was found in the strain with two copies of the tyrosine pathway, which reached 0.085 ​g/L. When glucose was replaced by glycerol, a preferred substrate for bioproduction, the best results, 0.104 ​g/L, were obtained in a strain combining the expression of the two synthesis pathways. Finally, the best producer strain was tested in bioreactor conditions where a production of 0.43 ​g/L was reached. This study suggests that Y. lipolytica is a promising host for resveratrol production from glycerol.

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Resveratrol can be produced in engineered Y. lipolytica via Tyrosine or Phenylalanine.

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The integration of multiple copies of the pathway genes further increased production.

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Engineered Y. lipolytica can produce 430 ​mg/L of resveratrol from glycerol.

Engineering the oleaginous yeast Yarrowia lipolytica for high-level resveratrol production

Resveratrol is a plant secondary metabolite with multiple health-beneficial properties. Microbial production of resveratrol in model microorganisms requires extensive engineering to reach commercially viable levels. Here, we explored the potential of the non-conventional yeast Yarrowia lipolytica to produce resveratrol and several other shikimate pathway-derived metabolites (p-coumaric acid, cis,cis-muconic acid, and salicylic acid). The Y. lipolytica strain expressing a heterologous pathway produced 52.1 ± 1.2 mg/L resveratrol in a small-scale cultivation. The titer increased to 409.0 ± 1.2 mg/L when the strain was further engineered with feedback-insensitive alleles of the key genes in the shikimate pathway and with five additional copies of the heterologous biosynthetic genes. In controlled fed-batch bioreactor, the strain produced 12.4 ± 0.3 g/L resveratrol, the highest reported titer to date for de novo resveratrol production, with a yield on glucose of 54.4 ± 1.6 mg/g and a productivity of 0.14 ± 0.01 g/L/h. The study showed that Y. lipolytica is an attractive host organism for the production of resveratrol and possibly other shikimate-pathway derived metabolites.

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Oleaginous yeast Y. lipolytica was engineered for production of aromatic compounds.

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High resveratrol production required increased activities of Aro4p and Aro7p.

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Multiple integration of resveratrol biosynthetic genes improved production.

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Fed-batch fermentation enabled de novo production of 12.4 g/L resveratrol.