Regulated preparation of Crocin-1 or Crocin-2' Triggered by the Cosolvent DMSO Using Bs-GT/At-SuSy One-Pot Reaction

Recent Advancements in the Biomanufacturing of Crocetin and Crocins: Key Enzymes and Metabolic Engineering

Crocetin and crocins are high-value apocarotenoids recognized for their role as food colorants as well as for their numerous industrial and therapeutic applications. Biotechnological platforms have the potential to replace traditional plant-based extraction of these compounds with a more sustainable approach. This review first introduced the catalytic characteristics of key enzymes involved in the biosynthetic pathway of crocetin and crocins, including carotenoid cleavage dioxygenases, aldehyde dehydrogenases, and uridine diphosphate glycosyltransferases. Next, we highlighted advanced metabolic engineering strategies aimed at enhancing crocetin and crocin production, such as increasing the pool of precursors and cofactors, protein mining and engineering, tuning protein expression, biosensor, genomic integration, and process optimization. Finally, the paper proposed potential strategies and tools associated with further boosting the heterologous production of crocetin and crocins to meet commercial-scale demands.

Rare crocins ameliorate thrombus in zebrafish larvae by regulating lipid accumulation and clotting factors

Crocin-4 is a water-soluble carotenoid that exhibits cardiovascular protection effects through anti-inflammatory and antioxidant effects. However, the pharmacodynamic effects and mechanisms of its analogues crocin-1 and crocin-2' have not been reported. In this study, we evaluated the protective effects of rare crocins on cardiovascular systems. In ox-LDL induced HUVECs model, 0.02, 0.1, 0.5, 1, 2, 3, 4, 5, 6 μg/mL crocin-1 and crocin-2' can increase cell viability by up to 80 %. Meanwhile, rare crocins at concentrations between 25-100 μg/mL crocin-1 and crocin-2' reduced the lipid accumulation by 30 % in cholesterol-induced zebrafish larvae. What's more, the therapeutic potential of rare crocins on thrombosis has also been explored. In vitro experiments, rare crocin-1 and crocin-2' at concentrations of 0.02, 0.05, 0.2, 0.5, 1, 2, 5, 10 μg/mL protected Human Umbilical Vein Endothelial Cells (HUVECs) against lipopolysaccharides-induced oxidative stress and inflammation. In vivo studies revealed that rare crocins at concentrations of 25, 50, 100, 150, 200, and 300 μg/mL exerted significant antithrombotic effect on arachidonic acid (AA)-induced zebrafish and there was nearly no potential risk for the deformity of zebrafish at 300 μg/mL dosages. In brief, rare crocins was viewed as a potentially useful candidate for the treatment of cardiovascular diseases because of its anti-inflammatory, antioxidant, and anticoagulant properties.

Recent Achievements in Antiviral Agent Development for Plant Protection

Plant virus disease is the second most prevalent plant diseases and can cause extensive loss in global agricultural economy. Extensive work has been carried out on the development of novel antiplant virus agents for preventing and treating plant virus diseases. In this review, we summarize the achievements of the research and development of new antiviral agents in the recent five years and provide our own perspective on the future development in this highly active research field.

Preparation and Anti-Tobacco Mosaic Virus Activities of Crocetin Diesters

The development of antiviral agents with an original structure and noticeable effect is always in great need. Natural products are important lead compounds in the development of new pesticides. Crocin-1 and crocin-2 were effectively isolated from Gardeniae fructus and found to have higher anti-tobacco mosaic virus (TMV) activity levels than ribavirin. A series of the crocetin diester derivatives were synthesized with separated crocetin-1 as material and evaluated for their anti-TMV activities. They could be dissolved in common organic solvents as dichloromethane, ethyl acetate, tetrahydrofuran, and methanol. Compounds 5, 9, 13, 14, and 15 displayed higher activities in vivo than ribavirin. Compound 14 with significantly higher antiviral activities than lead compounds (crocin-1 and crocin-2) emerged as a new antiviral candidate.

Highly Regioselective and Efficient Biosynthesis of Polydatin by an Engineered UGTBL1-AtSuSy Cascade Reaction

Polydatin, resveratrol-3-O-β-glucoside, possesses various biological activities. However, the regioselective glucosylation of resveratrol by UDP-glycosyltransferases (UGTs) constitutes a persistent problem. In this study, semi-rational design and iterative combinatorial mutagenesis were carried out to screen the mutants of UGT_BL1 and the high specificity with the glycosylation of the 3-OH group of resveratrol was explored. The triple mutant I62G/M112D/K143G exhibited near-perfect control of polydatin synthesis (regioselectivity ∼ 99%), and the ratio of polydatin to resveratrol-4'-O-β-glucoside was finally enhanced by 786-fold. Molecular docking revealed that the mutant could form three H-bonds between 3-, 5-, and 4'-OH groups of resveratrol and the residues around the active center, resulting in the oriented-binding of resveratrol. Furthermore, UGT_BL1 mutant coupling sucrose synthase AtSuSy can synthesize polydatin at an unprecedented high titer of 10.33 g/L, together with efficient UDPG regeneration (RC_max = 54). This study provides an efficient approach for the regioselective biosynthesis of polydatin.

Scale-Up Preparation of Crocins I and II from Gardeniajasminoides by a Two-Step Chromatographic Approach and Their Inhibitory Activity Against ATP Citrate Lyase

Crocins are highly valuable natural compounds for treating human disorders, and they are also high-end spices and colorants in the food industry. Due to the limitation of obtaining this type of highly polar compound, the commercial prices of crocins I and II are expensive. In this study, macroporous resin column chromatography combined with high-speed counter-current chromatography (HSCCC) was used to purify crocins I and II from natural sources. With only two chromatographic steps, both compounds were simultaneously isolated from the dry fruit of Gardenia jasminoides, which is a cheap herbal medicine distributed in a number of countries. In an effort to shorten the isolation time and reduce solvent usage, forward and reverse rotations were successively utilized in the HSCCC isolation procedure. Crocins I and II were simultaneously obtained from a herbal resource with high recoveries of 0.5% and 0.1%, respectively, and high purities of 98.7% and 99.1%, respectively, by HPLC analysis. The optimized preparation method was proven to be highly efficient, convenient, and cost-effective. Crocins I and II exhibited inhibitory activity against ATP citrate lyase, and their IC₅₀ values were determined to be 36.3 ± 6.24 and 29.7 ± 7.41 μM, respectively.

The Beneficial Effects of Saffron Extract on Potential Oxidative Stress in Cardiovascular Diseases

Saffron is commonly used in traditional medicines and precious perfumes. It contains pharmacologically active compounds with notably potent antioxidant activity. Saffron has a variety of active components, including crocin, crocetin, and safranal. Oxidative stress plays an important role in many cardiovascular diseases, and its uncontrolled chain reaction is related to myocardial injury. Numerous studies have confirmed that saffron exact exhibits protective effects on the myocardium and might be beneficial in the treatment of cardiovascular disease. In view of the role of oxidative stress in cardiovascular disease, people have shown considerable interest in the potential role of saffron extract as a treatment for a range of cardiovascular diseases. This review analyzed the use of saffron in the treatment of cardiovascular diseases through antioxidant stress from four aspects: antiatherosclerosis, antimyocardial ischemia, anti-ischemia reperfusion injury, and improvement in drug-induced cardiotoxicity, particularly anthracycline-induced. Although data is limited in humans with only two clinically relevant studies, the results of preclinical studies regarding the antioxidant stress effects of saffron are promising and warrant further research in clinical trials. This review summarized the protective effect of saffron in cardiovascular diseases and drug-induced cardiotoxicity. It will facilitate pharmacological research and development and promote utilization of saffron.

Efficient Biocatalytic Preparation of Rebaudioside KA: Highly Selective Glycosylation Coupled with UDPG Regeneration

Rebaudioside KA is a diterpene natural sweetener isolated in a trace amount from the leaves of Stevia rebaudiana. Selective glycosylation of rubusoside, a natural product abundantly presented in various plants, is a feasible approach for the biosynthesis of rebaudioside KA. In this study, bacterial glycosyltransferase OleD was identified to selectively transfer glucose from UDPG to 2′-hydroxyl group with a β-1,2 linkage at 19-COO-β-D-glucosyl moiety of rubusoside for the biosynthesis of rebaudioside KA. To eliminate the use of UDPG and improve the productivity, a UDPG regeneration system was constructed as an engineered Escherichia coli strain to couple with the glycosyltransferase. Finally, rubusoside at 22.5 g/L (35.0 mM) was completely converted to rebaudioside KA by the whole cells without exogenous addition of UDPG. This study provides an efficient and scalable method for highly selective biosynthesis of rebaudioside KA.

Advances in engineering UDP-sugar supply for recombinant biosynthesis of glycosides in microbes

Plant glycosides are of great interest for industries. Glycosylation of plant secondary metabolites can greatly improve their solubility, biological activity, or stability. This allows some plant glycosides to be used as food additives, cosmetic products, health products, antisepsis and anti-cancer drugs. With the continuous expansion of market demand, a variety of biological fermentation technologies has emerged. This review focuses on recombinant microbial biosynthesis of plant glycosides, which uses UDP-sugars as precursors, and summarizes various strategies to increase the yield of glycosides with a key concentration on UDP-sugar supply based on four aspects, i.e., gene overexpression, UDP-sugar recycling, mixed fermentation, and carbon co-utilization. Meanwhile, the application potential and advantages of various techniques are introduced, which provide guidance to the development of high-yield strains for recombinant microbial production of plant glycosides. Finally, the technical challenges of glycoside biosynthesis are pointed out with discussions on future directions of improving the yield of recombinantly synthesized glycosides.

Biocatalytic Synthesis of Calycosin-7-O-β-D-Glucoside with Uridine Diphosphate–Glucose Regeneration System

Calycosin-7-O-β-D-glucoside (Cy7G) is one of the principal components of Radix astragali. This isoflavonoid glucoside is regarded as an indicator to assess the quality of R. astragali and exhibits diverse pharmacological activities. In this study, uridine diphosphate-dependent glucosyltransferase (UGT) UGT88E18 was isolated from Glycine max and expressed in Escherichia coli. Recombinant UGT88E18 could selectively and effectively glucosylate the C7 hydroxyl group of calycosin to synthesize Cy7G. A one-pot reaction by coupling UGT88E18 to sucrose synthase (SuSy) from G. max was developed. The UGT88E18–SuSy cascade reaction could recycle the costly uridine diphosphate glucose (UDPG) from cheap sucrose and catalytic amounts of uridine diphosphate (UDP). The important factors for UGT88E18–SuSy cascade reaction, including UGT88E18/SuSy ratios, different temperatures, and pH values, different concentrations of dimethyl sulfoxide (DMSO), UDP, sucrose, and calycosin, were optimized. We produced 10.5 g L−1 Cy7G in the optimal reaction conditions by the stepwise addition of calycosin. The molar conversion of calycosin was 97.5%, with a space–time yield of 747 mg L−1 h−1 and a UDPG recycle of 78 times. The present study provides a new avenue for the efficient and cost-effective semisynthesis of Cy7G and other valuable isoflavonoid glucosides by UGT–SuSy cascade reaction.

Biocatalytic synthesis of ginsenoside Rh2 using Arabidopsis thaliana glucosyltransferase-catalyzed coupled reactions

Ginsenoside Rh2, a rare protopanaxadiol (PPD)-type triterpene saponin isolated from Panax ginseng, exhibits notable anticancer and immune-system-enhancing activities. Glycosylation catalyzed by uridine diphosphate-dependent glucosyltransferase (UGT) is the final biosynthetic step of ginsenoside Rh2. In this study, UGT73C5 isolated from Arabidopsis thaliana was demonstrated to selectively transfer a glucosyl moiety to the C3 hydroxyl group of PPD to synthesize ginsenoside Rh2. UGT73C5 was coupled with sucrose synthase (SuSy) from A. thaliana to regenerate costly uridine diphosphate glucose (UDPG) from cheap sucrose and catalytic amounts of uridine diphosphate (UDP). The UGT73C5/SuSy ratio, temperature, pH, cofactor UDP, and PPD concentrations for UGT73C5-SuSy coupled reactions were optimized. Through the stepwise addition of PPD, the maximal ginsenoside Rh2 production was 3.2 mg mL^-1, which was the highest yield reported to date. These promising results provided an efficient and cost-effective approach to semisynthesize the highly valuable ginsenoside Rh2.