Novel tandem biotransformation process for the biosynthesis of a novel compound, 4-(2,3,5,6-tetramethylpyrazine-1)-4'-demethylepipodophyllotoxin

Biotransformation of selected secondary metabolites by Alternaria species and the pharmaceutical, food and agricultural application of biotransformation products

Biotransformation is a process in which molecules are modified in the presence of a biocatalyst or enzymes, as well as the metabolic alterations that occur in organisms from exposure to the molecules. Microbial biotransformation is an important process in natural product drug discovery as novel compounds are biosynthesised. Additionally, biotransformation products offer compounds with improved efficacy, solubility, reduced cytotoxic and allows for the understanding of structure activity relationships. One of the driving forces for these impeccable findings are associated with the presence of cytochrome P450 monooxygenases that is present in all organisms such as mammals, bacteria, and fungi. Numerous fungal strains have been used and reported for their ability to biotransform different compounds. This review focused on studies using Alternaria species as biocatalysts in the biotransformation of natural product compounds. Alternaria species facilitates reactions that favour stereoselectivity, regioselectivity under mild conditions. Additionally, microbial biotransformation products, their application in food, pharmaceutical and agricultural sector is discussed in this review.

Discovery of Novel c-Jun N-Terminal Kinase 1 Inhibitors from Natural Products: Integrating Artificial Intelligence with Structure-Based Virtual Screening and Biological Evaluation

c-Jun N-terminal kinase 1 (JNK1) is currently considered a critical therapeutic target for type-2 diabetes. In recent years, there has been a great interest in naturopathic molecules, and the discovery of active ingredients from natural products for specific targets has received increasing attention. Based on the above background, this research aims to combine emerging Artificial Intelligence technologies with traditional Computer-Aided Drug Design methods to find natural products with JNK1 inhibitory activity. First, we constructed three machine learning models (Support Vector Machine, Random Forest, and Artificial Neural Network) and performed model fusion based on Voting and Stacking strategies. The integrated models with better performance (AUC of 0.906 and 0.908, respectively) were then employed for the virtual screening of 4112 natural products in the ZINC database. After further drug-likeness filtering, we calculated the binding free energy of 22 screened compounds using molecular docking and performed a consensus analysis of the two methodologies. Subsequently, we identified the three most promising candidates (Lariciresinol, Tricin, and 4′-Demethylepipodophyllotoxin) according to the obtained probability values and relevant reports, while their binding characteristics were preliminarily explored by molecular dynamics simulations. Finally, we performed in vitro biological validation of these three compounds, and the results showed that Tricin exhibited an acceptable inhibitory activity against JNK1 (IC₅₀ = 17.68 μM). This natural product can be used as a template molecule for the design of novel JNK1 inhibitors.

Potential Multifunctional Bioactive Compounds from Dysosma versipellis Explored by Bioaffinity Ultrafiltration-HPLC/MS with Topo I, Topo II, COX-2 and ACE2

Background

Dysosma versipellis (D. versipellis) has been traditionally used as a folk medicine for ages. However, the specific phytochemicals responsible for their correlated anti-inflammatory, anti-proliferative and antiviral activities remain unknown.

Purpose

This study aimed to explore the specific active components in D. versipellis responsible for its potential anti-inflammatory, anti-proliferative, and antiviral effects, and further elucidate the corresponding mechanisms of action.

Methods

Bioaffinity ultrafiltration coupled to liquid chromatography–mass spectrometry (UF-LC/MS) was firstly hired to fast screen for the anti-inflammatory, anti-proliferative and antiviral compounds from rhizomes of D. versipellis, and then further validation was conducted using in vitro inhibition assays and molecular docking.

Results

A total of 12, 12, 9 and 12 phytochemicals with considerable affinities to Topo I, Topo II, COX-2 and ACE2 were fished out, respectively. The anti-proliferative assay in vitro indicated that podophyllotoxin and quercetin exhibited comparably strong inhibitory rates on A549 and HT-29 cells compared with 5-FU and etoposide. Meanwhile, kaempferol displayed prominent dose-dependent inhibition against COX-2 with IC₅₀ value at 0.36 ± 0.02 μM lower than indomethacin at 0.73 ± 0.07 μM. Furthermore, quercetin exerted stronger inhibitory effect against ACE2 with IC₅₀ value at 104.79 ± 8.26 μM comparable to quercetin 3-O-glucoside at 135.25 ± 6.54 μM.

Conclusion

We firstly showcased an experimental investigation on the correlations between bioactive phytochemicals of D. versipellis and their multiple drug targets reflecting its potential pharmacological activities, and further constructed a multi-target and multi-component network to decipher its empirical traditional applications. It could not only offer a reliable and valuable experimental basis to better comprehend the curative effects of D. versipellis but also provide more new insights and strategies for other traditional medicinal plants.

Application of tandem biotransformation for biosynthesis of new pentacyclic triterpenoid derivatives with neuroprotective effect

Tandem whole-cell biotransformation was applied successfully to deliver novel pentacyclic triterpenoid derivatives for the first time. In this process, the starting substrate oleanolic acid (1) was biotransformed into a hydroxylated metabolite 1a by Rhizopus chinensis CICC 40335 and then was further glycosylated to 1b by Bacillus subtilis ATCC 6633. Moreover, metabolite 1a was furtherly oxidized by Streptomyces griseus ATCC 13273 and generated two new derivatives as 1c and 1d. To validate the feasibility, tandem biotransformation of 18β-glycyrrhetinic acid (2) by R. chinensis and B. subtilis was also conducted and offered a glycosylated derivative (2c). Finally, the neuroprotective effects of the derivatives were assessed on neural injury PC12 cell model induced by cobalt chloride.

An Alkylpyrazine Synthesis Mechanism Involving l-Threonine-3-Dehydrogenase Describes the Production of 2,5-Dimethylpyrazine and 2,3,5-Trimethylpyrazine by Bacillus subtilis

Alkylpyrazines are important contributors to the flavor of traditional fermented foods. Here, we studied the synthesis mechanisms of 2,5-dimethylpyrazine (2,5-DMP) and 2,3,5-trimethylpyrazine (TMP). Substrate addition, whole-cell catalysis, stable isotope tracing experiments, and gene manipulation revealed that l-threonine is the starting point involving l-threonine-3-dehydrogenase (TDH) and three uncatalyzed reactions to form 2,5-DMP. TDH catalyzes the oxidation of l-threonine. The product of this reaction is l-2-amino-acetoacetate, which is known to be unstable and can decarboxylate to form aminoacetone. It is proposed that aminoacetone spontaneously converts to 2,5-DMP in a pH-dependent reaction, via 3,6-dihydro-2,5-DMP. 2-Amino-3-ketobutyrate coenzyme A (CoA) ligase (KBL) catalyzes the cleavage of l-2-amino-acetoacetate, the product of TDH, into glycine and acetyl-CoA in the presence of CoA. Inactivation of KBL could improve the production of 2,5-DMP. Besides 2,5-DMP, TMP can also be generated by Bacillus subtilis 168 by using l-threonine and d-glucose as the substrates and TDH as the catalytic enzyme.IMPORTANCE Despite alkylpyrazines' contribution to flavor and their commercial value, the synthesis mechanisms of alkylpyrazines by microorganisms remain poorly understood. This study revealed the substrate, intermediates, and related enzymes for the synthesis of 2,5-dimethylpyrazine (2,5-DMP), which differ from the previous reports about the synthesis of 2,3,5,6-tetramethylpyrazine (TTMP). The synthesis mechanism described here can also explain the production of 2,3,5-trimethylpyrazine (TMP). The results provide insights into an alkylpyrazine's synthesis pathway involving l-threonine-3-dehydrogenase as the catalytic enzyme and l-threonine as the substrate.

Fungal synthesis of chiral phosphonic synthetic platform - Scope and limitations of the method

Chiral hydroxyphosphonates due to their wide range of biological properties are industrially important chemicals. Chemical synthesis of their optical isomers is expensive, time consuming and not friendly to the environment, so biotransformations are under consideration. Among others, these compounds act as enzymes inhibitors. This makes the bioconversions of phosphonates, especially scaling experiments, hard to perform. Biocatalysis is one of the methods that can be applied in synthesis of optically pure compounds. To increase the efficiency of the process with whole cell biocatalysts, it is essential to ensure optimal reaction conditions that minimize cellular stress and can enhance the metabolic activity of cells. The present investigation focuses on the scaling up of the kinetic resolution of racemic mixture of 2-butyryloxy-2-(ethoxy-P-phenylphosphinyl)acetic acid, applying free and immobilized form of the fungal biocatalysts and two operation systems: shake flask and recirculated fixed-bed batch reactor. Protocols of effective mycelium immobilization on polyurethane foams were set for T. purpurogenus IAFB 2512, F. oxysporum, P. commune. The best results of biotransformation were obtained with the immobilized P. commune in the column recirculated fixed-bed batch reactor. The conversion reaches 56% (maximal for the kinetic process) and the enantiomeric enrichment of the isomers mixture ranges between 82 and 93% (93% for ester of R_P,R conformation). All biocatalysts exhibit S_P-preference toward tested compound, what is essential because of importance of the phosphorus atom chirality for its biological activity.

Recent Advances in the Chemistry and Biology of Podophyllotoxins

Podophyllotoxin and its related aryltetralin cyclolignans belong to a family of important products that exhibit various biological properties (e.g., cytotoxic, insecticidal, antifungal, antiviral, anti-inflammatory, neurotoxic, immunosuppressive, antirheumatic, antioxidative, antispasmogenic, and hypolipidemic activities). This Review provides a survey of podophyllotoxin and its analogues isolated from plants. In particular, recent developments in the elegant total chemical synthesis, structural modifications, biosynthesis, and biotransformation of podophyllotoxin and its analogues are summarized. Moreover, a deoxypodophyllotoxin-based chemosensor for selective detection of mercury ion is described. In addition to the most active podophyllotoxin derivatives in each series against human cancer cell lines and insect pests listed in the tables, the structure-activity relationships of podophyllotoxin derivatives as cytotoxic and insecticidal agents are also outlined. Future prospects and further developments in this area are covered at the end of the Review. We believe that this Review will provide necessary information for synthetic, medicinal, and pesticidal chemistry researchers who are interested in the chemistry and biology of podophyllotoxins.