Chemotaxonomic investigation of plant terpenoids with an established database (TeroMOL)

Organic fertilizer mitigated the oxidative stress of tomato induced by nanoplastics through affecting rhizosphere soil microorganisms and bacteriophage functions

Nanoplastics (NPs), which are widely present in agricultural soils, are difficult to remove and are potentially harmful to plant growth and development. However, few studies have focused on how to mitigation the oxidative stress in plants induced by soil NPs exposure. Therefore, in this study, the effects of organic and chemical fertilizers on the oxidative stress of tomato under exposure to polystyrene nanoplastics (PS-NPs) in soil were investigated. Compared with chemical fertilizer under exposure to PS-NPs, the organic fertilizer reduced the reactive oxygen species (ROS) content by 25.63 % and the H2O2 content by 34.58 % in tomato stems, whereas no significant effects were observed with respect to the amount of PS-NP internalized in tomato. Additionally, organic fertilizer increased the accumulation of the phytohormones salicylic acid (SA) and abscisic acid (ABA) by 76.53 % and 22.54 %, respectively, and these factors are key for reducing the ROS and H2O2 contents in stems. In the rhizosphere microbiome of organic fertilizer group under exposure to PS-NPs, enrichment in Actinomycetes and an increased abundance of terpenoids and polyketides metabolism were the main factors affecting the accumulation of ABA and SA. Moreover, bacteriophage activity in the rhizosphere indirectly contributed to the increase in this function. These changes ultimately resulted in a reduction in oxidative stress in tomato stems and protected tomato growth. The results of this study will provide a better understanding of the interaction between plants and nanoplastics in soil and provide a new reference for alleviating the oxidative stress caused by nanoplastics in plants.

Phytochemical and biological studies on rare and endangered plants endemic to China. Part XLIV. Integrated NMR/EI-MS/LC-PDA-ESIMS approach for dereplication and targeted isolation of fortunefuroic acids from Keteleeria fortunei across diverse geographical origins

Secondary metabolites in plants of the same species, though originating from distinct geographical regions, frequently display both similarities and notable variations. A prior study on the vulnerable Chinese endemic conifer Keteleeria fortunei, collected from Yunnan province (KFYN), led to the isolation of fortunefuroic acids (FFAs) A-I. These compounds represent a unique class of triterpenoids characterized by a rare furoic acid moiety within the lateral chain. The distinct 23,27-epoxy-23,25(27)-dien-26-oic acid unit present in FFAs can be readily identified by characteristic proton NMR signals (δH-24: ca 6.36 ppm; δH-27: ca 7.97 ppm), a prominent ion fragment at m/z 125 in the EI-MS, and typical UV absorption peak around λmax 245 nm. In this study, an integrated approach was employed to dereplicate and isolate FFA-type compounds from K. fortunei collected from Fujian Province (KFFJ). This approach combined NMR, EI-MS, and LC-PDA-ESIMS data to detect and analyze compounds with molecular weights in the range of 464-468 Da, a distinguishing feature of FFA-type compounds. Consequently, six previously undescribed FFAs K-P (1-6) were obtained, alongside the re-isolation of FFAs A-D and H. Compound 1 exhibits a rare 17,14-friedo-cyclaorane type skeleton, while compound 2 is characterized as a 3,4-seco-cyclaorane-3,26-dioic acid. Compounds 3-6 are identified as derivatives of 9βH-lanost-26-oic FFAs. Additionally, a previously unreported lanost-26-oic acid derivative (7) was also identified, exhibiting an inhibitory effect on ATP-citrate lyase. Their chemical structures and absolute configurations were determined through spectroscopic analysis, GIAO NMR calculations combined with DP4+ probability analyses, and electronic circular dichroism calculations. The isolated FFAs have the potential to serve as chemotaxonomic markers for the genus Keteleeria within the Pinaceae family. This study marks the first application of integrated NMR/EI-MS/LC-PDA-ESIMS methods for both dereplication and the discovery of new natural products. Notably, the KFFJ samples were collected from a location approximately 1500 km away from that of KFYN. Understanding the impact of geographical origins on specialized metabolites may provide valuable insights into the sustainable utilization and conservation of endangered plant species.

An Effective Computational Strategy for UGTs Catalytic Function Prediction

The GT-B type glycosyltransferases play a crucial post-modification role in synthesizing natural products, such as triterpenoid and steroidal saponins, renowned for their diverse pharmacological activities. Despite phylogenetic analysis aiding in enzyme family classification, distinguishing substrate specificity between triterpenoid and steroidal saponins, with their highly similar cyclic scaffolds, remains a formidable challenge. Our studies unveil the potential transport tunnels for the glycosyl donor and acceptor in PpUGT73CR1, by molecular dynamics simulations. This revelation leads to a plausible substrate transport mechanism, highlighting the regulatory role of the N-terminal domain (NTD) in glycosyl acceptor binding and transport. Inspired by these structural and mechanistic insights, we further analyze the binding pockets of 44 plant-derived UGTs known to glycosylate triterpenes and sterols. Notably, sterol UGTs are found to harbor aromatic and hydrophobic residues with polar residues typically present at the bottom of the active pocket. Drawing inspiration from the substrate binding and product release mechanism revealed through structure-based molecular modeling, we devised a fast sequence-based method for classifying UGTs using the pre-trained ESM2 protein model. This method involved extracting the NTD features of UGTs and performing PCA clustering analysis, enabling accurate identification of enzyme function, and even differentiation of substrate specificity/promiscuity between structurally similar triterpenoid and steroidal substrates, which is further validated by experiments. This work not only deepens our understanding of substrate binding mechanisms but also provides an effective computational protocol for predicting the catalytic function of unknown UGTs.

A molecular representation system with a common reference frame for analyzing triterpenoid structural diversity

Researchers have uncovered hundreds of thousands of natural products, many of which contribute to medicine, materials, and agriculture. However, missing knowledge about the biosynthetic pathways of these products hinders their expanded use. Nucleotide sequencing is key to pathway elucidation efforts, and analyses of the molecular structures of natural products, although seldom discussed explicitly, also play an important role by suggesting hypothetical pathways for testing. Structural analyses are also important in drug discovery, for which many molecular representation systems-methods of representing molecular structures in a computer-friendly format-have been developed. Unfortunately, pathway elucidation investigations seldom use these representation systems. This gap likely occurs because those systems are primarily built to document molecular connectivity and topology rather than the absolute positions of bonds and atoms in a common reference frame, which would enable chemical structures to be connected with potential underlying biosynthetic steps. Here, we expand on recently developed skeleton-based molecular representation systems by implementing a common-reference-frame-oriented system. We tested this system using triterpenoid structures as a case study and explored its applications in biosynthesis and structural diversity tasks. The common-reference-frame system can identify structural regions of high or low variability on the scale of atoms and bonds and enable hierarchical clustering that is closely connected to underlying biosynthesis. Combined with information on phylogenetic distribution, the system illuminates distinct sources of structural variability, such as different enzyme families operating in the same pathway. These characteristics outline the potential of common-reference-frame molecular representation systems to support large-scale pathway elucidation efforts.

Biosynthesis of triterpenoids in plants: Pathways, regulation, and biological functions

Plant triterpenoids, a vast and diverse group of natural compounds derived from six isoprene units, exhibit an extensive array of structural diversity and remarkable biological activities. In this review, we update the recent research progress in the catalytic mechanisms underlying triterpene synthesis and summarize the current insights into the biosynthetic pathways and regulatory mechanisms of triterpenoids. We emphasize the biosynthesis of pharmacologically active triterpenoids and the role of triterpenoid synthesis in plant growth, development, defense mechanisms, and plant-microbe interactions. This insight review offers a comprehensive perspective on the applications and future avenues of triterpenoid research.

The role and mechanisms of canonical and non-canonical tailoring enzymes in bacterial terpenoid biosynthesis

Covering: up to April 2024Terpenoids represent the largest and structurally most diverse class of natural products. According to textbook knowledge, this diversity arises from a two-step biosynthetic process: first, terpene cyclases generate a vast array of mono- and polycyclic hydrocarbon scaffolds with multiple stereocenters from a limited set of achiral precursors, a process extensively studied over the past two decades. Subsequently, tailoring enzymes further modify these complex scaffolds through regio- and stereocontrolled oxidation and other functionalization reactions, a topic of increasing interest in recent years. The resulting highly functionalized terpenoids exhibit a broad spectrum of unique biological activities, making them promising candidates for drug development. Recent advances in genome sequencing technologies along with the development and application of sophisticated genome mining tools have revealed bacteria as a largely untapped resource for the discovery of complex terpenoids. Functional characterization of a limited number of bacterial terpenoid biosynthetic pathways, combined with in-depth mechanistic studies of key enzymes, has begun to reveal the versatility of bacterial enzymatic processes involved in terpenoid modification. In this review, we examine the various tailoring reactions leading to complex bacterial terpenoids. We first discuss canonical terpene-modifying enzymes, that catalyze the functionalization of unactivated C-H bonds, incorporation of diverse functional groups, and oxidative and non-oxidative rearrangements. We then explore non-canonical terpene-modifying enzymes that facilitate oxidative rearrangement, cyclization, isomerization, and dimerization reactions. The increasing number of characterized tailoring enzymes that participate in terpene hydrocarbon scaffold fomation, rather than merely decorating pre-formed scaffolds suggests that a re-evaluation of the traditional two-phase model for terpenoid biosynthesis might be warranted. Finally, we address the potential and challenges of mining bacterial genomes to identify terpene biosynthetic gene clusters and expand the bacterial terpene biosynthetic and chemical space.

Major specialized natural products from the endangered plant Heptacodium miconioides, potential medicinal uses and insights into its longstanding unresolved systematic classification

A comprehensive phytochemical investigation of the flower buds and leaves/twigs of Heptacodium miconioides, a cultivated ornamental plant native to China and categorized as 'vulnerable', has led to the isolation of 45 structurally diverse compounds, which comprise 18 phenylpropanoids (1-4, 7-20), 11 pentacyclic triterpenoids (5, 6, 21-29), eight secoiridoid glycosides (30-37), three quinic acid derivatives (38-40), and a few miscellaneous components (41-45). Among them, (+)-α-intermedianol (1), (+)-holophyllol A (2), and (-)-pseudolarkaemin A (3) represent previously unreported enantiomeric lignans, while (+)-7'(R)-hydroxymatairesinol (4) is an undescribed naturally occurring lignan. Heptacoacids A (5) and B (6) are undescribed 24-nor-urs-28-oic acid derivatives. Their chemical structures were determined by 2D-NMR, supplemented by evidence from specific rotations and circular dichroism spectra. Given the uncertainty surrounding the systematic position of Heptacodium, integrative taxonomy (ITA), a method utilized to define contentious species, is applied. Chemotaxonomy, a vital aspect of ITA, becomes significant. By employing hierarchical clustering analysis (HCA) and syntenic pattern analysis methods, a taxonomic examination based on the major specialized natural products from the flower buds of H. miconioides and two other Caprifoliaceae plants (i.e., Lonicera japonica and Abelia × grandiflora) could offer enhanced understanding of the systematic placement of Heptacodium. Additionally, compounds 39 and 40 displayed remarkable inhibitory activities against ATP-citrate lyase (ACL), with IC50 values of 0.11 and 1.10 μM, respectively. In summary, the discovery of medical properties and refining systematic classification can establish a sturdy groundwork for conservation efforts aimed at mitigating species diversity loss while addressing human diseases.

Functional Redundancy and Dual Function of a Hypothetical Protein in the Biosynthesis of Eunicellane-Type Diterpenoids

Many complex terpenoids, predominantly isolated from plants and fungi, show drug-like physicochemical properties. Recent advances in genome mining revealed actinobacteria as an almost untouched treasure trove of terpene biosynthetic gene clusters (BGCs). In this study, we characterized a terpene BGC with an unusual architecture. The selected BGC includes, among others, genes encoding a terpene cyclase fused to a truncated reductase domain and a cytochrome P450 monooxygenase (P450) that is split over three gene fragments. Functional characterization of the BGC in a heterologous host led to the identification of several new members of the trans-eunicellane family of diterpenoids, the euthailols, that feature unique oxidation patterns. A combination of bioinformatic analyses, structural modeling studies, and heterologous expression revealed a dual function of the pathway-encoded hypothetical protein that acts as an isomerase and an oxygenase. Moreover, in the absence of other tailoring enzymes, a P450 hydroxylates the eunicellane scaffold at a position that is not modified in other eunicellanes. Surprisingly, both the modifications installed by the hypothetical protein and one of the P450s exhibit partial redundancy. Bioactivity assays revealed that some of the euthailols show growth inhibitory properties against Gram-negative ESKAPE pathogens. The characterization of the euthailol BGC in this study provides unprecedented insights into the partial functional redundancy of tailoring enzymes in complex diterpenoid biosynthesis and highlights hypothetical proteins as an important and largely overlooked family of tailoring enzymes involved in the maturation of complex terpenoids.

Plant specialized metabolism: Diversity of terpene synthases and their products

Terpenoids are ubiquitous to all kingdoms of life and are one of the most diverse groups of compounds, both structurally and functionally. Despite being derived from common precursors, isopentenyl diphosphate and dimethylallyl diphosphate, their exceptional diversity is partly driven by the substrate and product promiscuity of terpene synthases that produce a wide array of terpene skeletons. Plant terpene synthases can be subdivided into different subfamilies based on sequence homology and function. However, in many cases, structural architecture of the enzyme is more essential to product specificity than primary sequence alone, and distantly related terpene synthases can often mediate similar reactions. As such, the focus of this brief review is on some of the recent progress in understanding terpene synthase function and diversity.

A terpenoids database with the chemical content as a novel agronomic trait

Natural products play a pivotal role in drug discovery, and the richness of natural products, albeit significantly influenced by various environmental factors, is predominantly determined by intrinsic genetics of a series of enzymatic reactions and produced as secondary metabolites of organisms. Heretofore, few natural product-related databases take the chemical content into consideration as a prominent property. To gain unique insights into the quantitative diversity of natural products, we have developed the first TerPenoids database embedded with Content information (TPCN) with features such as compound browsing, structural search, scaffold analysis, similarity analysis and data download. This database can be accessed through a web-based computational toolkit available at http://www.tpcn.pro/. By conducting meticulous manual searches and analyzing over 10 000 reference papers, the TPCN database has successfully integrated 6383 terpenoids obtained from 1254 distinct plant species. The database encompasses exhaustive details including isolation parts, comprehensive molecule structures, chemical abstracts service registry number (CAS number) and 7508 content descriptions. The TPCN database accentuates both the qualitative and quantitative dimensions as invaluable phenotypic characteristics of natural products that have undergone genetic evolution. By acting as an indispensable criterion, the TPCN database facilitates the discovery of drug alternatives with high content and the selection of high-yield medicinal plant species or phylogenetic alternatives, thereby fostering sustainable, cost-effective and environmentally friendly drug discovery in pharmaceutical farming. Database URL: http://www.tpcn.pro/.

NIMO: A Natural Product-Inspired Molecular Generative Model Based on Conditional Transformer

Natural products (NPs) have diverse biological activity and significant medicinal value. The structural diversity of NPs is the mainstay of drug discovery. Expanding the chemical space of NPs is an urgent need. Inspired by the concept of fragment-assembled pseudo-natural products, we developed a computational tool called NIMO, which is based on the transformer neural network model. NIMO employs two tailor-made motif extraction methods to map a molecular graph into a semantic motif sequence. All these generated motif sequences are used to train our molecular generative models. Various NIMO models were trained under different task scenarios by recognizing syntactic patterns and structure-property relationships. We further explored the performance of NIMO in structure-guided, activity-oriented, and pocket-based molecule generation tasks. Our results show that NIMO had excellent performance for molecule generation from scratch and structure optimization from a scaffold.

Molecular mechanism of miRNA mediated biosynthesis of secondary metabolites in medicinal plants

Plant secondary metabolites are important raw materials for the pharmaceutical industry, and their biosynthetic processes are subject to diverse and precise regulation by miRNA. The identification of miRNA molecules in medicinal plants and exploration of their mechanisms not only contribute to a deeper understanding of the molecular genetic mechanisms of plant growth, development and resistance to stress, but also provide a theoretical basis for elucidating the pharmacological effects of authentic medicinal materials and constructing bioreactors for the synthesis of medicinal secondary metabolite components. This paper summarizes the research reports on the discovery of miRNA in medicinal plants and their regulatory mechanisms on the synthesis of secondary metabolites by searching the relevant literature in public databases. It summarizes the currently discovered miRNA and their functions in medicinal plants, and summarizes the molecular mechanisms regulating the synthesis and degradation of secondary metabolites. Furthermore, it provides a prospect for the research and development of medicinal plant miRNA. The compiled information contributes to a comprehensive understanding of the research progress on miRNA in medicinal plants and provides a reference for the industrial development of related secondary metabolite biosynthesis.

Sequence-Structure Analysis Unlocking the Potential Functional Application of the Local 3D Motifs of Plant-Derived Diterpene Synthases

Plant-derived diterpene synthases (PdiTPSs) play a critical role in the formation of structurally and functionally diverse diterpenoids. However, the specificity or functional-related features of PdiTPSs are not well understood. For a more profound insight, we collected, constructed, and curated 199 functionally characterized PdiTPSs and their corresponding 3D structures. The complex correlations among their sequences, domains, structures, and corresponding products were comprehensively analyzed. Ultimately, our focus narrowed to the geometric arrangement of local structures. We found that local structural alignment can rapidly localize product-specific residues that have been validated by mutagenesis experiments. Based on the 3D motifs derived from the residues around the substrate, we successfully searched diterpene synthases (diTPSs) from the predicted terpene synthases and newly characterized PdiTPSs, suggesting that the identified 3D motifs can serve as distinctive signatures in diTPSs (I and II class). Local structural analysis revealed the PdiTPSs with more conserved amino acid residues show features unique to class I and class II, whereas those with fewer conserved amino acid residues typically exhibit product diversity and specificity. These results provide an attractive method for discovering novel or functionally equivalent enzymes and probing the product specificity in cases where enzyme characterization is limited.

Discovery of plant-derived anti-tumor natural products: Potential leads for anti-tumor drug discovery

Natural products represent a paramount source of novel drugs. Numerous plant-derived natural products have demonstrated potent anti-tumor properties, thereby garnering considerable interest in their potential as anti-tumor drugs. This review compiles an overview of 242 recently discovered natural products, spanning the period from 2018 to the present. These natural products, which include 69 terpenoids, 42 alkaloids, 39 flavonoids, 21 steroids, 14 phenylpropanoids, 5 quinolines and 52 other compounds, are characterized by their respective chemical structures, anti-tumor activities, and mechanisms of action. By providing an essential reference and fresh insights, this review aims to support and inspire researchers engaged in the fields of natural products and anti-tumor drug discovery.

Recent advances in anti-inflammatory active components and action mechanisms of natural medicines

Inflammation is a series of reactions caused by the body's resistance to external biological stimuli. Inflammation affects the occurrence and development of many diseases. Anti-inflammatory drugs have been used widely to treat inflammatory diseases, but long-term use can cause toxic side-effects and affect human functions. As immunomodulators with long-term conditioning effects and no drug residues, natural products are being investigated increasingly for the treatment of inflammatory diseases. In this review, we focus on the inflammatory process and cellular mechanisms in the development of diseases such as inflammatory bowel disease, atherosclerosis, and coronavirus disease-2019. Also, we focus on three signaling pathways (Nuclear factor-kappa B, p38 mitogen-activated protein kinase, Janus kinase/signal transducer and activator of transcription-3) to explain the anti-inflammatory effect of natural products. In addition, we also classified common natural products based on secondary metabolites and explained the association between current bidirectional prediction progress of natural product targets and inflammatory diseases.

Unraveling the role of prenyl side-chain interactions in stabilizing the secondary carbocation in the biosynthesis of variexenol B

Terpene cyclization reactions involve a number of carbocation intermediates. In some cases, these carbocations are stabilized by through-space interactions with π orbitals. Several terpene/terpenoids, such as sativene, santalene, bergamotene, ophiobolin and mangicol, possess prenyl side chains that do not participate in the cyclization reaction. The role of these prenyl side chains has been partially investigated, but remains elusive in the cyclization cascade. In this study, we focus on variexenol B that is synthesized from iso-GGPP, as recently reported by Dickschat and co-workers, and investigate the possibility of through-space interactions with prenyl side chains using DFT calculations. Our calculations show that (i) the unstable secondary carbocation is stabilized by the cation-π interaction from prenyl side chains, thereby lowering the activation energy, (ii) the four-membered ring formation is completed through bridging from the exomethylene group, and (iii) the annulation from the exomethylene group proceeds in a barrier-free manner.

Developing TeroENZ and TeroMAP modules for the terpenome research platform TeroKit

Terpenoids and their derivatives are collectively known as the terpenome and are the largest class of natural products, whose biosynthesis refers to various kinds of enzymes. To date, there is no terpenome-related enzyme database, which is a desire for enzyme mining, metabolic engineering and discovery of new natural products related to terpenoids. In this work, we have constructed a comprehensive database called TeroENZ (http://terokit.qmclab.com/browse_enz.html) containing 13 462 enzymes involved in the terpenoid biosynthetic pathway, covering 2541 species and 4293 reactions reported in the literature and public databases. At the same time, we classify enzymes according to their catalytic reactions into cyclase, oxidoreductase, transferase, and so on, and also make a classification according to species. This meticulous classification is beneficial for users as it can be retrieved and downloaded conveniently. We also provide a computational module for isozyme prediction. Moreover, a module named TeroMAP (http://terokit.qmclab.com/browse_rxn.html) is also constructed to organize all available terpenoid enzymatic reactions into an interactive network by interfacing with the previously established database of terpenoid compounds, TeroMOL. Finally, all these databases and modules are integrated into the web server TeroKit (http://terokit.qmclab.com/) to shed light on the field of terpenoid research. Database URL http://terokit.qmclab.com/.

Heteromerization of short-chain trans-prenyltransferase controls precursor allocation within a plastidial terpenoid network

Terpenes are the largest and most diverse class of plant specialized metabolites. Sesterterpenes (C25), which are derived from the plastid methylerythritol phosphate pathway, were recently characterized in plants. In Arabidopsis thaliana, four genes encoding geranylfarnesyl diphosphate synthase (GFPPS) (AtGFPPS1 to 4) are responsible for the production of GFPP, which is the common precursor for sesterterpene biosynthesis. However, the interplay between sesterterpenes and other known terpenes remain elusive. Here, we first provide genetic evidence to demonstrate that GFPPSs are responsible for sesterterpene production in Arabidopsis. Blockage of the sesterterpene pathway at the GFPPS step increased the production of geranylgeranyl diphosphate (GGPP)-derived terpenes. Interestingly, co-expression of sesterTPSs in GFPPS-OE (overexpression) plants rescued the phenotypic changes of GFPPS-OE plants by restoring the endogenous GGPP. We further demonstrated that, in addition to precursor (DMAPP/IPP) competition by GFPPS and GGPP synthase (GGPPS) in plastids, GFPPS directly decreased the activity of GGPPS through protein-protein interaction, ultimately leading to GGPP deficiency in planta. Our study provides a new regulatory mechanism of the plastidial terpenoid network in plant cells.

Phytochemical Composition of Combretum molle (R. Br. ex G. Don.) Engl. & Diels Leaf and Stem Extracts

The demand for medicinal plants is on a rise due to their affordability, accessibility and relatively non-toxic nature. Combretum molle (Combretaceae) is used in African traditional medicine to treat a number of diseases. This study aimed to screen the phytochemical composition of the hexane, chloroform and methanol extracts of C. molle leaves and stems using qualitative phytochemical screening. Additionally, the study aimed to identify the functional phytochemical groups, determine the elemental composition and provide a fluorescence characterization of the powdered leaves and stems by performing Fourier transform infrared spectroscopy (FTIR), energy-dispersive X-ray (EDX) microanalyses and fluorescence microscopy. Phytochemical screening revealed the presence of alkaloids, flavonoids, phenolic compounds, polyphenols, terpenoids, tannins, coumarins, saponins, phytosterols, gums, mucilage, carbohydrates, amino acids and proteins within all leaf and stem extracts. Lipids and fixed oils were additionally present within the methanol extracts. FTIR demonstrated significant peaks in absorption frequency in the leaf at wavelengths of 3283.18, 2917.81, 1617.72, 1318.83, 1233.97, 1032.32 and 521.38 cm^-1, and in the stem at 3318.91, 1619.25, 1317.13, 1032.68, 780.86 and 516.39 cm^-1. These corresponded to the functional groups of chemical compounds including alcohols, phenols, primary amines, alkyl halides, alkanes and alkyl aryl ethers, corroborating the presence of the detected phytochemicals within the plant. EDX microanalyses showed the elemental composition of the powdered leaves (68.44% C, 26.72% O, 1.87% Ca, 0.96% Cl, 0.93% Mg, 0.71% K, 0.13% Na, 0.12 % Mn and 0.10% Rb) and stems (54.92% C, 42.86% O, 1.7% Ca, 0.43% Mg and 0.09% Mn). Fluorescence microscopy provided a characteristic evaluation of the plant in its powdered form and revealed distinct colour changes in the material when treated with various reagents and viewed under ultraviolet light. In conclusion, the phytochemical constituents of the leaves and stems of C. molle confirm the suitability of this species for use in traditional medicine. The findings from this study suggest the need to validate the use of C. molle in the development of modern medicines.

Efficient production of clerodane and ent-kaurane diterpenes through truncated artificial pathways in Escherichia coli

The clerodane and ent-kaurane diterpenoids are two typical categories of diterpenoid natural products with complicated polycyclic carbon skeletons and significant pharmacological activities. Despite exciting advances in organic chemistry, access to these skeletons is still highly challenging. Using synthetic biology to engineer microbes provides an innovative alternative to bypass synthetic challenges. In this study, we constructed two truncated artificial pathways to efficiently produce terpentetriene and ent-kaurene, two representative clerodane and ent-kaurane diterpenes, in Escherichia coli. Both pathways depend on the exogenous addition of isoprenoid alcohol to reinforce the supply of IPP and DMAPP via two sequential phosphorylation reactions. Optimization of these constructs provided terpentetriene and ent-kaurene titers of 66 ± 4 mg/L and 113 ± 7 mg/L, respectively, in shake-flask fermentation. The truncated pathways to overproduce clerodane and ent-kaurane skeletons outlined here may provide an attractive route to prepare other privileged diterpene scaffolds.