Boswellia sacra has the properties of activating blood circulation, fixing pain, subduing swelling and promoting muscle growth. However, the anti-inflammatory active ingredients and molecular mechanisms of Boswellia sacra are still not clearly explored. Boswellia sacra was grounded and extracted using 95% ethanol, the extracts were separated by column chromatography preparation to give compounds. Spectral analysis and quantum calculations confirmed the structures of compounds and identified compound 1 as a new compound. Compounds 1-3 showed potent inhibitory activities and their effects on inflammatory mediator NO and inflammatory cytokines were examined by ELISA assay. Furthermore, their modulatory mechanism on inflammatory signal pathways was explored.

Stevioside is a secondary metabolite of diterpenoid glycoside production in plants. It has been used as a natural sweetener in various foods because of its high sweetness and low-calorie content. In this study, we constructed a Saccharomyces cerevisiae strain for the complete synthesis of stevioside using a metabolic engineering strategy. Firstly, the synthesis pathway of steviol was modularly constructed in S. cerevisiae BY4742, and the precursor pathway was strengthened. The yield of steviol was used as an indicator to investigate the expression effect of different sources of diterpene synthases under different combinations, and the strains with further improved steviol yield were screened. Secondly, glycosyltransferases were heterologously expressed in this strain to produce stevioside, the sequence of glycosyltransferase expression was optimized, and the uridine diphosphate-glucose (UDP-Glc) supply was enhanced. Finally, the results showed that the strain SST-302III-ST2 produced 164.89 mg/L of stevioside in a shake flask experiment, and the yield of stevioside reached 1104.49 mg/L in an experiment employing a 10 L bioreactor with batch feeding, which was the highest yield reported. We constructed strains with a high production of stevioside, thus laying the foundation for the production of other classes of steviol glycosides and holding good prospects for application and promotion.

Eight previously undescribed diterpenoids, caesamins A-H (1-8), were separated and identified from the seeds of Caesalpinia minax Hance. Their structures were characterized by extensive spectroscopic data and X-ray crystallographic analysis. Structurally, caesamin A (1) is the first cassane-type diterpenoid with a C23 carbon skeleton containing an unusual isopropyl. Caesamin F (6) represents the first example of cleistanthane diterpenoid from the genus Caesalpinia. Caesamins B (2) and F (6) exhibited inhibitory activity against LPS-induced nitric oxide production in RAW 264.7 macrophages with IC50 values of 45.67 ± 0.92 and 42.99 ± 0.24 μM, comparable to positive control 43.69 ± 2.62 μM of NG-Monomethyl-L-arginine. Furthermore, the chemotaxonomic significance of the isolates was discussed.

Sclareol, a diterpene alcohol, is the most common starting material for the synthesis of ambrox, which serves as a sustainable substitute for ambergris, a valuable fragrance secreted by sperm whales. Sclareol has also been proposed to possess antibacterial, antifungal, and anticancer activities. However, in nature, sclareol is only produced by a few plant species, including Cistus creticus, Cleome spinosa, Nicotiana glutinosa, and Salvia sclarea, which limits its commercial application. In this study, we cloned the two genes responsible for sclareol biosynthesis in S. sclarea, labda-13-en-8-ol diphosphate synthase (LPPS) and sclareol synthase (SS), and overexpressed them in tobacco (Nicotiana tabacum L.). The best transgenic tobacco lines accumulated 4.1 μg/cm2 of sclareol, which is comparable to the sclareol production of N. glutinosa, a natural sclareol producer. Thus, sclareol synthesis in tobacco represents a potential alternative means for the production of this high-value compound.

Croton laui (Euphorbiaceae) is a traditional medicinal plant used by the Li ethnic group in China to treat headaches, stomachaches, and diphtheria. To understand the pharmacological basis of its medicinal use, an extensive investigation of the ethanolic extract of the bark of C. laui was performed. After repeated chromatography, twenty-four undescribed labdane-type diterpenoids, lauinoids A-X (1-24), and five known analogs (25-29) were isolated. Their structures and absolute configurations were established using a combination of spectroscopic analyses, electronic circular dichroism, nuclear magnetic resonance calculations, and single-crystal X-ray diffraction. Among them, compounds 1-3 exhibited an 11(12 → 13)-abeo-16-nor-labdane skeleton, which originated putatively from 9 through a plausible pathway that involves a semipinacol rearrangement process. Compounds 11 and 12 belong to the rare class of 14,15-dinor-labdane diterpenoids. Compounds 18 and 28 exhibited substantial inhibitory effects by suppressing lipopolysaccharide-induced NO production in RAW 264.7 macrophages, with IC50 values of 3.37 ± 0.23 and 5.82 ± 0.28 μM, respectively. This study has greatly expanded the chemical diversity of labdane diterpenoids from C. laui and will guide future research on this ethnomedicinal plant.

Cancer incidences are rising each year. In 2020, approximately 20 million new cancer cases and 10 million cancer-related deaths were recorded. The World Health Organization (WHO) predicts that by 2024 the incidence of cancer will increase to 30.2 million individuals annually. Considering the invasive characteristics of its diagnostic procedures and therapeutic methods side effects, scientists are searching for different solutions, including using plant-derived bioactive compounds, that could reduce the probability of cancer occurrence and make its treatment more comfortable. In this regard, oridonin (ORI), an ent-kaurane diterpenoid, naturally found in the leaves of Rabdosia rubescens species, has been found to have antitumor, antiangiogenesis, antiasthmatic, antiinflammatory, and apoptosis induction properties. Extensive research has been performed on ORI to find various mechanisms involved in its anticancer activities. This review article provides an overview of ORI\'s effectiveness on murine and human cancer populations from 1976 to 2022 and provides insight into the future application of ORI in different cancer therapies.

A new labdane diterpene (1), two new norsesquiterpenoids (2-3), as well as eight known terpenoids (4-11) were isolated from the seeds of Alpinia galanga (Zingiberaceae). Their structures and absolute configurations were elucidated by 1D, 2D NMR, MS, and comparison of their experimental and calculated electronic circular dichroism (ECD). The acetylcholinesterase (AChE) inhibitory activities of all the isolated compounds (1-11) were evaluated and the result showed that compounds 6 and 9 had inhibitory activity against AChE, with IC50 values at 295.70 and 183.91 μM, whereas other compounds did not show any inhibitory activity.

A chemical investigation on the fruiting bodies of Ganoderma lucidum led to the isolation and identification of five undescribed ergosteroids including two des-D-steroids (3 and 4) and one rare 6/6/7/5-fused carbon skeletal ergosterol (5) along with one 19-nor labdane-type diterpenoid (6). Their structures including their absolute configurations, were assigned by spectroscopic methods, ECD calculations, and X-ray diffraction analysis. In addition, the anti-inflammatory activities of all the isolates were evaluated. The results indicated that compound 1 can significantly down-regulate the protein expression of iNOS and COX-2 at 20 μM in LPS- stimulated RAW264.7 cells.

Ent-kaurane diterpenes are a large group of natural products, with more than 1,000 compounds since their discovery. Due to their excellent biological activities and complex polycyclic structures, these compounds have attracted organic synthesis chemists around the world to be devoted to achieve their total synthesis. At present, the isolated C-20-oxygenated ent-kaurane diterpenes are the most abundant of these natural products, reaching more than 350 in number. However, only total syntheses of 3,20-epoxy, 7,20-epoxy and 19,20-lactone ent-kaurane diterpenes have been reported. In this review, we elaborate the synthesis of these three types of C-20 oxygenated ent-kaurane natural products, discuss these synthetic strategies in detail, and provide good guidance and reference for the synthesis of other C-20 oxygenated compounds.

The natural variation of plant-specialized metabolites represents the evolutionary adaptation of plants to their environments. However, the molecular mechanisms that account for the diversification of the metabolic pathways have not been fully clarified. Rice plants resist attacks from pathogens by accumulating diterpenoid phytoalexins. It has been confirmed that the composition of rice phytoalexins exhibits numerous natural variations. Major rice phytoalexins (momilactones and phytocassanes) are accumulated in most cultivars, although oryzalactone is a cultivar-specific compound. Here, we attempted to reveal the evolutionary trajectory of the diversification of phytoalexins by analyzing the oryzalactone biosynthetic gene in Oryza species. The candidate gene, KSLX-OL, which accounts for oryzalactone biosynthesis, was found around the single-nucleotide polymorphisms specific to the oryzalactone-accumulating cultivars in the long arm of chromosome 11. The metabolite analyses in Nicotiana benthamiana and rice plants overexpressing KSLX-OL indicated that KSLX-OL is responsible for the oryzalactone biosynthesis. KSLX-OL is an allele of KSL8 that is involved in the biosynthesis of another diterpenoid phytoalexin, oryzalexin S and is specifically distributed in the AA genome species. KSLX-NOL and KSLX-bar, which encode similar enzymes but are not involved in oryzalactone biosynthesis, were also found in AA genome species. The phylogenetic analyses of KSLXs, KSL8s, and related pseudogenes (KSL9s) indicated that KSLX-OL was generated from a common ancestor with KSL8 and KSL9 via gene duplication, functional differentiation, and gene fusion. The wide distributions of KSLX-OL and KSL8 in AA genome species demonstrate their long-term coexistence beyond species differentiation, suggesting a balancing selection between the genes.