Two novel triterpenoids from Dysoxylum hainanense

Transcriptome analysis and differential expression in Arabidopsis thaliana in response to rohitukine (a chromone alkaloid) treatment

Rohitukine is a chromone alkaloid and precursor of potent anticancer drugs flavopiridol, P-276-00, and 2,6-dichloro-styryl derivative (11d) (IIIM-290). The metabolite is reported to possess anticancer, anti-inflammatory, antiadipogenic, immunomodulatory, gastroprotective, anti-implantation, antidyslipidemic, anti-arthritic, and anti-fertility properties. However, the physiological role of rohitukine in plant system is yet to be explored. Here, we studied the effect of rohitukine isolated from Dysoxylum gotadhora on Arabidopsis thaliana. The A. thaliana plants grown on a medium fortified with different rohitukine concentrations showed a significant effect on the growth and development. The root growth of A. thaliana seedlings showed considerable inhibition when grown on medium containing 1.0 mM of rohitukine. Transcriptomic analysis indicated the expression of 895 and 932 genes in control and treated samples respectively at a cut-off of FPKM ≥ 1 and P-value < 0.05. Gene ontology (GO) analysis revealed the upregulation of genes related to photosynthesis, membrane transport, antioxidation, xenobiotic degradation, and some transcription factors (TFs) in response to rohitukine. Conversely, rohitukine downregulated several genes including RNA helicases and those involved in nitrogen compound metabolism. The RNA-seq result was also validated by real-time qRT-PCR analysis. In light of these results, we discuss (i) likely ecological importance of rohitukine in parent plant as well as (ii) comparison between responses to rohitukine treatment in plants and mammals.

Triterpenoids from Dysoxylum genus and their biological activities

This study aims to analyze the ethnobotanical, chemical, and biological activities of triterpenoid compounds isolated from the Dysoxylum genus of the Meliaceae family between 1974 and 2021. The species are mainly distributed in Africa, Asia, and Australia, and used as a traditional medicine to treat various diseases. Triterpenoid was first isolated in 1976 and as tetranortriterpenoid or limonoid, it was named dysobinin. Several studies were conducted for more than 40 years on the plants' stems, bark, and leaves, where approximately 279 triterpenoid compounds from several groups such as dammarane, nortriterpenoid, oleanane, lupane, tirucallane, cyclolanostane, or cycloartane, glabretal, and cycloapoeuphane-types were isolated with some synthetic products. In addition, the hypothetical route of triterpenes biosynthesis from this genus was identified, and tirucallane-type were reported to be 37.6% of the total compounds. The anti-malarial, anti-feedant, antimicrobial, anti-inflammatory, antioxidant, vasodilative effect, anti-viral, cortisone reductase, and cytotoxic activities of the extract were also evaluated. The results showed the necessity of using the triterpenoid compounds from the Dysoxylum genus in traditional medicine and the discovery of new drugs.

Total Synthesis of Macrocyclic Dysoxylactam A

The total synthesis of dysoxylactam A, a novel 17-membered macrolactam with potent multi-drug-resistant reversing activities, has been achieved, starting from 4-pentene-1-al in a longest linear sequence of 17 steps and 9.5% overall yield. The key transformations consist of iterative aldol and ring-closing metathesis reactions for the construction of the stereochemically enriched polypropionate scaffold and the macrocycle, respectively.

Plant triterpenoids with bond-missing skeletons: biogenesis, distribution and bioactivity

Covering: up to December 2018 The polycyclic ABCD(E) framework of triterpenoids can miss a single endocyclic C-C bond as a result of a modification of the cyclization cascade that triggers their formation (interrupted- or diverted cascades), or can be the result of post-cyclization ring cleavage by late-stage oxidative modifications (seco-triterpenoids). Because of mechanistic and biogenetic differences, ring opening associated with loss of a skeletal fragment, as in nor-seco-triterpenoids (limonoids, quassinoids), will not be covered, nor will compounds where ring opening is part of a fragmentation cascade or of a multiple diversion from it. Even with these limitations, 342 bond-missing triterpenoids could be retrieved from the literature, with transversal distribution in the plant kingdom. Their structural diversity translates into a variety of biological targets, with dominance of potential applications in the realm of cancer, neuroprotection, and anti-infective therapy. In addition to the bioactivity and chemotaxonomic relevance of bond-missing triterpenoids, current knowledge on the genetic basis of interrupted- and diverted oxidosqualene cyclases will be summarized. This untapped source of enzymes could be useful to selectively modify triterpenoids by metabolic engineering, circumventing the bottlenecks of their isolation (poor yield or inadequate supply chain) to explore new areas of their chemical space.

Antimicrobial activity of oleanolic and ursolic acids: an update

Triterpenoids are the most representative group of phytochemicals, as they comprise more than 20,000 recognized molecules. These compounds are biosynthesized in plants via squalene cyclization, a C30 hydrocarbon that is considered to be the precursor of all steroids. Due to their low hydrophilicity, triterpenes were considered to be inactive for a long period of time; however, evidence regarding their wide range of pharmacological activities is emerging, and elegant studies have highlighted these activities. Several triterpenic skeletons have been described, including some that have presented with pentacyclic features, such as oleanolic and ursolic acids. These compounds have displayed incontestable biological activity, such as antibacterial, antiviral, and antiprotozoal effects, which were not included in a single review until now. Thus, the present review investigates the potential use of these triterpenes against human pathogens, including their mechanisms of action, via in vivo studies, and the future perspectives about the use of compounds for human or even animal health are also discussed.

Discovery of structurally diverse and bioactive compounds from plant resources in China

This review describes the major discoveries of structurally diverse and/or biologically significant compounds from plant resources in China, mainly from the traditional Chinese medicines (TCMs) since the establishment of our research group in 1999. In the past decade, a large array of biologically significant and novel structures has been identified from plant resources (or TCM) in our laboratory. The structural modification of several biologically important compounds led to more than 400 derivatives, some of which exhibited significantly improved activities and provided opportunities to elucidate the structure-activity relationship of the related compound class. These findings are important for drug discovery and help us understand the biological basis for the traditional applications of these plants in TCM.

Limonoids and triterpenoids from the twigs and leaves of Dysoxylum hainanense

Four new limonoids, dysohainanins A–D (1–4), and two new triterpenoids, dysohainanins E and F (5 and 6), together with seven known ones were isolated from the twigs and leaves of Dysoxylum hainanense Merr. The structures of the new compounds were determined by a variety of spectroscopic methods. The cytotoxic activities of these compounds were evaluated, and the known compound ent-19-nor-4,16,18-trihydroxy-8(14)-pomaren-15-one (13) showed in vitro cytotoxicity against HL-60, A-549, MCF-7, and SW480 cells, with IC₅₀ values of 24.3, 28.1, 30.7, and 22.5 µM, respectively. Compounds 2 and 3 were tested their insecticidal activities using brine shrimp and both of them were inactive.

Triterpenes and a triterpene glucoside from Dysoxylum cumingianum

Six triterpenes and a triterpene glucoside were isolated from the MeOH extract of the leaves of Dysoxylum cumingianum together with three known triterpenes. Their structures were elucidated by extensive spectroscopic analyses. In cytotoxicity assays against three human cancer cell lines, including a multi-drug resistant cancer cell line (KB-C2), compounds 1, 2 and 5 demonstrated significantly enhanced cytotoxicity against KB-C2 cells in the presence of 2.5 μM colchicine, as compared with those in the absence of colchicine. This result suggested that these triterpenes might show some MDR-reversing effects.

Triterpenoids

This review covers the isolation and structure determination of triterpenoids including squalene derivatives, protostanes, lanostanes, holostanes, cycloartanes, dammaranes, euphanes, tirucallanes, tetranortriterpenoids, lupanes, oleananes, friedelanes, ursanes, hopanes, isomalabaricanes and saponins; 574 references are cited.