Bioactive Diterpenoids from the Stems of Euphorbia antiquorum

Cycloartane-type triterpenoids and steroids from Trichilia connaroides and their multidrug resistance reversal activities

Four undescribed cycloartane-type triterpenoids (1-4) and seven undescribed steroids (6-12), along with five known analogues (5 and 13-16), were isolated from the leaves of Trichilia connaroides. Their structures were identified based on the NMR data and HRESIMS, and the absolute configurations were determined through single-crystal X-ray diffraction analysis, Mosher's method, and ECD calculations. The multidrug resistance (MDR) reversal activities of all the isolates were assessed, and compounds 10 and 11 showed significant activities to reverse the MDR of MCF-7/DOX cells with IC50 values of 2.90 and 3.76 μM, respectively. These bioactive compounds may bring fresh insights into the research and development of MDR reversal agents.

Discovery of two ent-atisane diterpenoid lactones with AChE inhibitory activity from the roots of Euphorbia fischeriana

Euphorlactone A (1), a rare rearranged ent-atisane norditerpenoid with an undescribed 3-nor-2,4-olide-ent-atisane scaffold, and euphorlactone B (2), a new ent-atisane diterpenoid with an unprecedented seven-membered lactone ring C, were isolated from the roots of Euphorbia fischeriana. Their planar structures with absolute configurations were extensively elucidated by analysis of 1D and 2D NMR data, electronic circular dichroism (ECD) calculations, Rh2(OCOCF3)4-induced ECD curves, and single-crystal X-ray diffraction. Euphorlactone A (ELA) showed a remarkable AChE (acetylcholinesterase) inhibitory activity (IC50 = 2.13 ± 0.06 μM and Ki = 0.058 μM), which was five times stronger than that of the positive control (rivastigmine, IC50 = 12.46 ± 0.82 μM), and further in vitro enzyme inhibition kinetic analysis and molecular docking studies were performed to investigate the AChE inhibitory mechanism.

Diterpenoids from Euphorbia lactea and their anti-HIV-1 activity

Nine undescribed diterpenoids, euphlactenoids A-I (1-9), including four ingol-type diterpenoids (1-4) with a 5/3/11/3-tetracyclic framework and five ent-pimarane-type diterpenoids (5-9), together with thirteen known diterpenoids (10-22), were identified from the leaves and stems of Euphorbia lactea Haw. The structures and absolute configurations of compounds 1-9 were unequivocally elucidated on the basis of spectroscopic analysis, ECD calculations and single crystal X-ray diffraction. Compounds 3 and 16 showed anti-HIV-1 effects with IC₅₀ values of 1.17 μM (SI = 16.54) and 13.10 μM (SI = 1.93), respectively.

Secotrijugins A-D, four highly oxidized and rearranged limonoids from Trichilia sinensis and their anti-inflammatory activity

Four undescribed highly oxidized and rearranged limonoids, secotrijugins A-D, were purified from the leaves and twigs of Trichilia sinensis. Within them, secotrijugin A was characterized as a rare 30-nortrijugin-type limonoid with an unusual cleavage of 1,14-ether bond, secotrijugins B and C represented new examples with the cleavage of δ-lactone ring D, and secotrijugin D was a rare trijugin-type limonoid with an unusual 2,6-oxygen bridge. The structures of limonoids were characterized by means of spectroscopic analysis and ECD calculations. The cellular screening revealed that secotrijugin B was the most active against LPS-stimulated NO production in BV-2 cells, which played an anti-inflammatory role by downregulating COX-2 and iNOS protein expression. The further in vivo experiments confirmed that secotrijugin B had strong in vivo anti-inflammatory effect via suppressing NO and ROS generation.

Phytochemical and pharmacological review of diterpenoids from the genus Euphorbia Linn (2012-2021)

ETHNOPHARMACOLOGICAL RELEVANCE

Euphorbia is one of the major genera in angiosperms, which is widely distributed all over the world, including Asia, Africa and Central and South America. The roots or tubers of Euphorbia are famous for medicinal purposes, especially in China. Many of them, such as Euphorbia pekinensis Rupr, Euphorbia fischeriana Steud and Euphorbia Kansui S.L.Liou ex S.B.Ho. . are used as Chinese herbal medicines.

AIM OF THE STUDY

This paper reviews the diterpenoids isolated from the genus Euphorbia species and the pharmacological activities of these compounds to evaluate its traditional use and potential future development.

MATERIALS AND METHODS

Information on the studies of the genus Euphorbia Linn was collected from scientific journals, books and reports via library and electronic data search (Scifinder, Web of Science, PubMed, Elsevier, Scopus, Google Scholar, Springer, Science Direct, Wiley, ACS, CNKI and Kew Plants of the Word Online). Meanwhile, it was also obtained from published works of material medica, folk records, ethnophmacological literatures, Ph.D. and Masters dissertations.

RESULTS

Known as the main constituents of the genus Euphorbia Linn, Diterpenoids possess many pharmacological properties such as anti-inflammation, antiviral activities and cytotoxicity. To date, various types of diterpenoids were identified from this genus, including isopimarane, rosane, abietane, ent-kaurane, ent-atisane. cembrane, casbane, lathyrane, myrsinane, jatropholane, tigliane, ingenane, jatrophane, paraliane, pepluane, and euphoractin.

CONCLUSIONS

This review describes 14 types of diterpenoid isolated from 45 Euphorbia species from 2012 to 2021, a total of 615 compounds. Among them, mainly include jatrophane (171), lathyrane (92), myrsinane (62), abietane (70), ent-atisane (36), ent-kaurane (7), tigliane (26) and ingenane (19). The possible biological pathways of these compounds were presumed. At the same time, more than 10 biological activities of these compounds were summarized, such as anti-inflammation, antiviral activities and cytotoxicity.

Euphorbia diterpenoids: isolation, structure, bioactivity, biosynthesis, and synthesis (2013-2021)

Covering: 2013 to 2021As the characteristic metabolites of Euphorbia plants, Euphorbia diterpenoids have always been a hot topic in related science communities due to their intriguing structures and broad bioactivities. In this review, we intent to provide an in-depth and extensive coverage of Euphorbia diterpenoids reported from 2013 to the end of 2021, including 997 new Euphorbia diterpenoids and 78 known ones with latest progress. Multiple aspects will be summarized, including their occurrences, chemical structures, bioactivities, and syntheses, in which the structure-activity relationship and biosynthesis of this class will be discussed for the first time.

Diverse diterpenoids with α-glucosidase and β-glucuronidase inhibitory activities from Euphorbia milii

Four undescribed regular rosane-type diterpenoids euphominoids M-P and three undescribed rearranged rosane-type diterpenoids euphomilones C-E were isolated from the whole plants of Euphorbia milii Des Moul., along with nine known compounds. Their structures were elucidated by detailed interpretation of the NMR and mass spectroscopy. The absolute configurations were established by single-crystal X-ray diffraction experiments, as well as comparative analyses of calculated and experimental ECD spectra. Euphominoid M featured a highly oxygenated ring A and a rare four-membered oxygen ring while euphomilones C-E possessed 7/5/6 or 5/7/6 fused ring systems, which were rarely occurring in rosane-type diterpenoids. In the in-vitro bioassays, 19-norrosa-1,3,5(10),15-tetraene-2,3-diol and antiquorin showed more potent α-glucosidase inhibitory activity than the positive control acarbose while euphominoid C exhibited significant inhibitory activity against both α-glucosidase and β-glucuronidase. To the best of our knowledge, it was the first time that rosane-type diterpenoids were reported as β-glucuronidase inhibitors.

Diterpenoids from the genus Euphorbia: Structure and biological activity (2013-2019)

Euphorbiaceae is one of the largest families of higher plants, including 7500 species, and many of them are used as medicines in China. From 2013 to 2019, a total of 455 previously undescribed diterpenoids were isolated from 53 species of Euphorbia, and some skeleton types were first discovered from the genus Euphorbia. Most of the diterpenoids isolated from Euphorbia spp. have been tested for their biological activity, and some of them were first reported for Euphorbia diterpenoids in recent years, such as neuroprotection, antimalarial activity and inhibition of osteoclast formation. In this review, we summarize all the isolated diterpenoids from the genus Euphorbia according to their skeleton types, classify all these diterpenoids into 26 normal classes and 37 novel skeleton types, and summarize their biological activity.

Alpha-Glucosidase Inhibitory Diterpenes from Euphorbia antiquorum Growing in Vietnam

Bioactive-guided phytochemical investigation of Euphorbia antiquorum L. growing in Vietnam led to the isolation of five ent-atisanes, one seco-ent-atisane, and one lathyrane (ingol-type). The structures were elucidated as ent-1α,3α,16β,17-tetrahydroxyatisane (1), ethyl ent-3,4-seco-4,16β,17-trihydroxyatisane-3-carboxylate (2), ent-atisane-3-oxo-16β,17-acetonide (3), ent-3α-acetoxy-16β,17-dihydroxyatisane (4), ent-16β,17-dihydroxyatisane-3-one (5), calliterpenone (6), and ingol 12-acetate (7). Their chemical structures were unambiguously determined by analysis of one-dimensional (1D) and two-dimensional (2D) nuclear magnetic resonance (NMR) and high resolution mass spectrometry, as well as by comparison with literature data. Among them, 1 is a new compound while 2 is an ethylated artifact of ent-3,4-seco-4,16β,17-trihydroxyatisane-3-carboxylic acid, a new compound. Isolates were evaluated for alpha-glucosidase inhibition. Compound 3 showed the most significant inhibitory activity against alpha-glucosidase with an IC₅₀ value of 69.62 µM. Further study on mechanism underlying yeast alpha-glucosidase inhibition indicated that 3 could retard the enzyme function by noncompetitive.

ent-Atisane diterpenoids: isolation, structure and bioactivity

Covering: up to 2020 ent-Atisane diterpenoids are a class of over 150 members with diverse structures and valuable bioactivities. These compounds share a curious history in which the synthesis of the archetypal member preceded its isolation from natural sources. In this review, we provide a comprehensive summary of the isolation, structure, and bioactivity of ent-atisane diterpenoids from their discovery in 1965 to the present day.

Diterpenoids from the aerial parts of Euphorbia antiquorum and their efficacy on nitric oxide inhibition

Eight previously undescribed diterpenoids of different types were isolated from ethyl acetate extract of the aerial parts of Euphorbia antiquorum L., along with fifteen known diterpenoids. Their structures and configurations were determined by 1D and 2D NMR, MS, and electronic circular dichroism (ECD). Additionally, the absolute configuration of ent-12-oxo-2,3-secobeyer-15-en-2,3-dioic acid-3-methyl ester was confirmed through single-crystal X-ray diffraction. Efficacy of the compounds on lipopolysaccharide (LPS)-stimulated nitric oxide (NO) production in murine macrophage J774.A1 cells was evaluated. ent-15-Acetoxylabda-8(17),13E-diene-3-one, ent-15-oxolabda-8(17),13E-diene-3-one and rhizophorin B was significantly suppressed NO production with IC₅₀ values of 11.7, 12.5 and 16.1 μM, respectively.

Anti-Inflammatory ent-Kaurane Diterpenoids from Isodon serra

Ten new ent-kaurane diterpenoids, including two pairs of epimers 1/2 and 4/5 and a 6,7-seco-ent-kauranoid 10, were obtained from the aerial parts of Isodon serra. The structures of the new compounds were confirmed by extensive spectroscopic methods and electronic circular dichroism (ECD) data analysis. An anti-inflammatory assay was applied to evaluate their nitric oxide (NO) inhibitory activities by using LPS-stimulated BV-2 cells. Compounds 1 and 9 exhibited notable NO production inhibition with IC₅₀ values of 15.6 and 7.3 μM, respectively. Moreover, the interactions of some bioactive diterpenoids with inducible nitric oxide synthase (iNOS) were explored by employing molecular docking studies.

Euphnerins A and B, Diterpenoids with a 5/6/6 Rearranged Spirocyclic Carbon Skeleton from the Stems of Euphorbia neriifolia

Euphnerins A (1) and B (2), two extremely modified diterpenoids possessing an unprecedented 5/6/6 rearranged spirocyclic carbon skeleton, and a biosynthetically related known diterpenoid (3) were purified from the stems of Euphorbia neriifolia. Their structures were identified by NMR experiments and X-ray diffraction analysis, as well as experimental and calculated electronic circular dichroism data comparison. A putative biosynthetic relationship of 1 and 2 with their presumed precursor 3 is proposed. Compound 1 showed NO inhibitory effects in lipopolysaccharide-stimulated BV-2 cells with an IC₅₀ value of 22.4 μM.

New diterpenoids from the stems of Euphorbia antiquorum growing in Vietnam

Phytochemical analysis of Euphorbia antiquorum stem extracts afforded two new ent-atisane compounds, ent-3α-acetoxy-16β,17,18-trihydroxyatisane (1) and ent-3α,14,16β,17-tetrahydroxyatisane (2) together with three known compounds, 20-deoxy-16-hydroxyingenol (3), ent-14[S],16α,17-trihydroxyatisan-3-one (4), and agallochaol C (5). Their structures were elucidated by spectroscopic data analysis and comparison with published NMR data. Compounds 1-5 were evaluated for α-glucosidase inhibition and cytotoxicity. Compounds 1, 4, and 5 revealed significant inhibitory activity against α-glucosidase with the IC₅₀ values of 119.9, 135.5, and 134.3 µM, respectively. None showed activity in cytotoxicity assay.

Novel Pathway for Chloramphenicol Catabolism in the Activated Sludge Bacterial Isolate Sphingobium sp. CAP-1

The chlorinated nitroaromatic antibiotic chloramphenicol (CAP) is a refractory contaminant that is widely present in various environments. However, few CAP-mineralizing bacteria have been documented, and a complete CAP catabolism pathway has yet to be identified. In this study, the bacterial strain Sphingobium sp. CAP-1 was isolated from an activated sludge sample and was shown to be capable of aerobically subsisting on CAP as the sole carbon, nitrogen, and energy source while simultaneously and efficiently degrading CAP. p-Nitrobenzoic acid (PNBA), p-nitrobenzaldehyde (PNBD), protocatechuate (PCA), and the novel side chain C₃-hydroxy-oxygenated product of CAP (O-CAP) were identified during CAP degradation. Strain CAP-1 was able to convert O-CAP to intermediate product PNBA. The putative functional genes associated with PNBA catabolism into the tricarboxylic acid cycle via PCA and floc formation were also identified by genome sequencing and comparative proteome analysis. A complete pathway for CAP catabolism was proposed. The discovery of a novel CAP oxidation/detoxification process and a complete pathway for CAP catabolism enriches the fundamental understanding of the bacterial catabolism of antibiotics, providing new insights into the microbial-mediated fate, transformation, and resistance risk of CAP in the environment. The molecular basis of CAP catabolism and floc formation in strain CAP-1 also offers theoretical guidance for the enhanced bioremediation of CAP-containing environments.

Anti-inflammatory neo-Clerodane Diterpenoids from Ajuga pantantha

Eight new neo-clerodane diterpenoids (1-8) were acquired from the aerial parts of Ajuga pantantha. Spectroscopic data analysis permitted the definition of their structures, and experimental and calculated electronic circular dichroism data were used to define their absolute configurations. Compounds 2 and 4-8 were found to have NO inhibitory effects with IC₅₀ values of 20.2, 45.5, 34.0, 27.0, 45.0, and 25.8 μM, respectively. The more potent compounds 2, 6, and 8 were analyzed to establish their anti-inflammatory mechanism, including regulation of the expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) proteins as well as their binding interactions with the two proteins.

Diterpenoids from the leaves of Casearia kurzii showing cytotoxic activities

A phytochemical investigation to obtain bioactive substances as lead compounds or agents for cancer led to the obtainment of six new and two known clerodane diterpenoids from the leaves of Casearia kurzii. Their structures were elucidated using NMR techniques and electronic circular dichroism (ECD) calculations. The subsequent biological cytotoxicity evaluation of these isolates toward human lung cancer A549, human cervical cancer HeLa, human chronic myeloid leukemia K562, and human hepatocellular carcinoma HepG2 was carried out. The most active compound 4 with an IC₅₀ value of 9.7 μM against HepG2 cells was selected to examine the cytotoxic mechanism, which induced the apoptosis and arrested the HepG2 cell cycle at S stage. The in vivo zebrafish experiments revealed that compound 4 had the property of inhibiting tumor proliferation and migration.