Chuktabularins E-T, 16-Norphragmalin Limonoids from Chukrasia tabularis var. velutina

Chukrasia tabularis limonoid plays anti-inflammatory role by regulating NF-κB signaling pathway in lipopolysaccharide-induced macrophages

Background

Chukrasia tabularisis, a well-known tropical tree native to southeastern China, has anti-inflammatory and antioxidant activities, and contains large amounts of limonoids and triterpenoids.

Objective

The aim of this study was to investigate the potential anti-inflammatory activity of limonoids from C. tabularis on lipopolysaccharide (LPS)-mediated RAW264.7 cells.

Methods and results

Using a bioassay-guided approach, the chemical fraction with high anti-inflammatory activity was found and its chemical constituents were investigated. Phytochemical studies on active extracts resulted in the separation of three novel phragmalin limonoids (1-3), together with two known limonoids (4-5) and 11 tirucallane triterpenes (6-16). The activity of these isolated compounds in the production of nitric oxide (NO) on LPS-reated macrophages was evaluated. Limonoid 2 indicated significant anti-inflammatory activities with IC50 value of 4.58 μM. Limonoid 2 notably inhibited the production of NO, interleukin- 6 and tumor necrosis factor-α on macrophage. Signal transduction and activation of STAT and NF-κB activators were effectively blocked by limonoid 2.

Conclusions

These results indicate that limonoid 2 has an anti-inflammatory effect by the inhibiting JAK2/STAT3, iNOS/eNOS, and NF-κB signaling pathways and regulating inflammatory mediators.

Phragmalin-Type Limonoids from the Fruits of Chukrasia tabularis and Their Anti-Inflammatory Activity

Phytochemical investigation on the fruits of C. tabularis led to the isolation of five new phragmalin-type limonoids (1-5) and four known ones (6-9). The structures of the new compounds 1-5, named chuktabamalins A-E, were elucidated via spectroscopic techniques (HRESIMS, 1D and 2D NMR) and were comparable with the literature data of known compounds. In addition, new compounds were evaluated for in vitro anti-inflammatory activity. Compounds 1, 2, 3 and 5 showed moderate anti-inflammatory activity with IC₅₀ values of 21.72 ± 2.79, 23.29 ± 1.00, 47.08 ± 3.47 and 66.67 ± 2.89 μM, respectively.

Cucurbitane-type triterpenoids from the fruits of Citrullus colocynthis

A phytochemical investigation of the fruits of Citrullus colocynthis resulted in the isolation of 21 structurally diverse cucurbitane triterpenoids, including 9 previously undescribed ones, colocynins A-I (1-9). Their absolute configurations were elucidated by means of quantum chemical electronic circular dichroism (ECD) calculations, CD exciton chirality method, and single-crystal X-ray crystallography. Colocynins A-C (1-3) represent the first examples of nonanorcucurbitane-type triterpenoids. An anti-acetylcholinesterase activity assay showed that 6, 10, 13, 18, and 20 exhibited inhibitory activities, with IC₅₀ values ranging from 5.0 to 21.7 μM. In addition, 18 and 21 showed significant cytotoxicity against PACA, A431, and HepG2 cells, with IC₅₀ values ranging from 0.042 to 0.60 and 3.6-14.4 μM, respectively.

Bioactivity-guided isolation of anti-inflammatory limonins from Chukrasia tabularis

Chukrasia tabularis is an economically important tree and widely cultured in the southeast of China. Its barks, leaves, and fruits are consumed as a traditional medicine and perceived as a valuable source for bioactive limonin compounds. The extracts from root barks of C. tabularis showed significant anti-inflammatory effect. The aim of this research was to explore the material basis of C. tabularis anti-inflammatory activity, and to purify and identify anti-inflammatory active ingredients. By a bioassay-guided isolation of dichloromethane fraction obtained two novel phragmalin limonins, Chukrasitin D and E (1 and 2), together with 12 known limonins (3-14). The chemical structure of these compounds is determined on the basis of extensive spectral analysis and chemical reactivity. In addition, the activities of these isolated limonins on the production of nitric oxide (NO), tumor necrosis factor alpha (TNF-α), and nuclear factor kappa B (NF-κB) in RAW264.7 cells induced by lipopolysaccharide (LPS) were evaluated. Limonins 1 and 2 indicated significant anti-inflammatory activity with IC50 values of 6.24 and 6.13 μM. Compound 1 notably inhibited the production of NF-κB, TNF-α and interleukin 6 (IL-6) in macrophages. The present results suggest that the root barks of C. tabularis exhibited anti-inflammatory effect and the limonins may be responsible for this activity.

Dracomolphin A-E, new lignans from Dracocephalum moldavica

Eight new lignans, dracomolphin A-E (1-8), together with eight known lignans (9-16) were isolated from the aerial part of Dracocephalum moldavica. The structures of the isolated compounds were established based on NMR and HRESIMS data. Dracomolphin A (1-4) was elucidated as a lignan possessed a 5-membered ketal ring formed between C-8' and C-3, C-4. The two stereogenic centers rendered dracomolphin A as a mixture of two diastereomeric pairs of enantiomers (1-4). All of the four isomers were separated successfully by using chiral HPLC and their stereochemical features were determined by CD spectra. Bioactivity screening revealed that compounds 1-4, 6, 7, 12, 15 and 16 were potential Nrf2 transcriptional activators. Dracomolphin E (8) reduced cell viability of lung cancer NCI-H292 cells associated with apoptosis.

Carapanins A-C: new limonoids from andiroba (Carapa guianensis) fruit oil

Carapanins A-C (1-3) were isolated from the fruit oil of Carapa guianensis. Compounds 1 and 2 are limonoids with unique structures. Namely, compound 1 is an andirobin-type limonoid with a C-15/C-30 γ-lactone instead of the δ-lactone of the D-ring, and compound 2 is a mexicanolide-type limonoid with a C-16/C-30 δ-lactone ring. The absolute structures of 1 and 2 were determined using X-ray crystallography, whereas the structure of 3 was established mainly via NMR and mass spectroscopy. The inhibitory effects of 1-3 on nitric oxide production were evaluated, and it was revealed that 2 and 3 were potent nitric oxide inhibitors.

Ciliatasecones A–C, three rearranged limonoids from Toona ciliata var. yunnanensis

Three rearranged limonoids with a novel ring-seco model and an unprecedented cycle system were isolated from Toona ciliata var. yunnanensis.

Six New Phragmalin Limonoids from the Stems of Chukrasia tabularis A. Juss

Six new phragmalin limonoids, named moluccensin Z1 (1), moluccensin Z2 (2), carapanolide Y (3), tabulalin N (4), chukvelutilide A1 (5), and velutinasin J (6), as well as two known compounds, chukvelutilide A (7) and velutinasin D (8) were isolated from the stems of Chukrasia tabularis A. Juss. The structures of the new compounds 1–6 were confirmed by spectroscopic methods, including IR and HRESIMS, as well as 1D and 2D NMR, and by comparisons with the data of known analogues. All compounds were tested for α-glucosidase and acetylcholinesterase inhibitory activities. However, none of the compounds was active against α-glucosidase and acetylcholinesterase in vitro.

Two new phragmalin-type limonoids from Chukrasia tabularis and their α-glucosidase inhibitory activity

Phytochemical investigation on the stems of C. tabularis (Meliaceae) led to the isolation of two new phragmalin-type limonoids, named tabularisins S and T (1-2), along with five known ones (3-7). The structures of the new limonoids were established by spectroscopic methods including UV, IR, HRESIMS, and 1D and 2D NMR. All the compounds were evaluated for α-glucosidase inhibitory activity in vitro. Compounds 2 and 3 exhibited significant inhibitory activity against α-glucosidase with IC50 values of 0.15 and 0.03 mM, respectively (acarbose as positive control, IC50 0.95 mM).

New Phragmalin-Type Limonoids from Chukrasia tabularis and Their α-Glucosidase Inhibitory Activity

Phytochemical investigation on the stems of C. tabularis led to the isolation of five new phragmalin-type limonoids and six known ones. The structures of the new compounds 1–5, named chukbularisins A–E, were elucidated by spectroscopic techniques (IR, HRESIMS, 1D and 2D NMR) and comparisons with published data. All the compounds were evaluated for in vitro α-glucosidase inhibitory activity. Compounds 2, 3, 4, 5, and 8 exhibited inhibitory activity against α-glucosidase with IC₅₀ values of 0.06 ± 0.008, 0.04 ± 0.002, 0.52 ± 0.039, 1.09 ± 0.040, and 0.20 ± 0.057 mM, respectively (using acarbose as positive control, IC₅₀ 0.95 ± 0.092 mM).

Limonoids with diverse frameworks from the stem bark of Entandrophragma angolense and their bioactivities

Entangolensins A–P (1–16), sixteen new limonoids with diverse frameworks, were obtained from the stem bark of Entandrophragma angolense.

Further C-15-acyl phragmalin derivatives from Chukrasia tabularis A. Juss

Relying on characteristic double UV absorptions (210 and 270 nm), sixteen phragmalins with three types of enolic acyl substituents at C-15 were isolated directly from EtOH extracts of the seeds of Chukrasia tabularis A. Juss. Eight of these compounds possessed a C-15-acetyl phragmalin skeleton, and the basic carbon skeleton and absolute configuration of one of these was determined by NMR and X-ray diffraction analysis, while the structures of the other phragmalins were determined via NMR, HR-MS, and CD spectra. Additionally, all of the isolates were tested for inhibition against lipopolysaccharide (LPS)-induced nitric oxide (NO) production in RAW264.7 macrophages and cytotoxicity in SMMC-7721, MCF-7 and U2OS tumor cells.

An overview on chemical aspects and potential health benefits of limonoids and their derivatives

Limonoids are heavily oxygenated, modified triterpenes dominant in Meliaceae and Rutaceae plant families. The term 'limonoid' is derived from limonin, which was first identified as the bitter constituent of Citrus seeds in 1841. This group of secondary metabolites exhibits a wide range of biological properties, including anticancer, antibacterial, antifungal, antimalarial, and antiviral activities. Significant progress on the role of limonoids as promising candidates for cancer chemoprevention and/or therapy has been achieved in particular in recent years. The aim of this review article is to discuss the recent developments on limonoids chemical aspects and biological activities with the relationship between structure and activity, supporting the new possibilities for the medicinal and/or nutraceutical use of these compounds.

A,D-seco-limonoids from the stems of Clausena emarginata

Twelve new A,D-seco-limonoids, clauemargines A-L (1-12), and three known analogues were isolated from the stems of Clausena emarginata. The absolute configurations of 1 and 5 were confirmed by X-ray crystallography and ECD spectroscopy, respectively. Compounds 1, 2, 8-10, and 13 showed moderate inhibitory effects on LPS-induced NO production (IC50 values<10 μM).

Cassane-type diterpenoids from the seed kernels of Caesalpinia bonduc

Seven new cassane diterpenoids (1-7), along with three known compounds (8-10), were isolated from the seed kernels of Caesalpinia bonduc. The structures were elucidated by extensive 1D and 2D NMR (HSQC, HMBC and ROESY) and mass (HRESIMS) spectroscopic data analyses. The structure and absolute configuration of compound 1 were confirmed by a single-crystal X-ray diffraction experiment. All isolates were tested for their cytotoxicity against HepG-2, MCF-7 and MG-63 cells, and 8-10 showed weak inhibitory activities.

Bioactive norditerpenoids from Flickingeria fimbriata

11 new diterpenoids determined by NMR, X-ray diffraction, calculated ECD and CD exciton chirality methods were isolated from Flickingeria fimbriata.

Natural products chemistry research 2010's progress in China

This article reviews the progresses made by Chinese scientists in the field of natural products chemistry in 2010. Selected compounds with unique structural features and/or promising bioactivities were described herein on the basis of structural types.

Two new phragmalin-type limonoids from Chukrasia tabularis var. velutina

Two new phragmalin-type limonoids with different structural skeletons, chuktabrin K (1) and tabulalin J (2), were isolated from the stem barks of Chukrasia tabularis var. velutina in the course of our ongoing research work in this area. Compound 1 was a 16-norphragmalin with an enolic alkyl appendage at C-15, and the carbonate moiety in 1 was also rare in natural organic molecules. The basic skeleton of compound 2 was a D-ring-opened phragmalin. Their structures were elucidated on HR-ESI-MS, ¹H and ¹³C-NMR, HSQC, HMBC, and ROESY experiments.

Triterpenoids

This review covers the isolation and structure determination of triterpenoids, including squalene derivatives, protostanes, lanostanes, holostanes, cycloartanes, dammaranes, euphanes, tirucallanes, tetranortriterpenoids, quassinoids, lupanes, oleananes, friedelanes, ursanes, hopanes, serratanes and saponins; 305 references are cited.

Phragmalin-type limonoid orthoesters from Chukrasia tabularis var. velutina

Nine new phragmalin-type limonoid orthoesters, tabulalides F-N (1-9), together with three known compounds, tabulalides C and D, and tabularisin N (10-12), were isolated from the stem bark of Chukrasia tabularis var. velutina. Extensive spectroscopic technologies were applied to elucidate the structures of these new compounds, including the application of circular dichroism (CD) exciton chirality method for the determination of the absolute configurations of 1 and 2. Tabulalide F (1) has a rare orthoisobutylate moiety in phragmalin-type limonoid orthoesters. These compounds were evaluated for cytotoxic activity against five human cancer cell lines in vitro. Tabulalide G (2) exhibits moderate cytotoxic activity against MCF-7 with IC(50) value of 20.4 µmol/l, and other compounds have weak inhibitory effects on the growth of tested tumor cells.

Two new limonoids from the stem barks of Chukrasia tabularis var. velutina

Two new phragmalin-type limonoid orthoesters, C-15 enolic acyl type and 13/14/18-cyclopropanyl type, named chukvelutilide H (1) and tabularin R (2), together with three known limonoid orthoesters (3-5), were isolated from the stem barks of Chukrasia tabularis var. velutina. The structures of these two new compounds were elucidated on their extensive HR-ESI-MS, 1D, and 2D spectroscopic analysis including HSQC, HMBC, and ROESY experiments.