Ceramicine A and walsogyne A, novel limonoids from two species of Meliaceae

Limonoids isolated from Chisocheton ceramicus Miq. and the antiadipogenic mechanism of action of ceramicine B

Different types of limonoids have been isolated from plants of the Chisocheton genus, notably from the species Chisocheton ceramicus Miq. which is largely distributed in the Indonesian archipelago and Malaysia region. A variety of natural products have been found in the bark of the tree and characterized as antimicrobial and/or antiproliferative agents. The isolated limonoids include chisomicines A-E, proceranolide, and a few other compounds. A focus is made on a large series of limonoids designated ceramicines A to Z including derivatives with antiparasitic activities, antioxidant, antimelanogenic, and antiproliferative effects and/or acting as regulators of lipogenesis. The lead compound in the series is ceramicine B functioning as a potent inhibitor of lipid droplet accumulation (LDA). Extracts from Chisocheton ceramicus and ceramicines have shown anti-LDA effects, with little or no cytotoxic effects. Ceramicine B is the most active compound functioning as a regulator of lipid storage in cells and tissues. Ceramicine B is a transcriptional repressor of peroxisome proliferator-activated receptor γ (PPARγ) and an inhibitor of phosphorylation of the transcription factor FoxO1, acting via an upstream molecular target. Targeting of glycogen synthase kinase-3β is proposed, based on the analogy with structurally related limonoids known to target this enzyme, and supported by a molecular docking analysis. The target and pathway implicated in ceramicine B activity are discussed. The analysis shed light on ceramicine B as a natural product precursor for the design of novel compounds capable of reducing LDA in cells and of potential interest for the treatment of obesity, liver diseases, and other pathologies.

Ceramicines U-Z from Chisocheton ceramicus and structure-antimalarial activity relationship study

Ceramicines are a series of limonoids which were isolated from the barks of Malaysian Chisocheton ceramicus (Meliaceae), and were known to show various biological activity. Six new limonoids, ceramicines U-Z (1-6), with a cyclopentanone[α]phenanthrene ring system with a β-furyl ring at C-17 were isolated from the barks of C. ceramicus. Their structures were determined on the basis of the 1D and 2D NMR analyses, and their absolute configurations were investigated by CD spectroscopy. Ceramicine W (3) exhibited potent antimalarial activity against Plasmodium falciparum 3D7 strain with IC50 value of 1.2 µM. In addition, the structure-antimalarial activity relationship (SAR) of the ceramicines was investigated to identify substituent patterns that may enhance activity. It appears that ring B and the functional groups in the vicinity of rings B and C are critical for the antimalarial activity of the ceramicines. In particular, bulky ester substituents with equatorial orientation at C-7 and C-12 greatly increase the antimalarial activity.

Antimalarial ceramicines Q-T from Chisocheton ceramicus

Ceramicines are a series of limonoids that were isolated from the bark of Malaysian Chisocheton ceramicus (Meliaceae) and were known to show various biological activity. Four new limonoids, ceramicines Q-T (1-4) were isolated from the barks of C. ceramicus, and their structures were determined on the basis of the 1D and 2D NMR analyses in combination with calculated 13C chemical shift data. Ceramicines Q-T (1-4) were established to be new limonoids with a cyclopentanone[α]phenanthren ring system with a β-furyl ring at C-17, and without a tetrahydrofuran ring like ceramicine B, which is characteristic of known ceramicines. Ceramicine R (2) exhibited potent antimalarial activity against Plasmodium falciparum 3D7 strain with IC50 value of 2.8 µM.

The Genus Walsura: A Rich Resource of Bioactive Limonoids, Triterpenoids, and Other Types of Compounds

Medicinal plants of the genus Walsura (family Meliaceae) are native to tropical zones of a number of Asian countries, and have been used in systems of folk medicine. Several original research articles on Walsura species are available, but an overview highlighting the phytochemical and biological aspects of the compounds isolated to date is so far absent. Since the 1970s, phytochemical investigations on the genus Walsura have been undertaken, and more than 220 compounds from ten species have been identified. Natural products from Walsura species that have received the most attention are limonoids (114 compounds) and triterpenoids (72 compounds). Walsura limonoids have been characterized structurally as having diverse skeletons and more than 100 such compounds are new to the literature, while dammaranes, tirucallanes, and apotirucallanes are the main triterpenoid types from this genus. Other Walsura constituents comprise sesquiterpenoids, flavonoids, sterols, lignans, xanthones, and anthraquinones. Walsura species constituents have also been studied in natural product drug discovery screening programs. Many in vitro biological and some in vivo pharmacological investigations have been carried out on Walsura species isolated compounds. Walsura components display properties such as cancer cell cytotoxicity, antimicrobial, antidiabetes, anti-inflammatory, antioxidant, antifeedant, antifertility, ichthyotoxic, and neuroprotection activities.

A Novel Trimeric Triterpene From Chisocheton ceramicusMiq

A novel trimeric triterpene, bismoronic ceramicine (1), was isolated from the bark of Chisocheton ceramicus Miq. The structure was elucidated based on spectroscopic data and chemical correlations. Bismoronic ceramicine (1) showed moderate antimalarial activity against Plasmodium falciparum strain 3D7.

Walsogynes H-O from Walsura chrysogyne

Eight new limonoids, walsogynes H–O (1–8) were isolated from the barks of Walsura chrysogyne, and their structures were determined on the basis of the 1D and 2D NMR data. Walsogynes H–M (1–6) and O (8) were concluded to be 11,12-seco limonoids with a dodecahydro-1H-naphtho[1,8-bc:3,4-c′]difuran skeleton, and walsogyne N (7) to be 11,12-seco limonoid sharing a unique dodecahydronaphtho[1,8-bc:5,4-b′c′]difuran skeleton. Walsogynes H–O (1–8) exhibited potent antimalarial activity against Plasmodium falciparum 3D7 strain with IC₅₀ value of 2.5, 2.6, 1.6, 2.5, 1.5, 2.6, 2.1, and 1.1 µM, respectively.

A New Apotirucallane from Walsura trichostemon Leaves and Its Antibacterial and α-Glucosidase Inhibitory Activities

Phytochemical investigation of Walsura trichostemon leaves led to the isolation of a new apotirucallane-type triterpenoid, 11,25-dideacetyl-16-hydroxytrichostemonate (1), along with two known apotirucallane-type triterpenoids (2 and 3), two known tirucallane-type triterpenes (4 and 5), and two known steroids (6 and 7). Their structures were identified by intensive analysis of 1D and 2D nuclear magnetic resonance, infrared, and mass spectrometry data, which were compared with data reported in the literature. Compounds 2, 3, and 5 exhibited moderate antibacterial activity against Pseudomonas aeruginosa (minimum inhibitory concentration (MIC) value: 64 μg/mL), and compound 4 showed weak antibacterial activity against P. aeruginosa (MIC: 128 μg/mL). Furthermore, compound 5 displayed activity against Bacillus cereus (MIC: 64 μg/mL). In addition, compound 4 showed stronger α-glucosidase inhibitory activity than the control, acarbose. The active compound 4 was subjected to molecular docking experiments using AutoDock4 and revealed precise interactions with the active gorge of the enzyme through hydrogen bonding, supporting the in vitro results.

Triterpenoids from Walsura trichostemon

Bioactivity guided separation of Walsura trichostemon stem methanolic extract led to the isolation of four new dammarane (1-4) and two new apotirucallane triterpenoids (5-6), together with one limonoid (7), 11,25-dideacetyltrichostemonate, 12β, 20S, 24R-trihydroxydammar-25-en-3-one and 12β, 20S, 25-trihydroxydammar-23-en-3-one. Compounds 1-7 showed in vitro inhibitory activity on the proliferation of A549, human lung adenocarcinoma cell line.

Remote C-H Activation Strategy Enables Total Syntheses of Nortriterpenoids (±)-Walsucochin B and (±)-Walsucochinoids M and N

Total syntheses of (±)-walsucochin B and (±)-walsucochinoids M and N have been achieved from farnesyl bromide. The key steps of the synthetic sequence are the titanocene-mediated radical cyclization and base-induced cycloaromatization for the rapid construction of the 6/6/5/6-fused tetracyclic skeleton. Importantly, a Cu-mediated remote C-H hydroxylation reaction has been developed to site-selectively install the oxygen function at the C-7 position of the target molecules, thus solving the biggest challenge for the synthesis of the compounds.

Chemical Constituents from Walsura pinnata (Meliaceae)

A phytochemical study on the bark of Walsura pinnata has led to the isolation of a new oleanane triterpene acid, 3-oxo-olean-9(11),12-dien-28-oic acid (1), together with nine known compounds (2–10). Their structures were established on the basis of the detailed spectroscopic analysis, including one- and two-dimensional NMR, ESI-MS and HR-ESI-MS techniques. Compounds 2, 3, 5, 6 and 8 were isolated from W. pinnata for the first time. Compounds 3 and 4 showed in vitro growth inhibitory activity against two human cancer cell lines MCF-7 and SK-OV-3 with IC50 values within the range of 8.85 - 18.28 μg/mL. To the best of our knowledge, this is the first report on the cytotoxic activity of compound 3 towards both cancer cell lines.

Ceramicines M-P from Chisocheton ceramicus: isolation and structure-activity relationship study

Ceramicines are a series of limonoids which were isolated from the bark of Malaysian Chisocheton ceramicus (Meliaceae) and show various biological activities. Ceramicine B, in particular, has been reported to show a strong lipid droplet accumulation (LDA) inhibitory activity on a mouse pre-adipocyte cell line (MC3T3-G2/PA6). With the purpose of discovering compounds with stronger activity than ceramicine B, we further investigated the constituents of C. ceramicus. As a result, from the bark of C. ceramicus four new ceramicines (ceramicines M–P, 1–4) were isolated, and their structures were determined on the basis of NMR and mass spectroscopic analyses in combination with NMR chemical shift calculations. LDA inhibitory activity of 1–4 was evaluated. Compounds 1–3 showed LDA inhibitory activity, and 3 showed better selectivity than ceramicine B while showing activity at the same order of magnitude as ceramicine B. Since 3, which possess a carbonyl group at C-7, showed better selectivity than 5, which possess a 7α-OH group, while showing activity at the same order of magnitude as 5, we also investigated the effect of the substituent at C-7 by synthesizing several derivatives and evaluating their LDA inhibitory activity. Accordingly, we confirmed the importance of the presence of a 7α-OH group to the LDA inhibitory activity.

Apowalsogynes A and B, Two Highly Oxidized 3,4-Seco-Apotirucallane Triterpenoids from Walsura chrysogyne

Two new 3,4- seco-apotirucallane triterpenoids, Apowalsogynes A and B (1 and 2), were isolated from the barks of Walsura chrysogyne, and their structures were determined on the basis of the NMR and CD spectra, and by using the modified Mosher's method. In addition, the cytotoxic activities of 1 and 2 against various cancer cell lines were evaluated.

Diverse tritepenoids from the fruits of Walsura robusta and their reversal of multidrug resistance phenotype in human breast cancer cells

Four 18 (13 → 14)-abeo limonoids, five cedrelone limonoids, and five walsurin limonoids were isolated from the fruits of Walsura robusta together with 21 known compounds. Their structures were determined by extensive studies of their one- and two-dimensional NMR spectra and mass spectroscopy results. Among all the isolated compounds, the absolute configurations of 11-oxo-dihydrocedrelone, walsuronoid B, dysoxylumosin G, and walsunoid H were confirmed by single crystal X-ray diffraction. Selected compounds were evaluated for their reversal of multidrug resistance (MDR) phenotype in human breast cancer cells in vitro. Walsurin A showed significant effect in sensitization of these resistant cancer cells at non-toxic concentration to doxorubicin with the modulation factor of 62.76.

Anti-melanin deposition activity of ceramicines from Chisocheton ceramicus

The ceramicines, a series of limonoids from Chisocheton ceramicus (Meliaceae), were evaluated for anti-melanin deposition activity on α-melanocyte stimulating hormone (α-MSH) and 3-isobutyl-1-methylxanthine (IBMX)-treated B16-F10 melanoma cell, and several ceramicines were found to be active. The structure-activity relationship of ceramicines as anti-melanin deposition inhibitors was deduced. Furthermore, the mechanism of anti-melanin deposition activity of ceramicine B, a major constituent of C. ceramicus that showed potent anti-melanin deposition activity, was investigated. Tyrosinase enzymatic activity and tyrosinase mRNA expression were not affected by ceramicine B. The anti-melanin deposition activity of ceramicine B was shown to be related to the downregulation of tyrosinase protein expression. These results suggest that ceramicines have potential to be used as depigmentation agents.

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).

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.

Plant natural products as an anti-lipid droplets accumulation agent

Recently people often suffer from unhealthy energy metabolism balance as they tend to take more energy than required. Normally, excess energy taken in is converted into triglyceride and stored in adipocyte as lipid droplets. Recent studies have suggested that irregular accumulation of triglyceride in adipocyte might be a cause of many metabolic diseases. Thus, the awareness of the detrimental effects on health of excessive lipid droplets accumulation (LDA) has urged the development or finding of drugs to counter this effect, including those from botanical origins. This review summarized recent progress in this field from the viewpoint of crude drug studies with references to their anti-LDA activity. Possible mechanisms involved in their anti-LDA effect and isolations of the relevant bioactive compounds were also discussed.

New rearranged limonoids from Walsura cochinchinensis

This paper describes the discovery of a rare class of rearranged limonoids from Walsura cochinchinensis.

Ceramicine B, a limonoid with anti-lipid droplets accumulation activity from Chisocheton ceramicus

The Meliaceae family of plants has been shown to contain a vast number of compounds with the potential to be developed for medicinal purposes. We have previously reported the isolation of limonoids from a plant in the Meliaceae family named Chisocheton ceramicus. Ceramicine B was identified as an active compound in inhibiting lipid droplets accumulation (LDA) in the mouse preadipocyte cell line MC3T3-G2/PA6. The presence of ceramicine B was found to inhibit the expression of glucose transporter type 4, lipoprotein lipase, and 11-beta hydroxysteroid dehydrogenase mRNA, and also adipogenic master regulator, peroxisome proliferator-activated receptor-γ, and CCAAT-enhancer-binding protein-α (C/EBPα) mRNA. However, for early adipogenic regulators, such as C/EBPβ and C/EBPδ, and intermediary adipogenic regulators, Krüppel-like factors were unaffected. Western blot analysis showed that ceramicine B was found to inhibit the phosphorylation of Forkhead box O1 (Foxo1), a key process in the insulin signaling pathway. This suggested that the mechanism of anti-LDA activity of ceramicine B was partly via the inhibition of Foxo1 phosphorylation.

Ceramicines from Chisocheton ceramicus as lipid-droplets accumulation inhibitors

In our search for lipid-droplets accumulation (LDA) inhibitors, some ceramicines, a series of limonoids isolated from the barks of Chisocheton ceramicus, were discovered to be active as anti-LDA. Preliminary structure-activity relationships (SAR) of ceramicines as LDA inhibitors based on ceramicines A-L (1-12) and ceramicine B derivatives were described.

Ceramicines J-L, new limonoids from Chisocheton ceramicus

Three new limonoids, ceramicines J (1), K (2), and L (3), were isolated from the hexane layer of Chisocheton ceramicus bark extract. Their structures were elucidated from 1D and 2D NMR data. Ceramicines J-L (1-3) exhibited dose-dependent moderate cytotoxicity against the HL-60 cell line.

Chisomicines A-C, limonoids from Chisocheton ceramicus

Three new limonoids, chisomicines A-C (1-3), have been isolated from the bark of Chisocheton ceramicus. Their structures were determined by 2D NMR, CD spectroscopic methods, and X-ray analysis. Chisomicine A (1) exhibited NO production inhibitory activity in J774.1 cells stimulated by LPS dose-dependently at high cell viability.

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.

Chrotacumines A-D, chromone alkaloids from Dysoxylum acutangulum

Four new chromone alkaloids, chrotacumines A-D (1-4), consisting of a 5,7-dihydroxy-2-methylchromone, an N-Me piperidine ring, and an ester side chain were isolated from Dysoxylum acutangulum, and their structures including absolute configurations were elucidated on the basis of spectroscopic data interpretation including 2D NMR, CD spectra, and X-ray analysis. The known compound rohitukine (5) showed moderate cytotoxicity against human HL-60 promyelocytic leukemia and HCT-116 colon cancer cells.