Protolimonoids and norlimonoids from the stem bark of Toona ciliata var. pubescens

Meliasanines A-L, tirucallane-type triterpenoids from Melia toosendan with anti-inflammatory properties via NF-κB signaling pathway

Meliasanines A-L, twelve previously unreported tirucallane-type triterpenoids, together with fifteen known ones, have been isolated from the stem bark of Melia toosendan. Their structures and absolute configurations were determined based on HRESIMS, and NMR, combined with calculated ECD and single-crystal X-ray diffraction analyses. Subsequently, all compounds except 10 were evaluated for their inhibitory effect on the production of nitric oxide induced by lipopolysaccharide in RAW264.7 macrophage cells. The results indicated that seven compounds (1, 13, 14, 16, 20, 22, and 23) exhibited significant NO inhibitory effects, with IC50 values ranging from 1.35 to 5.93 μM, which were more effective than the positive control indomethacin (IC50 = 13.18 μM). Moreover, the corresponding results of Western blot analysis revealed that meliasanine A (1) can significantly suppress the protein expression of inducible nitric oxide synthase and cyclooxygenase 2 in a concentration-dependent manner. The mechanism study suggested that meliasanine A exerts an anti-inflammatory effect via the nuclear factor-κB signaling pathway by suppressing phosphorylation of P65 and IκBα.

Isolation, Characterization, and Antiproliferative Activity of Terpenoids from the Tropical Plant Turraea delphinensis

The isolation, structure determination, and biological evaluation of constituents from the organic extract of Turraea delphinensis Wahlert (Meliaceae) resulted in the isolation of 51 secondary metabolites, including 14 new terpenoids (six cycloartanes, four tirucallanes/euphanes, three limonoids, and a 7-keto sterol). Among the new compounds, 1 is the first triterpenoid with a trioxaspiro[4.4]nonane side chain, while 11-13 are the first 17-γ-lactone tetranortriterpenoids with four oxygenated functional groups at C-1, -3, -6, and -7. The isolated compounds were evaluated for antiproliferative activity against five human tumor cell lines, including a vinblastine-resistant cell line.

Isolation of two new cucurbitane-type triterpenoids from Kedrostis gijef

Two new cucurbitane-type triterpenoids (2,3), together with two known compounds (1,4), were isolated from the aerial parts of Kedrostis gijef. The structure of all compounds was elucidated based on NMR, HRESIMS analyses, and by comparison with the literature. Additionally, the cytotoxic activity against HeLa, Caco-2, and SH-SY5Y cell lines was determined using MTT colorimetric assay.

Paraxylines A-G: Highly oxygenated preurianin-type limonoids with immunomodulatory TLR4 and cytotoxic activities from the stem bark of Dysoxylum parasiticum

Seven previously undescribed preurianin-type limonoids, namely paraxylines A-G, and three known analogs were isolated from stem bark of Dysoxylum parasiticum. The structures, including absolute configurations, were established through spectroscopic analyses, quantum chemical calculations using the density functional theory method, as well as the DP4+ algorithm. Paraxylines A-G were identified as the first preurianin-type with full substitution at C, D-rings, leading to the highly oxygenated seco-limonoids skeleton. The secreted alkaline phosphate assay against an engineered human and murine TLR4 of HEK-Blue cells was performed to evaluate the immune regulating effects. Among them, paraxyline B was found to be a remarkable TLR4 agonist whereas two analogs (toonapubesins A and B) were found to antagonise lipopolysaccharide stimulation of the TLR4 pathway. Paraxylines A and C-E acted either as agonists or antagonists depending on the origin of the TLR4 receptor (human or mouse). The effect of these selected compounds on the expression of pro-inflammatory cytokines TNF-α, IL-1α, IL-1β, and IL-6 of the NF-κB signaling pathway were examined in macrophage cell lines, revealing dose-dependent effects. Additionally, paraxylines A, C, D, and G also presented modest cytotoxic activity against MCF-7 and HeLa cell lines with IC50 values ranging from 23.1 to 43.5 μM.

Two New Protolimonoids from the Chinese Mangrove Xylocarpus granatum Koenig

Two new compounds including one apotirucallane protolimonoid, xylogranatriterpin A (1), and one glabretal protolimonoid, xylocarpusin A (2), along with three known related compounds were isolated from the twigs and leaves of the Chinese mangrove Xylocarpus granatum. The apotirucallane xylogranatriterpin A (1) bears an unprecedented 24-ketal carbon connecting ring E with an epoxide ring. The structures of new compounds were elucidated by extensive spectroscopic analysis and by comparison of the spectroscopic data with those reported in the literatures. Plausible biosynthetic pathway to xylogranatriterpin A (1) was also proposed. None of them showed cytotoxic, neuroprotective, or protein tyrosine phosphatase 1B (PTP1B) inhibitory activity.

Five new limonoids isolated from Walsura robusta

Five new toosendanin limonoids with highly oxidative furan ring walsurobustones A-D (1-4), and one new furan ring degraded limonoid walsurobustone E (5) together with one known compound toonapubesic acid B (6) were isolated from the leaves of Walsura robusta. Their structures were elucidated by NMR and MS data. Especially, the absolute configuration of toonapubesic acid B (6) was confirmed by X-ray diffraction study. Compounds 1-6 exhibited good cytotoxicity against the cancer cell lines HL-60, SMMC-7721, A-549, MCF-7, and SW480.

Triterpenoids from the fruits of Melia azedarach L. and their cytotoxic activities

Eleven undescribed tetracyclic triterpenoids, meliazedarachins A-K, along with twenty-six known compounds were isolated from the fruits of Melia azedarach L.. Their structures were determined by HRESIMS, UV, IR, NMR, X-ray diffraction, electronic circular dichroism (ECD) spectra, and the modified Mosher's method. The cytotoxic activities of all the isolates were measured. Meliazedarachin K and mesendanin N showed cytotoxicity against five human cancer cell lines with IC₅₀ values ranging from 9.02 to 31.31 μM. Meliazedarachin K showed significant cytotoxicity against HCT116 cell line with IC₅₀ value of 9.02 ± 0.84 μM. 21α-methylmelianodiol showed significant cytotoxicity against HCT116 and RKO cell lines with IC₅₀ values of 10.16 ± 1.22 and 8.57 ± 0.80 μM, respectively.

Research progress of meliaceous limonoids from 2011 to 2021

Covering: July 2010 to December 2021Limonoids, a kind of natural tetranortriterpenoids with diverse skeletons and valuable insecticidal and medicinal bioactivities, are the characteristic metabolites of most plants of the Meliaceae family. The chemistry and bioactivities of meliaceous limonoids are a continuing hot area of natural products research; to date, about 2700 meliaceous limonoids have been identified. In particular, more than 1600, including thirty kinds of novel rearranged skeletons, have been isolated and identified in the past decade due to their wide distribution and abundant content in Meliaceae plants and active biosynthetic pathways. In addition to the discovery of new structures, many positive medicinal bioactivities of meliaceous limonoids have been investigated, and extensive achievements regarding the chemical and biological synthesis have been made. This review summarizes the recent research progress in the discovery of new structures, medicinal and agricultural bioactivities, and chem/biosynthesis of limonoids from the plants of the Meliaceae family during the past decade, with an emphasis on the discovery of limonoids with novel skeletons, the medicinal bioactivities and mechanisms, and chemical synthesis. The structures, origins, and bioactivities of other new limonoids were provided as ESI. Studies published from July 2010 to December 2021 are reviewed, and 482 references are cited.

Ethnomedicinal Use, Phytochemistry, and Pharmacology of Xylocarpus granatum J. Koenig

The mangrove plants are the potential sources of foods and remedies for people living in the forests and nearby communities. Xylocarpus granatum J. Koenig is traditionally used to treat various diseases including diarrhea, cholera, dysentery, fever, malaria, and viral infections, among others. To summarize critically the taxonomy, ethnomedicinal, phytochemistry, and pharmacological activities of X. granatum, information was collected from different databases. An up-to-date search (till June 2020) was carried out with the help of various scientific web resources from databases such as PubMed, Science Direct, Google Scholar, and various patent offices (e.g., WIPO, CIPO, and USPTO) using the keywords “Xylocarpus granatum” and then paired with ethnomedicinal use and phytochemical, phytochemistry, and pharmacological activity (in vitro, ex vivo, and in vivo studies). Findings revealed that seeds, fruits, stem bark, leaf, and twigs of X. granatum exhibited a wide range of key phytochemicals including limonoids, phragmalin, limonoid-based alkaloids, mexicanolides, protolimonoids, flavonols, and lactones. The plant possessed potent antioxidant, anticancer, antidiabetic, antimicrobial, antimalarial, antifeedant, and neuroprotective activities. No clinical studies have been reported in the databases. Ethnomedicinal assessment indicated the application of X. granatum in various fields of medical science specially to treat various human ailments, and this was attributed to the presence of enormous alkaloids as confirmed by pharmacological studies. However, to understand the mechanism of action in-depth studies are required. In view of these findings, more research is necessary to explore and characterize the chemical compounds and toxicological aspects of this medicinal mangrove plant. Overall, it can be stated that X. granatum may be one of the hopeful medicinal herbs for the treatment of various diseases in human beings.

Limonoids and other triterpenoids from Entandrophragma angolense

Four new compounds (1-4) were isolated from the stem bark of Entandrophragma angolense along with eleven known structures (5-15). The chemical structures were elucidated on the basis of spectroscopic and HRMS data, and the absolute configuration was established with the aid of electronic circular dichroism. Compound 5 displayed moderate cytotoxicity against MDA-MB-231, OVCAR3, MDA-MB-435, and HT29 cell lines, with IC₅₀ values ranging from 2.0-5.9 μM.

Medicinal chemistry insights into novel CDC25 inhibitors

Cell division cycle 25 (CDC25) phosphatases, a kind of cell cycle regulators, have become an attractive target for drug discovery, as they have been found to be over-expressed in various human cancer cells. Several CDC25 inhibitors have achieved significant attention in clinical trials with possible mechanistic actions. Prompted by the significance of CDC25 inhibitors with medicinal chemistry prospect, it is an apt time to review the various drug discovery methods involved in CDC25 drug discovery including high throughput screening (HTS), virtual screening (VS), fragment-based drug design, substitution decorating approach, structural simplification approach and scaffold hopping method to seek trends and identify promising new avenues of CDC25 drug discovery.

The axial chirality hidden in vitamin D and its application in cocrystal prediction

An ECD titration method was developed to detect hydrogen-bonding interaction in solution and to predict cocrystal formation in the solid state.

Structurally Diverse Highly Oxygenated Triterpenoids from the Roots of Ailanthus altissima and Their Cytotoxicity

Ten new triterpenoids, ailanaltiolides A-J (1-10), and three known analogues (11-13) were isolated from the roots of Ailanthus altissima. Compounds 1-7 are apotirucallane-type, compounds 8 and 9 are tirucallane-type, and compound 10 is a trinordammarane-type triterpenoid. This is the first study indicating the genus Ailanthus as a potential source for apotirucallane derivatives, which contain an α,β-unsaturated-ε-lactone A-ring and diversely modified C-17 side chains. Spectroscopic data interpretation, electronic circular dichroism analysis, and X-ray crystallographic data defined the structures and absolute configurations of these triterpenoids. Compounds 2, 7, and 8 showed cytotoxicity against four tumor cell lines (HeLa, 786-O, HepG2, and A549). In particular, compound 2 exhibited the highest activity against 786-O cells with an IC₅₀ value of 8.2 μM in vitro.

Novel and Neuroprotective Tetranortriterpenoids from Chinese Mangrove Xylocarpus granatum Koenig

Eight new tetranortriterpenoids (1–8) were isolated from the twigs and leaves of the Chinese mangrove plant Xylocarpus granatum, together with four related known ones (9–12). The structures of new compounds were elucidated by detailed spectroscopic analysis. The absolute configuration of 9-epixylogranatin A (1) was determined by time-dependent density functional theory-electronic circular dichroism (TDDFT-ECD) calculations of the solution conformers. Xylogranatumin A (2) represents the first example of the 9, 10-seco limonoid with an unprecedented oxygen-bridged B ring (2,7-dioxabicyclo[2.2.1]-heptane). All the isolates were evaluated for the in vitro neuroprotective activity, both compounds 11 and 12 displayed moderate effects against H₂O₂-induced neurotoxicity in PC12 cells at the concentration of 10 μM, with an increase in cell viability of 12.0% and 11.6%, respectively.

Tirucallane-type triterpenoids from the fruit of Ficus carica and their cytotoxic activity

Nine new tirucallane-type triterpenoids, ficutirucins A-I (1-9), were isolated from the fruit of Ficus carica. Their structures were established on the basis of spectroscopic data and chemical methods. All isolates were evaluated for their cytotoxic activities against three human cancer cell lines, MCF-7, HepG-2, and U2OS. Compounds 1-3, 6, 7, and 9 exhibited moderate cytotoxic activities with IC50 values of 11.67-45.61 µM against one or more of the three cancer cell lines.

Antiplasmodial and cytotoxic activities of the constituents of Turraea robusta and Turraea nilotica

ETHNOPHARMACOLOGICAL RELEVANCE

Turraea robusta and Turraea nilotica are African medicinal plants used for the treatment of a wide variety of diseases, including malaria. The genus Turraea is rich in limonoids and other triterpenoids known to possess various biological activities.

MATERIALS AND METHODS

From the stem bark of T. robusta six compounds, and from various parts of T. nilotica eleven compounds were isolated by the use of a combination of chromatographic techniques. The structures of the isolated compounds were elucidated using NMR and MS, whilst the relative configuration of one of the isolated compounds, toonapubesin F, was established by X-ray crystallography. The antiplasmodial activities of the crude extracts and the isolated constituents against the D6 and W2 strains of Plasmodium falciparum were determined using the semiautomated micro dilution technique that measures the ability of the extracts to inhibit the incorporation of (G-(3)H, where G is guanine) hypoxanthine into the malaria parasite. The cytotoxicity of the crude extracts and their isolated constituents was evaluated against the mammalian cell lines African monkey kidney (vero), mouse breast cancer (4T1) and human larynx carcinoma (HEp2).

RESULTS

The extracts showed good to moderate antiplasmodial activities, where the extract of the stem bark of T. robusta was also cytotoxic against the 4T1 and the HEp2 cells (IC50<10 μg/ml). The compounds isolated from these extracts were characterized as limonoids, protolimonoids and phytosterol glucosides. These compounds showed good to moderate activities with the most active one being azadironolide, IC50 2.4 ± 0.03 μM and 1.1 ± 0.01 μM against the D6 and W2 strains of Plasmodium falciparum, respectively; all other compounds possessed IC50 14.4-40.5 μM. None of the compounds showed significant cytotoxicity against vero cells, yet four of them were toxic against the 4T1 and HEp2 cancer cell lines with piscidinol A having IC50 8.0 ± 0.03 and 8.4 ± 0.01 μM against the 4T1 and HEp2 cells, respectively. Diacetylation of piscidinol A resulted in reduced cytotoxicity.

CONCLUSION

From the medicinal plants T. robusta and T. nilotica, twelve compounds were isolated and characterized; two of the isolated compounds, namely 11-epi-toonacilin and azadironolide showed good antiplasmodial activity with the highest selectivity indices.

Limonoids and Triterpenoids from Dysoxylum mollissimum var. glaberrimum

Seven new limonoids, dysomollides A-G (1-7), and two new cycloapotirucallane-type triterpenoids, dysomollins A and B (8 and 9), together with three known compounds, dysoxylumin A (10) and toonapubesins A (11) and B (12), were isolated from the twigs of Dysoxylum mollissimum var. glaberrimum. The structures of 1-9 were elucidated on the basis of spectroscopic methods. Compound 10 showed inhibitory activity against A549 cells with an IC50 value of 2.1 μM, and compound 11 exhibited activity against P388 cells with an IC50 value of 6.7 μM.

Apotirucallane protolimonoids from the Chinese mangrove Xylocarpus granatum Koenig

A series of previously unreported compounds including seven new apotirucallane protolimonoids, xylogranatumines A-G (1-7), were isolated together with three known analogues (8-10) from the twigs and leaves of the Chinese mangrove, Xylocarpus granatum. The structures of these new compounds were elucidated by extensive spectroscopic analysis including 1D and 2D NMR and high-resolution electrospray ionization mass spectrometry (HRESIMS) and by comparison with those of related known compounds in the literature. Xylogranatumine F (6) exhibited cytotoxic activity against A549 tumor cell in vitro.

Triterpenoids and Sterols from the Leaves and Twigs of Melia azedarach

Two new triterpenoids (1 and 2) and a new sterol (3), together with six known constituents (4-9), were isolated from the leaves and twigs of Melia azedarach. Their chemical structures were elucidated on the basis of spectroscopic analysis.

Cipatrijugin G, a new trijugin-type limonoid bearing an uncommon γ-hydroxybutenolide unit from the aerial parts of Cipadessa cinerascens

A new trijugin-type limonoid, cipatrijugin G (1), together with the related known cipatrijugin A (2), were isolated from the aerial parts of Cipadessa cinerascens. The structure of the new compound was determined by extensive analysis of its spectroscopic data and by comparison of its NMR data with those reported in the literature. Compound 1 showed cytotoxicity against tumor cell line A549 with an IC₅₀ value of 9.78 μM. This is the first report of a trijugin-type limonoid bearing a γ-hydroxybutenolide unit, in comparison to the common furan unit as ring E.

Lepidotrichilins A and B, new protolimonoids with cytotoxic activity from Trichilia lepidota (Meliaceae)

Two novel protolimonoids, named lepidotrichilins A (1) and B (2), four known protolimonoids, 21,23-epoxy-7α-21α-dihydroxyapotirucalla-14,24-dien-3-one (3), 21,23-epoxy-7α-21β-dihydroxyapotiru-calla-14,24-dien-3-one (4), dysorone D (5), deoxy-flindissone (6), and the two steroids β-sitosterol (7) and stigmasterol (8) were identified in leaves of Trichilia lepidota subsp. schumanniana (Harms) T.D. Pennington. From wood the coumarin scopoletin (9) was isolated. The structures were established by NMR (1D ¹H and ¹³C-NMR and 2D ¹H-¹H COSY, HMQC and HMBC), mass spectroscopy and infrared (IR) spectral data. The hexane and methanol extracts of the leaves, the protolimonoids lepidotrichilins A (1) and B (2) (IC₅₀ 42.7 µg mL⁻¹) and the protolimonoid deoxy-flindissone (6; IC₅₀ 9.3 µgmL⁻¹) exhibited significant cytotoxic activity against the MOLT-4 and U937 leukemic cell lines.

Triterpenoids

This review covers the isolation and structure determination of triterpenoids including squalene derivatives, lanostanes, holostanes, cycloartanes, cucurbitanes, dammaranes, euphanes, tirucallanes, tetranortriterpenoids, quassinoids, lupanes, oleananes, friedelanes, ursanes, hopanes, onoceranes and saponins; 308 references are cited.

Bioactive natural products from Chinese marine flora and fauna

In recent decades, the pharmaceutical application potential of marine natural products has attracted much interest from both natural product chemists and pharmacologists. Our group has long been engaged in the search for bioactive natural products from Chinese marine flora (such as mangroves and algae) and fauna (including sponges, soft corals, and mollusks), resulting in the isolation and characterization of numerous novel secondary metabolites spanning a wide range of structural classes and various biosynthetic origins. Of particular interest is the fact that many of these compounds show promising biological activities, including cytotoxic, antibacterial, and enzyme inhibitory effects. By describing representative studies, this review presents a comprehensive summary regarding the achievements and progress made by our group in the past decade. Several interesting examples are discussed in detail.