Tetranortriterpenoids from Walsura yunnanensis

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.

Limonoids and insecticidal activity on Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) of Trichilia catigua A. Juss. (Meliaceae)

The aim of the study was to evaluate the effects of the seeds, exocarp and aril extracts from Trichilia catigua A. Juss. (Meliaceae) against Spodoptera frugiperda and present the phytochemical study carried out with the aril extract of T. catigua. Limonoids were isolated from the aril of T. catigua through chromatographic techniques and their structures were proposed by spectroscopic analysis and comparison with literature data. The effects of the seeds, exocarp and aril extracts from T. catigua against S. frugiperda were evaluated considering as parameters the duration and mortality of the larval phase, in addition to the pupal weight. Phytochemical investigation of the aril extracts of T. catigua has led to the identification of the limonoids 6α-O-acetyl-7-deacetyl-14,15-dihydro-15-oxo-nimocinol (1), cedrelone (2) and 6α-O-acetyl-7-deacetylnimocinol (3). The hexane and CH2Cl2 extracts of the aril showed a high rate of larval mortality (100 and 90%, respectively). In addition, a prolongation of larval phase and a reduction in the pupal weight were observed for insects treated with hexane, CH2Cl2 and methanol extracts of seeds and with CH2Cl2 extract of exocarp of T. catigua.

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.

Identification of limonoids from Walsura yunnanensis and evaluation of their cytotoxicity against cancer cell lines

Three new limonoids, walsurauias A-C (1-3), along with four known ones, were isolated from the leaves and twigs of Walsura yunnanensis C. Y. Wu. Their structures were determined on the basis of comprehensive spectroscopic data analysis. The new limonoids were screened for their cytotoxic activity (IC₅₀ 0.81-5.73 μM) against four human cancer cell lines, including A549, HepG2, HCT116 p21KO and CNE-2. And α,β-unsaturated ketone moieties in rings A and B are essential for their cytotoxic activity. Selected compounds were further investigated. Compounds 1-3 effectively induced G2/M cell cycle arrest and apoptosis in a dose-dependent manner in cancer cells. In addition, compounds 1-3 inhibited the colony formation and compounds 2 and 3 suppressed the migration of cancer cells.

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.

Toonaones A-I, limonoids with NLRP3 inflammasome inhibitory activity from Toona ciliata M. Roem

Nine undescribed limonoids, 18(13 → 14)-abeo-15β,21-dihydroxy-24,25,26,27-tetranor-3,7-dioxoapotirucalla-1,9(11),13(17),20(22)-tetraen-23,21-olide (Toonaone A), 21-hydroxy-24,25,26,27-tetranor-3,7,15-trioxoapotirucalla-1,9(11),20(22)-trien-23,21-olide (Toonaone B), 7α,21-dihydroxy-12α-isobutyryl-24,25,26,27-tetranor-3,15-dioxoapotirucalla-1,20(22)-dien-23,21-olide (Toonaone C), 7,8-seco-7-methyl ester-11β-acetoxy-14β,15β-epoxy-21-hydroxy-24,25,26,27-tetranor-3-oxoapotirucalla-1,8(30),20(22)-trien-23,21-olide (Toonaone D), 7,8-seco-7-methyl ester-11β-acetoxy-14β,15β-epoxy-23-hydroxy-24,25,26,27-tetranor-3-oxoapotirucalla-1,8(30),20(22)-trien-21,23-olide (Toonaone E), 7,8-seco-7-methyl ester-11β-acetoxy-14β,15β-epoxy-6β,21-dihydroxy-24,25,26,27-tetranor-3-oxoapotirucalla-1,8(30),20(22)-trien-23,21-olide (Toonaone F), 7,8-seco-7-methyl ester-14β,15β-epoxy-8α,21-dihydroxy-24,25,26,27-tetranor-3-oxoapotirucalla-1,20(22)-dien-23,21-olide (Toonaone G), 7,8-seco-7-methyl ester-14β,15β-epoxy-6β,8α,21-trihydroxy-24,25,26,27-tetranor-3-oxoapotirucalla-1,20(22)-dien-23,21-olide (Toonaone H), 7,8-seco-7-methyl ester-14β,15β-epoxy-6β,8α,21-trihydroxy-24,25,26,27-tetranor-3-oxoapotirucalla-1,20(22)-dien-21,23-diimide (Toonaone I), and five known analogues were isolated from the twigs of Toona ciliata M. Roem. (Meliaceae). Toonaone A possesses the first rare 18(13 → 14)-abeo-limonoid skeleton reported from the genus Toona. Their structures were elucidated using spectroscopic data analyses and quantum chemistry calculations. Biological evaluation showed that toonaone C, toonaone D, toonaone G, toonaciliatavarin F, and toonaciliatavarin G exhibited significant anti-NLRP3 inflammasome activity with IC₅₀ values ranging from 3.74 to 18.7 μM. GMDMD, IL-1β, and caspase-1 analyses suggested that toonaone D inhibited NLRP3 inflammasome activation and blocked macrophage pyroptosis.

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.

Bioactive A-ring rearranged limonoids from the root barks of Walsura robusta

Screening active natural products, rapid identification, and accurate isolation are of great important for modern natural lead compounds discovery1. We hereby reported the isolation of seven new neotecleanin-type limonoids (1-7), seven new limonoids with 5-oxatricyclo[5.4.0.11., 4.]hendecane ring system (8-14), and two new precursors (15-16) together with four known limonoids (17-20) from the root barks of Walsura robusta. Their structures, including their absolute configurations, were elucidated based on analyses of HR-ESI-MS, 1D/2D NMR, ECD spectrum calculations and single-crystal X-ray diffraction techniques. Compounds 2, 8, 9, 11, 13, 14, 18 showed significant anti-inflammatory activities in LPS-induced RAW 264.7 cell line, BV2 microglial cells, and Propionibacterium acnes-stimulated THP-1 human monocytic cells. Walrobsin M (11) exhibited anti-inflammatory activity with IC50 value of 7.96±0.36 μmol/L, and down-regulated phosphorylation levels of ERK and p38 in a dose-dependent manner.

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-influenza triterpenoid saponins (saikosaponins) from the roots of Bupleurum marginatum var. stenophyllum

This study to investigate antiviral components from the roots of Bupleurum marginatum var. stenophyllum led to the isolation of five novel saikosaponins, namely 6″-O-crotonyl-saikosaponin a (1), tibesaikosaponin I (2), tibesaikosaponin II (3), tibesaikosaponin III (4), tibesaikosaponin IV (5), along with 9 known analogues (6-14). Their structures were established by spectral data analyses (IR, MS, 1D and 2D NMR) and by comparison of spectral data with those of the related known compounds. Antiviral testing of all compounds against influenza A virus A/WSN/33 (H1N1) in 293TGluc cells showed that nepasaikosaponin k (12), saikosaponin n (13) and saikosaponin h (14) behaved more potent inhibitory activity and selectivity than the positive control, Ribavirin. The preliminary structure-activity relationship studies suggest that the 13, 28-epoxy group, the type of sugar chain and the type of olefinic bonds are significant for antiviral activity and selectivity.

Toxicity of Secondary Metabolites from Meliaceae Against Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae)

The study was carried out to evaluate the bioactivity of secondary metabolites from Trichilia pallida, Trichilia pallens, and Toona ciliata against fall armyworm Spodoptera frugiperda (J. E. Smith) larvae. The studied compounds included (+/-)-catechins, a triglyceride, and cedrelone isolated from T. ciliata branches, fruits, and stems, respectively; dammaradienol isolated from T. pallida leaves; and scopoletin isolated from T. pallens branches. The compounds' activity was evaluated through ingestion and topic treatment. Treated artificial diet was offered to first instar larvae to evaluate ingestion effect, while an application on the dorsal thoracic region of third instar larvae was used to evaluate the topic effect. Mortality was assessed daily, and larval weight was recorded after 7 days for ingestion and 5 days for topic application. Scopoletin and triglyceride caused low mortality rates and reduction in larval weight by ingestion, (+/-)-catechins caused larval weight reduction by ingestion, and scopoletin reduced survival by topic treatment. The most effective compound was cedrelone that affected larval survival and development mainly by ingestion. The estimated LC₅₀, LC₉₀, and EC₅₀ for cedrelone were 0.0365, 0.0659, and 0.0095%, respectively. Further, cedrelone-treated corn leaf discs were offered to fourth instar larvae during 16 h in choice and no-choice tests. The deterrence indexes obtained in the choice tests were 23.5 and 36.3% at concentrations of 0.0365 and 0.0659, respectively. Consumption of cedrelone-treated leaf discs at the concentration of 0.0659% was lower compared to the control in the no-choice test. Thus, cedrelone caused lethal and sublethal effects and phagodeterrence on S. frugiperda and should be further studied.

Limonoids and Triterpenoids as 11β-HSD1 Inhibitors from Walsura robusta

Nine new cedrelone-type limonoid derivatives, walsunoids A-I (1-9), and 11 known compounds were isolated from the leaves of Walsura robusta. Walsunoid A (1) is a new degradation product of cedrelone-type limonoids, and walsunoid I (9) is a rare cedrelone-type limonoid amide. Their structures and absolute configurations were determined by spectroscopic data, single-crystal X-ray diffraction, and ECD data analyses. Five compounds showed moderate inhibitory activities against human and/or mouse 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) with IC50 values ranging from 0.69 to 9.9 μM.

Cytotoxic limonoids from Trichilia americana leaves

Ten cedrelone limonoids were isolated from the leaves of Trichilia americana. These compounds include americanolides A-D (1-4), 1,2-dihydrodeacetylhirtin (5), 1α-hydroxy-1,2-dihydrodeacetylhirtin (6), 1α-hydroxy-1,2-dihydrohirtin (7), 1α-methoxy-1,2-dihydrodeacetylhirtin (8), 11β-hydroxy-12α-propanoyloxycedrelone (9), and 1α,11β-dihydroxy-1,2-dihydrocedrelone (10), as well as two previously reported compounds, deacetylhirtin (11) and hirtin (12). Their structures were characterized on the basis of spectroscopic studies, and the assignment of the absolute configuration of americanolide A (1) was supported by single-crystal X-ray diffraction studies. The cytotoxic activities of all isolated compounds were also evaluated against five human tumour cell lines (HL-60, SMMC-7721, A-549, MCF-7, and SW-480) using an MTS assay. Compounds 11 and 12 showed significant cytotoxicity with IC50 values ranging from 0.1 to 0.5 μM, and compounds 5, 6, 7, 8, 9, and 10 exhibited potent or selective cytotoxic activity with IC50 values ranging from 1.0 to 39.6 μM.

Whole-Cell Mediated 11β-Hydroxylation on the Basic Limonoid Skeleton by Cunninghamella echinulata

Regio- and stereoselective 11β-hydroxylation was achieved on the basic limonoid skeleton through microbial transformation. Whole cells of Cunninghamella echinulata efficiently converted basic limonoids such as epoxyazadiradione, azadiradione, and gedunin to their 11β-hydroxy analogues as the sole metabolite. Fermentation conditions affecting the efficiency (96%) of biotransformation including substrate concentration, incubation period, pH, and temperature were optimized. The position and stereochemistry of hydroxyl functionality on the isolated metabolites were established through extensive spectroscopic and spectrometric studies (1D, 2D NMR, ESI-MS, and MS/MS).

A new butenolide cinnamate and other biological active chemical constituents from Polygonum glabrum

Phytochemical investigation of the methanol extract of the aerial parts of Polygonum glabrum afforded one new natural product (-)-2-methoxy-2-butenolide-3-cinnamate (1) along with six known compounds, β-hydroxyfriedalanol (2), 3-hydroxy-5-methoxystilbene (3), (-) pinocembrin (4), sitosterol-(6'-O-palmitoyl)-3-O-β-D-glucopyranoside (5), (-) pinocembrin-5-methyl ether (6) and sitosterol-3-O-β-D-glucopyranoside (7). Compound 1 showed promising in vitro anti-HIV-1 activity against primary isolates HIV-1(UG070) (X4, subtype D) and HIV-1(VB59) (R5, subtype C) assayed using TZM-bl cell line with IC50 in the range of 15.68-22.43 μg/mL. The extract showed TI in the range of 19.19-27.37 with IC50 in the range of 10.90-15.55 μg/mL. Compounds 1, 3 and 4 exhibited in vitro anti-mycobacterium activity against Mycobacterium tuberculosis H37Ra with IC50 values of 1.43, 3.33 and 1.11 μg/mL in dormant phase and 2.27, 3.33 and 1.21 μg/mL in active phase, respectively. Compound 4 was found to be the most active antiproliferative with IC50 values of 1.88-11.00 μg/mL against THP-1, A549, Panc-1, HeLa and MCF7 cell lines.

Limonoids from the Leaves and Twigs of Walsura yunnanensis

Nine new cedrelone limonoids, namely, walsuranolide B (1), 11β-hydroxy-23-O-methylwalsuranolide (2), yunnanolide A (3), yunnanol A (4), 11β-hydroxyisowalsuranolide (5), 11β-hydroxy-1,2-dihydroisowalsuranolide (6), 1α,11β-dihydroxy-1,2-dihydroisowalsuranolide (7), 11β-hydroxy-1α-methoxy-1,2-dihydroisowalsuranolide (8), and yunnanolide B (9), together with a new cycloartane triterpenoid, (24S*,25R*)-cycloartane-3β,24,25,26-tetrol (10), were isolated from the leaves and twigs of Walsura yunnanensis. Their structures were elucidated on the basis of spectroscopic analysis and by comparison with literature data. Compounds 3 and 5 exhibited potent cytotoxicity against five human tumor cell lines with IC50 values in the range 2.2-4.2 μM.

Cytotoxic and anti-inflammatory triterpenoids from Toona ciliata

Toonaciliatavarins A-H (1-8), including three new protolimonoids (1-3), two new tirucallane-type triterpenoids (4 and 5), and three new tetranortriterpenoids (6-8), and 10 known compounds were isolated from the stem barks of Toona ciliata Roem. var. henryi. Their structures were identified on the basis of spectroscopic analysis. The absolute configurations of 2 and 8 were determined by ECD calculation. The new isolates were evaluated for their cytotoxicities using six human cancer cell lines and also for their inhibitory effects on lipopolysaccharide-induced nitric oxide production in RAW264.7 cells. Compounds 4 and 5 showed moderate cytotoxicities, and the protolimonoids (1-3) exhibited marked inhibitory effects on LPS-stimulated NO production.

Limonoids from the fruits of Melia toosendan

Fifteen limonoids, meliatoosenins E-S (1-15), and 10 known compounds were isolated from the fruits of Melia toosendan. Their structures were elucidated on the basis of extensive spectroscopic methods including DEPT, HSQC, HMBC, (1)H-(1)H COSY, and ROESY experiments. All the compounds were evaluated for antiproliferative activity using A-549 and HL-60 cell lines.

Oxygenated Terpenoids from the Australian Sponges Coscinoderma matthewsi and Dysidea sp., and the Nudibranch Chromodoris albopunctata

The isolation and structure elucidation of seven new oxygenated terpenoids and eight known terpene metabolites from marine invertebrates collected at the Inner Gneerings Reef, South East Queensland, is discussed. Investigation of the sponge Coscinoderma matthewsi yielded an epoxylactone derivative (1) of the known furanoterpene tetradehydrofurospongin-1 (2). A chemical investigation of the dissected nudibranch Chromodoris albopunctata provided the new oxygenated diterpenes 12α-acetoxyspongian-16-one (10), 20-acetoxyspongian-16-one (12), 20-oxyspongian-16-one propionate (13) and 12α,20-dioxyspongian-16-one dipropionate (14) in conjunction with three other known diterpene metabolites, while two new chromodorolides, D (17) and E (18), in addition to four known diterpenes were isolated from a Dysidea sp.

Tetranortriterpenoids fromSpathelia sorbifolia(Rutaceae)

Two new tetranortriterpenoids were obtained by chromatography of the acetone extract of the wood of Spathelia sorbifolia L.; these compounds were characterized as their p-bromobenzoyl derivatives (2, 3). This extract also yielded a known tetranortriterpenoid and the chromones allopteroxylin, spatheliabischromene and anhydrosorbifolin.

A Pregnane Derivative and an Anti-plasmodial Labdane Diterpenoid from the Stem Bark of Turraenthus Africanus

Chemical investigation of the stem bark of Turraeanthus africanus (Meliaceae) afforded a new pregnane derivative, 17α,20S-dihydroxypregn-4-ene-3,16-dione, named turraeasterodione, together with three known diterpenoids, methyl 14,15-epoxylabda-8(17),12E-dien-16-oate, 16-oxolabda-8(17),12E-dien-15-oic acid, and 16-acetoxy-12R,15-epoxylabda-8(17),13(16)-dien-15β-ol. Their structures were elucidated by spectroscopic and spectrometric methods. Methyl 14,15-epoxylabda-8(17),12E-dien-16-oate was found to exhibit anti-plasmodial activity against a chloroquine-resistant strain of Plasmodium falciparum.

New Antioxidant Phenolic Glycosides fromWalsura yunnanensis

Four new polyphenolic glycosides (1-4) were isolated from the BuOH extract of the bark of Walsura yunnanenis C. Y. Wu. These compounds comprise two lignans, i.e., the 9-O-alpha-L-arabinopyranosides 1 and 2 of (-)-isolariciresinol and of (+)-5-methoxyisolariciresinol, respectively, and the two phenolic glycosides 3,4,5-trimethoxyphenyl 2-O-(alpha-L-fucopyranosyl)-beta-D-glucopyranoside (3) and 3,5-dihydroxyphenyl 6-O-(4-hydroxy-3,5-dimethoxybenzoyl)-beta-D-glucopyranoside (walsuraside; 4). In addition, three known compounds, 3,4,5-trimethoxyphenyl beta-D-glucopyranoside, asperglaucide, and butyl alpha-D-fructofuranoside were identified. Their structures were elucidated spectroscopically and by chemical transformation (hydrolysis). The new compounds 1, 2, and 4 displayed significant antioxidant activities, with IC(50) values in the range of ca. 42 to 49 microg/ml.