Limonoids and Diterpenoids from Toona ciliata Roem. var. yunnanensis

Toonanoronoids A-E, five new limonoids from Toona ciliata var. yunnanensis

Five new B-seco-limonoids, namely toonanoronoids A-E (1-5), in conjunction with three previously reported compounds, were isolated from the EtOAc extract of the twigs and leaves of Toona ciliata var. yunnanensis. Their structures were elucidated through comprehensive spectroscopic and X-ray crystallographic analysis. The cytotoxic activities of new compounds against five human tumor cell lines (HL-60, SMMC-7721, A549, MCF-7, and SW480) were screened, Compounds 4 and 5 exerted inhibition toward two tumor cell lines (HL-60, SW-480) with IC50 values between 1.7 and 5.9 μM.

Limonoids with anti-inflammatory activity: A review

The natural limonoids distributed mainly in the Meliaceae and Rutaceae plants are known for their unique and complex structure with high degree oxidation and cyclic rearrangement. However, these compounds exhibit a broad range of biological activities such as insecticidal, antibacterial, antifungal, antimalarial, antioxidant, anticancer, antiviral, and anti-inflammatory. There is still limited report about the biological activity of the anti-inflammatory effect of limonoids isolated from plants. Therefore, this study aimed to examine the effect of intact, deformed and rearranged limonoids as anti-inflammatory agents. The majority of anti-inflammatory investigations were evaluated by in vitro and in vivo assays of the isolated pure compounds and their derivatives. For the in vitro study, intact and C-ring seco limonoids showed a potent inhibitory effect against NO production. The in vivo analysis of Intact, C-seco, and AD-seco limonoids showed a potent effect based on the inhibition of pro-inflammatory cytokines expression, indicating their potency as anti-inflammatory agents.

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.

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.

Four New Limonoids from the Barks of Toona ciliata

Four new limonoids, toonayunnanaes F - I (1 - 4), and six known compounds (5 - 10) were isolated from the barks of Toona ciliata. Their structures were elucidated by thoroughly analyzing of NMR and HRMS data, and single-crystal X-ray diffraction of 1. The oxetane ring moiety in 1 was rare in limonoids and other natural products. Compound 1 showed nitric oxide (NO) inhibitory effect with an IC₅₀ 38.45 ± 0.41 µM in lipopolysaccharide (LPS)-activated RAW 264.7 macrophages.

Limonoids From Choerospondias axillaris

Eight limonoids (1-8), including 1 new compound named as axillariol A (1), were isolated from the dichloromethane extract of Choerospondias axillaris branches and leaves using various chromatographic separations. Their structures were confirmed by detailed analysis of the 1-dimensional (1D), 2D nuclear magnetic resonance, and high-resolution electrospray ionization quadrupole time-of-flight mass spectra. In addition, toonaciliatins N (6) and toonaciliatins O (7) showed selective and significant cytotoxicity on the rhabdomyosarcoma human cancer cell line with half-maximal inhibitory concentration values of 9.12 and 7.79 µM, respectively.

Cytotoxic Limonoids from the Twigs and Leaves of Toona ciliata

Eight new limonoids, toononoids A-H (1-8), eight new B-seco-29-norlimonoids, toonanoronoids A-H (9-16), and seven known analogues were obtained from the EtOAc extract of the twigs and leaves of Toona ciliata. Compounds 2, 4, 8, and 16 are rare lactam-bearing limonoids. Compounds 1, 14, and 15 possess an unusual γ-methoxybutenolide moiety at C-17, while compounds 9, 10, and 15 have a rare 3β-hydroxy group. Their 2D structure and relative configurations were identified using spectroscopic data. The absolute configurations of 1, 9, 14, and 15 were established via X-ray diffraction crystallography or comparison of experimental and calculated ECD data. The cytotoxicity of the compounds was assessed toward five human tumor cell lines, and their anti-inflammatory activity was assessed based on NO production using LPS-stimulated RAW264.7 macrophages. Compounds 11 and 12 exerted inhibition toward two tumor cell lines (MCF-7, SW-480) with IC₅₀ values between 2.1 and 3.7 μM, while 18-22 inhibited the proliferation of HL-60, MCF-7, and SW-480 cells (IC₅₀ 0.6-4.0 μM). Only compound 4 exhibited weak anti-inflammatory activity with an IC₅₀ value of 28.3 μM.

Toonamicrocarpavarin, a new tirucallane-type triterpenoid from Toona Ciliata

Toonamicrocarpavarin (1), a new tirucallane-type triterpenoid, along with eight known ones, piscidinol A (2), toonaciliatavarin E (3), toonayunnanin A (4), 7-acetyneotrichilenone (5), hispidol A (6), odoratone (7), phellochin (8), toonaciliatavarin D (9), were isolated from T. ciliata. Their structures were identified on the basis of ESIMS, HREIMS and 1 D/2D NMR analysis. The cytotoxic activity of the new compound was also evaluated. All compounds were obtained from T. ciliata for the first time, which plays an important role in chemotaxonomy of the plant T. ciliata.

Rearranged limonoids with unique 6/5/6/5 tetracarbocyclic skeletons from Toona ciliata and biomimetic structure divergence

Rearranged limonoids with 6/5/6/5 carbon skeletons, were characterized as metabolite and biomimetic products.

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.

Discovery of structurally diverse and bioactive compounds from plant resources in China

This review describes the major discoveries of structurally diverse and/or biologically significant compounds from plant resources in China, mainly from the traditional Chinese medicines (TCMs) since the establishment of our research group in 1999. In the past decade, a large array of biologically significant and novel structures has been identified from plant resources (or TCM) in our laboratory. The structural modification of several biologically important compounds led to more than 400 derivatives, some of which exhibited significantly improved activities and provided opportunities to elucidate the structure-activity relationship of the related compound class. These findings are important for drug discovery and help us understand the biological basis for the traditional applications of these plants in TCM.