Turrapubesins A and B, First Examples of Halogenated and Maleimide-Bearing Limonoids in Nature fromTurraeapubescens

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.

High temperature molecular-based phase transition compounds with tunable and switchable dielectric properties

Molecular-based dielectric switching compounds [ClEt-Dabco][ReO4]2 and [BrEt-Dabco][ReO4]2 with high-temperature phase transition.

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.

Natural product sciences: an integrative approach to the innovations of plant natural products

The study on plant natural products not only helps us understand that their structural diversity is the inevitable result of plant species diversity, but also helps us understand certain rules and unity of the inevitable connection between the two. The diversity and complexity of chemical structures of many natural products are beyond imagination before we elucidated their structures. The question that follows is what is the biological significance of these natural products. Intrigued by the relationship between plant resources, natural products and biological functions, the Hao laboratory has taken an integrative approach that employs tools and knowledge from multi-disciplines, including natural product chemistry, chemical ecology and chemical biology, to unveil the effects of plant natural products on plant resistance to diseases, and environmental acclimations. Collaborating with cell biologists, the research has resulted in discovery of new mechanisms of cellular signaling and lead compounds.

Highly oxygenated and rearranged limonoids from the stem barks of Entandrophragma utile

Seventeen highly oxygenated and rearranged limonoids, including nine previously undescribed phragmalin-type limonoids with 1,8,9- and 8,9,30-orthesters (entanutilins C-K, 1-9), three undescribed limonoids with rare rearranged-6/6/7/5 skeleton (entanutilins L-N, 10-12), and 5 known limonoids, were isolated from the stem barks of Entandrophragma utile from Ghana (Africa). Their structures including absolute configurations were elucidated based on comprehensive spectroscopic analyses, such as HRESIMS, 1D/2D-NMR, CD exciton chirality method, time-dependent density functional theory (TDDFT)/ECD calculations, and single-crystal X-ray diffraction. Bioactivity screenings suggested that some of these compounds effectively reversed resistance in MCF-7/DOX cells at a nontoxic concentration of 30 μM with 6- to 19-fold enhancing effects.

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.

C-17 lactam-bearing limonoids from the twigs and leaves of Amoora tsangii

Twelve new lactam-bearing limonoids, amooramides A-L (1-12), were isolated from the twigs and leaves of Amoora tsangii, and their structures fully elucidated by spectroscopic analysis. These compounds represent the first examples of rings A,B-seco-limonoids bearing unusual lactam side chains at C-17, including a 3-substituted 1,5-dihydro-2H-pyrrol-2-one moiety in 1-7 and a 4-substituted 1,5-dihydro-2H-pyrrol-2-one unit in 8-12. Compound 9 inhibited TNFα-induced NF-κB activity by 64% at a concentration of 10 μM.

Synthesis of the B-seco limonoid core scaffold

Synthetic investigations towards the structurally complex and highly decorated framework of B-seco limonoid natural products by means of a [3,3]-sigmatropic rearrangement are described. Detailed model studies reveal, that an Ireland-Claisen rearrangement can be employed to construct the central C9-C10 bond thereby giving access to the B-seco limonoid scaffold. However, application of the developed strategy ended up failing in more complex and sterically demanding systems.

Bioactive limonoid and triterpenoid constituents of Turraea pubescens

Eleven new limonoids, turrapubins A-K (1-11), and three new triterpenoids (12-14), along with 14 known compounds, were isolated from the twigs of Turraea pubescens. The structures of 1-14 were elucidated on the basis of NMR and MS analysis. Compounds 12, 16, 18, and 19 exhibited inhibitory activities against lipopolysaccharide-induced nitric oxide production in RAW264.7 cells. In addition, compounds 2, 11, 18, and 26 exhibited inhibitory activities against brine shrimp larvae (Artemia salina) at 100 ppm with the corrected mortality ranging from 81.7% to 100%.

Limonoids from the fruits of Aphanamixis polystachya (Meliaceae) and their biological activities

Seven new prieurianin-type limonoids, aphapolynins C-I (1-7), and a new aphanamolide-type limonoid, aphanamolide B (8), along with seventeen known compounds, were isolated from the fruits of Aphanamixis polystachya. The structures of these compounds were established on the basis of spectroscopic studies. The absolute configurations were determined by combination of electronic circular dichroism (ECD) calculation, CD exciton chirality method, and single crystal X-ray diffraction. All these isolates were evaluated for their cytotoxicities against three human cancer cell lines, for their inhibitory effects on lipopolysaccharide (LPS) induced RAW264.7 murine macrophages, and for their fungicidal, herbicidal, and insecticidal activities. Compounds 1, 14, 16, and 17 exhibited significant fungicidal activities; 1 and 25 in particular showed good insecticidal activities. The α,β-unsaturated lactone and 14,15-epoxy ring moieties were essential for the insecticidal activity.

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.

Tirucallane-type alkaloids from the bark of Dysoxylum laxiracemosum

Eight novel tirucallane-type alkaloids (1-8) and 11 known compounds were isolated from a methanol extract of the bark of Dysoxylum laxiracemosum. The structures of 1-8 were elucidated using extensive NMR spectrometric and mass spectroscopic methods. Compounds 1 and 5, named laxiracemosins A and E, showed significant cytotoxicity against five human cancer cell lines.

Mesendanins A-J, limonoids from the leaves and twigs of Melia toosendan

Ten new limonoids, namely, mesendanins A-J (1-10), together with 14 known compounds, have been isolated from the leaves and twigs of Melia toosendan. Their structures were established on the basis of spectroscopic data analysis.

Farinomalein, a maleimide-bearing compound from the entomopathogenic fungus Paecilomyces farinosus

A new maleimide-bearing compound, farinomalein (1), was isolated from the entomopathogenic fungus Paecilomyces farinosus HF599. The structure was determined on the basis of spectroscopic analyses and chemical conversion. Compound 1 showed potent activity (5 mug/disk) against the plant pathogenic Phytophthora sojae P6497.

Terpenoids from Toona ciliata

Three new norlimonoids (1-3), two new tirucallane-type triterpenoids (4 and 5), and a new pimaradiene-type diterpenoid (6), along with two known limonoids and eight known tirucallane-type triterpenoids, were isolated from the leaves and twigs of Toona ciliata. Their structures were elucidated on the basis of spectroscopic data. Toonaciliatin M (6) showed moderate antifungal activity against Trichophyton rubrum with an MIC of 12.5 microg/mL.

Cadinane sesquiterpenes from the leaves of Eupatorium adenophorum

Four new cadinane sesquiterpenes (1- 4), including a dimeric cadinane derivative (2) and a peroxide cadinane analogue (3), have been isolated from the leaves of Eupatorium adenophorum. Their structures including absolute configurations were determined on the basis of spectroscopic data interpretation and single-crystal X-ray crystallography. Compound 4 showed in vitro cytotoxicity against the HCT-8, Bel-7402, and A2780 cancer cell lines.

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, isomalabaricanes and saponins. The literature from January 2005 to December 2006 is reviewed and 478 references are cited.

Limonoids and sesquiterpenoids from Amoora tsangii

Seven new limonoids, amotsangins A-G (1-7), two known limonoids, and four known sesquiterpenoids were isolated from the twigs and leaves of Amoora tsangii. Their structures were elucidated primarily on the basis of spectroscopic data.

Nortriterpenoids from Chukrasia tabularis var. velutina

Five new limonoids, tabularisins E-I ( 1- 5), and a new dinorcycloartane, (24 R)-28,29-dinor-cycloartane-3beta,24,25-triol ( 6), together with three known compounds, were isolated from the twigs and leaves of Chukrasia tabularis var. velutina. Their structures were elucidated primarily on the basis of spectroscopic methods.