Meliaceous Limonoids: Chemistry and Biological Activities

Limonoids from the fruits of Khaya ivorensis

Two new limonoids, namely 14,15-didehydroruageanin A (1) and 3-O-methyl- butyrylseneganolide A (2), were isolated from the fruits of Khaya ivorensis along with six known limonoids: seneganolide A (3), 1,3-dideacetylkhivorin (4), 7-deacetylkhivorin (5), 3-deacetylkhivorin (6), 1-deacetylkhivorin (7), and 3-deacetyl-7-oxokhivorin (8). All the compounds were evaluated for their cytotoxicity against five tumor cell lines.

Methyl angolensate and mexicanolide-type limonoids from the seeds of Cipadessa baccifera

Six new methyl angolensate type (1-6) and three new mexicanolide-type (7-9) limonoids, along with six known limonoids (10-15), were isolated from the seeds of Cipadessa baccifera. The structures of all these compounds were established by extensive 1D, 2D NMR, and HRESIMS experiments, and structures of 11 and 13 were further confirmed by a single crystal X-ray diffraction analysis, which are reported for the first time. The cytotoxic activities of these isolates were also studied against A549, MCF7, ME-180, HT-29, B-16, ACHN cancer cell lines using MTT assay, and results indicated that compounds 4, 10, and 14 displayed potent cytotoxic activity against B-16, ACHN cell lines with an IC50 values of 8.51 and 7.0 μg/mL, respectively.

Diterpenoids and Limonoids from the Leaves and Twigs of Swietenia mahagoni

Three new compounds, including two diterpenoids, nemoralisins H and I (1 and 2), and a limonoid, 2-methoxy khayseneganin E (3), along with four known constituents (4-7), were isolated from the leaves and twigs of Swietenia mahagoni. Their chemical structures were elucidated by means of spectroscopic analysis. The cytotoxities of these isolated constituents were assayed.

Biocatalyst mediated functionalization of salannin, an insecticidal limonoid

Novel and efficient modification was achieved on the furan moiety of salannin by fungi mediated biocatalysis.

Strategic innovation in the total synthesis of complex natural products using gold catalysis

This review has been organized from the perspective of synthetic target families, with emphasis on the use of gold-catalyzed transformations and cascade reactions that significantly increase molecular complexity.

Structural diversity and bioactivities of natural benzophenones

Natural benzophenones are a class of compounds with more than 300 members, mainly in the Clusiaceae family. We review key benzophenones, and provide an in-depth discussion of their great structural diversity and biological activity.

Physiological and biochemical effect of neem and other Meliaceae plants secondary metabolites against Lepidopteran insects

This review described the physiological and biochemical effects of various secondary metabolites from Meliaceae against major Lepidopteran insect pest including, Noctuidae and Pyralidae. The biochemical effect of major Meliaceae secondary metabolites were discussed more in this review. Several enzymes based on food materials have critical roles in nutritional indices (food utilization) of the insect pest population. Several research work has been referred and the effect of Meliaceae secondary metabolites on feeding parameters of insects by demonstrating food consumption, approximate digestibility of consumed food, efficiency of converting the ingested food to body substance, efficiency of converting digested food to body substance and consumption index was reviewed in detail. Further how the digestive enzymes including a-Amylases, α and β-glucosidases (EC 3.2.1.1), lipases (EC 3.1.1) Proteases, serine, cysteine, and aspartic proteinases affected by the Meliaceae secondary metabolites was reviewed. Further effect of Meliaceae secondary metabolites on detoxifying enzymes have been found to react against botanical insecticides including general esterases (EST), glutathione S-transferase (GST) and phosphatases was reviewed. Alkaline phosphatase (ALP, E.C.3.1.3.1) and acid phosphatase (ACP, E.C.3.1.3.2) are hydrolytic enzymes, which hydrolyze phosphomonoesters under alkaline or acid conditions, respectively. These enzymes were affected by the secondary metabolites treatment. The detailed mechanism of action was further explained in this review. Acethylcholine esterase (AChE) is a key enzyme that terminates nerve impulses by catalyzing the hydrolysis of neurotransmitter, acetylcholine, in the nervous system of various organisms. How the AChE activity was altered by the Meliaceae secondary metabolites reviewed in detail.

In vivo antimalarial evaluation of MAMA decoction on Plasmodium berghei in mice

The use of decoctions of different plant materials is common practice in antimalarial ethnomedicine in Africa. Scientific evaluation of such herbal combinations to verify the claims is important. The study has evaluated the antimalarial efficacy of MAMA decoction (MD), a multicomponent herbal preparation and its individual plant components, namely leaves of Morinda lucida Benth [Rubiaceae] (ML), Azadirachta indica A. Juss [Meliaceae] (AI), Alstonia boonei De Wild [Apocynaceae] (AB) and Mangifera indica L [Anacardiaceae] (MI) in Plasmodium berghei-infected mice. Each decoction was prepared by boiling the powdered leaf in water, concentrated in vacuo and freeze-dried. The acute toxicity of MD (LD50=3.8 g/kg) was determined using Lorke's method. The antimalarial activities of MD and its plant components were evaluated by oral administration of the freeze-dried extracts (15-240 mg/kg) using the early malaria infection test model. The established malaria infection test was used to evaluate MD (60-240 mg/kg) while amodiaquine [10 mg/kg] (AQ) and distilled water were employed as the positive and negative controls, respectively. From the early malaria infection test, the effective doses at 50 % (ED50) and 90 % (ED90) for MD, AB, AI, ML, MI and AQ were 43, 79, 140, 134, 208 and 3.9 mg/kg and 202, 276, 291, 408, 480 and 9.2 mg/kg, respectively. For the established infection test, MD (240 mg/kg) and AQ gave parasite clearance of 55 and 95 % on day 5 of treatment. MD possesses antimalarial activity and is relatively safe.

Xylogranin B: a potent Wnt signal inhibitory limonoid from Xylocarpus granatum

Xylogranin B (2) was isolated from Xylocarpus granatum (Meliaceae) leaves, by use of a cell-based luciferase screening system targeting a Wnt signaling pathway. Compound 2 inhibited TCF/β-catenin transcriptional activity (IC50 48.9 nM) and exhibited strong cytotoxicity against colon cancer cell lines. Compound 2 significantly decreased β-catenin protein levels in nuclei but not in the cytosol. These results indicated that a decrease in β-catenin levels in nuclei by 2 resulted in the Wnt signal inhibitory effects of 2.

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.

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.

11β-HSD1 inhibitors from Walsura cochinchinensis

A search for inhibitors of 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) from Walsura cochinchinensis yielded 10 new limonoids, cochinchinoids A-J (1-10), and two new triterpenoids, 3-epimesendanin S (11) and cochinchinoid K (12). Their structures were assigned on the basis of spectroscopic data, with the absolute configurations of 1 and 12 being established by X-ray diffraction analysis. Of these compounds, cochinchinoid K (12) displayed inhibitory activity against mouse 11β-HSD1 with an IC50 value of 0.82 μM.

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 Melia azedarach and their cytotoxic activities

Thirty-one limonoids and one tirucallane-type triterpenoid were isolated from the fruits of Melia azedarach (Meliaceae). The structures of 14 of these isolated compounds were elucidated on the basis of spectroscopic analyses and comparison with literature. All of these compounds were evaluated for their cytotoxic activities against HL60, A549, AZ521, and SK-BR-3 human cancer cell lines. Meliarachin C (IC50 0.65 μM) and 3-O-deacetyl-4'-demethyl-28-oxosalannin (IC50 2.8 μM) exhibited potent cytotoxic activity against HL60 cells, and this was demonstrated mainly due to the induction of apoptosis by flow cytometry. Western blot analysis suggested that both compounds induced apoptosis via both the mitochondrial and death receptor-mediated pathways. In addition, 25 compounds were evaluated for their inhibitory effects against the Epstein-Barr virus early antigen (EBV-EA) activation induced by 12-O-tetradecanoylphorbol-13-acetate (TPA) in Raji cells.

Chemical components of Dysoxylum densiflorum

Three new diterpenoids, including two halimanes, 5(10),13E-halimadiene-3α,15-diol (1), and 5(10),14-halimadiene-3α,13ξ-diol (2), one labdane, 12-(3-methyl-furan)-labd-8(17)-en-19-oic acid (3), together with sixteen known compounds were isolated from the barks of Dysoxylum densiflorum. All compounds were elucidated by extensive spectroscopic analysis.

New limonoids and a dihydrobenzofuran norlignan from the roots of Toona sinensis

Two new limonoids, toonins A (1) and B (2), and one new dihydrobenzofuran norlignan, toonin C (3), were isolated from the roots of Toona sinensis together with the ten known compounds 4-methoxy-6-(2′,4′-dihydroxy-6′-methylphenyl)-pyran-2-one (4), bourjotinolone A (5), proceranone (6), matairesinol (7), 4-hydroxy-3-methoxybenzene-ethanol (8), syringic acid (9), isoscopoletin (10), lyoniresinol (11), aloeemodin (12), and β-sitosterol (13). Their structures were elucidated on the basis of one- and two-dimensional spectroscopic analysis. Isolation of compounds 4, 6–13 from this plant is reported here for the first time.

New triterpenoids from the kernels of Azadirachta indica

Three new limonoids (1–3) and a new intact triterpenoid (4), along with three known constituents (5–7), were isolated from the dried kernels (after extracting azadirachtin) of Azadirachta indica. The structures of the new compounds 1-benzoyl-3-deacetyl-1-detigloyl salannin (1), 7-tigloyl-12-oxo vilasini (2), azadiralactone (3) and azadirahemiacetal (4) were elucidated by means of spectroscopic analysis. The cytotoxities of these isolated constituents were assayed.

A draft of the genome and four transcriptomes of a medicinal and pesticidal angiosperm Azadirachta indica

Background

The Azadirachta indica (neem) tree is a source of a wide number of natural products, including the potent biopesticide azadirachtin. In spite of its widespread applications in agriculture and medicine, the molecular aspects of the biosynthesis of neem terpenoids remain largely unexplored. The current report describes the draft genome and four transcriptomes of A. indica and attempts to contextualise the sequence information in terms of its molecular phylogeny, transcript expression and terpenoid biosynthesis pathways. A. indica is the first member of the family Meliaceae to be sequenced using next generation sequencing approach.

Results

The genome and transcriptomes of A. indica were sequenced using multiple sequencing platforms and libraries. The A. indica genome is AT-rich, bears few repetitive DNA elements and comprises about 20,000 genes. The molecular phylogenetic analyses grouped A. indica together with Citrus sinensis from the Rutaceae family validating its conventional taxonomic classification. Comparative transcript expression analysis showed either exclusive or enhanced expression of known genes involved in neem terpenoid biosynthesis pathways compared to other sequenced angiosperms. Genome and transcriptome analyses in A. indica led to the identification of repeat elements, nucleotide composition and expression profiles of genes in various organs.

Conclusions

This study on A. indica genome and transcriptomes will provide a model for characterization of metabolic pathways involved in synthesis of bioactive compounds, comparative evolutionary studies among various Meliaceae family members and help annotate their genomes. A better understanding of molecular pathways involved in the azadirachtin synthesis in A. indica will pave ways for bulk production of environment friendly biopesticides.

Synthesis of CDE molecular fragments related to sendanin mediated by titanocene(III)

A practical, brief, and diastereoselective synthesis of limonoid CDE fragments from a readily available starting material is described. The key step was the titanocene(III)-promoted cyclization of unsaturated epoxylactones, readily prepared from α-cyclocitral. In this way, we confirm the viability of our procedure for the synthesis of a limonoid model with different functionalization patterns. We also report the antifeedant activity of epoxylactones 18 and 19, which show significant antifeedant activity against Spodoptera littoralis and Spodoptera frugiperda, two insect species with different feeding ecologies.

Five new mexicanolide type limonoids from Heynea trijuga

Five new mexicanolide-type limonoids, heytrijunolides A–E (1–5) were isolated from the branches and leaves of Heynea trijuga. The structures of these new compounds were elucidated on the basis of extensive spectroscopic analysis. Compound 3 showed weak cytotoxicity against HL-60, SMMC-7721 and A-549 human tumor cell lines with the IC₅₀ values of 21.88, 20.66 and 12.70 µM, respectively.

The limonoids and their antitobacco mosaic virus (TMV) activities from Munronia unifoliolata Oliv

Five new limonoids, named munronoids K-O (1-5), together with three known limonoids were isolated from Munronia unifoliola Oliv. These limonoids were involved in the skeletons of evodulone, gedunin, and peieurianin types of limonoids, and their structures were established on the basis of spectroscopic data. Compound 5 featuring a γ-lactone ring instead of the β-substituted furan ring was found in the peieurianin type for the first time. The antitobacco mosaic virus (anti-TMV) activities of compounds 1-8 were also evaluated with half-leaf, enzyme-linked immunosorbent assay, and Western blot methods, and limonoids 1, 5, and 8 showed stronger anti-TMV treatment activities than the positive control ningnanmycin. Six compounds (1-5 and 8) exhibited infection inhibition activities against TMV.

Schilancitrilactones A-C: three unique nortriterpenoids from Schisandra lancifolia

Three unique nortriterpenoids, schilancitrilactones A-C (1-3), were isolated from the stems of Schisandra lancifolia . Compound 1 possesses a 5/5/7/5/5/5-fused hexacyclic ring system with a C(29) backbone, while 2 and 3 feature a C(27) skeleton with a 5/7/5/5/5-fused pentacyclic ring system. Their absolute stereochemistries were established by CD and single-crystal X-ray diffraction experiments. Compound 3 showed anti-HIV-1 activity with an EC(50) value of 27.54 μg/mL, and 1 exhibited antifeedant activity at 15.73 μg/cm(2).