Rings D-seco and B,D-seco tetranortriterpenoids from root bark of Entandrophragma angolense

Investigation of the root bark extract of Entandrophragma angolense led to identification of two gedunin-type limonoids 5-hydroxy-7-deacetoxy-7-oxogedunin and 5,6-dehydro-7-deacetoxy-7-oxogedunin, and three methyl angolensate derivatives, 6-deacetoxydomesticulide D, 6-deacetoxydomesticulide D 21-methylether, and entangosin, together with known compounds, methyl angolensate, 6-acetoxymethyl angolensate and secomahoganin. Their structures were established by extensive NMR experiments in conjunction with mass spectrometry. Entangosin is a rare example of a limonoid derivative having a fully O-substituted furan moiety.     

Structure and stereochemistry of limonoids of Cabralea eichleriana

From Cabralea eichleriana seeds, the following compounds have been isolated: cabraleone, cabraleadiol, fissinolide, 3-deacetylfissinolide, gedunin, 7-deacetoxy-7-oxygedunin, 7-deacetoxy-7-hyd-roxygedunin, methyl angolensate, and three new compounds, 7-deacetoxy-7-hydroxyphotogedunin, cabralin, and isocabralin. Cabralin has also been obtained by photolysis of fissinolide.     

Cytotoxic scalarane sesterterpenes from a Korean marine sponge Psammocinia sp.

Three novel scalarane sesterterpenes were isolated from a Korean marine sponge, Psammocinia sp., along with four known derivatives. Their structures were elucidated on the basis of NMR, MS and IR spectroscopic data. The three new compounds are 12-deacetoxy-23-hydroxyscalaradial (1), 12-dehydroxy-23-hydroxyhyrtiolide (2) and 12-O-acetyl-16-deacetoxy-23-acetoxyscalarafuran (3), respectively, and the four known compounds are 12-deacetoxy-23-hydroxyheteronemin (4), 12-deacetoxy-23-acetoxy-19-O-acetylscalarin (5), 12-deacetoxy-23-O-acetoxyheteronemin (6) and 12-deacetoxyscalaradial (7). They exhibited cytotoxicity against intractable human cancer cell lines A498, ACHN, MIA-paca and PANC-1, with an IC₅₀ range of 0.4–48 μM.     

Gedunin and Azadiradione: Human Pancreatic Alpha-Amylase Inhibiting Limonoids from Neem (Azadirachta indica) as Anti-Diabetic Agents

Human pancreatic α-amylase (HPA) inhibitors offer an effective strategy to lower postprandial hyperglycemia via control of starch breakdown. Limonoids from Azadirachta indica known for their therapeutic potential were screened for pancreatic α-amylase inhibition, a known anti-diabetic target. Studies were carried out to reveal their mode of action so as to justify their hypoglycemic potential. Of the nine limonoids isolated/semi-synthesized from A.indica and screened for α-amylase inhibition, azadiradione and exhibited potential inhibition with an IC₅₀ value of 74.17 and 68.38 μM, respectively against HPA under in vitro conditions. Further screening on AR42J α-amylase secretory cell line for cytotoxicity and bioactivity revealed that azadiradione and gedunin exhibited cytotoxicity with IC₅₀ of 11.1 and 13.4μM. Maximal secreted α-amylase inhibition of 41.8% and 53.4% was seen at 3.5 and 3.3μM, respectively. Michaelis-Menten kinetics suggested a mixed mode of inhibition with maltopentaose (K _i 42.2, 18.6 μM) and starch (K _i ′ 75.8, 37.4 μM) as substrate with a stiochiometry of 1:1 for both azadiradione and gedunin, respectively. The molecular docking simulation indicated plausible π-alkyl and alkyl-alkyl interactions between the aromatic amino acids and inhibitors. Fluorescence and CD confirmed the involvement of tryptophan and tyrosine in ligand binding to HPA. Thermodynamic parameters suggested that binding is enthalpically and entropically driven with ΔG° of -21.25 kJ mol^-1 and -21.16 kJ mol^-1 for azadiradione and gedunin, respectively. Thus, the limonoids azadiradione and gedunin could bind and inactivate HPA (anti-diabetic target) and may prove to be lead drug candidates to reduce/control post-prandial hyperglycemia.     

Antimalarial activities of gedunin and 7-methoxygedunin and synergistic activity with dillapiol

Gedunin from Cedrela odorata (Meliaceae), a potent in vitro antimalarial agent, was investigated for its in vivo efficacy in CD‐1 mice infected with Plasmodium berghei. When orally administered at 50 mg kg‐1 day‐1 for 4 days, gedunin was able to suppress the parasitaemia level by 44%. However, no clear dose‐response effects were observed in the 0–100 mg kg‐1 day‐1 dose range. Preliminary pharmacokinetics in Sprague‐Dawley rats showed poor absorption. However, a binary treatment of 50 mg kg‐1 day‐1 gedunin with 25 mg kg‐1 day‐1 dillapiol, a cytochrome P450 inhibitor, increased parasitaemia clearance in mice to 75%. A clear dose‐response was observed in the 0–50 mg kg‐1 day‐1 gedunin dose range when administration was combined with 25 mg kg‐1 day‐1 dillapiol. In addition, 7‐methoxygedunin, a semi‐synthetic derivative which is more stable to degradation than gedunin, suppressed the level in mice by 67% at 50 mg kg‐1 day‐1. When administered at this dose in combination with 25 mg kg‐1 day‐1 dillapiol, clearance increased to 80%. These results demonstrate the potentialefficacy of antimalarial drugs and phytomedicines based on gedunin and the value of the combination therapy.     

中国红豆杉中一个新的紫杉烷二萜

从中国红豆杉(Taxus chinensis)枝叶中分离得到4个紫杉烷二萜,通过波谱分析分别确定为：1β-羟基-2α,7β-二去乙酰基巴卡亭I(1),1β-羟基巴卡亭I(2),2α,5α,7β,9α,10β,13α-六乙酰氧基紫杉-4(20),11-二烯(3)和2-去乙酰氧基-5-去肉桂酰taxinine J(4)其中化合物1为新化合物。     

Gedunin Inactivates the Co-chaperone p23 Protein Causing Cancer Cell Death by Apoptosis

Pharmacological inhibition of Hsp90 is an exciting option for cancer therapy. The clinical efficacy of Hsp90 inhibitors is, however, less than expected. Binding of the co-chaperone p23 to Hsp90 and induced overexpression of anti-apoptotic proteins Hsp70 and Hsp27 are thought to contribute to this outcome. Herein, we report that the natural product gedunin may provide a new alternative to inactivate the Hsp90 machine. We show that gedunin directly binds to p23 and inactivates it, without overexpression of Hsp27 and relatively modest induction of Hsp70. Using molecular docking and mutational analysis, we mapped the gedunin-binding site on p23. Functional analysis shows that gedunin inhibits the p23 chaperoning activity, blocks its cellular interaction with Hsp90, and interferes with p23-mediated gene regulation. Cell treatment with gedunin leads to cancer cell death by apoptosis through inactivation of p23 and activation of caspase 7, which cleaves p23 at the C terminus. These results provide important insight into the molecular mechanism of action of this promising lead compound.     

Molecular docking analysis of modified gedunin from neem with snake venom enzymes

Snakebites are a problem due to the increasing number of deaths and permanent disabilities. There is currently a shortage of antidotes for snakebite. The existing antibody antidote, produced from horse/sheep plasma/sera is expensive, species-dependent, and causes fatal side effects. Therefore, it is of interest use of natural flavonoid named gedunin from the Azadirachta indica (Neem) plant species to combat snakebites. Thus, we show the molecular docking analysis of gedunin (C26H31N2O6F) with enzymes (common in snake species) such as 5-nucleotidase, acetyl cholinesterase, L-aao, metalloproteinase, serine, thrombin and phospholipase A2. The modified gedunin in the enzyme pocket showed improved pharmacological properties for further consideration in combating snakebites.     

Perenniporiol derivatives six triterpenoids from the cultured mycelia of Perenniporia ochroleuca

Six new triterpenoids, (26S)-26-O-methylperenniporiol, (26S)-3-acetyl-26-O-methylperenniporiol, perenniporiol, 3-acetylperenniporiol, (26S-15-deacetoxy-7,11-dihydro-26-O-methylperenniporiol and 15-deacetoxy-7,11-dihydroperenniporiol were isolated from the cultured mycelia of Perenniporia ochroleuca. The structures of the first two compounds were determined using spectroscopic and X-ray analyses, and the structures of the other compounds were elucidated by spectroscopic data.     

Synthesis and interactions of 7-deoxy-, 10-deacetoxy, and 10-deacetoxy-7-deoxypaclitaxel with NCI/ADR-RES cancer cells and bovine brain microvessel endothelial cells

7-Deoxypaclitaxel, 10-deacetoxypaclitaxel and 10-deacetoxy-7-deoxypaclitaxel were prepared and evaluated for their ability to promote assembly of tubulin into microtubules, their cytotoxicity against NCI/ADR-RES cells and for their interactions with P-glycoprotein in bovine brain microvessel endothelial cells. The three compounds were essentially equivalent to paclitaxel in cytotoxicity against NCI/ADR-RES cells. They also appeared to interact with P-glycoprotein in the endothelial cells with the two 10-deacetoxy compounds having less interaction than paclitaxel and 7-deoxypaclitaxel.     

Screening and characterization of microorganisms with glutaryl-7 ADCA acylase activity

A screening of microorganisms producing glutaryl-7 ADCA acylase, an enzyme able to hydrolyse glutaric acid selectively from glutaryl-3-deacetoxy-7-aminocephalosporanic acid (glutaryl-7 ADCA), has been carried out in soil samples. Five microorganisms expressing acylase activity were isolated and classified as Bacillus cereus, Achromobacter xylosooxidans, Bacillus sp., Pseudomonas sp. and Pseudomonas paucimobilis. The screening was carried out by preparing enrichment cultures containing glutaryl-7-ADCA or cephalosporin C as the selective carbon source. Four model compounds (adipoyl-, glutamyl- and glutaryl-p-nitroanilide and glutarylcoumarin), mimicking the glutaryl-7 ADCA -lactam moiety, were synthesized as substrates suitable for the rapid screening of the microorganisms (2500) isolated from the enrichment cultures. A total of 300 strains were active on the model substrates and only 5 displayed acylase activity on glutaryl-7 ADCA. The fermentation parameters, such as pH and inducer concentration, for the optimal acylase expression and acylase specificity towards the model substrates were different for each strain.     

Antimalarial activity of anthothecol derived from Khaya anthotheca (Meliaceae)

Antimalarial activity of anthothecol, a limonoid of Khaya anthotheca (Meliaceae) against Plasmodium falciparum was tested using a [³H]-hypoxanthine and 48 h culture assay in vitro. Anthotechol showed potent antimalarial activity against malaria parasites with IC₅₀ values of 1.4 and 0.17 μM using two different assays. Also, gedunin had antimalarial activity with IC₅₀ values of 3.1 and 0.14 μM. However, the citrus limonoids, limonin and obacunone did not show any antimalarial activity. The antimalarial activities were compared with the three currently used antimalarial medicines quinine, chloroquinine and artemisinin.     

Delta 2- and delta 3-cephalosporins, penicillinate and 6-unsubstituted penems. Intrinsic reactivity and interaction with beta-lactamases and D-alanyl-D-alanine-cleaving serine peptidases.

The intrinsic reactivity of delta 2- and delta 3-deacetoxy-7-phenylacetamidocephalosporanates, penicillanate, unsubstituted, 2-methyl- and 2-phenyl-penems and other beta-lactam antibiotics has been expressed in terms of the second-order rate constant (M-1.s-1(OH-)) for the hydrolysis of the beta-lactam amide bond by OH- at 37 degrees C. The values thus obtained have been compared with the second-order rate constants (M-1.s-1(enzyme) for the opening of the same beta-lactam amide bond during interaction with the beta-lactamases of Streptomyces albus G and Actinomadura R39 and the D-alanyl-D-alanine-cleaving serine peptidases of Streptomyces R61 and Actinomadura R39. Depending on the cases, the accelerating effect due to enzyme action and expressed by the ratio M-1.s-1(enzyme)/M-1.s-1(OH) varies from less than 2 to more than 1 x 10(6). The primary parameter that governs enzyme action is the goodness of fit of the beta-lactam molecule to the enzyme cavity rather than its intrinsic reactivity. With the D-alanyl-D-alanine-cleaving serine peptidases, the three penems studied form intermediate complexes characterized by very short half lives of 14-100 s, values significantly lower than those exhibited by most beta-lactam compounds.     

An antibacterial hydroxy fusidic acid analogue from Acremonium crotocinigenum

A fusidane triterpene, 16-deacetoxy-7-beta-hydroxy-fusidic acid (1), was isolated from a fermentation of the mitosporic fungus Acremonium crotocinigenum. Full unambiguous assignment of all (1)H and (13)C data of 1 was carried out by extensive one- and two-dimensional NMR studies employing HMQC and HMBC spectra. Compound 1 was tested against a panel of multidrug-resistant (MDR) and methicillin-resistant Staphylococcus aureus (MRSA) strains and showed minimum inhibitory concentration values of 16 microg/ml.     

Fluorinated and rearranged gedunin derivatives

When treated with (diethylamino)sulfur trifluoride (DAST), 11α-hydroxygedunin gave 11β-fluorogedunin and 9,11-didehydrogedunin, whereas deacetylgedunin afforded two skeletal rearranged products 6 and 7, in which the Me-30 had shifted from position 8 to position 7. Of those products, 11β-fluorogedunin and 6 were shown to be more cytotoxic than gedunin on P-388 leukemia cells.     

Insect growth regulatory effects of some extracts and sterols from Myrtillocactus geometrizans (Cactaceae) against Spodoptera frugiperda and Tenebrio molitor

A methanol extract from the roots and aerial parts of Myrtillocactus geometrizans (Cactaceae) yielded peniocerol 1, macdougallin 2, and chichipegenin 3. The natural products 1, 2 their mixtures, MeOH and CH(2)Cl(2) extracts showed insecticidal and insect growth regulatory activity against fall armyworm [Spodoptera frugiperda J. E. Smith (Lepidoptera: Noctuidae)], an important insect pest of corn, and [Tenebrio molitor (Coleoptera)], a pest of stored grains in Mexico. The most active compounds were 1, 2, and a mixture (M(2)) of 1 and 2 (6:4). All these extracts, compounds and the mixture had insect growth regulating (IGR) activity between 5.0 and 50.0 ppm and insecticidal effects between 50 and 300 ppm in diets. The extracts were insecticidal to larvae, with lethal doses between 100 and 200 ppm. These compounds appear to have selective effects on the pre-emergence metabolism of Coleoptera, because in all treatments of the larvae of T. molitor, pupation were shortened and this process show precociousness in relation to controls. In contrast to S. frugiperda larvae, onset of pupation was noticeably delayed. Emergence in both cases was drastically diminished. In both pupae and in the few adults that were able to emerge, many deformations were observed. The results of these assays indicated that the compounds were more active than other known natural insect growth inhibitors such as gedunin and methanol extracts of Cedrela salvadorensis and Yucca periculosa. Peniocerol, macdougallin and chichipegenin, as well as mixtures of these substances, may be useful as natural insecticidal agents.     

Lin28-mediated control of let-7 microRNA expression by alternative TUTases Zcchc11 (TUT4) and Zcchc6 (TUT7)

The pluripotency factor Lin28 recruits a 3' terminal uridylyl transferase (TUTase) to selectively block let-7 microRNA biogenesis in undifferentiated cells. Zcchc11 (TUTase4/TUT4) was previously identified as an enzyme responsible for Lin28-mediated pre-let-7 uridylation and control of let-7 expression. Here we investigate the protein and RNA determinants for this interaction. Biochemical dissection and reconstitution assays reveal the TUTase domains necessary and sufficient for Lin28-enhanced pre-let-7 uridylation. A single C2H2-type zinc finger domain of Zcchc11 was found to be responsible for the functional interaction with Lin28. We identify Zcchc6 (TUTase7) as an alternative TUTase that functions with Lin28 in vitro, and accordingly, we find Zcchc11 and Zcchc6 redundantly control let-7 biogenesis in embryonic stem cells. Our study indicates that Lin28 uses two different TUTases to control let-7 expression and has important implications for stem cell biology as well as cancer.     

A systematic protocol for the characterization of Hsp90 modulators

Several Hsp90 modulators have been identified including the N-terminal ligand geldanamycin (GDA), the C-terminal ligand novobiocin (NB), and the co-chaperone disruptor celastrol. Other Hsp90 modulators elicit a mechanism of action that remains unknown. For example, the natural product gedunin and the synthetic anti-spermatogenic agent H2-gamendazole, recently identified Hsp90 modulators, manifest biological activity through undefined mechanisms. Herein, we report a series of biochemical techniques used to classify such modulators into identifiable categories. Such studies provided evidence that gedunin and H2-gamendazole both modulate Hsp90 via a mechanism similar to celastrol, and unlike NB or GDA.     

Several Antifeedants from Neem Oil,Azadirachta indica A. Juss., against Reticulitermes speratus Kolbe (Isoptera: Rhinotermitidae)

A methanol extract of neem oil indicated antifeedant activity at 200 μg/disc by a no-choice bioassay against Reticulitermes speratus Kolbe. The extract was purified by recycling HPLC to isolate 11 compounds of variable termite antifeedant potency. Deacetylgedunin was the most active compound (95% protective concentration or PC₉₅ = 113.7 μg/disc). This was followed by salannin, gedunin, 17-hydroxyazadiradione, nimbandiol, azadiradione, deacetylsalannin, and deacetylnimbin, with PC₉₅ estimates of 203.3, 218.4, 235.6, 245.4, 827.5, 1373.1, and 1581.2 μg/disc, respectively. Epoxyazadiradione, 17-epiazadiradione, and nimbin were not active (PC₉₅ estimates were beyond the bioassay limits). It could be presumed, by comparing their structures and activities, that the furan ring, αβ-unsaturated ketone and hydroxyl group each played an important role in determining the antifeedant activity.     

Taxoid from the needles of the Himalayan yew Taxus wallichiana with cytotoxic and immunomodulatory activities

The needles of Taxus wallichiana gave a taxoid 1-hydroxy- 2-deacetoxy-5-decinnamoyl-taxinine j, whose structure has been established by spectroscopic data and confirmed by X-ray crystallography. The taxoid possesses significant cytotoxic and immunomodulatory activity.