The Effect Of Celastrol, A Triterpene With Antitumorigenic Activity, On Conformational And Functional Aspects Of The Human 90kda Heat Shock Protein Hsp90α, A Chaperone Implicated In The Stabilization Of The Tumor Phenotype.

Hsp90 is a molecular chaperone essential for cell viability in eukaryotes that is associated with the maturation of proteins involved in important cell functions and implicated in the stabilization of the tumor phenotype of various cancers, making this chaperone a notably interesting therapeutic target. Celastrol is a plant-derived pentacyclic triterpenoid compound with potent antioxidant, anti-inflammatory and anticancer activities; however, celastrol's action mode is still elusive. In this work, we investigated the effect of celastrol on the conformational and functional aspects of Hsp90α. Interestingly, celastrol appeared to target Hsp90α directly as the compound induced the oligomerization of the chaperone via the C-terminal domain as demonstrated by experiments using a deletion mutant. The nature of the oligomers was investigated by biophysical tools demonstrating that a two-fold excess of celastrol induced the formation of a decameric Hsp90α bound throughout the C-terminal domain. When bound, celastrol destabilized the C-terminal domain. Surprisingly, standard chaperone functional investigations demonstrated that neither the in vitro chaperone activity of protecting against aggregation nor the ability to bind a TPR co-chaperone, which binds to the C-terminus of Hsp90α, were affected by celastrol. Celastrol interferes with specific biological functions of Hsp90α. Our results suggest a model in which celastrol binds directly to the C-terminal domain of Hsp90α causing oligomerization. However, the ability to protect against protein aggregation (supported by our results) and to bind to TPR co-chaperones are not affected by celastrol. Therefore celastrol may act primarily by inducing specific oligomerization that affects some, but not all, of the functions of Hsp90α. To the best of our knowledge, this study is the first work to use multiple probes to investigate the effect that celastrol has on the stability and oligomerization of Hsp90α and on the binding of this chaperone to Tom70. This work provides a novel mechanism by which celastrol binds Hsp90α.

Screening of Filamentous Fungi to Identify Biocatalysts for Lupeol Biotransformation

The goal of the study was to evaluate the ability of filamentous fungi to biotransform the pentacyclic triterpene lupeol. The microbial transformations were carried out in shake flasks in different media. Experiments were also run with control flasks. Samples of each culture were taken every 24 hours, extracted with ethyl acetate, and analyzed by GC-MS. The biotransformation of lupeol by Aspergillus ochraceus and Mucor rouxii afforded two compounds in each culture, which were detected in the cultures developed for more than seven days only in the Koch's K1 medium. The obtained data demonstrated that A. ochraceus is a good biocatalyst to introduce double bonds in the lupeol structure, whereas M. rouxii exhibits ability to biocatalyze oxygen insertions in that pentacyclic triterpene. Mass spectrometry was demonstrated to be an efficient analytical method to select promising biocatalysts for the compound investigated in this study. The biotransformation processes were influenced by the culture medium and incubation period. The obtained results open the perspective of using A. ochraceus and M. rouxii in pentacyclic triterpene biotransformations.

Trypanocidal Activity of Limonoids and Triterpenes from Cedrela fissilis

Chagas` disease is an illness that affects millions of people in Central and South America, The search for both a prophylactic drug to be added to human blood as well as a safe and reliable therapeutic drug are greatly needed to control such disease. Herein, we report the trypanocidal activity of 15 crude extracts and 14 Compounds (limonoids and triterpenes) as well as the isolation of 25 known compounds (6 limonoids, 12 triterpenes, 1 sesquiterpene, 5 steroids, and 1 flavonoid) from Cedrela fissilis. The present study shows that this plant is a Promising Source of active compounds for the control of Chagas` disease. The inhibitory activity found for odoratol indicates that it is potentially useful as an alternative for the chemoprophylactic gentian violet.

Triterpenes and antitubercular activity of Byrsonima crassa

We evaluated the potential antitubercular activity of triterpenes obtained from leaves and bark of Byrsonima crassa. From chloroform extracts of the leaves, by bioassay-guided fractionation, we obtained mixtures of known triterpenes: α-amyrin, β-amyrin and their acetates, lupeol, oleanolic acid, ursolic acid and α-amyrinone. Tested against Mycobacterium tuberculosis, the triterpenes exhibited minimum inhibitory concentrations (MICs) of 31.25 - 312.25 µg/mL. β-amyrin and friedelin, isolated from the chloroform extract of bark, showed MICs of 312.25 and 125 µg/mL respectively. This is the first report of the identification and determination of the activity of B. crassa triterpenes against M. tuberculosis.

Antifungal iridoids, triterpenes and phenol compounds from Alibertia myrciifolia Sprunge Ex. Schum

The new iridoid glucoside 10-O-vanilloyl-geniposidic acid has been isolated from the aerial parts of Alibertia myrciifolia along with hydroxyhopanone, 3α,22-dihydroxyhopane, ursolic acid, luteolin-3´,4´-dimethyl ether, caffeic acid and geniposidic acid. The structures of the isolated compounds were determined by means of mass spectrometry and nuclear magnetic resonance spectral analyses. The antifungal activities of the iridoids 10-O-vanilloyl-geniposidic acid and geniposidic acid were evaluated against the phytopathogenic fungi strains Colletotrichum gloeosporioides, Fusarium solani and Aspergillus niger.

Triterpenes and new saponins from Ilex chamaedryfolia: chemotaxonomic tool to ilex species differentiation

Three saponins were isolated from leaves of Ilex chamaedryfolia. Their structures were established by spectroscopic and mass spectrometry data as the new saponin 3β-O-β-D-glucopyranosyl-(1-3)-α-L-arabinopyranosyl-20( S)-19α-hydroxyurs-12-en-28-oic acid 28-O-β-D-glucopyranosyl-(1-3)-β-D-glucopyranosyl ester, the new saponin 3β-O-β-D-glucopyranosyl-(1-3)-α-L-arabinopyranosyl-20( S)-19α-hydroxyurs-12-en-28-oic acid 28-O-β-D-glucopyranosyl ester and the known saponin 3β-O-β-D-glucuronopyranosyl-20(R )-19α-hydroxyurs-12-en-28-oic acid 28-O-β-D-glucopyranosyl ester. Ursolic acid and α-amyrin were also isolated.

Quinoline alkaloids and friedelane-type triterpenes isolated from leaves and wood of Esenbeckia alata kunt (Rutaceae)

This work describes the phytochemical exploration of the ethanol extract from leaves and wood of Esenbeckia alata, leading to the isolation and identification of quinoline alkaloids 4-methoxy-3-(3'-methyl-but-2'-enyl)-N-methyl-quinolin-2(1 H)-one, N-methylflindersine, dictamine, kokusaginine, Γ-fagarine, flindersiamine, as well as the fridelane-type triterpenes, frideline, fridelanol and its acetate derivative. Identification of these compounds was based on full analyses of spectroscopic data (¹H, 13C, 1D, 2D, IR, MS) and comparison with data reported in literature. Compound 4-methoxy-3-(3'-methyl-but-2'-enyl)-N-methyl-quinolin-2(1 H)-one is reported for the first time for the genus Esenbeckia.

Bioactive triterpenes and phenolics of leaves of Eugenia brasiliensis

A chemical investigation of Eugenia brasiliensis Lam. (Myrtaceae) leaves led to the isolation of α-amyrin and β-amyrin (in a mixture), betulin, 29-hydroxy-oleanolic acid, quercetin, catechin and gallocatechin. Herein, the identification of 29-hydroxy-oleanolic acid is reported for the first time in the Myrtaceae family. Moreover, in this study, the extract, fractions and six of the seven compounds were monitored for toxicity toward Artemia salina, antibacterial and acetylcholinesterase inhibitory activity. The crude ethanol extract of the leaves and fractions were found be active on A. salina toxicity bioassay.

Triterpenes from Minquartia guianensis (Olacaceae) and in vitro antimalarial activity

Minquartia guianensis, popularly known as acariquara, was phytochemically investigated. The following triterpenes were isolated from the dichloromethane extract of leaves: lupen-3-one (1), taraxer-3-one (2) and oleanolic acid (3). The dichloromethane extract of branches yielded the triterpene 3β-methoxy-lup-20(29)-ene (4). The chemical structures were characterized by NMR data. Plant extracts, substance 3, squalene (5) and taraxerol (6), (5 and 6 previously isolated), were evaluated by in vitro assay against chloroquine resistant Plasmodium falciparum. The dichloromethane extract of leaves and the three triterpenes assayed have shown partial activity. Thus, these results demonstrated that new potential antimalarial natural products can be found even in partially active extracts.

Preparative droplet counter-current chromatography for the separation of the new nor-seco-triterpene and pentacyclic triterpenoids from Qualea parviflora

The methanolic extract of the bark of the medicinal plant Qualea parviflora (Vochysiaceae) contains new nor-seco-triterpene and pentacyclic triterpenoids. They were separated in a preparative scale using droplet counter-current chromatography. The optimum solvent used was composed of a mixture of CHCl3/MeOH/H2O (43:37:20, v/v) in the descending mode and led to a successful separation of the new compound 28-nor-17, 22-seco-2 alpha, 3 beta, 19, 22, 23-pentahydroxy-Delta(12)-olecinane, besides the known triterpenoids bellericagenin B, bellericaside B and arjunglucoside I. Identification was performed by ESI-MS, H-1 NMR and C-13 NMR analyses.

Evaluation of Antioxidant Capacity and Synergistic Associations of Quinonemethide Triterpenes and Phenolic Substances from Maytenus ilicifolia (Celastraceae)

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Triterpenes and antitubercular activity of Byrsonima crassa

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Identification of triterpenes and sterols from pterogyne nitens (fabaceae-caesalpinioideae) using high-resolution gas chromatography

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Antioxidant phenolic and quinonemethide triterpenes from Cheiloclinium cognatum

The triterpenes, 22beta-hydroxypristimerin and cognatine, were isolated together with the known compounds pristimerin, maytenin, 20alpha-hydroxymaytenin, 22beta-hydroxymaytenin, netzahualcoyol, netzahualcoyondiol and netzahualcoyone from root bark of Chei-Ioclinium cognatum. The structures of the isolated compounds were elucidated by interpretation of their spectral data, including gHMQC and gHMBC experiments. The isolates were investigated for their radical scavenging abilities through a spectrophotometric assay involving reduction of 2,2-diphenyl-picryl hydrazyl (DPPH). (C) 2004 Elsevier Ltd. All rights reserved.

Antioxidant quinonemethide triterpenes from Salacia campestris

A new quinonemethide triterpene named as salacin, has been isolated from the root bark of Salacia campestris in addition to the known pristimerin, maytenin, 20 alpha-hydroxymaytenin, and netzahualcoyene. Salacin was identified on the basis of NMR-spectral and mass spectrometric analysis. The free-radical scavenging activities of the quinonemethide triterpenes salacin (1), pristimerin (2), maytenin (3), 20a-hydroxymaytenin (4), and netzahualcoyene (5) towards DPPH have been evaluated and showed absorbance variation (AA) of 19, 20, 39, 28, 55, and 10%, respectively, having rutin (74% at 50 pm) and BHT (7% at 50 mu M) as standard compounds.