Cassane diterpenoid derivative induces apoptosis in IDH1 mutant glioma cells through the inhibition of glutaminase in vitro and in vivo

BackgroundGlioblastoma multiforme (GBM) is the most frequent, lethal and aggressive tumour of the central nervous system in adults. The discovery of novel anti-GBM agents based on the isocitrate dehydrogenase (IDH) mutant phenotypes and classifications have attracted comprehensive attention.PurposeDiterpenoids are a class of naturally occurring 20-carbon isoprenoid compounds, and have previously been shown to possess high cytotoxicity for a variety of human tumours in many scientific reports. In the present study, 31 cassane diterpenoids of four types, namely, butanolide lactone cassane diterpenoids (I) (1-10), tricyclic cassane diterpenoids (II) (11-15), polyoxybutanolide lactone cassane diterpenoids (III) (16-23), and fused furan ring cassane diterpenoids (IV) (24-31), were tested for their anti-glioblastoma activity and mechanism underlying based on IDH1 mutant phenotypes of primary GBM cell cultures and human oligodendroglioma (HOG) cell lines.ResultsWe confirmed that tricyclic-type (II) and compound 13 (Caesalpin A, CSA) showed the best anti-neoplastic potencies in IDH1 mutant glioma cells compared with the other types and compounds. Furthermore, the structure-relationship analysis indicated that the carbonyl group at C-12 and an α, β-unsaturated ketone unit fundamentally contributed to enhancing the anti-glioma activity. Studies investigating the mechanism demonstrated that CSA induced oxidative stress via causing glutathione reduction and NOS activation by negatively regulating glutaminase (GLS), which proved to be highly dependent on IDH mutant type glioblastoma. Finally, GLS overexpression reversed the CSA-induced anti-glioma effects in vitro and in vivo, which indicated that the reduction of GLS contributed to the CSA-induced proliferation inhibition and apoptosis in HOG-IDH1-mu cells.ConclusionTherefore, the present results demonstrated that compared with other diterpenoids, tricyclic-type diterpenoids could be a targeted drug candidate for the treatment of secondary IDH1 mutant type glioblastoma through negatively regulating GLS.     

Cassane-Type Diterpenoids from the Seeds of Caesalpinia bonduc (L.) Roxb.

Ten new cassane-type diterpenoids were isolated from the seeds of Caesalpinia bonduc (L.) Roxb., including 6α-hydroxycaesalpinin P ( 1 ), 14-epi-caesalpinin E1 ( 2 ), 6-deacetylcaesalmin Z ( 3 ), 14-epi-caesalmin Z ( 4 ), caesalpinolides I ( 5 ), K ( 6 ), L ( 7 ), M ( 9 ) and N ( 10 ), and 14-epi-neocaesalpin L ( 8 ). Their planar structures and absolute configurations were fully determined by comprehensive spectroscopic methods, including 2D NMR and electronic circular dichroism spectra. Compounds 1 – 4 are tetracyclic cassane diterpenoids possessing a furan ring, and compounds 5 – 10 are tetracyclic cassane diterpenoids possessing a fused butenolide moiety. The anti-inflammatory and cytotoxic activities of the isolates were evaluated, while none of them showed obvious effects. The current study identified ten new cassane-type diterpenoids from the seeds of C. bonduc (L.) Roxb., which enriched the chemical diversity of the titled herbal medicine.     

Chemical study of the seeds of Erythrophleum ivorense A. Chev. (Fabaceae)

The Chemical study of methanolic extract of the seeds from Erythrophleum ivorense led to the isolation of one original cassane diterpenoid (1) along with six known cassane diterpenoids (2–7). In addition, the known compounds (2–7) are isolated for the first time in E. ivorense. Their structures were established according to their spectral data (NMR, HRESIMS, IR). This result confirms that cassane-type diterpenoids are one of the major constituents of Erythrophleum species. The identification of these compounds and their chemotaxonomic significance is discussed.     

Six new cassane diterpenoids from the seeds of Caesalpinia sappan

Six new cassane diterpenoids (1–6) and 15 known compounds were isolated and identified from the seeds of Caesalpinia sappan. The structures of the new compounds were determined based on the spectroscopic methods, including 1D and 2D NMR techniques. Compound 1 is a rare cassane diterpenoid featuring a nitrogen containing bridge between C-19 and C-20. Compounds 1 and 2 exhibited moderate cytotoxicity against HCT116, AGS, and HepG2 cell lines with IC₅₀ values ranging from 6.36 to 27.86 μM.     

Neo-clerodane diterpenoids from Teucrium pyrenaicum and T. subspinosum

From the aerial parts of teucrium pyrenaicum two new neo-clerodane diterpenoids, teupyrins A and B, have been isolated. The structures of teupyrin A [3β,12S-diacetoxy-4α,18; 15,16-diepoxy-6-keto-neo-cleroda-13(16),14-diene-20R,19-hemiacetal] and teupyrin B [6α-acetoxy-4α,18; 15,16-diepoxy-3β,12ξ,19-trihydroxy-neo-cleroda-13(16),14-diene] were established mainly by spectroscopic means and, in the case of teupyrin A, by X-ray diffraction analysis. The acetone extract of the aerial parts of T. subspinosum yielded four previously known neo-clerodane diterpenoids: teucvin, teuflin, teucrin H2 and 6α-hydroxyteuscordin.     

Diterpenoids from Premna integrifolia

Premna integrifolia is an important constituent of famous herbal formulation “Dashmula” of Indian Ayurvedic system of medicines. The plant is known to possess hypoglycaemic, anti-inflammatory, antiarthritic and broad-spectrum antimicrobial activities due to the presence of several diterpenoids and spermine alkaloids in its decoction. In order to develop chemical markers for quality assurance of this herb in Ayurvedic formulation, we report here the isolation of three novel diterpenoids from the root bark of P. integrifolia namely 1β,3α,8β-trihydroxy-pimara-15-ene (1), 6α,11,12,16-tetrahydroxy-7-oxo-abieta-8,11,13-triene (2) and 2α,19-dihydroxy-pimara-7,15-diene (3). 1,3-Dihydroxy and 2-hydroxy diterpenes belong to a limited number of families and their isolation is also interesting from chemotaxonomic point of view. These diterpenoids were also evaluated for antibacterial activity.     

Diterpenoids from Sideritis foetens

From the aerial parts of Sideritis foetens, the previously known ent-13(16),14-labdadiene-6α,8α,18-triol (andalusol) has been isolated. In addition, two new natural andalusol monoacetates and the novel ent-6α-acetoxy-13(16),14-labdadiene-3β,8α-diol have also been obtained from the same source. The structures of these new diterpenoids have been established by chemical and spectroscopic means.     

Zierane sesquiterpene lactone,cembrane and fusicoccane diterpenoids,from the Tahitian liverwort Chandonanthus hirtellus

Cembrane-type diterpenoids, 13,18,20-epi-iso-chandonanthone (1) and (8E)-4α-acetoxy-12α,13α-epoxycembra-1(15),8-diene (2), two fusicoccane-type diterpenoids, fusicoauritone 6α-methyl ether (3) and 6β,10β-epoxy-5β-hydroxyfusicocc-2-ene (4) and a zierane sesquiterpene γ-lactone, chandolide (5) were isolated from the Tahitian liverwort Chandonanthus hirtellus (Web.) Mitt., together with eight known diterpenoids, chandonanthine (6), fusicogigantone A (7), fusicogigantone B (8), fusicogigantepoxide (9), anadensin (10), fusicoauritone (11), ent-verticillol (12) and ent-epi-verticillol (13). Their structures were established by a combination of extensive NMR spectroscopy and/or X-ray crystallographic analyses. Compounds 1, 5 and 10 showed weak cytotoxic activity against HL-60. Compound 3 also indicated weak cytotoxic activity against KB cell lines.     

New diterpenoids from Caesalpinia species and their cytotoxic activity

Chemical investigation on Caesalpinia crista afforded two new diterpenoids, 6β-cinnamoyloxy-7β-acetoxyvouacapen-5α-ol and 6β,7β-dibenzoyloxyvouacapen-5α-ol and on Caesalpinia pulcherrima another new diterpenoid, 12-demethyl neocaesalpin F along with several known constituents. The structures of the new compounds were settled from their 1D and 2D NMR spectral data. The cytotoxicity of these compounds was measured on two different cancer cell lines.     

Neo-clerodane diterpenoids from Teucrium pyrenaicum

From the aerial part of Teucrium pyrenaicum three new neo-clerodane diterpenoids have been isolated. Their structures, 3β-acetoxy-4α,18:12S,2OS: 15,16:19, 2OS-tetraepoxy-neo-cleroda-13(16),14-dien-6-one (teupyrenone), 3β,6α,19-triacetoxy- 4α,18:15,16-diepoxy-neo-cleroda-13(16),14-dien-20,12S-olide (teupyreinin), and 3β, 6α,19,2OS-tetra-acetoxy-4α,18:12S,2OS: 15,16-triepoxy-neo-cleroda-13(16), 14-diene (teupyreinidin), were established mainly by spectroscopic means.     

Neo-clerodane diterpenoids from Teucrium massiliense

From the aerial part of Teucrium massiliense three new neo-clerodane diterpenoids, deacetylajugarin-II, teumassilin and 6,19-diacetylteumassilin, have been isolated, besides the previously known diterpenes montanin C and teucjaponin A. The structures of deacetylajugarin-II (4α,18-epoxy-6α,19-dihydroxy-neo-clerodan-13-en-15,16-olide), teumassilin (4α,18:15,16-diepoxy-6α,12S,19-trihydroxy-neo-cleroda-13(16),14-diene) and 6,19-diacetylteumassilin (6α,19-diacetoxy-4α,18:15,16-diepoxy-12S-hydroxy-neo-cleroda-13(16),14-diene) were established by chemical and spectroscopic means. In addition, the previously known flavones salvigenin and cirsimaritin have also been obtained from the same source.     

Isoeriocephalin and 20-deacetyleriocephalin,Neoclerodane Diterpenoids from Teucrium lanigerum

From the aerial part of Teucrium lanigerum two new neo-clerodane diterpenoids, 20-deacetyleriocephalin and isoeriocephalin, have been isolated, together with the previously known diterpene eriocephalin. The structures of 20-deacetyleriocephalin [19-acetoxy 4α,18:15,16-diepoxy-7α-hydroxy-6-keto-neo-cleroda-13(16),14-diene-20S,12S-hemiacetal] and isoeriocephalin [19-acetoxy-4α,18:15,16-diepoxy-6α-hydroxy-7-keto-neo-cleroda-13(16),14-diene (20-acetyl)-20S,12S-hemiacetal] were established by chemical and spectroscopic means and by correlation with known compounds.     

Caesalpanins A–C,Three Dimeric Cassane Diterpenoids from the Seeds of Caesalpinia sappan L.

Three dimeric cassane diterpenoids, caesalpanins A–C, were isolated from the seeds of Caesalpinia sappan L., as well as three known compounds. Their structures were determined via analysis of 1D‐, 2D‐NMR, and HR‐ESI‐MS data. Caesalpanins A and B were the second and third compounds that presented a nitrogen‐containing cassane diterpenoid dimer linked through one ether bond between C‐19 and C‐20′. Caesalpanin B exhibited moderate cytotoxic activity against MCF‐7 cell lines with IC₅₀ value of 29.98 μm . Caesalpanins A and B had weak inhibitory effects against LPS‐induced nitric oxide (NO) production in RAW 264.7 macrophages at 50 μm with inhibitory rate of 36.01 % and 32.93 %, respectively.     

Diterpenoids from Salvia greggii

From the aerial part of Salvia greggii a previously known diterpenoid, isopimaric acid, and four new natural substances, 3β- and 14α-hydroxy-isopimaric acids, 14α,18-dihydroxy-7,15-isopimaradiene and 7,8β-dihydro-salviacoccin, have been isolated. The structures of these diterpenoids have been established by chemical and spectroscopic means and, in some cases, by comparison with previously known synthetic compounds.     

Cleonioic acid,a new diterpenoid from Cleonia lusitanica

From the aerial parts of Cleonia lusitanica four previously known diterpenoids have been isolated. In addition, a new isopimarane derivative, cleonioic acid, has been obtained and the structure 11α-acetoxy-7,15-iso-pimaradien-18-oic acid established by chemical and spectroscopic means and by correlation with 7,15-isopimaradien-18-ol.     

Marine sterols. VII. Synthesis of patinosterol,a minor constituent of sterols of the scallop, Patinopecten yessoensis

The structure of patinosterol, a minor sterol from the scallop, Patinopecten yessoensis, was established as 22-trans-27-nor- (24S)-24-methyl-5α-cholest-22-en-3β-ol by synthesis through Wittig reaction.     

Biotransformation of 7α-hydroxy- and 7-oxo-ent-atis-16-ene derivatives by the fungus Gibberella fujikuroi

The microbiological transformation of 7α,19-dihydroxy-ent-atis-16-ene by the fungus Gibberella fujikuroi gave 19-hydroxy-7-oxo-ent-atis-16-ene, 13(R),19-dihydroxy-7-oxo-ent-atis-16-ene, 7α,11β,19-trihydroxy-ent-atis-16-ene and 7α,16β,19-trihydroxy-ent-atis-16-ene, while the incubation of 19-hydroxy-7-oxo-ent-atis-16-ene afforded 13(R),19-dihydroxy-7-oxo-ent-atis-16-ene and 16β,17-dihydroxy-7-oxo-ent-atisan-19-al. The biotransformation of 7-oxo-ent-atis-16-en-19-oic acid gave 6β-hydroxy-7-oxo-ent-atis-16-en-19-oic acid, 6β,16β,17-trihydroxy-7-oxo-19-nor-ent-atis-4(18)-ene and 3β,7α-dihydroxy-6-oxo-ent-atis-16-en-19-oic acid.     

Four new cassane diterpenes from the seeds of Caesalpinia minax

In our survey on the chemical composition of traditional Chinese medicines to further elucidate their chemical substances for the treatment of diseases, we investigated the chemical constituents of the seeds of plants Caesalpinia minax. The investigation led to the isolation and identification of four new cassane diterpenes, caesalpines A–D (1–4). Their structures were elucidated on the basis of extensive 1D and 2D NMR (COSY, HMQC, HMBC, and NOESY) and mass (ESIMS and HR-ESIMS) spectroscopic data analyses. The phytochemical results imply that cassane diterpenes are maybe regarded as the characteristic constituents of C. minax.     

Teuchamaedrin C,a neo-clerodane diterpenoid from Teucrium chamaedrys

A new neo-clerodane diterpenoid, teuchamaedrin C, has been isolated from the aerial parts of Teucrium chamaedrys. Its structure, (12S,18S)-15,16-epoxy-neo-clerodane-13(16)14-dien-19,20-olide-18,6β-hemiacetal, was established by spectroscopic and chemical means. In addition, the previously known diterpenoids 6α-hydroxyteuscordin and dihydroteugin were isolated from the same source.