Modified ent-Abietane Diterpenoids from the Leaves of Suregada zanzibariensis.

The leaf extract of Suregada zanzibariensis gave two new modified ent-abietane diterpenoids, zanzibariolides A (1) and B (2), and two known triterpenoids, simiarenol (3) and ß-amyrin (4). The structures of the isolated compounds were elucidated based on NMR and MS data analysis. Single-crystal X-ray diffraction was used to establish the absolute configurations of compounds 1 and 2. The crude leaf extract inhibited the infectivity of herpes simplex virus 2 (HSV-2, IC50 11.5 µg/mL) and showed toxicity on African green monkey kidney (GMK AH1) cells at CC50 52 µg/mL. The isolated compounds 1-3 showed no anti-HSV-2 activity and exhibited insignificant toxicity against GMK AH1 cells at ≥100 µM.

A Spectroscopic Study on Secondary Structure and Thermal Unfolding of the Plant Toxin Gelonin Confirms Some Typical Structural Characteristics and Unravels the Sequence of Thermal Unfolding Events.

Gelonin from the Indian plant Gelonium multiflorum belongs to the type I ribosome-inactivating proteins (RIPs). Like other members of RIPs, this toxin glycoprotein inhibits protein synthesis of eukaryotic cells; hence, it is largely used in the construction of immunotoxins composed of cell-targeted antibodies. Lysosomal degradation is one of the main issues in targeted tumor therapies, especially for type I RIP-based toxins, as they lack the translocation domains. The result is an attenuated cytosolic delivery and a decrease of the antitumor efficacy of these plant-derived toxins; therefore, strategies to permit their release from endosomal vesicles or modifications of the toxins to make them resistant to degradation are necessary to improve their efficacy. Using infrared spectroscopy, we thoroughly analyzed both the secondary structure and the thermal unfolding of gelonin. Moreover, by the combination of two-dimensional correlation spectroscopy and phase diagram method, it was possible to deduce the sequence of events during the unfolding, confirming the typical characteristic of the RIP members to denature in two steps, as a sequential loss of tertiary and secondary structure was detected at 58 °C and at 65 °C, respectively. Additionally, some discrepancies in the unfolding process between gelonin and saporin-S6, another type I RIP protein, were detected.

Ent-abietane diterpenoids from Suregada zanzibariensis Baill. (Euphorbiaceae), their cytotoxic and anticancer properties.

The stem bark extract of Suregada zanzibariensis afforded a previously undescribed ent-abietane diterpenoid trivially named mangiolide (1) and a known jolkinolide B (2) via anticancer bioassay-guided fractionation. The CH2Cl2:MeOH extract of S. zanzibariensis was initially analysed for its anticancer properties against three cancer cell lines, renal (TK10), melanoma (UACC62), and breast (MCF7) and was found to be potent at low µg/mL ranges. Compound 1, 6α-acetoxy-14-keto-ent-abieta-7(8),13(15)-diene-16,12-olide (mangiolide) inhibited the growth of renal (TK10) with a GI50 of 0.02 µg/mL; a GI50 of 0.03 µg/mL for melanoma (UACC62) and a GI50 of 0.05 µg/mL for breast (MCF7) cancer cell lines. Compound 2, 8,13-diepoxy-13,15-ent-abietene-16,12-olide (jolkinolide B) inhibited the growth (GI50) of the cell lines at 3.31 µg/mL for renal (TK10), 0.94 µg/mL for melanoma (UACC62) and 2.99 µg/mL for the breast (MCF7). The structures were established on the basis of their spectroscopic analysis and the absolute stereostructures assigned using electronic circular dichroism (ECD).

Bauerenol, a triterpenoid from Indian Suregada angustifolia: Induces reactive oxygen species-mediated P38MAPK activation and apoptosis in human hepatocellular carcinoma (HepG2) cells.

The triterpenoid, bauerenol, from Suregada angustifolia (Baill. ex Muell.-Arg.) Airy Shaw (Euphorbiaceae) was screened for anti-cancer property using hepatocellular carcinoma cell line, HepG2. Bauerenol exhibited growth inhibitory and apoptosis inducing potential against HepG2 cancer cells. 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide cytotoxic assay revealed that bauerenol treatment significantly reduced the growth of HepG2 cells in a time- and dose-dependent manner with 50% growth inhibitory concentration doses of 45 and 25 µg/mL at 24 and 48 h treatments, respectively. Bauerenol-induced cell death reflected apoptotic morphological features, that is, cell membrane blebbing, vacuolization, chromatin condensation, and nuclear fragmentation. In addition, bauerenol treatment diminished the mitochondrial membrane potential, by inducing the efflux of cytochrome c, downregulating the levels of anti-apoptotic Bcl-2 as well as upregulating the levels of pro-apoptotic Bax, and inducing caspase activation and poly (ADP-ribose) polymerase cleavage. Moreover, bauerenol treatment activates p38MAPK and inactivates the anti-apoptotic kinases Akt and ERK1/2 through the induction of reactive oxygen species. Furthermore, bauerenol-mediated S-phase arrest was associated with downregulation of cell cycle-rate-limiting factor (cyclin D1) and upregulation of cyclin-dependent kinase inhibitor p21 and tumor suppressor p53. Interestingly, pre-treatment of cells with reactive oxygen species inhibitor and p38 inhibitor significantly decreases bauerenol-induced cytotoxicity, Bax upregulation, and p38 activation. This study clearly states that bauerenol induces cell cycle arrest and apoptosis through the reactive oxygen species-dependent p38MAPK activation in HepG2 cancer cells.

Pyrrolidine-type iminosugars from leaves of Suregada glomerulata.

Phytochemical investigation of the H2O extract of leaves of Suregada glomerulata led to the isolation of ten pyrrolidine-type iminosugars. The chemical structures of the six new compounds (4-6, 8-10) were elucidated as 2,5-imino-2,4,5-trideoxy-d-manno-heptitol (4-deoxy-homoDMDP) (4), 2,5-imino-2,4,5-trideoxy-d-gulo-heptitol (5), 2,5-imino-2,4,5,6-tetradeoxy-d-gulo-heptitol (6), 6-C-butyl-4-deoxy-DMDP (8), 6-C-(8-hydroxyoctyl)-DMDP (9), and 6-C-(8-hydroxyoctyl)-2,5-dideoxy-2,5-imino-d-galactitol (10), respectively, on the basis of spectroscopic data analysis (NMR and HRESIMS). Compounds 4-6 and 8 were characterized as rarely seen 4-deoxy pyrrolidine-type iminosugars. Pyrrolidine-type iminosugars with a long-side chain have been found in the restrictive plant families Moraceae, Campanulaceae, and Hyacinthaceae. The discovery of compounds 9 and 10 with a C8 side chain from S. glomerulata (Euphorbiaceae) expands the range of distribution for the iminosugars in plants. The 8-hydroxyoctyl side-chain represents a new addition for the molecular diversity of iminosugars. The compounds 1-10 were evaluated for inhibitory activity against rat intestinal α-glucosidase. However, all the test compounds showed no significant inhibitory activities to the glucosidase.

α-Glucosidase-inhibitory iminosugars from the leaves of Suregada glomerulata.

A water extract of the leaves of Suregada glomerulata (Euphorbiaceae) was found to inhibit rat small intestinal α-glucosidase. An examination of the extract afforded 20 iminosugars including one pyrrolidine and 19 piperidines. The structures of the 10 new compounds (11-20) were determined by NMR, and MS spectroscopic data analyses, and chemical correlations. The novelty of the identified compounds mainly stems from the loss of a hydroxy at C-4 and the presence of an 8-hydroxyoctyl side chain. Nine N-alkyl derivatives including N-methyl (1a, 8a, and 13a), N-butyl (1b, 2b, and 9b) and N,N-dimethyl (1c, 2c, and 9c) were synthesized. The compounds were tested for rat small intestinal α-glucosidase inhibitory activity. In total, 15 compounds, including compounds 11, 12, 15, and 19 and the three derivatives 8a, 9b, and 13a, showed inhibitory activity with IC50 values less than 40µM. In vivo results showed that total alkaloids of S. glomerulata (10mg/kg) and four major iminosugars 1, 2, 3, and 9 (10mg/kg) can lower the postprandial blood glucose level after sucrose and starch load in healthy male ICR mice.

Chemically and biologically synthesized CPP-modified gelonin for enhanced anti-tumor activity.

The ineffectiveness of small molecule drugs against cancer has generated significant interest in more potent macromolecular agents. Gelonin, a plant-derived toxin that inhibits protein translation, has attracted much attention in this regard. Due to its inability to internalize into cells, however, gelonin exerts only limited tumoricidal effect. To overcome this cell membrane barrier, we modified gelonin, via both chemical conjugation and genetic recombination methods, with low molecular weight protamine (LMWP), a cell-penetrating peptide (CPP) which was shown to efficiently ferry various cargoes into cells. Results confirmed that gelonin-LMWP chemical conjugate (cG-L) and recombinant gelonin-LMWP chimera (rG-L) possessed N-glycosidase activity equivalent to that of unmodified recombinant gelonin (rGel); however, unlike rGel, both gelonin-LMWPs were able to internalize into cells. Cytotoxicity studies further demonstrated that cG-L and rG-L exhibited significantly improved tumoricidal effects, with IC50 values being 120-fold lower than that of rGel. Moreover, when tested against a CT26 s.c. xenograft tumor mouse model, significant inhibition of tumor growth was observed with rG-L doses as low as 2 µg/tumor, while no detectable therapeutic effects were seen with rGel at 10-fold higher doses. Overall, this study demonstrated the potential of utilizing CPP-modified gelonin as a highly potent anticancer drug to overcome limitations of current chemotherapeutic agents.

Three new water-soluble alkaloids from the leaves of Suregada glomerulata (Blume) Baill.

Three new water-soluble alkaloids (1-3) together with twelve known compounds (4-15) have been isolated from the water extract of leaves of Suregada glomerulata. Their structures were determined by spectroscopic analysis and chemical method. Compounds 1-3 were evaluated for their in vitro inhibitory activity against α-glucosidase and HIV-1 replication. However, no significant activities were found.

Constituents of the essential oil of Suregada zanzibariensis leaves are repellent to the mosquito, Anopheles gambiae s.s.

In traditional African communities, repellent volatiles from certain plants generated by direct burning or by thermal expulsion have played an important role in protecting households against vectors of malaria and other diseases. Previous research on volatile constituents of plants has shown that some are good sources of potent mosquito repellents. In this bioprospecting initiative, the essential oil of leaves of the tree, Suregada zanzibariensis Verdc. (Angiospermae: Euphobiaceae) was tested against the mosquito, Anopheles gambiae s.s. Giles (Diptera: Culicidae) and found to be repellent. Gas chromatography (GC), GC-linked mass spectrometry (GC-MS) and, where possible, GC-co-injections with authentic compounds, led to the identification of about 34 compounds in the essential oil. About 56% of the constituents were terpenoid ketones, mostly methyl ketones. Phenylacetaldehyde (14.4%), artemisia ketone (10.1%), (1S)-(-)-verbenone (12.1%) and geranyl acetone (9.4%) were the main constituents. Apart from phenylacetaldehyde, repellent activities of the other main constituents were higher than that of the essential oil. The blends of the main constituents in proportions found in the essential oil were more repellent to An. gambiae s.s. than was the parent oil (p < 0.05), and the presence of artemisia ketone in the blend caused a significant increase in the repellency of the resulting blend. These results suggested that blends of some terpenoid ketones can serve as effective An. gambiae s.s. mosquito repellents.

ent-Abietane and ent-kaurane diterpenoids from the roots of Suregada glomerulata.

Twelve ENT-abietane and ENT-kaurane type diterpenoids, 1- 12, including five new compounds 1- 5, were isolated from the roots of Suregada glomerulata. The structures of the new compounds were elucidated on the basis of 1D and 2D NMR and other spectroscopic studies, and the structures of 1 and 2 were confirmed by X-ray crystallography. Cytotoxic activities against five human tumor cell lines were evaluated.

Diterpenoids from the roots of Suregada glomerulata.

Six new diterpenoids, 7beta,8alpha-dihydroxy-12-oxo- ent-abietan-16,14-olide ( 1), 3,4,18beta-cyclopropa-7beta,17-dihydroxy- ent-abieta-8(14),13(15)-dien-16,12-olide ( 2), 3alpha,7beta-dihydroxy- ent-abieta-8(14),13(15)-dien-16,12-olide ( 3), 3-oxo-8beta,14beta-epoxy- ent-abieta-11,13(15)-dien-16,12-olide ( 4), 17-hydroxy- ent-pimara-8(14),15-dien-3-one ( 5), and 3alpha,6beta-dihydroxy- ent-kaur-16-ene ( 6), and two known compounds, 7beta-hydroxy- ent-abieta-8(14),13(15)-dien-16,12-olide ( 7) and jolkinolide B, were isolated from roots of Suregada glomerulata. The structures of the new compounds were elucidated on the basis of 1D and 2D NMR and other spectroscopic studies. The structure of compound 1 was confirmed by X-ray crystallography. Cytotoxic activities were evaluated against five human tumor cell lines.

[Studies on chemical constituents of Suregada glomerulata II].

OBJECTIVE: To study the chemical constituents of Suregada glomeruldata. METHOD: Isolation and purification were carried out on silica gel, sephardex LH -20, ODS column chromatography etc. Constituents were identified by physicochemical properties and spectral analysis. RESULT: Nine compounds, Jolkinolide B (1), 8alpha, 14-dihydro-7-oxo-jolkinolide E (2), helioscopinolide B (3), ent-kauran-16beta, 17-diol (4), 7-oxo-beta-sitosterol (5), scopoletin (6), adenosine (7), 1'-sinapoylglucose (8), sucrose (9), were obtained and identified. CONCLUSION: Compounds 2-9 were isolated from S. glomerulata for the first time.

Potential anti-allergic ent-kaurene diterpenes from the bark of Suregada multiflora.

Two ent-kaurene diterpenes, ent-16-kaurene-3beta,15beta,18-triol (1) and ent-3-oxo-16-kaurene-15beta,18-diol (2), were isolated from a dichloromethane extract of the bark of Suregada multiflora along with five known diterpenes:ent-16-kaurene-3beta,15beta-diol (3), abbeokutone (4), helioscopinolide A (5), helioscopinolide C (6) and helioscopinolide I (7). Their structures were elucidated on the basis of spectroscopic analysis. Compounds 1-7 possessed appreciable anti-allergic activities in RBL-2H3 cells model with IC50 values ranging from 22.5 to 42.2 microM.

Antibacterial potential from Indian Suregada angustifolia.

Phytochemical analysis of the leaves from Indian Suregada angustifolia (Baill. ex Muell. Arg.) Airy Shaw (Euphorbiaceae) resulted in the isolation and identification of six known compounds, viz. friedelin, epi-friedelinol, n-octacosanol, alpha-amyrin, beta-sitosterol and beta-sitosterol-3-beta-D-glucopyranoside. Aqueous (room temperature, boiled and autoclaved) and various solvent (methanol, chloroform and hexane) extracts of leaves were tested against 12 human pathogenic bacteria by the agar well-diffusion method. Aqueous extracts did not express any activity. Antibacterial activity was recorded in the order of methanol, hexane and chloroform extracts. Maximum activity recorded against Staphylococcus aureus (skin infections) in methanol and hexane extracts and moderate activity recorded against diarrhoea causing bacteria, Vibrio vulnificus (hexane extract) and Vibrio cholerae (chloroform extract).

Six new diterpenoids from Suregada multiflora.

Six new diterpenoids were isolated from a CH(2)Cl(2)-MeOH extract of the bark of Suregada multiflora. The structures were established on the basis of one- and two-dimensional NMR and other spectroscopic studies and chemical derivatizations. Two compounds, suregadolides C (1) and D (2), were identified as new diterpene lactones of two antipodal series, containing a cyclopropane ring bridging C-3 and C-4 of the basic abietane skeleton. Suremulide A (3) was found to be a new abietene diterpene lactone. Bannaringaolide A (4), a diterpene lactone, based on a novel carbon skeleton with a seven-membered ring, possibly formed by the rearrangement of the exocyclic C-17 in ring C of an ent-pimarane framework, has also been isolated. A kaurane triol, suremulol A (5), and a kaurane diol, suremulol B (6), were also identified as new metabolites.