Bromination Reactivity of Oxygen-Terminated Edges of Graphene

The bromination reactivity of various types of polycyclic aromatic hydrocarbons (PAHs) with oxygen atoms and graphene with oxygen atoms was estimated by density functional theory calculation and experimentally clarified by analyzing bromination of PAHs using gas chromatography–mass spectrometry. In the experimental and theoretical bromination reactivity of PAHs, the presence of hydroxyl group increased the reactivity of PAHs because of electron-donating nature of the hydroxyl group but the other oxygen-containing functional groups such as lactone, ether, and ketone decreased the reactivity due to the electron-withdrawing nature of those groups. These effects of functional groups on the reactivity were also confirmed in graphene. The tendency of theoretical bromination reactivity of graphene was graphene with hydroxyl group > graphene with no group > graphene with lactone group > graphene with ether group > graphene with ketone group. Our study on the estimation of bromination reactivity of graphene edges provides the groundwork for the bromination of graphene edges.

Highly Regioselective and Stereoselective Biohydroxylations of Oxandrolone

Microbially catalyzed reactions are a powerful and valuable tool for organic synthesis of many compounds with potential biological activity. Herein, we report efficient hydroxylations of the steroidal anabolic-androgenic lactone, oxandrolone, in the cultures of three strains of fungi, Fusarium culmorum, Mortierella isabellina, and Laetiporus sulphureus. These reactions resulted in the production of four metabolites identified as 12β-hydroxyoxandrolone (2), 9α-hydroxyoxandrolone (3), 6α-hydroxyoxandrolone (4), and 15α-hydroxyoxandrolone (5), the latter being a new compound. The high substrate conversion rates and the product yields achieved indicate that these strains offer a new way to generate steroidal hydroxylactones with potential pharmaceutical interest. The structures of the isolated derivatives were characterized on the basis of spectroscopic data. The effect of modification of the A-ring structure of the steroid by the lactone group on the selectivity of hydroxylation in cultures of the tested fungi is also discussed.

Synthesis and Characterization of Cry2Ab–AVM Bioconjugate: Enhanced Affinity to Binding Proteins and Insecticidal Activity

Bacillus thuringiensis insecticidal proteins (Bt toxins) have been widely used in crops for agricultural pest management and to reduce the use of chemical insecticides. Here, we have engineered Bt toxin Cry2Ab30 and bioconjugated it with 4”-O-succinyl avermectin (AVM) to synthesize Cry2Ab–AVM bioconjugate. It was found that Cry2Ab–AVM showed higher insecticidal activity against Plutella xylostella, up to 154.4 times compared to Cry2Ab30. The binding results showed that Cry2Ab–AVM binds to the cadherin-like binding protein fragments, the 10th and 11th cadherin repeat domains in the P. xylostella cadherin (PxCR10–11), with a much higher affinity (dissociation equilibrium constant KD = 3.44 nM) than Cry2Ab30 (KD = 28.7 nM). Molecular docking suggested that the macrolide lactone group of Cry2Ab–AVM ligand docking into the PxCR10–11 is a potential mechanism to enhance the binding affinity of Cry2Ab–AVM to PxCR10–11. These findings offer scope for the engineering of Bt toxins by bioconjugation for improved pest management.

Adsorpsi Logam Ni dan Cu pada Limbah Cair Laboratorium Kimia menggunakan Biosorben Batang Jagung Termodifikasi Asam Sitrat

<p class="BodyAbstract">Corn stalk contains 40-50% cellulose, 20-40% hemicellulose, 4-15% lignin which had potential as biosorbent in binding metal ions. In this study, demineralization and modification by adding citric acid (1.5 M and 2 M) of corn stalk were conducted to convert hydroxyl groups into carboxylic. Then, it was analyzed its functional groups using Boehm titration and FTIR. The modified corn stalk was applied directly to chemical laboratory liquid waste which contains multicomponent of heavy metal ions. By modifying the corn stalk, the number of hydroxyl and carboxylic groups increased, but the number of lactone group was constant. The success of the modification was characterized by the appearance of ester uptake at 1734 cm^-1 and increased adsorption ability. The variations in the concentration of citric acid in modification corn stalk showed that biosorbent with addition 1.5 M citric acid had higher in the number of acid site than addition 2 M citric acid to absorb Ni and Cu.</p><p> <br /> Keywords: Corn stalk, citric acid, biosorbent, functional group</p><p class="BodyAbstract"><strong> </strong></p><p class="BodyAbstract"><strong> </strong></p><p>Batang jagung mengandung sekitar 40-50% selulosa, 20-40% hemiselulosa, 4-15% lignin yang berpotensi sebagai biosorben pengikat ion logam. Pada penelitian ini dilakukan demineralisasi dan modifikasi dengan penambahan asam sitrat (1,5 M dan 2 M) untuk mengubah gugus hidroksil pada selulosa membentuk karboksilat. Selanjutnya, dianalisis gugus fungsinya menggunakan titrasi Boehm dan FTIR. Hasil modifikasi diaplikasikan langsung pada limbah cair laboratorium kimia yang mengandung banyak jenis ion logam berat. Biosorben batang jagung setelah dimodifikasi mengalami peningkatan jumlah gugus fungsi hidroksil dan karboksilat, tetapi gugus lakton tetap. Keberhasilan modifikasi ditandai dengan munculnya serapan ester pada 1734 cm^-1dan peningkatan kemampuan adsorpsi. Dari hasil variasi konsentrasi asam sitrat diperoleh informasi bahwa biosorben dengan penambahan asam sitrat 1,5 M mempunyai situs asam lebih tinggi dan mempunyai kemampuan adsorpsi terhadap ion logam Ni dan Cu lebih besar dibanding penambahan asam sitrat 2 M.</p><p><span style="text-decoration: line-through;"> </span></p><p>Kata kunci: Batang jagung, asam sitrat, biosorben, gugus fungsi</p>

New Drugs from Old Natural Compounds: Scarcely Investigated Sesquiterpenes as New Possible Therapeutic Agents

Sesquiterpenes are natural products that have been extensively studied for their bioactivities, evidencing their potentiality as useful scaffolds for the development of drugs. Considering the different derivatives, the sesquiterpene lactones have been evaluated, especially on cancer cell and antineoplastic efficacy in in vivo studies. Their bioactivity is strictly related to the presence of the reactive α-methylene-γ-lactone group (αMγL). Nevertheless, several other sesquiterpenes lacking αMγL are known and have been studied for their biological effects and potential usefulness in the development of new drugs. In this review, we focused on several sesquiterpenes that are not presenting the αMγL moiety and may have future potential as scaffold for the development of new drugs, namely the bicyclic compounds belonging to the carotane type (daucanes) that present significant effects as antiproliferative and estrogenic agents. The monocyclic humulane derivatives correlated to zerumbone, and the bicyclic compound beta-caryophyllene and its derivatives that have been considered in the field of cancer and inflammation. It is noteworthy that published studies on sesquiterpenes, reported in this review, focus on pathologies of increasing importance, like estrogen, anti-proliferative, bone loss, immunity deficiency and anti-tumour activities. Some of the natural “old” sesquiterpenes can be considered for their possible role in drug discovery and in counteracting these “new” challenges.

PREDICTED BINDING MODE OF ANDROGRAPHOLIDE AND ITS DERIVATIVES BOUND TO PLASMODIUM FALCIPARUM GERANYLGERANYL PYROPHOSPHATE SYNTHASE

Objective: Andrographolide is a major secondary metabolite in the Indonesian herb sambiloto (Andrographis paniculata). It displays a moderateantiplasmodial activity against the chloroquine-resistant strain of Plasmodium falciparum. This study aimed to investigate andrographolide inhibitionof geranylgeranyl pyrophosphate synthase (GGPPS) by andrographolide molecular docking.Methods: A comparative modeling of P. falciparum GGPPS was conducted using one of the Plasmodium vivax GGPPS crystal structures as a template.The best model from this comparative modeling was then used in a molecular docking to investigate the binding mode of andrographolide in theP. falciparum GGPPS active site.Results: In the P. falciparum GGPPS active site, andrographolide is situated with its double rings pointing toward the hydrophobic pocket, while itslactone group is positioned between first aspartate-rich motif and second aspartate-rich motif of the catalytic pocket.Conclusions: In the active site, andrographolide is situated with its double rings pointing toward the hydrophobic pocket, while its lactone group ispositioned in the catalytic pocket.

Sesquiterpene Lactones fromArtemisiaGenus: Biological Activities and Methods of Analysis

Sesquiterpene lactones are a large group of natural compounds, found primarily in plants ofAsteraceaefamily, with over 5000 structures reported to date. Within this family, genusArtemisiais very well represented, having approximately 500 species characterized by the presence of eudesmanolides and guaianolides, especially highly oxygenated ones, and rarely of germacranolides. Sesquiterpene lactones exhibit a wide range of biological activities, such as antitumor, anti-inflammatory, analgesic, antiulcer, antibacterial, antifungal, antiviral, antiparasitic, and insect deterrent. Many of the biological activities are attributed to theα-methylene-γ-lactone group in their molecule which reacts through a Michael-addition with free sulfhydryl or amino groups in proteins and alkylates them. Due to the fact that most sesquiterpene lactones are thermolabile, less volatile compounds, they present no specific chromophores in the molecule and are sensitive to acidic and basic mediums, and their identification and quantification represent a difficult task for the analyst. Another problematic aspect is represented by the complexity of vegetal samples, which may contain compounds that can interfere with the analysis. Therefore, this paper proposes an overview of the methods used for the identification and quantification of sesquiterpene lactones found inArtemisiagenus, as well as the optimal conditions for their extraction and separation.

Practical Isolation of Bullatacin from Annona muricata Leaves Extract Using an Open Column Chromatography Technique

Annonaceous acetogenins are bioactive compounds present in the leaves of Annona muricata (soursop) with significant anti-cancer activities. In this study, acetogenin-rich ethanol fraction extracted from soursop leaves was further separated and isolated using a simple open column chromatography technique with silica gel as the stationary phase. The separation procedure consists of three steps, each step employing sequential elution with organic solvents having different polarity as the eluent. Eluted fractions rich in acetogenin compounds were identified using the Kedde reagent which formed a distinctive dark green complex with the unsaturated γ-lactone group present in all of the annonaceous acetogenin compounds. HPLC analysis showed that the initial methanol fraction, as well as isolates from the second and the third isolation steps, contain bullatacin, squamocin, squamostatin-A, and squamostatin-D. Bullatacin produced from this study can be used further as a standard compound for quantitative analysis of other acetogenin compounds contained in soursop leaves extract.