Mohammad Rashedul Haque

Chemical and biological studies of Kalanchoe pinnata (Lam.) growing in Bangladesh

Abstract Objective To isolate compounds from K. pinnata and elucidate their structures and to explore preliminary antioxidant, antimicrobial, cytotoxic and thombolytic activities of extractives of the plant. Methods The methanol extract of whole plant of K. pinnata has been subjected to different chromatographic separation and purification processes to isolate the secondary metabolites. The structures of the isolated compounds have been elucidated by extensive NMR studies. The free radical scavenging activity of the crude extract and its different Kupchan fractions were determined on stable radical DPPH. In vitro antimicrobial activity was determined by the disk diffusion method. Cytotoxicity screening has been performed against Artemia salina . Total phenolics content, membrane stabilizing activity and thombolytic activities were assessed by following established protocol. Results The isolated compounds were identified as glut-5(6)-en-3-one, taraxerone, 3β-friedelanol, β-amyrin-3-acetate, 3,5,7,3′,5′-pentahydroxyflavone and β-sitosterol. The chloroform soluble fraction showed potent antioxidant activity of (IC 50 = 80.0 μg/mL) and significant cytotoxicity, while the crude extract demonstrated noticeable total polyphenol content (149.24 mg of GAE/gm of extractive), moderate membrane stabilizing activity and inhibition of clot lysis of blood. Conclusions The obtained results rationalize the folkloric use of the plant and can be further investigated to isolate the active compounds responsible for the biological activities.

A novel small-molecule inhibitor of IL-6 signalling

A small library of pyrrolidinesulphonylaryl molecules has been synthesized via an efficient 4-step route, and members evaluated for their ability to inhibit IL-6 signalling. One molecule (6a) was found to have promising activity against IL-6/STAT3 signalling at the low micromolar level, and to selectively inhibit phosphorylation of STAT3 (but not STAT1) in IL-6 stimulated MDA-MB-231 breast cancer and HeLa cell lines. It was also selectively cytostatic in MDA-MB-231 (STAT3-dependent) versus A4 (STAT3-null) cells suggesting STAT3-specific inhibitory properties.

Crispene A, B, C and D, Four New Clerodane Type Furanoid Diterpenes from Tinospora crispa (L.).

Background: Tinospora crispa (L.) is used to alleviate the symptoms of diabetes mellitus in folk medicine. It is also used for hypertension and to treat malaria, remedy for diarrhea, and as vermifuge. Materials and Methods: Stems of T. crispa were collected, sun dried for several days followed by oven dried for 24 h at a considerably low temperature and then ground into coarse powder. The powdered stems were soaked in methanol at room temperature for 14 days with occasional shaking. The extract was collected by filtration, and the solvent was evaporated under reduced pressure in a rotary evaporator to obtain a solid residue which was then subjected to fractionation using the modified Kupchan partitioning method into n-hexane, CCl4, CHCl3and aqueous soluble fractions. The n-hexane soluble fraction was chromatographed over sephadex (LH-20) and the column was eluted with n-hexane: CH2Cl2:MeOH (2:5:1) followed by CH2Cl2:MeOH (9:1) and MeOH (100%) in order to increase the polarities. The column fractions were then concentrated and subjected to thin layer chromatography screening and the fractions with a satisfactory resolution of compounds were rechromatographed over silica gel to isolate the pure compounds. Results: Four new furanoid diterpenes of clerodane types, Crispene A, B, C, and D (1–4), including one known furanoid diterpene glucoside, borapetoside E (5), were isolated from the stems of T. crispa. The structures of these compounds were elucidated by means of extensive spectroscopic analysis and by comparison of their spectral data with closely related compounds. Conclusion: We have reported four new furanoid diterpenes of clerodane types, including one known furanoid diterpene glucoside. This is the first report of any clerodane diterpene having olefinic bond between C-6 and C-7.

Chemical Investigation of Mesua nagassarium (Burm. f.) Kosterm

Repeated chromatographic separation and purification of pet-ether and carbon tetrachloride soluble fractions of a methanol extract of stem bark of Mesua nagassarium (Burm. f.) Kosterm yielded five compounds. Extensive spectroscopic studies, including high field NMR analyses was conducted to identify these compounds which resulted to be friedelin ( 1 ), 3β-friedelanol ( 2 ), lupeol ( 3 ), 3-oxo-betulin ( 4 ) and spinasterol ( 5 ). Although compounds 1 - 3 have been reported from various plant species, but 3-oxo-betulin and spinasterol have been discovered from M. nagassarium (Burm. f.) Kosterm for the first time.

Isolation of flavonoids from the bark of Entada rheedii Spreng

The methanol extract of the bark of Entada rheedii has been fractionated to afford petroleum ether, dichloromethane, ethyl acetate and aqueous soluble fraction through modified Kupchan partitioning protocol and those fractions has been subjected to repeated-chromatographic separation by Sephadex size exclusion chromatography and purification processes to isolate the secondary metabolites. A total of seven compounds have been isolated from the bark of E. rheedii, which were identified as epicatechin (1), liquiritigenin (2), glabridin (3), 4′-O-methylglabridin (4), isoliquiritigenin (5), hispaglabridin A (6) and shinflavanone (7). This is the first report of isolation of these compounds from E. rheedii.

Abstract 5454: Novel STAT3:STAT3 small-molecule inhibitors as potential anticancer agents

Transcription factors are important targets for cancer therapy. The inhibition of protein-protein interactions (PPIs) within signalling pathways known to be key regulators of transcriptional activity is a viable approach to novel chemotherapeutic strategies. Proof-of-concept studies in cell-culture and animal models have validated the potential of small-molecule inhibitors of STAT3 signalling in cancer therapy. In particular, the protein-protein interaction between two STAT3 monomers (i.e., the dimerisation event in the signalling cascade) has been identified as a valid target to inhibit DNA-binding and the resultant transcriptional activation. Of the approximately 20 small-molecule STAT3 inhibitors reported in the literature to date, only three are described as potential STAT3:STAT3 dimerisation inhibitors, and these have IC 50 values in STAT3-expressing cell lines of between 10-90 μM. Using in silico and medicinal chemistry-based approaches based on a published X-Ray structure of STAT3 (PDB: ID-1BG1) to identify “hit” inhibitors, a focussed library (approx. 50 members) was designed around one such “hit” and synthesized employing an efficient 4-step linear approach. Library members were then entered into a screening cascade involving initial evaluation of their ability to inhibit STAT3:STAT3 interaction in a Fluorescent Polarisation (FP)-based primary PPI binding assay. “Hit” molecules from this primary assay were then studied in two cell-based assays designed to test for STAT3 selectivity. The first was a comparative MTS assay between STAT3-expressing MDA MB231 breast cancer cells and STAT3-null colon A4 cells. The second was a luciferase reporter assay designed to measure transcription inhibition in STAT3-Luc-transformed Hela cells compared to SV40-Luc-transformed Hela control cells. A potential “lead” molecule, RH06, emerged from this screening cascade with potentially selective STAT3 inhibitory activity in the low micromolar (i.e., ∼1 µM) region. RH06 is currently being studied for its effect on STAT3 and pSTAT3 signal activation, and its potentially differential effect on upstream and downstream mediators (i.e., JAK2, Bcl-xl, Cyclin D1 and pSTAT1). Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 5454.