Shabir H. Lone

Synthesis and biological evaluation of amino analogs of Ludartin: Potent and selective cytotoxic agents

Diverse amino analogs of Ludartin, a cytotoxic guaianolide and a position isomer of an anticancer drug, Arglabin were prepared through Michael type addition at its highly active α-methylene-γ-lactone motif. The semisynthetic derivatives were subjected to sulphorhodamine B cytotoxicity assay against a panel of four different human cancer cell lines viz. lung (A-549), leukemia (THP-1), prostate (PC-3) and colon (HCT-116) to look into structure-activity relationship. Few of the analogs displayed potent selective cytotoxicity compared to the parent molecule-Ludartin (1). (11R)-13-(Diethyl amine)-11,13-dihydroludartin (6) and (11R)-13-(piperidine)-11,13-dihydroludartin (10) showed almost same cytotoxicity against leukemia cell lines (THP-1) as that of parent molecule-Ludartin, but were more active against colon (HCT-116) cancer cells. (11R)-13-(Morpholine)-11,13-dihydroludartin (11) displayed selectively better cytotoxicity against Leukemia cancer cells (THP-1) exhibiting IC50 of 2.8 μM. (11R)-13-(6-Nitroindazole)-11,13-dihydroludartin (17) was four times more potent than Ludartin with selective cytotoxic effects against prostate cancer cells (2.2 μM) while as (11R)-13-(6-nitroindazole)-11,13-dihydroludartin (18) exhibited three-fold selective cytotoxicity for Lung (A-549) cancer cell lines exhibiting IC50 of 2.6 μM.

Click chemistry inspired facile synthesis and bioevaluation of novel triazolyl analogs of Ludartin

A convenient and modular synthesis involving diastereoselective Michael addition followed by regioselective Huisgen 1,3-dipolar cycloaddition reaction was carried out to furnish 1,4-disubstituted-1,2,3-triazoles of Ludartin. This reaction scheme involving Michael addition followed by regioselective Huisgen 1,3-dipolar cycloaddition reaction leading to the formation of triazolyl analogs is being reported for the first time. All the triazolyl products were characterised using spectral data analysis. Sulphorhodamine B cytotoxicity screening of the resulting products against a panel of five human cancerous cell-lines revealed that few of the analogs display promising broad spectrum cytotoxic effect. Among all the synthesized compounds, only 3q displayed the best cytotoxic effect with IC50 values of 12, 11, 38, 39 and 8.5 μM but less than the standard Ludartin (1) with IC50 values of 6.3, 7.4, 7.5, 6.9 and 0.5 μM against human neuroblastoma (T98G), lung (A-549), prostate (PC-3), colon (HCT-116) and breast (MCF-7) cancer cell lines, respectively. The present synthesis was designed based on the previous literature reports of Ludartin as an aromatase inhibitor. Our work provides an initial study on structure-activity relationship of triazolyl analogs of sesquiterpene lactones in general and Ludartin (1) in particular.

Design and Synthesis of Antitumor Heck-Coupled Sclareol Analogues: Modulation of BH3 Family Members by SS-12 in Autophagy and Apoptotic Cell Death.

Sclareol, a promising anticancer labdane diterpene, was isolated from Salvia sclarea. Keeping the basic stereochemistry-rich framework of the molecule intact, a method for the synthesis of novel sclareol analogues was designed using palladium(II)-catalyzed oxidative Heck coupling reaction in order to study their structure-activity relationship. Both sclareol and its derivatives showed an interesting cytotoxicity profile, with 15-(4-fluorophenyl)sclareol (SS-12) as the most potent analogue, having IC50 = 0.082 μM against PC-3 cells. It was found that SS-12 commonly interacts with Bcl-2 and Beclin 1 BH3 domain proteins and enhances autophagic flux by modulating autophagy-related proteins. Moreover, inhibition of autophagy by autophagy inhibitors protected against SS-12-induced apoptosis. Finally, SS-12 effectively suppressed tumor growth in vivo in Ehrlichs ascitic and solid Sarcoma-180 mouse models.

LC-MS guided isolation, quantification and antioxidant evaluation of bioactive principles from Epimedium elatum

This article presents the isolation, quantification and antioxidant evaluation of bioactive principles from Epimedium elatum. LC-MS guided isolation technique was applied for the separation of target constituents. Three isolates; magnoflorine, chrysin and dibenzylideneacetone (DBA) were isolated for the first time from E. elatum using LC-MS guided isolation method. Nine natural products, viz. icariin, epimedoside A, epimedin A, epimedin B, epimedin C, ikarisoside C, baohuoside II, magnoflorine and chrysin were simultaneously quantified by reverse phase HPLC-UV-DAD method. The HPLC method was validated in terms of precision and accuracy. Excellent specificity and linearity within test ranges for all standard calibration curves having regression coefficient of different linear equations in the range of 0.9966-0.9999 were observed. Relative recovery rates varied between 98.09±0.44 and 105.34±1.89% with relative standard deviation of less than 3%. This modified HPLC method is in accordance with yinyanghuo. All the 10 isolated constituents were screened for DPPH radical scavenging activity. Dibenzylideneacetone (DBA) turned out to be the most potent isolate with IC(50) of 4.32 μM.

Arglabin: From isolation to antitumor evaluation.

Arglabin belongs to guaianolide class of sesquiterpene lactones, isolated from Artemisia species. The molecule bears a 5,7,5-tricyclic ring system having five contiguous stereo centers in which the two five membered rings are trans-annulated. Arglabin shows promising antitumor activity against different tumor cell lines. The antitumor activity of arglabin proceeds through its inhibition of farnesyl transferase which leads to the activation of RAS proto-oncogene, a process that is believed to play a pivotal role in 20-30% of all human tumors. It actually inhibits the incorporation of farnesyl pyrophosphate into human H-ras proteins by the enzyme farnesyl transferase (FTase). The present review is an attempt to summarize the chemistry and biology of this molecule since its isolation in 1982. It embodies the isolation, structure elucidation, stereo chemical description, structural classification, chemical synthesis, structural modifications and antitumor evaluation reported till date.

Essential oil composition of Senecio graciliflorus DC: comparative analysis of different parts and evaluation of antioxidant and cytotoxic activities.

The essential oil of different parts of Senecio graciliflorus DC was obtained by hydrodistillation and analysed by GC-FID and GC-MS for the first time. A total of 17, 20, 19 and 17 constituents were identified comprising 99.90, 95.50, 98.93 and 95.96% of the essential oil of flower, leaf, stem and root parts of Senecio graciliflorus respectively. Monoterpene hydrocarbons predominated in the essential oil with 85.28% in flower, 57.53% in leaf, 67.74% in stem and 64.98% in root oil. α-pinene, cis-ocimene, 1,2,3-trimethylcyclohexane and β-pinene were the major constituents of the essential oil. The flower essential oil exhibited a strong antioxidant potential displaying IC50 values of 21.6±0.6 and 26.0±1.0μg/ml in DPPH and hydroxyl radical assays respectively. On the other hand the essential oil of flower and root displayed highest cytotoxicity against lung (A-549) cancer cell lines (IC50=19.1±0.9 and 21.3±1.1μg/ml respectively. This study which represents the first report of the essential oil composition and bioevaluation of Senecio graciliflorus, can serve as a new source of cytotoxic and antioxidant activity.

Isolation, characterization and HPLC quantification of compounds from Aquilegia fragrans Benth: Their in vitro antibacterial activities against bovine mastitis pathogens

ETHNO-PHARMACOLOGICAL RELEVANCE The underground parts of Aquilegia fragrans are traditionally used for the treatment of wounds and various inflammatory diseases like bovine mastitis. However, there are no reports on the phytochemical characterization and antibacterial studies of A. fragrans. AIM OF THE STUDY To isolate compounds from the methanol extract of the underground parts of A. fragrans and determine their antibacterial activity against the pathogens of bovine mastitis. The study was undertaken in order to scientifically validate the traditional use of A. fragrans. MATERIALS AND METHODS Five compounds were isolated from the methanol extract of the underground parts of A. fragrans using silica gel column chromatography. Structural elucidation of the isolated compounds was done using spectral data analysis and comparison with literature. High performance liquid chromatography (HPLC) was used for the qualitative and quantitative determination of isolated compounds in the crude methanol extract. The methanol extract and isolated compounds were evaluated for antibacterial activities against mastitis pathogens using broth micro-dilution technique. RESULTS The five isolated compounds were identified as (1) 2, 4-dihydroxyphenylacetic acid methyl ester (2) β-sitosterol (3) Aquilegiolide (4) Glochidionolactone-A and (5) Magnoflorine. A quick and sensitive HPLC method was developed for the first time for qualitative and quantitative determination of four isolated marker compounds from A. fragrans. The crude methanol extract and compound 5 exhibited weak antibacterial activities that varied between the bacterial species (MIC=500-3000 µg/ml). CONCLUSIONS The above results show that the crude methanol extract and isolated compounds from A. fragrans exhibit weak antibacterial activities. Further phytochemical and pharmacological studies are required for proper scientific validation of the folk use of this plant species in the treatment of various inflammatory diseases like bovine mastitis.

ISOLATION, IDENTIFICATION, AND SIMULTANEOUS QUANTIFICATION OF FIVE MAJOR FLAVONOIDS IN EPIMEDIUM ELATUM BY HIGH PERFORMANCE LIQUID CHROMATOGRAPHY

A simple and reliable HPLC-UV-DAD method was developed for rapid resolution, identification, and quantitation of prenylated flavonoids in Epimedium elatum, a plant endemic to Kashmir Himalayas. Five major prenylated flavonoids namely epimedoside A, epimedin A, epimedin B, epimedin C, and icariin were isolated using repeated column chromatography and simultaneously quantified using HPLC in both underground and aerial parts of E. elatum. All calibration curves showed good linearity (r2 > 0.998) within test ranges and recoveries were 96.8 to 101.2%. The optimized method was successfully applied for the analysis of five major flavonoids in 18 samples of E. elatum collected from three different ecogeographical zones in three different harvesting seasons. The contents of five investigated compounds were greatly variant ranging from 8.73% to 10.96% in aerial parts and 2.52% to 5.06% in underground parts. The concentration of epimedin C was found to be the highest (6.42%) among the five quantified compounds in one of the accessions. The method established in this paper is simple and reliable and could be used for the quality control of E. elatum.

LC-MS Guided Isolation of Bioactive Principles from Iris hookeriana and Bioevaluation of Isolates for Antimicrobial and Antioxidant Activities.

The genus Iris is diverse both in the abundance of secondary metabolities as well as the biological activities. The rhizomes of Iris hookeriana exhibit significant anthelminthic activity against gastrointestinal nematodes of sheep. Although Iris hookeriana has been a subject of the study of so many phytochemical studies, yet we report some constituents for the first time from this plant using a different isolation approach. This manuscript presents the isolation, antimicrobial and antioxidant evaluation of bioactive principles from Iris hookeriana. LC-MS guided isolation technique was applied for the separation of target constituents. The isolates were characterised by spectral techniques and subjected to antioxidant evaluation by DPPH assay. Four compounds; resveratrol, resveratroloside, junipeginin C and isorhamnetin-3-O-neohesperidoside were isolated for the first time along with 3 known compounds viz piceid, irigenin and iridin from I. hookeriana using this approach. The antioxidant activity screening of the isolates revealed that all the 4 constituents isolated for the first time, have strong antioxidant potential with IC50 of 14.0 µg/ml (resveratroloside), 19.7 µg/ml (junipeginen C), 12.8 µg/ml (resveratrol) and 19.8 µg/ml (isorhamnetin-3-O-neohesperodoside). So it can be safely concluded that LC-MS guided isolation of chemical compounds from Iris hookeriana has furnished 4 antioxidant constituents. Thus Iris hookeriana can act as as a good source of wonder molecule resveratrol and its 2 glycosides, resveratrolside and piceid which upon hydrolysis can be converted into the parent drug resveratrol.

Hemisynthesis, computational and molecular docking studies of novel nitrogen containing steroidal aromatase inhibitors: testolactam and testololactam

Testololactone (10) and testolactone (11) represent aromatase inhibitors containing lactone rings. We previously reported their hemisynthesis from the most common phytosterols, which are highly abundant in nature. Herein, we report the synthesis of their nitrogen congeners: testololactam (3) and testolactam (8). The reaction process involves the conversion of 4-androstene-3,17-dione to its corresponding oxime using hydroxylamine hydrochloride, whose Beckmann rearrangement under acid conditions yielded the desired testololactam (3). However, testolactam (8) was formed by the Beckmann rearrangement of the oxime (7) of 1,4-androstene-3,17-dienone (6). This expeditious reaction scheme may be exploited for the bulk production of testololactam (3) and testolactam (8). Theoretical DFT studies concerning the structural and electronic properties of all the end products were carried out using the Becke three-parameter Lee–Yang–Parr function (B3LYP) and 6-31G(d,p) level of theory. Molecular electrostatic potential map and frontier orbital analysis were carried out. The HOMO–LUMO energy gap was calculated, which allowed the calculation of relative reactivity descriptors like chemical hardness, chemical inertness, chemical potential, nucleophilicity and electrophilicity index of the synthesized products. The molecular docking studies of testololactam (3), testolactam (8) and testololactone (10), with aromatase (CYP19) revealed binding free energies of (ΔGb) = −9.85, −9.62 and −10.14 kcal mol−1 respectively, compared to the standard testolactone (11), a well-known aromatase inhibitor sold under the brand name TESLAC, which exhibited a binding free energy (ΔGb) of −10.29 kcal mol−1 with an inhibition constant Ki of 28.87 nM. The docking study revealed that the nitrogen congeners exhibit a relatively lower but appreciable therapeutic efficiency to be used as aromatase inhibitors.