Khursheed A. Bhat

Chemical composition, antioxidant and antibacterial activities of the leaf essential oil of Juglans regia L. and its constituents

The essential oil from the leaves of Juglans regia L. (Juglandaceae) growing wild in Kashmir (India) was obtained by hydrodistillation and analysed by a combination of capillary GC-FID and GC-MS. A total of 38 compounds, representing 92.7% of the oil, were identified and the major components were found to be α-pinene (15.1%), β-pinene (30.5%), β-caryophyllene (15.5%) germacrene D (14.4%) and limonene (3.6%). The essential oil and the main individual constituents were screened for antibacterial activity and the essential oil evaluated for antioxidant activity. Antibacterial activity was evaluated using the disc diffusion and microdilution methods against a group of clinically significant Gram-positive (Staphylococcus epidermidis MTCC-435, Bacillus subtilis MTCC-441, Staphylococcus aureus) and Gram-negative bacteria (Proteus vulgaris MTCC-321, Pseudomonas aeruginosa MTCC-1688, Salmonella typhi, Shigella dyssenteriae, Klebsiella pneumonia and Escherichia coli). The essential oil and its major components exhibited broad spectrum inhibition against all the bacterial strains with Gram-positive being more susceptible to the oil than Gram-negative bacteria. Antioxidant activity of the oil was evaluated by the scavenging effect on DPPH (2,2-diphenyl-1-picrylhydrazyl) and hydroxyl radicals. In general, the essential oil exhibited high antioxidant activity which was comparable to the reference standards at the same dose (ascorbic acid and butylated hydroxyl toluene, BHT) with IC(50) values of 34.5 and 56.4μg/ml calculated by DPPH and hydroxyl radical scavenging assays respectively.

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.

Isolation, characterisation and antibacterial activity studies of coumarins from Rhododendron lepidotum Wall. ex G. Don, Ericaceae

Six coumarins daphnin (1), daphnetin (2), daphnetin glucoside (3), rhodonetin (4), rhodonin (5) and umbelliferone (6) were isolated from the methanolic extract of Rhododendron lepidotum Wall. ex G. Don, Ericaceae (aerial part). The compounds and their acetyl derivatives were screened for antibacterial activity against Staphylococcus aureus ATCC-29213, methicillin resistant Staphylococcus aureus ATCC-15187, Escherichia coli ATCC-8739, Pseudomonas aeruginosa ATCC-9027 by microdilution method as compared to the reference ciprofloxacin. Compound 2 displayed the best antibacterial activity with MIC 125 μg/mL against S. aureus ATCC-29213 and MRSA ATCC-15187 followed by 4 which exhibited the MIC value of 250 μg/mL against all the four tested strains. All molecules showed better antibacterial activity than their acyl derivatives.

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.

Chemical composition of the essential oils of Nepeta laevigata and Nepeta elliptica from India

The genus Nepeta (Lamiaceae), also called Glechoma and Cataria, is a multiregional genus and consists of about 250 species of perennial herbs distributed in central and southern parts of Europe, Asia, and the Middle East [1–3]. These plants are commonly known as catmint [4], and about 30 species occur in India. Many Nepeta species have been reported to be biologically active and are used in folk medicine because of their spasmodic, diuretic, antiseptic, antitussive, antiasthmatic, and febrifuge activities [5–9]. Several Nepeta species are also reported to reduce serum lipids and to possess anti-inflammatory effects [10, 11]. Most Nepeta species are rich in essential oils, and various biologically active iridoids/monoterpene nepetalactones have been reported in several Nepeta species possessing diverse biological activities, viz., feline attractant, canine attractant, insect repellant, arthropod defense [12, 13], antibacterial, antifungal, and antiviral activities [14]. N. laevigata and N. elliptica are distributed through Afghanistan, China, Nepal, Pakistan, and India. In India, the two plant species are largely confined to Himachal Pradesh, Jammu and Kashmir, and Uttar Pradesh. Nepeta laevigata, also known as Betonica laevigata, is a perennial aromatic herb that grows to a height of 80 cm, is white pubescent, and has petiole 2–12 mm and leaf blade ovate to triangular, while N. elliptica is a small ascending or flexuous herb, 30–60 cm high. Both N. laevigata and N. elliptica are used in traditional medicine. Nepeta laevigata, is reported to be used locally in fevers and for sore throat, while, as an infusion of the seeds, N. elliptica is used in dysentery. According to our finding, there is no report on the chemical compostion of the essential oil of N. laevigata and N. elliptica growing in J & K, India, so the aim of the present work was to compare the chemical composition of these two Nepeta species. The chemical constituents of the volatile oils were analyzed by capillary GC-FID and GC-MS. The components of the oils of the air-dried aerial parts of N. laevigata and N. elliptica are listed in Table 1 with their percentages and relative retention indices (RRI). The different chemical constituents of the essential oils are listed in order of their elution from an RTX-5 column. As shown, 24 components belonging to different class of compounds were identified in the oil of N. laevigata, making up 86.7% of the total oil. -Citronellol (16.5%), germacrene D (19.4%), -caryophyllene (10.8%), -bisabolol oxide B (12.4%), -bourbonene (4.5%), -humulene (3.5%), spathulenol (3.9%), and -bisabolol (5.3%) were the major ones. Other constituents such as 4a,7,7a-nepetalactone (2.0%), allo-aromadendrene (1.1%), and caryophyllene oxide (3.2%) were present in small amounts. In addition, some other constituents such as -pinene, 1,8-cineole, linalool, geraniol, citronellyl acetate, etc. were present in trace amounts. The essential oil composition is dominated by the presence of sesquiterpene hydrocarbons, oxygenated sesquiterpenes, and oxygenated monoterpenes constituting 40.9%, 25.1%, and 20.7%, respectively, of the total oil composition. Of the various nepetalactone isomers, viz., 4a,7,7a-nepetalactone, 4a,7,7a-nepetalactone, and 4a,7,7a-nepetalactone, which have been labeled as the biochemical markers of the Nepeta essential oils and are very useful in chemotaxonomic studies, only one nepetalactone isomer viz., 4a, 7, 7a-nepetalactone, as a minor constituent, was present in the essential oil of Nepeta laevigata. -Caryophyllene, which is one of the major constituents of the essential oil, has been reported in some Nepeta species such as N. depauperata [15], N. flavida [16], and N. nuda [17] as the major component. Likewise, germacrene-D, the other major constituent of the oil sample, has also been reported in various other Nepeta species such as Nepeta macrosiphon [18] and Nepeta sintensii [19]. In addition, the other major components such as -bourbonene and spathulenol have been reported in N.depauperata [15], N. macrosiphon [18], and N. sintensii [19].

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.