Mohammad Akbar Khuroo

New natural compounds from Rhododendron lepidotum

Phytochemical investigation of the aerial parts of Rhododendron lepidotum yielded 8-[2′,6′-dimethoxy-4′-(1″,2″,3″-trihydroxy-propyl)-phenyl]-7-hydroxy benzopyranone (1), 3-O-β-d-glycopyranosyl betulinic amide (2) and 8-hydroxy-7,7′-oxydicoumarin (4) and five known compounds. Among the known molecules, betulinic amide (3) was earlier reported as a semi-synthetic product. The structures of new molecules 1, 2 and 4 were elucidated on the basis of extensive spectroscopic investigations (1D NMR, 2D NMR and mass spectrometry).

Triterpenoids from Arctium lappa

Phytochemical investigation of the leaves of Arctium lappa led to the isolation of two triterpenoids, characterised by NMR, IR and MS as 3α-hydroxylanosta-5,15-diene and 3α-acetoxy-hop-22(29)-ene. 3α-hydroxylanosta-5,15-diene is a new triterpenoid and is isolated for the first time from this genus.

Computational survey of ligand properties on iron(III)–iron(II) redox potential: exploring natural attenuation of nitroaromatic compounds

This study is a computational investigation of the ligand effect on the redox potential of iron redox couple aimed at screening these systems for novel applications. The influence of common and naturally available organic compounds with diverse ligand characteristics (nature of donor site, chelation, pre-organization, degree of back acceptance) on the redox potential of iron(III)–iron(II) redox couple has been theoretically calculated using an appropriate level of density functional theory (DFT). The DFT calculated redox potentials of iron complexes are explored to supplement, corroborate, and predict the experimental behavior of the studied systems towards environmental reduction of nitroaromatic compounds to corresponding anilines. The comparative avidity of iron complexes with cysteine derivatives for the reduction of nitroaromatic compounds has been theoretically explored and based on structure–activity relationship; new iron complexes with a range of reactivity and enhanced ability towards nitroaromatic reduction have been predicted.Graphical abstract

9,10-seco-9,19-cyclolanostane triterpene from Salix caprea L. (Goat Willow)

Chemical investigation of low polar solvent extract of Salix caprea through chromatographic techniques led to the isolation of new triterpene as 1α,3β,25-trihydroxy-9(11)-ene-16-one-9,10-seco-9,19-cyclolanostane (1) along with fatty alcohols. The structure of compound 1 was established by IR, HRESI/MS and NMR including 1D and 2D experiments. The compound 1 showed moderate in vitro antiplasmodial activity.

Phytochemical Screening and HPLC Analysis of Artemisia amygdalina

This chapter deals with the qualitative analysis of wild and tissue culture raised regenerants of Artemisia amygdalina, for the amount of bioactive principles particularly the antimalarial compound, artemisinin. Phytochemical screening of extracts revealed the presence of terpenes, alkaloids, phenolics, tannins (polyphenolics), cardiac glycosides, and steroids in wild (aerial, inflorescence) and tissue culture regenerants (in vitro grown plant, callus,and greenhouse acclimatized plants). Further, HPLC of A. amygdalina extracts has revealed the presence of artemisinin in petroleum ether extracts of wild aerial part, tissue culture raised plant, and greenhouse acclimatized plants. Acetonitrile and water in 70:30 ratios at a flow rate of 1 ml/min have been optimized as mobile phase. It has been observed that wild inflorescences and callus do not produce artemisinin.

Biological Profile of Artemisia amygdalina

This chapter deals with the biochemical pharmacology depicted by the plant Artemisia amygdalina. The important biological activities that have been reported till date include those of free radical scavenging potential of the in vitro raised and greenhouse acclimatized plants, anti-inflammatory, and immunomodulatory activity of the plant and the anti-diabetic and anti-hyperlipidemic effect of A. amygdalina. The methanolic extract of the in vitro grown and greenhouse acclimatized plants revealed the highest inhibitory activity, 92.11 and 91.2 % (IC50 = 26.06 µg mL−1), respectively, against DPPH radical. Carrageenan paw edema model has been employed to study the potential of the plant extracts in inflammation in wistar rats. SRBC-specific haemagglutination-titer and DTH assays have been carried out in Balb/C mice for observing the effect of extracts on immune system. The methanolic fraction has been observed to have the maximum effect on the inhibition of paw edema formation with the inhibitory potential of 42.26 %, while in the immunomodulation studies the plant extracts have been found to have the immunosuppressant activity with methanolic fraction again showing the maximum potential for the suppression of both humoral (55.89 and 47.91 %) and cell-mediated immunity (62.27 and 57.21 %). Petroleum ether, ethyl acetate, methanol, and hydroethanolic extracts of A. amygdalina have been tested for their anti-diabetic potentials in diabetic rats. The hydroethanolic and methanolic extracts each at doses of 250 and 500 mg/kg b.w. have significantly reduced glucose levels in diabetic rats. The other biochemical parameters like cholesterol, triglycerides, low density lipoproteins (LDL), serum creatinine, serum glutamate pyruvate transaminase (SGPT), serum glutamate oxaloacetate transaminase (SGOT), and alkaline phosphatise (ALP), have been found to be reduced by the hydroethanolic and methanolic extracts. The extracts have also shown reduction in the feed and water consumption of diabetic rats when compared with the diabetic control.

Phytochemical Analysis and Chemobiological Standardization of Artemisia amygdalina

This chapter deals with the bioactivity guided isolation of Artemisia amygdalina Decne. The hexane extracts of both shoot and root parts of Artemisia amygdalina Decne have displayed potent cytotoxic effects. Phytochemical analysis of these active extracts has led to the isolation of six cytotoxic constituents, viz., 7,22-ergostadien-3β-ol (1), ludartin (2), 5-hydroxy-6,7,3′,4′-tetramethoxyflavone (3) (from shoots) and trans-matricaria ester (4), diacetylenic spiroenol ether (5) and cis-matricaria ester (6) (from root) from this plant. The constituents have been identified using spectral and analytical techniques in the light of literature. Sulphorhodamine B cytotoxicity screening of the isolated constituents has been carried out against four human cancer cell lines including lung (A-549), leukemia (THP-1), prostate (PC-3), and colon (HCT-116) cell lines. Ludartin (2) exhibited the highest cytotoxicity with IC50 values of 7.4, 3.1, 7.5 and 6.9 µM against lung (A-549), leukemia (THP-1), prostate (PC-3), and colon (HCT-116) cancer cell lines, respectively. To test against in vitro skin cancer models [human dermal fibroblasts (CRL-1635)], all the isolates have been further subjected to 3-(4,5-dimethylthiazol-yl)-diphenyl tetrazolium bromide (MTT) cytotoxicity screening. Ludartin being highly cytotoxic has been evaluated against mouse melanoma (B16F10) and human epidermoid carcinoma (A-431) cells by MTT assay displaying IC50 values of 6.6 µM and 19.0 µM respectively. Finally a simple and reliable HPLC method has been developed (RP-HPLC-DAD) and validated for the simultaneous quantification of these cytotoxic constituents in A. amygdalina Decne. Excellent specificity and high linearity for all the standard calibration curves, having regression coefficients of the respective linear equations in the range of 0.9962 − 0.9999, has been observed. Relative recovery rates varied between 98.37 ± 0.90 and 105.15 ± 1.74 with relative standard deviation less than 4 %. Based on these results, the developed method features good quantification parameters, accuracy, and precision and can serve as effective quality control method for standardization of A. amygdalina Decne.

Volatile Composition of Artemisia amygdalina

This chapter deals with the analysis of mono and sesquiterpenoid composition in the leaves and stem of Artemisia amygdalina Decne obtained by hydrodistillation using a combination of capillary GC-FID and GC-MS analytical techniques. A total of 25 components in the leaf and 32 components in the stem essential oils have been reported. The leaf essential oil majorly consists of monoterpene hydrocarbons (38.2 %) and oxygenated monoterpenes (43.8 %) together constituting 82.0 % of the total oil composition. The principal components that have been identified include sabinene (10.2 %), p-cymene (14.7 %), 1,8-cineole (17.5 %), and borneol (19.8 %). The stem essential oil comprises monoterpene hydrocarbons (66.1 %), oxygenated monoterpenes (12.8 %) and sesquiterpene hydrocarbons (11.2 %). The major constituents were α-pinene (6.0 %), camphene (10.4 %), β-pinene (40.2 %), and borneol (5.7 %). A comparative analysis of the essential oil obtained from the leaves of micropropagated plants of A. amygdalina with that of the leaves of field grown parent plants has also been reported. The oil yield from the micropropagated plants has been found to be (0.05 % v/w) than the oil yield obtained from field-grown plants (0.2 % v/w). The major constituents of the field-grown plants include p-cymene (21.0 %), 1,8-cineole (24.9 %), α-terpineol (5.9 %), β-caryophyllene (4.7 %), germacrene-D (4.0 %), while as the major constituents of the micropropagated plants reported include p-cymene (11.3 %), 1,8-cineole (10.2 %), borneol (7.9 %), α-longipinene (5.5 %), α-copaene (5.5 %) and β-caryophyllene (17 %). The essential oil from field-grown plant is further dominated by the presence of oxygenated monoterpenes (41.5 %), monoterpene hydrocarbons (35.9 %) and sesquiterpene hydrocarbons (16.3 %) while as the essential oil of micropropagated plants is known to be characterized by sesquiterpene hydrocarbons (40.0 %), oxygenated monoterpenes (25.2 %) and monoterpene hydrocarbons (21.6 %).

Kinetic investigations into the synthesis of disulphides via tetrathiomolybdate as a sulphur-transfer reagent

Kinetic and mechanistic aspects of the conversion of halides to disulphides using benzyl triethyl ammonium tetrathiomolybdate as sulphur-transfer reagent were investigated. The reaction follows a 1:1 stoichiometry with overall second-order kinetics and involves the formation of monosulphides in addition to disulphides. In the light of our observations, we propose a nucleophilic substitution: carbon–metal–carbon (SN-CMC) reaction mechanism. The proposed mechanism, besides accounting for all of our experimental observations, also explains many aspects of such reactions that have been reported earlier by various groups.