Dharmendra Saikia

Antimicrobial potential of Glycyrrhiza glabra roots.

The present study was aimed to investigate antimicrobial potential of Glycyrrhiza glabra roots. Antimycobacterial activity of Glycyrrhiza glabra was found at 500 microg/mL concentration. Bioactivity guided phytochemical analysis identified glabridin as potentially active against both Mycobacterium tuberculosis H(37)Ra and H(37)Rv strains at 29.16 microg/mL concentration. It exhibited antimicrobial activity against both Gram-positive and Gram-negative bacteria. Our results indicate potential use of licorice as antitubercular agent through systemic experiments and sophisticated anti-TB assay.

Antitubercular potential of plants: a brief account of some important molecules.

Mycobacterium tuberculosis is the most lethal pathogen causing tuberculosis in human. After the discovery of antitubercular drugs pyrazinamide, rifampicin, isoniazid, streptomycin, and ethambutol (PRISE), the disease was controlled for a limited period. However, over the course of their usage, the pathogen acquired resistance and evolved into multi‐drug resistant, single‐drug resistant, and extensive drug resistant forms. A good number of plant secondary metabolites are reported to have antitubercular activity comparable to the existing antitubercular drugs or sometimes even better in potency. A well‐defined strategy is required to exploit these phytomolecules as antitubercular drugs. This review gives concise up‐to‐date information regarding the chemistry and pharmacology of plant‐based leads and some insight into their structure–activity relationship.

Antitubercular potential of some semisynthetic analogues of phytol

Phytol, a diterpene alcohol was modified to several semisynthetic analogues. Some of the modifications were done logically to enhance lipophilicity of the molecule. Analogues 14, 16 and 18 exhibited antitubercular activity (MIC 15.6-50microg/mL) better than phytol (100microg/mL). The most potent analogue 18 was evaluated for in vivo toxicity in Swiss albino mice and was well tolerated by the experimental animals up to 300mg/kg body weight as a single oral acute dose.

A bioactive labdane diterpenoid from Curcuma amada and its semisynthetic analogues as antitubercular agents

A labdane diterpene dialdehyde was first time isolated from the chloroform extract of rhizomes of Curcuma amada. This compound exhibited antitubercular activity (MIC=500 microg/mL) against Mycobacterium tuberculosis H(37)Rv strain in BACTEC-460 assay. Two of its semisynthetic analogues also exhibited antitubercular activity at 250-500 microg/mL. It is the first report on isolation and antimycobacterial activity of this dialdehyde from C. amada.

Antifungal activity of Glycyrrhiza glabra extracts and its active constituent glabridin.

Glabridin, an active constituent of Glycyrrhiza glabra roots, was found to be active against both yeast and filamentous fungi. Glabridin also showed resistance modifying activity against drug resistant mutants of Candida albicans at a minimum inhibitory concentration of 31.25–250 µg/mL. Although the compound was reported earlier to be active against Candida albicans, but this is the first report of its activity against drug resistant mutants. Copyright

Syntheses of lipophilic chalcones and their conformationally restricted analogues as antitubercular agents.

Lipophilic chalcones and their conformationally restricted analogues were synthesized and evaluated for their antitubercular efficacy against Mycobacterium tuberculosis H37Rv strain. Compounds 16, 24, 25a and 25c were found to be active MIC at 60, 30, 3.5 and 7.5 μg-mL(-1). In vitro cytotoxicity of compounds 16, 24, 25a, 25c and 26 in non-cancerous human epithelial kidney cell line (HEK-293) showed that most active compound 25a was approximately 2.85 times selective towards tubercular versus healthy cells whereas compound 24 was found to be 16 times selective.

Enhancement of artemisinin content through four cycles of recurrent selection with relation to heritability, correlation and molecular marker in Artemisia annua L.

Due to the high demand and low yield of the anti-malarial drug artemisinin in natural populations of Artemisia annua (Quinghao), an attempt has been made to enhance the artemisinin content through 4 cycles of recurrent selection (C(0)-C(3)) using selected genotypic and phenotypic traits. Based on their phenotypic and genotypic characteristics, the top 5% plants of each cycle were selected, and their seedlings were planted in poly-cross block to produce seeds for the subsequent generation. A significant increase in the artemisinin content (0.15% in C (0) to 1.16% in C (3), i.e., about 40% genetic gain over the generation) was observed. This enhancement was directly correlated with the plant height and branching intensity in all four cycles. Similarly, the PCV (phenotypic coefficient of variation) and GCV (genotypic coefficient of variation) have been observed to have a higher value for artemisinin content. The DNA marker (MAP 12) with relation to artemisinin was also identified for high yielding genotypes in all four cycles of selection. Over the four cycles of recurrent selection, the plant developed an oval appearance (Variety: CIM-Arogya) and a high artemisinin content (1.16%).

Antimycobacterial Activity of Lichens

Abstract Ethanol extracts of nine lichen species, namely Everniastrum cirrhatum. (Fr.) Hale ex Sipman (Parmeliaceae), Flavoparmelia caperata. (L) Hale (Parmeliaceae), Heterodermia leucomela. (L) Poelt (Physciaceae), Lecanora flavidorufa. Hue (Lecanoraceae), Leptogium pedicellatum. P.M. Jorg (Collemataceae), Lobaria isidiosa. (Bory) Trevisan (Stictaceae), Rimelia reticulata. (Taylor) Hale and Fletcher (Parmeliaceae), Phaeophyscia hispidula. (Ach.) Essl (Physciaceae), and Stereocaulon foliolosum. Nyl. (Stereocaulaceae), were evaluated for antimycobacteral properties against Mycobacterium tuberculosis. H37Rv and H37Ra strains using the radiometric BACTEC method. Among the tested lichens, the virulent strain of M. tuberculosis. H37Rv was found more susceptible to ethanol extract of F. caperata. and H. leucomela. (MIC 250 µg/mL). E. cirrhatum., R. reticulata., and S. foliolosum. were found active at the concentration of 500 µg/mL. L. isidiosa., L. pedicellatum., P. hispidula., and L. flavidorufa. did not exhibit activity at the maximum tested concentration of 1000 µg/mL.

Chemical Composition and Antimicrobial Potential of Aqueous Distillate Volatiles of Indian Peppermint (Mentha piperita) and Spearmint (Mentha spicata)

During the process of distillation, the hydrophilic part of the essential oil dissolves in the aqueous distillate that is generally considered waste and discarded. The decanted (main essential oil) and hydrophilic (recovered essential oil) fractions of peppermint (Mentha piperita cv Kukrail) and spearmint (Mentha spicata cv MSS-5) essential oils were investigated by gas chromatography and gas chromatography–mass spectrometry. The decanted essential oils of spearmint and peppermint were richer in monoterpene and sesquiterpene hydrocarbons compared to the recovered essential oils. In peppermint, oxygenated monoterpenes (82.85–85.59%), especially alcohols, were higher in recovered essential oil (58.22%) than decanted essential oil (41.03%). Similarly, in spearmint, the percentage of oxygenated monoterpenes was higher in recovered essential oil (83.08%) than decanted oil (59.84%). The recovered and decanted essential oils of both Mentha species demonstrated low to moderate antimicrobial activity against five bacterial strains.

Demethoxycurcumin and its Semisynthetic Analogues as Antitubercular Agents

Demethoxycurcumin, isolated from the rhizomes of Curcuma longa, was found to possess antitubercular activity against Mycobacterium tuberculosis H (37)Rv strain at 200 microg/mL. Derivatisation of this active principle yielded a potent agent 6, exhibiting considerable activity with a minimum inhibitory concentration (MIC) value of 7.8 microg/mL. H (37)Rv:Mycobacterium tuberculosis H (37)Rv strain MIC:minimum inhibitory concentration.