Karuna Shanker

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.

Synthesis of chalcone derivatives on steroidal framework and their anticancer activities

Chalcone derivatives on estradiol framework have been synthesized. Some of the derivatives showed potent anticancer activity against some human cancer cell lines. Compounds 9 and 19 showed potent activity against MCF-7, a hormone dependent breast cancer cell line. Chalcone 7 was further modified to the corresponding indanone derivative (19) using the Nazarov reaction, which showed better activity than the parent compound against the MCF-7 breast cancer cell line. Active anticancer derivatives were also evaluated for osmotic hemolysis using the erythrocyte as a model system. It was observed that chalcone derivatives showing cytotoxicity against cancer cell lines did not affect the fragility of erythrocytes and hence may be considered as non-toxic to normal cells.

Synergistic effect of silymarin and standardized extract of Phyllanthus amarus against CCl4-induced hepatotoxicity in Rattus norvegicus

In search of the effective and standardized hepatoprotective combination therapy, silymarin and standardized extract of Phyllanthus amarus has been evaluated against CCl(4)-induced hepatotoxicity in rats. Eight groups of rats were used. The animals of group A served as normal and were given only vehicle. The animals of group B served as toxin control and were administered with CCl(4) (50% solution of CCl(4) in liquid paraffin, 2 ml/kg b.w., intraperitoneally). The animals of groups C-H received silymarin (100 mg/kg b.w.), Phyllanthus amarus aqueous extract (100 mg/kg b.w.), Phyllanthus amarus ethanolic extract (100 mg/kg b.w.), silymarin (50 mg/kg b.w.)+P. amarus aq. ext. (50 mg/kg b.w.), silymarin (50 mg/kg b.w.)+P. amarus eth. ext. (50 mg/kg b.w.) and marketed formulation (M.F.) 5 ml/kg b.w. for 6 days orally as well as CCl(4) (2 ml/kg b.w.) on 4th day intraperitoneally. The test materials were found effective as hepatoprotective as evidenced by plasma and liver biochemical parameters. The combination of silymarin and Phyllanthus amarus showed synergistic effect for hepatoprotection and silymarin with ethanolic extract of P. amarus showed better activity due to the higher concentration of phyllanthin in ethanolic extract in comparison to aqueous extract of P. amarus as estimated by HPLC.

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

Wound Induced Tanscriptional Regulation of Benzylisoquinoline Pathway and Characterization of Wound Inducible PsWRKY Transcription Factor from Papaver somniferum

Wounding is required to be made in the walls of the green seed pod of Opium poppy prior exudation of latex. To withstand this kind of trauma plants regulate expression of some metabolites through an induced transcript level. 167 unique wound-inducible ESTs were identified by a repetitive round of cDNA subtraction after 5 hours of wounding in Papaver somniferum seedlings. Further repetitive reverse northern analysis of these ESTs revealed 80 transcripts showing more than two fold induction, validated through semi-quantitative RT-PCR & real time expression analysis. One of the major classified categories among identified ESTs belonged to benzylisoquinoline transcripts. Tissue specific metabolite analysis of benzylisoquinoline alkaloids (BIAs) in response to wounding revealed increased accumulation of narcotine and papaverine. Promoter analysis of seven transcripts of BIAs pathway showed the presence of W-box cis-element with the consensus sequence of TGAC, which is the proposed binding site for WRKY type transcription factors. One of the Wound inducible ‘WRKY’ EST isolated from our subtracted library was made full-length and named as ‘PsWRKY’. Bacterially expressed PsWRKY interacted with the W-box element having consensus sequence TTGACT/C present in the promoter region of BIAs biosynthetic pathway genes. PsWRKY further activated the TYDC promoter in yeast and transiently in tobacco BY2 cells. Preferential expression of PsWRKY in straw and capsule and its interaction with consensus W-box element present in BIAs pathway gene transcripts suggest its possible involvement in the wound induced regulation of BIAs pathway.

Methyl jasmonate-elicited transcriptional responses and pentacyclic triterpene biosynthesis in sweet basil

Transcript and metabolite analysis of the methyl jasmonate-elicited sweet basil identified the genes involved in the biosynthesis of the medicinally important pentacyclic triterpenes. Sweet basil (Ocimum basilicum) is well known for its diverse pharmacological properties and has been widely used in traditional medicine for the treatment of various ailments. Although a variety of secondary metabolites with potent biological activities are identified, our understanding of the biosynthetic pathways that produce them has remained largely incomplete. We studied transcriptional changes in sweet basil after methyl jasmonate (MeJA) treatment, which is considered an elicitor of secondary metabolites, and identified 388 candidate MeJA-responsive unique transcripts. Transcript analysis suggests that in addition to controlling its own biosynthesis and stress responses, MeJA up-regulates transcripts of the various secondary metabolic pathways, including terpenoids and phenylpropanoids/flavonoids. Furthermore, combined transcript and metabolite analysis revealed MeJA-induced biosynthesis of the medicinally important ursane-type and oleanane-type pentacyclic triterpenes. Two MeJA-responsive oxidosqualene cyclases (ObAS1 and ObAS2) that encode for 761- and 765-amino acid proteins, respectively, were identified and characterized. Functional expressions of ObAS1 and ObAS2 in Saccharomyces cerevisiae led to the production of β-amyrin and α-amyrin, the direct precursors of oleanane-type and ursane-type pentacyclic triterpenes, respectively. ObAS1 was identified as a β-amyrin synthase, whereas ObAS2 was a mixed amyrin synthase that produced both α-amyrin and β-amyrin but had a product preference for α-amyrin. Moreover, transcript and metabolite analysis shed light on the spatiotemporal regulation of pentacyclic triterpene biosynthesis in sweet basil. Taken together, these results will be helpful in elucidating the secondary metabolic pathways of sweet basil and developing metabolic engineering strategies for enhanced production of pentacyclic triterpenes.

Heteromeric and Homomeric Geranyl Diphosphate Synthases from Catharanthus roseus and Their Role in Monoterpene Indole Alkaloid Biosynthesis

Catharanthus roseus is the sole source of two most important monoterpene indole alkaloid (MIA) anti-cancer agents: vinblastine and vincristine. MIAs possess a terpene and an indole moiety derived from terpenoid and shikimate pathways, respectively. Geranyl diphosphate (GPP), the entry point to the formation of terpene moiety, is a product of the condensation of isopentenyl diphosphate (IPP) and dimethylallyl diphosphate (DMAPP) by GPP synthase (GPPS). Here, we report three genes encoding proteins with sequence similarity to large subunit (CrGPPS.LSU) and small subunit (CrGPPS.SSU) of heteromeric GPPSs, and a homomeric GPPSs. CrGPPS.LSU is a bifunctional enzyme producing both GPP and geranyl geranyl diphosphate (GGPP), CrGPPS.SSU is inactive, whereas CrGPPS is a homomeric enzyme forming GPP. Co-expression of both subunits in Escherichia coli resulted in heteromeric enzyme with enhanced activity producing only GPP. While CrGPPS.LSU and CrGPPS showed higher expression in older and younger leaves, respectively, CrGPPS.SSU showed an increasing trend and decreased gradually. Methyl jasmonate (MeJA) treatment of leaves significantly induced the expression of only CrGPPS.SSU. GFP localization indicated that CrGPPS.SSU is plastidial whereas CrGPPS is mitochondrial. Transient overexpression of AmGPPS.SSU in C. roseus leaves resulted in increased vindoline, immediate monomeric precursor of vinblastine and vincristine. Although C. roseus has both heteromeric and homomeric GPPS enzymes, our results implicate the involvement of only heteromeric GPPS with CrGPPS.SSU regulating the GPP flux for MIA biosynthesis.

Synthesis and anticancer activity of 2-benzylidene indanones through inhibiting tubulin polymerization.

In an attempt to discover a potent and selective anticancer agent, gallic acid has been modified to benzylidene indanones as tubulin polymerization inhibitors. These compounds were evaluated against several human cancer cell lines and also evaluated for inhibition of tubulin polymerase in in vitro assays. Three of the analogues exhibited strong cytotoxicity against human cancer cell lines IC(50)=10-880 nM and also showed tubulin polymerization inhibition (IC(50)=0.62-2.04 μM). Compound 9j, the best candidate of the series was found to be non-toxic in acute oral toxicity in Swiss-albino mice up to 1000 mg/kg dose.