Nisha Mathew

Bio: Nisha Mathew is an academic researcher from Indian Council of Medical Research. The author has contributed to research in topics: Aedes aegypti & Culex quinquefasciatus. The author has an hindex of 13, co-authored 25 publications receiving 528 citations.

Larvicidal activity of Saraca indica, Nyctanthes arbor-tristis, and Clitoria ternatea extracts against three mosquito vector species

Abstract: Screening of natural products for mosquito larvicidal activity against three major mosquito vectors Aedes aegypti, Culex quinquefasciatus, and Anopheles stephensi resulted in the identification of three potential plant extracts viz., Saraca indica/asoca, Nyctanthes arbor-tristis, and Clitoria ternatea for mosquito larval control. In the case of S. indica/asoca, the petroleum ether extract of the leaves and the chloroform extract of the bark were effective against the larvae of C. quinquefasciatus with respective LC50 values 228.9 and 291.5 ppm. The LC50 values of chloroform extract of N. arbor-tristis leaves were 303.2, 518.2, and 420.2 ppm against A. aegypti, A. stephensi, and C. quinquefasciatus, respectively. The methanol and chloroform extracts of flowers of N. arbor-tristis showed larvicidal activity against larvae of A. stephensi with the respective LC50 values of 244.4 and 747.7 ppm. Among the methanol extracts of C. ternatea leaves, roots, flowers, and seeds, the seed extract was effective against the larvae of all the three species with LC50 values 65.2, 154.5, and 54.4 ppm, respectively, for A. stephensi, A. aegypti, and C. quinquefasciatus. Among the three plant species studied for mosquito larvicidal activity, C. ternatea was showing the most promising mosquito larvicidal activity. The phytochemical analysis of the promising methanolic extract of the seed extract was positive for carbohydrates, saponins, terpenoids, tannins, and proteins. In conclusion, bioassay-guided fractionation of effective extracts may result in identification of a useful molecule for the control of mosquito vectors.

Macrofilaricidal activity of the plant Plumbago indica/rosea in vitro

Abstract: The macrofilaricidal property of the plant, Plumbago indica/rosea, was investigated in vitro against Setaria digitata, a filarial parasite of cattle. Adult worms were incubated in a medium containing crude extract at concentrations 0.05, 0.04, 0.02, and 0.01 mg mL−1 for various incubation periods of 30 min, 1 h, 2 h, and 6 h, respectively, at 37°C and the worm motility was compared with that of solvent control worms kept in drug-free medium. Complete inhibition of motility was observed for concentrations ranging from 0.02 to 0.05 mg mL−1, whereas in the control all the worms were active. Bioassay-guided fractionation of the crude extract by silica gel column chromatography resulted in the identification of a very active fraction. The activity of this fraction against adult worms was further confirmed by 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide–formazan colorimetric assay, which gave >50% inhibition for the active fraction at concentrations 0.05, 0.002, 0.005, and 0.0006 mg mL−1 at 30 min, 1 h, 2 h, and 6 h incubation periods, respectively. The physical and chemical data obtained from melting point determination, thin-layer chromatography and high-performance liquid chromatography analysis and IR, 1HNMR, 13CNMR, and gas chromatography-mass spectrometry spectral analysis have indicated the chemical structure of the active molecule as 5-hydroxy-2-methyl-1,4-naphthalenedione (plumbagin). Drug Dev. Res. 56:33–39, 2002. © 2002 Wiley-Liss, Inc.

Larvicidal activity of selected plant extracts and their combination against the mosquito vectors Culex quinquefasciatus and Aedes aegypti

Abstract: In order to develop an environment-friendly botanical mosquito larvicide alternative to the chemical larvicides, extracts were made from the leaves of Hyptis suaveolens, Lantana camara, Nerium oleander, and Tecoma stans with three organic solvents such as methanol (ME), chloroform (CH), and petroleum ether (PE) using a Soxhlet extractor. The plant extracts were screened for larvicidal activity individually and in combination against the larvae of Aedes aegypti and Culex quinquefasciatus as per WHO protocol. Among the extracts, the maximum larvicidal activity was shown by the PE extract of L. camara (LC50 10.63 mg/L) followed by the PE extract of T. stans (LC50 19.26 mg/L), ME extract of N. oleander (LC50 35.82 mg/L), and PE extract of H. suaveolens (LC50 38.39 mg/L) against Cx. quinquefasciatus. In the case of Ae. aegypti, the PE extract of T. stans showed maximum activity with LC50 value of 55.41 mg/L followed by H. suaveolens (LC50 64.49 mg/L), PE extract of L. camara (LC50 74.93 mg/L), and ME extract of N. oleander (LC50 84.09). A blend of these four extracts resulted in a combination with corresponding LC50 values of 4.32 and 7.19 mg/L against Cx. quinquefasciatus and Ae. aegypti. The predator safety factors were 12.55 and 20.88 for Gambusia affinis with respect to Aedes and Culex larvae for the extract combination. Chemical constituents in extracts were also identified by FT-IR and GC-MS data. The present investigations suggest the possible use of this blend of botanical extracts as an ideal ecofriendly, larvicide against Ae. aegypti and Cx. quinquefasciatus larvae.

Glutathione S-transferase (GST) inhibitors

Abstract: The glutathione S-transferases (GSTs; EC 2.5.1.18) comprise a family of widely distributed Phase II detoxication enzymes that catalyse the conjugation of a broad variety of reactive electrophiles to the nucleophilic sulfur atom of the major intracellular thiol, the tripeptide glutathione. The diverse functions, including catalytic GSH conjugation, passive ligandin-type binding and modulation of signal transduction, may be selectively targeted by different inhibitors. GST inhibitors are emerging as promising therapeautic agents for managing the development of resistance amongst anticancer agents. In diagnostic medicine, as well as in antiparasitic drug development, GST inhibitors are important lead molecules. In this review, the important molecules known for their GST inhibition together with potential therapeutic uses are summarised.

Polymorphism in glutathione S-transferase is associated with susceptibility to chemotherapy-induced leukemia

Abstract: Glutathione S-transferases (GSTs) detoxify potentially mutagenic and toxic DNA-reactive electrophiles, including metabolites of several chemotherapeutic agents, some of which are suspected human carcinogens Functional polymorphisms exist in at least three genes that encode GSTs, including GSTM1, GSTT1, and GSTP1 We hypothesize, therefore, that polymorphisms in genes that encode GSTs alter susceptibility to chemotherapy-induced carcinogenesis, specifically to therapy-related acute myeloid leukemia (t-AML), a devastating complication of long-term cancer survival Elucidation of genetic determinants may help to identify individuals at increased risk of developing t-AML To this end, we have examined 89 cases of t-AML, 420 cases of de novo AML, and 1,022 controls for polymorphisms in GSTM1, GSTT1, and GSTP1 Gene deletion of GSTM1 or GSTT1 was not specifically associated with susceptibility to t-AML Individuals with at least one GSTP1 codon 105 Val allele were significantly over-represented in t-AML cases compared with de novo AML cases [odds ratio (OR), 181; 95% confidence interval (CI), 111–294] Moreover, relative to de novo AML, the GSTP1 codon 105 Val allele occurred more often among t-AML patients with prior exposure to chemotherapy (OR, 266; 95% CI, 139–509), particularly among those with prior exposure to known GSTP1 substrates (OR, 434; 95% CI, 143–1320), and not among those t-AML patients with prior exposure to radiotherapy alone (OR,101; 95% CI, 050–207) These data suggest that inheritance of at least one Val allele at GSTP1 codon 105 confers a significantly increased risk of developing t-AML after cytotoxic chemotherapy, but not after radiotherapy

Larvicidal potential of silver nanoparticles synthesized using fungus Cochliobolus lunatus against Aedes aegypti (Linnaeus, 1762) and Anopheles stephensi Liston (Diptera; Culicidae)

Abstract: Larvicides play a vital role in controlling mosquitoes in their breeding sites. The present study was carried out to establish the larvicidal activities of mycosynthesized silver nanoparticles (AgNPs) against vectors: Aedes aegypti and Anopheles stephensi responsible for diseases of public health importance. The AgNPs synthesized by filamentous fungus Cochliobolus lunatus, characterized by UV–Vis spectrophotometry, Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The characterization studies confirmed the spherical shape and size (3–21 nm) of silver nanoparticles. The efficacy of mycosynthesized AgNPs at all the tested concentrations (10, 5, 2.5, 1.25, 0.625, and 0.3125 ppm) against second, third, and fourth instar larvae of A. aegypti (LC50 1.29, 1.48, and 1.58; LC90 3.08, 3.33, and 3.41 ppm) and against A. stephensi (LC50 1.17, 1.30, and 1.41; LC90 2.99, 3.13, and 3.29 ppm) were observed, respectively. The mortality rates were positively correlated with the concentration of AgNPs. Significant (P < 0.05) changes in the larval mortality was also recorded between the period of exposure against fourth instar larvae of A. aegypti and A. stephensi. The possible larvicidal activity may be due to penetration of nanoparticles through membrane. Toxicity studies carried out against non-target fish species Poecilia reticulata, the most common organism in the habitats of A. aegypti and A. stephensi showed no toxicity at LC50 and LC90 doses of the AgNPs. This is the first report on mosquito larvicidal activity of mycosynthesized nanoparticles. Thus, the use of fungus C. lunatus to synthesize silver nanoparticles is a rapid, eco-friendly, and a single-step approach and the AgNps formed can be potential mosquito larvicidal agents.

Essential oil composition and larvicidal activity of six Mediterranean aromatic plants against the mosquito Aedes albopictus (Diptera: Culicidae)

Abstract: Laboratory bioassays on insecticidal activity of essential oils (EOs) extracted from six Mediterranean plants (Achillea millefolium, Lavandula angustifolia, Helichrysum italicum, Foeniculum vulgare, Myrtus communis, and Rosmarinus officinalis) were carried out against the larvae of the Culicidae mosquito Aedes albopictus. The chemical composition of the six EOs was also investigated. Results from applications showed that all tested oils had insecticidal activity, with differences in mortality rates as a function of both oil and dosage. At the highest dosage (300 ppm), EOs from H. italicum, A. millefolium, and F. vulgare caused higher mortality than the other three oils, with mortality rates ranging from 98.3% to 100%. M. communis EO induced only 36.7% larval mortality at the highest dosage (300 ppm), a similar value to those recorded at the same dosage by using R. officinalis and L. angustifolia (51.7% and 55%, respectively). Identified compounds ranged from 91% to 99%. The analyzed EOs had higher content of monoterpenoids (80-99%) than sesquiterpenes (1-15%), and they can be categorized into three groups on the basis of their composition. Few EOs showed the hydrocarbon sesquiterpenes, and these volatile compounds were generally predominant in comparison with the oxygenated forms, which were detected in lower quantities only in H. italicum (1.80%) and in M. communis (1%).

Discovery of Cyclotides in the Fabaceae Plant Family Provides New Insights into the Cyclization, Evolution, and Distribution of Circular Proteins

Abstract: Cyclotides are plant proteins whose defining structural features are a head-to-tail cyclized backbone and three interlocking disulfide bonds, which in combination are known as a cyclic cystine knot. This unique structural motif confers cyclotides with exceptional resistance to proteolysis. Their endogenous function is thought to be as plant defense agents, associated with their insecticidal and larval growth-inhibitory properties. However, in addition, an array of pharmaceutically relevant biological activities has been ascribed to cyclotides, including anti-HIV, anthelmintic, uterotonic, and antimicrobial effects. So far, >150 cyclotides have been elucidated from members of the Rubiaceae, Violaceae, and Cucurbitaceae plant families, but their wider distribution among other plant families remains unclear. Clitoria ternatea (Butterfly pea) is a member of plant family Fabaceae and through its usage in traditional medicine to aid childbirth bears similarity to Oldenlandia affinis, from which many cyclotides have been isolated. Using a combination of nanospray and matrix-assisted laser desorption ionization-time-of-flight (MALDI-TOF) analyses, we examined seed extracts of C. ternatea and discovered cyclotides in the Fabaceae, the third-largest family of flowering plants. We characterized 12 novel cyclotides, thus expanding knowledge of cyclotide distribution and evolution within the plant kingdom. The discovery of cyclotides containing novel sequence motifs near the in planta cyclization site has provided new insights into cyclotide biosynthesis. In particular, MS analyses of the novel cyclotides from C. ternatea suggest that Asn to Asp variants at the cyclization site are more common than previously recognized. Moreover, this study provides impetus for the examination of other economically and agriculturally significant species within Fabaceae, now the largest plant family from which cyclotides have been described.