Pharmaceutical Statistics: Practical and Clinical Applications

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

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

We describe findings from the first large-scale cluster randomized controlled trial in a developing country that evaluates the uptake of a health-protecting technology, insecticide-treated bednets (ITNs), through micro-consumer loans, as compared to free distribution and control conditions. Despite a relatively high price, 52 percent of sample households purchased ITNs, highlighting the role of liquidity constraints in explaining earlier low adoption rates. We find mixed evidence of improvements in malaria indices. We interpret the results and their implications within the debate about cost sharing, sustainability and liquidity constraints in public health initiatives in developing countries.

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Micro-Loans, Insecticide-Treated Bednets and Malaria: Evidence from a Randomized Controlled Trial in Orissa (India)

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.

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

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%).

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

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.

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

Methanolic extracts of 20 medicinal plants were screened at 1-10 mg/ml for in vitro macrofilaricidal activity by worm motility assay against adult Setaria digitata, the cattle filarial worm. Four plant extracts showed macrofilaricidal activity by worm motility at concentrations below 4 mg/ml and an incubation period of 100 min. Complete inhibition of worm motility and subsequent mortality was observed at 3, 2, 1 and 1 mg/ml, respectively, for Centratherum anthelminticum, Cedrus deodara, Sphaeranthus indicus and Ricinus communis. 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide (MTT) reduction assay was carried out at 1 mg ml(-1) and 4-h incubation period, and the results showed that C. deodara, R. communis, S. indicus and C. anthelminticum exhibited 86.56, 72.39, 61.20 and 43.15% inhibition respectively in formazan formation compared to the control.

In vitro screening of medicinal plant extracts for macrofilaricidal activity

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.

Macrofilaricidal activity of the plant Plumbago indica/rosea in vitro

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.

Glutathione S-transferase (GST) inhibitors

Repellents play an important role in protecting humans from the bites of insect pests. An effective and safe repellent will be useful in reducing human-vector contact and thereby help in the interruption of vector borne disease transmission. Because of the unavailability of m-toluic acid in India for the manufacture of N,N-diethyl m-toluamide (DEET), there is a need to develop an alternate effective and safe insect repellent. In total, 120 substituted amides were synthesized and tested for repellency at 1.0 mg/cm2 under laboratory conditions. Among these amides, N,N-diethyl phenylacetamide (DEPA), applied at 1.0 mg/cm2 in different oil bases, was found to exhibit promising repellency (6-8 h) in the laboratory when tested against Aedes aegypti (L.) The repellent DEPA was evaluated on army personnel in comparison with dimethylphthalate (DMP) and DEET against mosquitoes, black flies, and land leeches under field condition in the North-East Frontier area of India. Both DEPA and DEET displayed broad-spectrum repellency. DEPA was more effective than DMP against all test organisms. However, no significant difference was noticed between DEPA and DEET for repellency at 0.25 and 0.5 mg/cm2 against black flies and mosquitoes. DMP was the least effective among the three compounds in the field studies. The relative potency of DEPA in comparison with DEET and DMP for repellency against Phlebotomine sand flies also was determined. At 0.1 mg/cm2, both DEPA and DEET were found to be equally effective with a protection time from 4.37 +/- 0.08 to 4.45 +/- 0.15 h. Both compounds were significantly more effective than DMP. At 0.2 mg/cm2, DEPA and DEET provided protection times of 6.52 +/- 0.08 and 7.15 +/- 0.15 h, respectively. DEPA was formulated into a vanishing cream, a pharmacologically safe polymer-based liquid, and a liposphere lotion. The vanishing cream and the two-polymer liquid formulations enhanced protection times from 4.4 to 6.5 and 7.13 h, respectively, compared with an alcohol solution applied at 0.5 mg/cm2 on the forearm of human volunteers. Formulations of DEPA and DEET applied at 0.5 mg/cm2 on rabbits exposed to Ae. aegypti enhanced protection times compared with an alcohol solution and the liposphere lotion from 4.0 to 6.0 h and 4.0 to 5.0 h, respectively. Comparison of mean protection times of DEET and DEPA applied at a rate of 0.3 mg/cm2 to human volunteers exposed to Cx. quinque-fasciatus under field conditions indicated that the lotion formulations of DEET and DEPA provided significantly (Duncan's multiple-range test, P < 0.05) higher protection times than did alcohol solutions. Toxicological studies revealed that DEPA is safe.

https://bioone.org/journals/Journal-of-Medical-Entomology/volume-43/issue-3/0022-2585(2006)43[518:NPDASA]2.0.CO;2/NN-Diethyl-Phenylacetamide-DEPA--A-Safe-and-Effective-Repellent/10.1603/0022-2585(2006)43[518:NPDASA]2.0.CO;2.pdf

M Kalyanasundaram

Papers

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

In vitro screening of medicinal plant extracts for macrofilaricidal activity

Macrofilaricidal activity of the plant Plumbago indica/rosea in vitro

Glutathione S-transferase (GST) inhibitors

N,N-Diethyl Phenylacetamide (DEPA): A Safe and Effective Repellent for Personal Protection Against Hematophagous Arthropods