Antibiotic Potentiation Through Phytochemical-Based Efflux Pump Inhibitors to Combat Multidrug Resistance Bacteria

BACKGROUND

Antimicrobial resistance development poses a significant danger to the efficacy of antibiotics, which were once believed to be the most efficient method for treating infections caused by bacteria. Antimicrobial resistance typically involves various mechanisms, such as drug inactivation or modification, drug target modification, drug uptake restriction, and drug efflux, resulting in decreased antibiotic concentrations within the cell. Antimicrobial resistance has been associated with efflux Pumps, known for their capacity to expel different antibiotics from the cell non-specifically. This makes EPs fascinating targets for creating drugs to combat antimicrobial resistance (AMR). The varied structures of secondary metabolites (phytomolecules) found in plants have positioned them as a promising reservoir of efflux pump inhibitors. These inhibitors act as modifiers of bacterial resistance and facilitate the reintroduction of antibiotics that have lost clinical effectiveness. Additionally, they may play a role in preventing the emergence of multidrug resistant strains.

OBJECTIVE

The objective of this review article is to discuss the latest studies on plant-based efflux pump inhibitors such as terpenoids, alkaloids, flavonoids, glycosides, and tetralones. It highlighted their potential in enhancing the effectiveness of antibiotics and combating the development of multidrug resistance. strains.

RESULTS

Efflux pump inhibitors (EPIs) derived from botanical sources, including compounds like lysergol, chanaoclavine, niazrin, 4-hydroxy-α-tetralone, ursolic acid, phytol, etc., as well as their partially synthesized forms, have shown significant potential as practical therapeutic approaches in addressing antimicrobial resistance caused by efflux pumps. Further, several phyto-molecules and their analogs demonstrated superior potential for reversing drug resistance, surpassing established agents like reserpine, niaziridin, etc. strains.

CONCLUSION

This review found that while the phyto-molecules and their derivatives did not possess notable antimicrobial activity, their combination with established antibiotics significantly reduced their minimum inhibitory concentration (MIC). Specific molecules, such as chanaoclavine and niaziridin, exhibited noteworthy potential in reversing the effectiveness of drugs, resulting in a reduction of the MIC of tetracycline by up to 16 times against the tested strain of bacteria. These molecules inhibited the efflux pumps responsible for drug resistance and displayed a stronger affinity for membrane proteins. By employing powerful EPIs, these molecules can selectively target and obstruct drug efflux pumps. This targeted approach can significantly augment the strength and efficacy of older antibiotics against various drug resistant bacteria, given that active drug efflux poses a susceptibility for nearly all antibiotics.

Evidence of the Anomalous Fluctuating Magnetic State by Pressure-Driven 4f Valence Change in EuNiGe3

In rare-earth compounds with valence fluctuation, the proximity of the 4f level to the Fermi energy leads to instabilities of the charge configuration and the magnetic moment. Here, we provide direct experimental evidence for an induced magnetic polarization of the Eu³⁺ atomic shell with J = 0, due to intra-atomic exchange and spin-orbital coupling interactions with the Eu²⁺ atomic shell. By applying external pressure, a transition from antiferromagnetic to a fluctuating behavior in EuNiGe₃ single crystals is probed. Magnetic polarization is observed for both valence states of Eu²⁺ and Eu³⁺ across the entire pressure range. The anomalous magnetism is discussed in terms of a homogeneous intermediate valence state where frustrated Dzyaloshinskii-Moriya couplings are enhanced by the onset of spin-orbital interaction and engender a chiral spin-liquid-like precursor.

A deep learning approach to detect blood vessels in basal cell carcinoma

PURPOSE

Blood vessels called telangiectasia are visible in skin lesions with the aid of dermoscopy. Telangiectasia are a pivotal identifying feature of basal cell carcinoma. These vessels appear thready, serpiginous, and may also appear arborizing, that is, wide vessels branch into successively thinner vessels. Due to these intricacies, their detection is not an easy task, neither with manual annotation nor with computerized techniques. In this study, we automate the segmentation of telangiectasia in dermoscopic images with a deep learning U-Net approach.

METHODS

We apply a combination of image processing techniques and a deep learning-based U-Net approach to detect telangiectasia in digital basal cell carcinoma skin cancer images. We compare loss functions and optimize the performance by using a combination loss function to manage class imbalance of skin versus vessel pixels.

RESULTS

We establish a baseline method for pixel-based telangiectasia detection in skin cancer lesion images. An analysis and comparison for human observer variability in annotation is also presented.

CONCLUSION

Our approach yields Jaccard score within the variation of human observers as it addresses a new aspect of the rapidly evolving field of deep learning: automatic identification of cancer-specific structures. Further application of DL techniques to detect dermoscopic structures and handle noisy labels is warranted.

Transition from spin glass to paramagnetism in the magnetic properties of PrAu2Si2

It is unexpected that a spin-glass (SG) transition, which generally occurs only in systems with some form of disorder, was observed in the ThCr₂Si₂-type compound PrAu₂Si₂at a temperature of ∼3 K. This puzzling phenomenon was later explained based on a novel dynamic frustration model that does not involve static disorder. We present the results of re-verification of the reported SG behaviors by measuring the physical properties of three polycrystalline PrAu₂Si₂samples annealed under different conditions. Indeed, in the sample annealed at 827 °C for one week, a SG transition does occur at a temperature ofT_f∼ 2.8 K as that reported previously in the literature. However, it is newly found that the SG effect is actually more pronounced in the as-cast sample, and almost completely disappears in the well-annealed (at 850 °C for four weeks) sample. The annealing effect observed in PrAu₂Si₂, that is, SG to paramagnetism transition is discussed by comparing with earlier results reported on the same system and other isomorphic compounds.

Antidiabetic Potential of Naturally Occurring Sesquiterpenes: A Review

Diabetes Mellitus (DM) is an endocrine disease, which is the 3rd leading cause of death in humans; additionally, it is one of the major key concerns over the globe. The high levels of glucose in the blood stream are as well characterized by hyperglycaemia leading to serious damage to the heart, blood vessels, kidney, eyes, and nerves. The best treatment of DM is still not available; many scientists worldwide are trying hard to seek out suitable treatment of DM. Though numerous synthetic drugs are developed for the treatment of diabetes but their utility has been hampered because of several side effects and poor efficacy. Among various approaches for the treatment of DM, herbal medicine, enriched extracts, and naturally derived molecules are most effective. Plant based herbal medicines contain many bioactive phytochemicals, such as terpenoids, alkaloids, flavonoids & phenolics, etc. which are used in the treatment of many diseases. The plant-derived molecules and their suitable structure modification have given many leads or drugs to the world like sesquiterpene; artemisinin and their derivatives artemether & artesunate as an antimalarial drugs. Sesquiterpenes are available in the human diet and are largely taken as components of the many folk medicines and dietary supplements. Sesquiterpenes have a wide range of biological activities, such as anti-cancer, anti-inflammatory, anti-nociceptive, immunomodulatory, antidiabetic and antimicrobial, which make them potential targets for the development of new therapeutics and their usage for medical purposes. Natural products have gained the attention of the world due to their large number of biological activities, high safety and fewer side effect. The review mainly focuses on bioactive sesquiterpenes such as β-caryophyllene, dysidine, farnesol & eremanthin, etc., a class of terpenoids that may play an important role in the treatment or prevention of this gruesome disorder like diabetes, with their underlying mechanisms for the blood-glucose-lowering property.

Magnetic and transport properties of new ternary uranium-based germanide U2Rh3Ge5

A new ternary uranium germanide U₂Rh₃Ge₅ has been successfully synthesized and investigated by means of magnetic susceptibility χ(T, H), isothermal magnetization M(T, H), electrical resistivity ρ(T), and specific heat C(T, H) measurements. This compound is found to crystallize in the U₂Co₃Si₅-type orthorhombic structure. The low-field χ(T) shows a clear peak at T _N = 41.5 K corresponding to an antiferromagnetic transition. The M(H) curve measured up to 70 kOe exhibits an H-linear behavior at 2 K with very small induced magnetic moments, while it shows upward curvature with increasing temperature, implying the possible presence of a metamagnetic transition in high-field region above 70 kOe. As the temperature decreases, ρ(T) increases slowly at T > T _N and decreases rapidly at T < T _N, which can be understood based on a semiconductor-like narrow band gap model (or the c-f hybridization effect) and an antiferromagnetic spin-wave model, respectively. No evidence of heavy-fermion behavior or superconductivity transition is observed at temperatures as low as 0.4 K. The obtained experimental results are discussed by comparing with those reported for the isomorphic compound U₂Ir₃Si₅ and the quasi-isomorphic compound U₂Rh₃Si₅.

Comparative Drug Resistance Reversal Potential of Natural Glycosides: Potential of Synergy Niaziridin & Niazirin

Background:

Due to the limited availability of antibiotics, Gram-negative bacteria (GNB) acquire different levels of drug resistance. It raised an urgent need to identify such agents, which can reverse the phenomenon of drug resistance.

Objective:

To understand the mechanism of drug resistance reversal of glycosides; niaziridin and niazirin isolated from the pods of Moringa oleifera and ouabain (control) against the clinical isolates of multidrug-resistant Escherichia coli.

Methods:

The MICs were determined following the CLSI guidelines for broth micro-dilution. In-vitro combination studies were performed by broth checkerboard method followed by Time-Kill studies, the efflux pump inhibition assay, ATPase inhibitory activity, mutation prevention concentration and in-silico studies.

Results:

The results showed that both glycosides did not possess antibacterial activity of their own, but in combination, they reduced the MIC of tetracycline up to 16 folds. Both were found to inhibit efflux pumps, but niaziridin was the best. In real time expression pattern analysis, niaziridin was also found responsible for the down expression of the two important efflux pump acrB & yojI genes alone as well as in combination. Niaziridin was also able to over express the porin forming genes (ompA & ompX). These glycosides decreased the mutation prevention concentration of tetracycline.

Conclusion:

This is the first ever report on glycosides, niazirin and niaziridin acting as drug resistance reversal agent through efflux pump inhibition and modulation of expression pattern drug resistant genes. This study may be helpful in preparing an effective antibacterial combination against the drug-resistant GNB from a widely growing Moringa oleifera.

Should vitamin D be routinely checked for all chronic obstructive pulmonary disease patients?

Aims and Objectives:

This study aimed to compare the vitamin D levels between chronic obstructive pulmonary disease (COPD) patients and healthy controls and to describe the correlation between vitamin D levels and lung functions.

Methods:

Fifty COPD patients (cases) and 30 healthy volunteers (controls) were recruited and their serum vitamin D level was measured together with lung function (forced vital capacity and forced expiratory volume in 1 s [FEV1]) by spirometry. vitamin D was categorized as ≤20 nmol/l: deficient, 21–50 nmol/l: inadequate, and ≥51 nmol/l as sufficient.

Results:

In this case–control cross-sectional study, lower vitamin D levels were associated with lower lung function in both cases as well as controls, the effect being more pronounced in cases. Mean FEV1 at vitamin D ≤20 nmol/l (0.98 ± 0.40 vs. controls 1.93 ± 0.24 with P = 0.006), mean FEV1 at vitamin D 21–50 nmol/l (1.55 ± 0.54 vs. 2.20 ± 0.31 with P = 0.000), and mean FEV1 at vitamin D ≥51 nmol/l (2.06 ± 0.54 vs. 2.20 ± 0.31 with P = 0.002). Moreover, the severity of predicted postbronchodilator FEV1% was also much lower among COPD cohort versus healthy volunteers (mean FEV1%: cases 47.88 ± 14.22 vs. controls 58.76 ± 15.05 with P = 0.002).

Conclusions:

Importantly, lung function in both the groups was affected by decreased vitamin D level; decrease in FEV1 was more pronounced among COPD patients compared to controls showing more expiratory airflow limitation. Vitamin D levels are associated with changes in lung function in cases of COPD as well as healthy controls. Larger studies to confirm the association in Indian context are required and routine assessment of vitamin D may be undertaken to obviate the effects of low vitmain D level on lung function.

Synergy of clavine alkaloid 'chanoclavine' with tetracycline against multi-drug-resistant E. coli

The emergence of multi drug resistance (MDR) in Gram-negative bacteria (GNB) and lack of novel classes of antibacterial agents have raised an immediate need to identify antibacterial agents, which can reverse the phenomenon of MDR. The purpose of present study was to evaluate synergy potential and understanding the drug resistance reversal mechanism of chanoclavine isolated from Ipomoea muricata against the multi-drug-resistant clinical isolate of Escherichia coli (MDREC). Although chanoclavine did not show antibacterial activity of its own, but in combination, it could reduce the minimum inhibitory concentration (MIC) of tetracycline (TET) up to 16-folds. Chanoclavine was found to inhibit the efflux pumps which seem to be ATPase-dependent. In real-time expression analysis, chanoclavine showed down-regulation of different efflux pump genes and decreased the mutation prevention concentration of tetracycline. Further, in silico docking studies revealed significant binding affinity of chanoclavine with different proteins known to be involved in drug resistance. In in silico ADME/toxicity studies, chanoclavine was found safe with good intestinal absorption, aqueous solubility, medium blood-brain barrier (BBB), no CYP 2D6 inhibition, no hepatotoxicity, no skin irritancy, and non-mutagenic indicating towards drug likeliness of this molecule. Based on these observations, it is hypothesized that chanoclavine might be inhibiting the efflux of tetracycline from MDREC and thus enabling the more availability of tetracycline inside the cell for its action.

Enhanced green upconversion photoluminescence from Ho3+/Yb3+ co-doped CaZrO3 phosphor via Mg2+ doping

This paper reports enhanced green upconversion photoluminescence from Ho³⁺/Yb³⁺ co-doped CaZrO₃ phosphor via Mg²⁺ doping synthesized through a solid state reaction method.

Drug Resistance Reversal Potential of Ursolic Acid Derivatives against Nalidixic Acid- and Multidrug-resistant Escherichia coli

As a part of our drug discovery program, ursolic acid was chemically transformed into six semi-synthetic derivatives, which were evaluated for their antibacterial and drug resistance reversal potential in combination with conventional antibiotic nalidixic acid against the nalidixic acid-sensitive and nalidixic acid-resistant strains of Escherichia coli. Although ursolic acid and its all semi-synthetic derivatives did not show antibacterial activity of their own, but in combination, they significantly reduced the minimum inhibitory concentration of nalidixic acid up to eightfold. The 3-O-acetyl-urs-12-en-28-isopropyl ester (UA-4) and 3-O-acetyl-urs-12-en-28-n-butyl ester (UA-5) derivatives of ursolic acid reduced the minimum inhibitory concentration of nalidixic acid by eightfold against nalidixic acid-resistant and four and eightfold against nalidixic acid-sensitive, respectively. The UA-4 and UA-5 were further evaluated for their synergy potential with another antibiotic tetracycline against the multidrug-resistant clinical isolate of Escherichia coli-KG4. The results showed that both these derivatives in combination with tetracycline reduced the cell viability in concentration-dependent manner by significantly inhibiting efflux pump. This was further supported by the in silico binding affinity of UA-4 and UA-5 with efflux pump proteins. These ursolic acid derivatives may find their potential use as synergistic agents in the treatment of multidrug-resistant Gram-negative infections.

Purification, characterization, and in vitro activity of 2,4-Di-tert-butylphenol from Pseudomonas monteilii PsF84: conformational and molecular docking studies

A novel strain of Pseudomonas monteilii, PsF84, was isolated from tannery waste soil from Jajmau, Kanpur, India. 16S rRNA gene sequence phylogenetic analysis confirmed the taxonomic affiliation of PsF84 as P. monteilii. An antifungal volatile organic compound (VOC) active against hyphal growth of Fusarium oxysporum (CIMAP-IMI-357464) in vitro was isolated from strain PsF84 by using chromatographic techniques. The molecular formula of the antifungal VOC was deduced to be C₁₄H₂₂O by EI-MS and 1D and 2D NMR spectral analysis. 2,4-Di-tert-butylphenol was found to be effective against an agriculturally important fungus, namely, F. oxysporum, in inhibiting spore germination and hyphal growth. Molecular docking analysis of 2,4-di-tert-butylphenol with β-tubulin further validated the potential of β-tubulin binding in F. oxysporum. Two residues of β-tubulin protein, HIS 118 and THR 117, showed hydrogen binding with ligand. To the authors' knowledge, this is the first report of antifungal VOC (2,4-di-tert-butylphenol) produced by P. monteilii PsF84 that can be a potent inhibitor of β-tubulin of F. oxysporum.

EuNiGe₃, an anisotropic antiferromagnet

Single crystals of EuNiGe3, crystallizing in the non-centrosymmetric BaNiSn3-type structure, were grown using In flux, enabling us to explore the anisotropic magnetic properties, which was not possible with previously reported polycrystalline samples. The EuNiGe3 single crystalline sample is found to order antiferromagnetically at 13.2 K, as revealed from the magnetic susceptibility, heat capacity and electrical resistivity data. The low temperature magnetization M (H) is distinctly different for the field parallel to the ab-plane and c-axis; the ab-plane magnetization varies almost linearly with the field before the occurrence of an induced ferromagnetic (FM) phase (spin-flip) at 6.2 Tesla. On the other hand M (H) along the c-axis is accompanied by two metamagnetic transitions followed by a spin-flip at 4.1 T. A model including anisotropic exchange and dipole-dipole interactions reproduces the main features of magnetization plots but falls short of full representation. (H,T) phase diagrams have been constructed for the field applied along the principal directions. From the (151)Eu Mössbauer spectra, we determine that the 13.2 K transition leads to an incommensurate antiferromagnetic (AFM) intermediate phase followed by a transition near 10.5 K to a commensurate AFM configuration.

Simple and reliable methods for the determination of three steroidal glycosides in the eight species of Solanum by reversed-phase HPLC coupled with diode array detection

INTRODUCTION

Solanum species are important ingredients of many traditional Indian medicines and thus the quality control of their herbal formulations is of paramount concern.

OBJECTIVE

To establish a simple and effective high-performance liquid chromatographic (HPLC) method to evaluate the quality of Solanum species and their herbal formulations.

METHODOLOGY

A rapid, simple, sensitive, robust and reproducible HPLC method was developed for the determination of three steroidal glycosides (SG); indioside D, solamargine and α-solanine in eight species of the genus Solanum. The analytes were separated on a monolithic performance RP-18e column (100 mm × 4.6 mm i.d.) using a gradient elution of acetonitile-water containing 0.1% trifluoroacetic acid (TFA) as the mobile phase with a flow rate 0.4 mL/min and UV detection at λ 210 nm.

RESULTS

The method was linear over the range 3-15 µg/mL (r > 9994). Accuracy, precision and repeatability were all within the required limits. The mean recoveries measured at the three concentrations were higher than 98.8% with RSD < 2% for the targets.

CONCLUSION

The established method is simple and can be used as a tool for quality control of plant material or herbal formulation containing SG.

Large-scale separation of antipsychotic alkaloids from Rauwolfia tetraphylla L. by pH-zone-refining fast centrifugal partition chromatography

pH-zone-refining centrifugal partition chromatography was successively applied in the large-scale separation of close R(f) antipsychotic indole alkaloids directly from CHCl(3) fraction of Rauwolfia tetraphylla leaves. Two experiments with increasing mass from 500 mg to 3 g of crude alkaloid extracts (1C) of R. tetraphylla were carried out in normal-displacement mode using a two-phase solvent system composed of methyl tert-butyl ether/ACN/water (4:1:5, v/v/v) where HCl (12 mM) was added to the lower aqueous stationary phase as a retainer and triethylamine (5 mM) to the organic mobile phase as an eluter. The two centrifugal partition chromatography separations afforded a total of 162.6 mg of 10-methoxytetrahydroalstonine (1) and 296.5 mg of isoreserpiline (2) in 97% and 95.5% purity, respectively, along with a 400.9 mg mixture of α-yohimbine and reserpiline (3 and 4). Further, this mixture was resolved over medium pressure LC using TLC grade silica gel H (average particle size 10 μm), which afforded 160.4 mg of α-yohimbine (3) and 150.2 mg of reserpiline (4) in >95% purities. The purity of the isolated antipsychotic alkaloids was analyzed by high-performance LC and their structures were characterized on the basis of their 1D, 2D NMR and electrospray ionization-mass spectroscopic data.

QSAR, docking and in vivo studies for immunomodulatory activity of isolated triterpenoids from Eucalyptus tereticornis and Gentiana kurroo

Two triterpenoids ursolic acid (1) and lupeol (2) isolated and characterized from Eucalyptus tereticornis and Gentiana kurroo were subjected to in silico QSAR modeling and docking studies and later the predicted results were confirmed through in vivo experiments. QSAR modeling results showed that both the triterpenoids possess immunomodulatory and anti-inflammatory activity comparable to boswellic and cichoric acids, but were less active than levamisol. Docking results suggested that both the triterpenoids (1 and 2) showed immune modulatory and anti-inflammatory activity due to high binding affinity to human receptors viz., NF-kappaB p52 (-50.549 kcal/mol), tumor necrosis factor (TNF-alpha) (-47.632 kcal/mol), nuclear factor NF-Kappa-B P50 (-16.798 kcal/mol) and cyclooxygenase-2 (-55.244 kcal/mol). Further both the triterpenoids (1 and 2) were subjected to in vivo immunomodulatory activity in female Swiss albino mice. The experimental mice were divided into nine groups, each comprised of six mice. These received oral treatment for a period of 28 days. The triterpenoids (1 and 2) showed significant increased in humoral immune function, but no significant changes were observed in cell mediated immune response and hematological parameters. The in silico and in vivo experimental data suggested that both the triterpenoids 1 and 2 may be considered as potential immunomodulatory drug-like molecules.

pH-Zone-refining centrifugal partition chromatography for preparative isolation and purification of steroidal glycoalkaloids from Solanum xanthocarpum

pH-Zone-refining centrifugal-partition chromatography (CPC) was successfully applied in the separation of complex polar steroidal glycoalkaloids of close Rf values, directly from a crude extract of Solanum xanthocarpum. The experiment was performed with a two phase solvent system composed of ethyl acetate/butanol/water (1:4:5 by volume) where triethylamine (5 mM) was added to the upper organic mobile phase as an eluter and TFA (10 mM) to the aqueous stationary phase as a retainer. Separation of 1 g of crude extract over CPC resulted in two distinct pH-zones. The fractions collected in pH-zone i afforded 72 mg of solasonine while the fractions collected in pH-zone ii were slightly impure, hence were purified over medium pressure LC, which afforded 30 mg of solasonine and further 15 mg of solamargine (SM). The steroidal glycoalkaloids, SM and solasonine were isolated in 93.3 and 91.6% purity, respectively. The isolated alkaloids were characterized on the basis of their (1)H, (13)C-NMR, and ESI-MS data.

Large-scale separation of clavine alkaloids from Ipomoea muricata by pH-zone-refining centrifugal partition chromatography

Centrifugal partition chromatography in the pH-zone-refining mode was successfully applied to the separation of alkaloids, directly from a crude extract of Ipomoea muricata. The experiment was performed with a two-phase solvent system composed of methyl tert-butyl ether (MtBE)-acetonitrile-water (4:1:5, v/v) where triethylamine (10 mM) was added to the upper organic stationary phase as a retainer and trifluoroacetic acid (10 mM) to the aqueous mobile phase as an eluter. From 4 g of crude extract, 210 mg lysergol and 182 mg chanoclavine were obtained in 97% and 79.6% purities. Total yield recovery was >95%. Isolated alkaloids were characterized on the basis of their (1)H, (13)C NMR and ESI-MS data.

Antimicrobial Activity and Chemical Composition of Callistemon Comboynensis and C. Citrinus Leaf Essential Oils from the Northern Plains of India

Biological and chemical investigations were carried out to evaluate the antimicrobial potential of Callistemon comboynensis and C. citrinus leaf oils for herbal medicines. Disk diffusion and micro broth dilution methods were used for the evaluation of the antimicrobial activity of the essential oils against selected strains of bacteria (Staphylococcus aureus, S. epidermidis, Streptococcus mutans, Enterococcus faecalis, Klebsiella pneumoniae, Pseudomonas aeruginosa, Enterobacter aerogenes and Escherichia coli) and fungi (Candida albicans, Cryptococcus neoformans, Trichophyton rubrum, Aspergillus flavus, A. niger and Sporothrix schenckii). Analysis of the leaf essential oils of C. comboynensis and C. citrinus using GC and GC-MS resulted in the identification of thirty and twenty eight compounds, respectively. 1,8-Cineole (58.5% and 58.0%), α-pinene (22.7% and 24.1%), and (E)-β-terpineol (6.4% and 1.8%), were the major constituents. The isolated essential oils could be of use for the future development of antimicrobial agents.

Assessment of groundwater quality with respect to fluoride

The study was conducted in the summer season (April-May 2007). The fluoride concentration along with physico-chemical parameters in ground water samples was determined in various villages of Kadi tehsil at Mehsana district of Gujarat state (India), since in most of the villages it is the only source of drinking water. The fluoride concentrations in these villages varied from 0.94 to 2.81 mg/L (1.37+/-0.56) with highest fluoride level at Visalpur (2.08 mg/L) and lowest at Adaraj (0.91 mg/L). There was found a positive correlation of pH with fluoride and a negative relationship of fluoride with bicarbonate which is generally observed in deep ground water.

Chemical composition of major ions in rainwater

The present study investigated the chemical composition of rainwater at Kabir nagar, Nari, Nagpur, Maharashtra, India. The rainwater samples were collected on event basis during June-July-August-2006 and were analyzed for pH, major anions Cl, NO(3), SO(4)) and cations (Ca, Mg, Na, K, NH4). The pH value varied from 6.0 to 7.3 (avg. 6.3 +/- 0.3) indicating alkaline nature of rainwater. The pH of the rainwater was found well above the reference pH (5.6), showing alkalinity during the monsoon season. The average and standard deviation of ionic composition was found to be 98.1 +/- 10.6 micro eql(-1). The total anions contribute 45.1% and cations 54.9%, respectively to rainwater. Neutralization factors (NF) followed a sequence of NF(Ca) > NF(Mg) > NF(NH4) with factors of 1.1, 0.38 and 0.15 indicating the crustal components are responsible for neutralization of anions. The average ratio of (NO(3) + Cl)/SO(4) observed as 1.1 indicates that nitric and hydrochloric acid influences the acidity of rainwater. The ratio of NH(4)/NO(3) and NH(4)/SO(4) was observed as 0.68 and 0.34 indicate that the possible compounds which may predominate in the atmosphere are NH(4)NO(3) and (NH(4))(2)SO(4). Ionic correlation was established to identify sources of origin. A good correlation was seen between Ca and Mg (r = 0.95); suggesting the common occurrence of these ions from crustal origin. Similarly, the acidic ions SO(4) and NO(3) correlated well (r = 0.60) indicating their origin from similar sources. Other relatively significant correlations were observed between Ca and SO4 (r = 0.92), Mg and SO(4) (r = 0.83), Ca and NO(3) (r = 0.09), Ca and Cl (r = 0.34) and Mg and Cl (r = 0.31), and Mg and NO(3) (r = 0.71). The observed rainwater ratio of Cl/Na (1.1) is closer to that of seawater ratio (1.16) indicates fractionation of sea-salt and modifications by non-marine constituents as the site is 834 km away from the sea coast. The nss-Ca contribution was observed as 95.7% suggesting their crustal origin whereas nss-Mg and nss-K shows their contribution as 87.9% and 83.2% indicating influence of soil sources. The nss-SO(4) contributed as 87.4% shows anthropogenic origin.