Iqbal Ahmad

Antimicrobial and phytochemical studies on 45 Indian medicinal plants against multi-drug resistant human pathogens

Ethanolic extracts of 45 Indian medicinal plants traditionally used in medicine were studied for their antimicrobial activity against certain drug-resistant bacteria and a yeast Candida albicans of clinical origin. Of these, 40 plant extracts showed varied levels of antimicrobial activity against one or more test bacteria. Anticandidal activity was detected in 24 plant extracts. Overall, broad-spectrum antimicrobial activity was observed in 12 plants (L. inermis, Eucalyptus sp., H. antidysentrica, H. indicus, C. equistifolia. T. belerica, T. chebula, E. officinalis, C. sinensis, S. aromaticum and P. granatum). No correlation was observed between susceptibility of test strains with plant extracts and antibiotic resistance behaviour of the microbial strains (Staphylococcus aureus, Salmonella paratyphi, Shigella dysenteriae, Escherichia coli, Bacillus subtilis, Candida albicans). Qualitative phytochemical tests, thin layer chromatography and TLC-bioautography of certain active extracts demonstrated the presence of common phytocompounds in the plant extracts including phenols, tannins and flavonoids as major active constituents.

Screening of some Indian medicinal plants for their antimicrobial properties

A total of 82 Indian medicinal plants traditionally used in medicines were subjected to preliminary antibacterial screening against several pathogenic and opportunistic microorganisms. Aqueous, hexane and alcoholic extracts of each plant were tested for their antibacterial activity using agar well diffusion method at sample concentration of 200 mg/ml. The results indicated that out of 82 plants, 56 exhibited antibacterial activity against one or more test pathogens. Interestingly, extracts of five plants showed strong and broad spectrum activity as compared to rest of 51 plant extracts which demonstrated moderate activity. On the whole the alcoholic extracts showed greater activity than their corresponding aqueous and hexane extracts. Among various extracts, only alcoholic extracts of Emblica officinalis, Terminalia chebula, Terminalia belerica, Plumbago zeylanica and Holarrhena antidysenterica were found to show potentially interesting activity against test bacteria. These active crude alcoholic extracts were also assayed for cellular toxicity to fresh sheep erythrocytes and found to have no cellular toxicity.

Broad spectrum antimutagenic activity of antioxidant active fraction of punica granatum L. peel extracts.

Over the past few decades, scientific research has indicated a credible basis for some of the traditional ethnomedicinal uses of pomegranate. This study aims to evaluate the broad spectrum antioxidant and antimutagenic activities of peel extracts of pomegranate. The sequentially extracted Punica granatum peel fractions were tested for their antioxidant activity by DPPH free radical scavenging, phosphomolybdenum, FRAP (Fe(3+) reducing power) and CUPRAC (cupric ions (Cu(2+)) reducing ability) assays. The methanol fraction showed highest antioxidant activity by all the four in vitro assays comparable to ascorbic acid and butylated hydroxy toluene (BHT) followed by activity in ethanol, acetone, and ethyl acetate fractions. Based on the promising antioxidant activities, the methanol fraction was evaluated for antimutagenic activity by Ames Salmonella/microsome assay against sodium azide (NaN(3)), methyl methane sulphonate (MMS), 2-aminofluorene (2-AF) and benzo(a)pyrene (B(a)P) induced mutagenicity in Salmonella typhimurium (TA97a, TA98, TA100 and TA102) tester strains. The methanol fraction showed no sign of mutagenicity at tested concentration of 10-80μg/mL. This fraction showed antimutagenic activity against NaN(3) and MMS with percent inhibition of mutagenicity ranging from 66.76% to 91.86% in a concentration-dependent manner. Similar trend of inhibition of mutagenicity (81.2-88.58%) against indirect mutagens (2-AF and B(a)P) was also recorded. Phytochemical analysis by HPLC, LC-MS and total phenolic content revealed high content of ellagitannins which might be responsible for promising antioxidant and antimutagenic activities of P. granatum peel extract. Further, contribution of bioactive compounds detected in this study is to be explored to understand the exact mechanism of action as well as their therapeutic efficacy.

Broad-spectrum antibacterial and antifungal properties of certain traditionally used Indian medicinal plants

Ethanolic extracts of 22 traditionally used Indian medicinal plants were studied for their antimicrobial activity against seven bacteria (Staphylococcus aureus, Salmonella typhimurium, S. paratyphi, S. typhi, E. coli, Shigella dysenteriae and Pseudomonas aeruginosa) and five filamentous fungi (Aspergillus niger, Alternaria alternata, Fusarium chlamydosporum, Rhizoctonia bataticola and Trichoderma viride) and a yeast Candida albicans of clinical origin. Of these, 16 plant extracts showed varied level of antibacterial activity against one or more test bacteria. Similarly antifungal and anticandidal activity was detected among 17 and 9 plant extracts respectively. Broad-spectrum antimicrobial activity (both antibacterial and antifungal) was detected among crude extracts of Bryophyllum pinnatum (leaves), Caesalpinia bonducella (seeds), Delonix regia (flower), Hedychium spicatum (fruits), Mangifera indica (leaves), Murraya coenigii (leaves) and Syzgium cumini (seeds). Similarly extracts of Cichorium intybus (roots), Ficus religiosa (leaves) and Trigonella foenum-graecum (leaves) demonstrated more antibacterial activity with less antifungal activity. On the other hand Pistacia integerrima (stems) and Rheum emodi (roots) demonstrated more antifungal activity with less antibacterial activity.

Brassinosteroids and their role in response of plants to abiotic stresses

Brassinosteroids (BRs) are polyhydroxylated steroidal plant hormones that play pivotal role in the regulation of various plant growth and development processes. BR biosynthetic or signaling mutants clearly indicate that these plant steroids are essential for regulating a variety of physiological processes including cellular expansion and proliferation, vascular differentiation, male fertility, timing senescence, and leaf development. Moreover, BRs regulate the expression of hundreds of genes, affect the activity of numerous metabolic pathways, and help to control overall developmental programs leading to morphogenesis. On the other hand, the potential application of BRs in agriculture to improve growth and yield under various stress conditions including drought, salinity, extreme temperatures, and heavy metal (Cd, Cu, Al, and Ni) toxicity, is of immense significance as these stresses severely hamper the normal metabolism of plants. Keeping in mind the multifaceted role of BRs, an attempt has been made to cover the various aspects mediated by BRs particularly under stress conditions and a possible mechanism of action of BRs has also been suggested.

Antibiofilm activity of certain phytocompounds and their synergy with fluconazole against Candida albicans biofilms

OBJECTIVES The aim of this study was to evaluate four phytocompounds (cinnamaldehyde, citral, eugenol and geraniol) for their in vitro inhibitory activity against pre-formed biofilms of Candida albicans alone or in combination with fluconazole and amphotericin B. These compounds were also tested at subinhibitory concentrations for their ability to inhibit biofilm formation. METHODS The XTT reduction assay, light microscopy and scanning electron microscopy (SEM) were employed to determine the inhibitory effect of the test compounds on biofilms. A chequerboard method was used for combination studies. RESULTS Both clinical and reference strains of C. albicans (C. albicans 04 and C. albicans SC5314, respectively) displayed formation of strong biofilms. Pre-formed Candida biofilms showed ≥1024× increased resistance to antifungal drugs and 2× increased resistance to cinnamaldehyde and geraniol, but no increased tolerance of eugenol. The test compounds were more active against pre-formed biofilms than amphotericin B and fluconazole. At 0.5× MIC, eugenol and cinnamaldehyde were the most inhibitory compounds against biofilm formation. Light and electron microscopic studies revealed the deformity of three-dimensional structures of biofilms formed in the presence of sub-MICs of eugenol and cinnamaldehyde. The cell membrane appeared to be the target site of compounds in both planktonic and sessile C. albicans cells, as observed by SEM. Combination studies showed that synergy was highest between eugenol and fluconazole (fractional inhibitory concentration index = 0.14) against pre-formed biofilms of C. albicans SC5314. CONCLUSIONS Promising antibiofilm activity was displayed by eugenol and cinnamaldehyde, which also showed synergy with fluconazole in vitro. Further evaluation in in vivo systems is required to determine whether these findings can be exploited in treating biofilm-associated candidiasis.

In vitro antifungal, anti-elastase and anti-keratinase activity of essential oils of Cinnamomum-, Syzygium- and Cymbopogon-species against Aspergillus fumigatus and Trichophyton rubrum.

This study was aimed to evaluate effects of certain essential oils namely Cinnamomum verum, Syzygium aromaticum, Cymbopogon citratus, Cymbopogon martini and their major components cinnamaldehyde, eugenol, citral and geraniol respectively, on growth, hyphal ultrastructure and virulence factors of Aspergillus fumigatus and Trichophyton rubrum. The antifungal activity of essential oils and their major constituents was in the order of cinnamaldehyde>eugenol>geraniol=C. verum>citral>S. aromaticum>C. citratus>C. martini, both in liquid and solid media against T. rubrum and A. fumigatus. Based on promising antifungal activity of eugenol and cinnamaldehyde, these oils were further tested for their inhibitory activity against ungerminated and germinated conidia in test fungi. Cinnamaldehyde was found to be more active than eugenol. To assess the possible mode of action of cinnamaldehyde, electron microscopic studies were conducted. The observations revealed multiple sites of action of cinnamaldehyde mainly on cell membranes and endomembranous structures of the fungal cell. Further, test oils were also tested for their anti-virulence activity. More than 70% reduction in elastase activity was recorded in A. fumigatus by the oils of C. verum, C. martini, eugenol, cinnamaldehyde and geraniol. Similar reduction in keratinase activity in A. niger was recorded for the oils of C. martini and geraniol. Maximum reduction (96.56%) in elastase activity was produced by cinnamaldehyde whereas; geraniol caused maximum inhibition (97.31%) of keratinase activity. Our findings highlight anti-elastase and anti-keratinase activity of above mentioned essential oils as a novel property to be exploited in controlling invasive and superficial mycoses.

Antifungal activity of essential oils and their synergy with fluconazole against drug-resistant strains of Aspergillus fumigatus and Trichophyton rubrum

The aim of this study was to screen certain plant essential oils and active compounds for antifungal activity and their in vitro interaction with fluconazole against drug-resistant pathogenic fungi. The methods employed in this work included disc diffusion, broth macrodilution, time kill methods and checkerboard microtiter tests. Oil compositions were evaluated by gas chromatography-mass spectrometry (GC-MS) analysis. Transmission electron microscopy was used to assess the effect of essential oils on cellular structures of test fungi. Test fungal strains exhibited resistance to at least two drugs (fluconazole and itraconazole). Among the 21 essential oils or active compounds tested, ten showed promising antifungal activity. GC-MS analysis revealed the presence of major active compounds in the essential oils used. Cinnamaldehyde showed the most promising antifungal activity and killing potency against Aspergillus fumigatus MTCC2550 and Trichophyton rubrum IOA-9. Cinnamaldehyde showed strongest synergy with fluconazole against A. fumigatus and T. rubrum by reducing the minimum inhibitory concentration of fluconazole up to 8-fold. Zones of lysis of the cell wall and cell membrane appeared to be where cinnamaldehyde acted on fungi. This study highlights the broad spectrum antifungal activity of essential oils and active compounds and their synergy with fluconazole against drug-resistant fungi.

Influence of clove oil on certain quorum-sensing-regulated functions and biofilm of Pseudomonas aeruginosa and Aeromonas hydrophila

Quorum sensing (QS) plays an important role in virulence, biofilm formation and survival of many pathogenic bacteria including Pseudomonas aeruginosa. This signalling pathway is considered as novel and promising target for anti-infective agents. In the present investigation, effect of the Sub-MICs of clove oil on QS regulated virulence factors and biofilm formation was evaluated against P. aeruginosa PAO1 and Aeromonas hydrophila WAF-38 strain. Sub-inhibitory concentrations of the clove oil demonstrated statistically significant reduction of las- and rhl-regulated virulence factors such as LasB, total protease, chitinase and pyocyanin production, swimming motility and exopolysaccharide production. The biofilm forming capability of PAO1 and A. hydrophila WAF-38 was also reduced in a concentration-dependent manner at all tested sub-MIC values. Further, the PAO1-preinfected Caenorhabditis elegans displayed an enhanced survival when treated with 1.6% v/v of clove oil. The above findings highlight the promising anti-QS-dependent therapeutic function of clove oil against P. aeruginosa.

Antioxidant and antimutagenic activity of Carum copticum fruit extracts.

The ajowain (Carum copticum (L.)) is a popular spice and traditionally used in Indian system of medicine. Considering the importance of natural products in modern phytomedicine, the antioxidant and antimutagenic activities of C. copticum fruits extract and its fractions were evaluated. The methanol fraction showed highest antioxidant activity by phosphomolybdenum (2087.7 micromol) and DPPH assay (90.2%) followed by other fractions comparable to ascorbic acid and BHT. Based on antioxidant activity, methanol fraction was evaluated for antimutagenic potential against direct acting mutagens sodium azide (NaN(3)) and methyl methane sulphonate (MMS) and indirect acting mutagens 2-aminofluorene (2-AF) and benzo(a)pyrene (B(a)P), using Salmonella typhimurium (TA97a, TA98, TA100, and TA102) tester strains. The methanolic fraction showed no sign of mutagenicity at tested concentrations (25-100 microg/plate). Antimutagenic activity was recorded with inhibition of mutagenicity ranging from 10.8% to 83.1% in a concentration dependent manner. The phytochemical analysis by IR, HPLC, GC-MS, and total phenolic assay revealed a high content of phenolic terpenoids. Further, characterization of active principle is needed to understand the mechanism of action and therapeutic efficacy in vivo.