Nam Hoang - Academia.edu (original) (raw)

Papers by Nam Hoang

Molecules

The gas-phase structures of the fruit ester methyl hexanoate, CH3-O-(C=O)-C5H11, have been determ... more The gas-phase structures of the fruit ester methyl hexanoate, CH3-O-(C=O)-C5H11, have been determined using a combination of molecular jet Fourier-transform microwave spectroscopy and quantum chemistry. The microwave spectrum was measured in the frequency range of 3 to 23 GHz. Two conformers were assigned, one with Cs symmetry and the other with C1 symmetry where the γ-carbon atom of the hexyl chain is in a gauche orientation in relation to the carbonyl bond. Splittings of all rotational lines into doublets were observed due to internal rotation of the methoxy methyl group CH3-O, from which torsional barriers of 417 cm−1 and 415 cm−1, respectively, could be deduced. Rotational constants obtained from geometry optimizations at various levels of theory were compared to the experimental values, confirming the soft degree of freedom of the (C=O)-C bond observed for the C1 conformer of shorter methyl alkynoates like methyl butyrate and methyl valerate. Comparison of the barriers to methy...

Antibiotics

Vibrio spp. cause vibriosis in many saltwater and freshwater aquatic species, such as fish, crust... more Vibrio spp. cause vibriosis in many saltwater and freshwater aquatic species, such as fish, crustaceans, and mollusks. Vibrio parahaemolyticus and Vibrio alginolyticus are among the few Vibrio species commonly found in infections in fish. This study aimed at investigating the chemical composition and evaluating the antibacterial activities of Salix babylonica L. The ethyl acetate (LL2) and methanolic (LL3) extracts were used to evaluate the resistance of strains as V. parahaemolyticus LBT6 and VTCC 12233, and two strains of V. alginolyticus, NG20 and ATCC 17749, and compared their efficacy with cefotaxime in order to find an alternative to antibiotics in the treatment of vibriosis. The obtained results show that the LL2 extract, with its major components identified as chrysoeriol, luteolin, and β-sitosterol, exhibited a bacteriostatic effect against all the tested strains. In parallel, the LL3 extract, with the four major compounds luteolin-7-O-β-D-glucopyranoside, salicin, p-hydrox...

L'objectif de cette these est d'evaluer les modifications du metabolisme secondaire des p... more L'objectif de cette these est d'evaluer les modifications du metabolisme secondaire des plantes contaminees aux elements trace metalliques (ETM) et leurs consequences sur les communautes bacteriennes rhizospheriques associees incluant des bacteries presentant des phenotypes de MultiDrug Resistance (MDR). Nous nous sommes focalises sur deux contextes de sols exposes aux metaux : la phytoremediation de sites miniers au Vietnam et la reconversion de sols agricoles contamines par la re-deposition atmospherique d'activites metallurgiques en France. Nos resultats ont mis en evidence que la contamination par differents types de metaux (dont Cu et Pb principalement) a conduit a une alteration de la production des metabolites secondaires des racines, tiges et feuilles de la plante hyperaccumulatrice Pteris vittata et que concernant les racines des tendances similaires dans les changements metaboliques ont pu etre observes dans un autre type de contexte de pollution (Zn et Pb plus...

Journal of Chemistry, 2020

In this study, the relationship between heavy metals (HMs) concentrations in soils and several we... more In this study, the relationship between heavy metals (HMs) concentrations in soils and several weeds including Cyclosorus parasiticus, Dicranopteris linearis, Pityrogramma calomelanos, and Pteris vittata in three mining sites (Cam Gia (Thai Nguyen city), Tan Long (Dong Hy district), and Ha Thuong (Dai Tu district)) in Thai Nguyen province, Vietnam, have been investigated. The levels of HMs varied among soil origins and showed the contaminations of As, Cu, and Pb in soil samples collected in Dong Hy and Dai Tu districts. In addition, the HM distribution and cocontamination phenomena in different soils significantly affected the HM residues and transportation abilities into different species as well as tissues. Moreover, based on the analysis of bioaccumulation factor (BF) and translocation factor (TF), C. parasiticus and D. linearis were found potentially for phytoextraction by roots, while P. calomelanos and P. vittata were suitable for hyperaccumulation in shoots and leaves. Conseq...

Molecules

Multi-drug resistance to antibiotics represents a growing challenge in treating infectious diseas... more Multi-drug resistance to antibiotics represents a growing challenge in treating infectious diseases. Outside the hospital, bacteria with the multi-drug resistance (MDR) phenotype have an increased prevalence in anthropized environments, thus implying that chemical stresses, such as metals, hydrocarbons, organic compounds, etc., are the source of such resistance. There is a developing hypothesis regarding the role of metal contamination in terrestrial and aquatic environments as a selective agent in the proliferation of antibiotic resistance caused by the co-selection of antibiotic and metal resistance genes carried by transmissible plasmids and/or associated with transposons. Efflux pumps are also known to be involved in either antibiotic or metal resistance. In order to deal with these situations, microorganisms use an effective strategy that includes a range of expressions based on biochemical and genetic mechanisms. The data from numerous studies suggest that heavy metal contamin...

Antibiotics

During the process of adapting to metal contamination, plants produce secondary metabolites that ... more During the process of adapting to metal contamination, plants produce secondary metabolites that have the potential to modulate multidrug-resistant (MDR) phenotypes; this is achieved by inhibiting the activity of efflux pumps to reduce the minimum inhibitory concentrations (MICs) of antimicrobial substrates. Our study evaluated the effect of secondary metabolites of belowground parts of Pteris vittata L. and Fallopia japonica, two metal-tolerant plants from northern Vietnam, on six antibiotic-resistant Stenotrophomonas maltophilia strains possessing efflux pump resistance mechanisms that were isolated from soil and clinical samples. The chemical composition of aqueous and dichloromethane (DCM) fractions extracted from P. vittata and F. japonica was determined using UHPLC-DAD-ESI/QTOF analysis. The antibacterial and efflux pump inhibitory activities of the four fractions were evaluated for the six strains (K279a, 0366, BurA1, BurE1, PierC1, and 502) using a microdilution assay at fra...

HAL (Le Centre pour la Communication Scientifique Directe), 2015

Environmental Science and Pollution Research

Biomedical Chromatography, 2021

The objective of this work was the development of a detailed, extensive and reliable database of ... more The objective of this work was the development of a detailed, extensive and reliable database of the metabolomes of P. vittata. Using an UPLC-QqQ-MS/MS system and based on the knowledge of retention time and mass spectral characteristics of an in-house collection of authentic standards, we screened for the presence of a large collection of natural compounds. The database represents 359 authenticated metabolites, comprising 220 primary and 139 secondary metabolites (70 flavonoids, 16 phenylpropanoic acid derivatives, 5 coumarins, 2 stilbenoids, 14 benzoic acids, 9 phenols, 20 alkaloids and 3 terpenoids). Comparison of the accumulation of these compounds in two tissues showed that the aerial parts are enriched in flavonols, whereas the subterranean parts were enriched in anthocyanins. The comprehensive database developed here can be highly beneficial in improving the understanding of the chemical basis of plant therapeutic profile by using multivariate analysis, with a particular example of antioxidant activity.

Applied Soil Ecology, 2018

Miscanthus x giganteus is well known for its ability to grow on metal contaminated soils. However... more Miscanthus x giganteus is well known for its ability to grow on metal contaminated soils. However, little is known concerning its metabolic changes including secondary metabolites under metal pressure. These changes might impact the diversity and function of associated bacterial populations. Thus, this study focused on evaluating the modifications of secondary metabolism production of M. x giganteus belowground parts (i.e. roots and rhizomes), and of rhizosphere bacterial communities under diverse contaminated conditions. Samples of M. x giganteus roots and rhizomes were collected from 3 sites exhibiting a gradient of metal pollution and extracted with MeOH:H 2 O. Secondary metabolic profiles of root and rhizome extracts were analyzed by UHPLC/DAD/ESI-QTOF. The structure and diversity of rhizosphere communities were studied using high-throughput sequencing. The results showed out the modification of the secondary metabolic profiles of M. x giganteus belowground parts, when they are grown on diversely contaminated soils. Major increased metabolites were identified as 3-and 5-feruloylquinic acid whereas decreased compound was 4-feruloylquinic acid. Metal contamination also led to a shift in rhizosphere bacterial composition and structure as well as the selection of some opportunistic pathogenic genera such as Pseudomonas or Stenotrophomonas but there was only a weak effect on the bacterial diversity and richness. In the context of a moderate metal contamination in agricultural soil slight changes were seen in the secondary metabolic profiles of M. x giganteus roots and rhizomes and their associated bacterial communities. Whether the metal-induced changes allow plants to recruit beneficial microbes that favor the adaptation process to this stress need to be further investigated.

Environmental science and pollution research international, Jan 31, 2017

Plants adapt to metal stress by modifying their metabolism including the production of secondary ... more Plants adapt to metal stress by modifying their metabolism including the production of secondary metabolites in plant tissues. Such changes may impact the diversity and functions of plant associated microbial communities. Our study aimed to evaluate the influence of metals on the secondary metabolism of plants and the indirect impact on rhizosphere bacterial communities. We then compared the secondary metabolites of the hyperaccumulator Pteris vittata L. collected from a contaminated mining site to a non-contaminated site in Vietnam and identified the discriminant metabolites. Our data showed a significant increase in chlorogenic acid derivatives and A-type procyanidin in plant roots at the contaminated site. We hypothesized that the intensive production of these compounds could be part of the antioxidant defense mechanism in response to metals. In parallel, the structure and diversity of bulk soil and rhizosphere communities was studied using high-throughput sequencing. The results...

Molecules

The gas-phase structures of the fruit ester methyl hexanoate, CH3-O-(C=O)-C5H11, have been determ... more The gas-phase structures of the fruit ester methyl hexanoate, CH3-O-(C=O)-C5H11, have been determined using a combination of molecular jet Fourier-transform microwave spectroscopy and quantum chemistry. The microwave spectrum was measured in the frequency range of 3 to 23 GHz. Two conformers were assigned, one with Cs symmetry and the other with C1 symmetry where the γ-carbon atom of the hexyl chain is in a gauche orientation in relation to the carbonyl bond. Splittings of all rotational lines into doublets were observed due to internal rotation of the methoxy methyl group CH3-O, from which torsional barriers of 417 cm−1 and 415 cm−1, respectively, could be deduced. Rotational constants obtained from geometry optimizations at various levels of theory were compared to the experimental values, confirming the soft degree of freedom of the (C=O)-C bond observed for the C1 conformer of shorter methyl alkynoates like methyl butyrate and methyl valerate. Comparison of the barriers to methy...

Antibiotics

Vibrio spp. cause vibriosis in many saltwater and freshwater aquatic species, such as fish, crust... more Vibrio spp. cause vibriosis in many saltwater and freshwater aquatic species, such as fish, crustaceans, and mollusks. Vibrio parahaemolyticus and Vibrio alginolyticus are among the few Vibrio species commonly found in infections in fish. This study aimed at investigating the chemical composition and evaluating the antibacterial activities of Salix babylonica L. The ethyl acetate (LL2) and methanolic (LL3) extracts were used to evaluate the resistance of strains as V. parahaemolyticus LBT6 and VTCC 12233, and two strains of V. alginolyticus, NG20 and ATCC 17749, and compared their efficacy with cefotaxime in order to find an alternative to antibiotics in the treatment of vibriosis. The obtained results show that the LL2 extract, with its major components identified as chrysoeriol, luteolin, and β-sitosterol, exhibited a bacteriostatic effect against all the tested strains. In parallel, the LL3 extract, with the four major compounds luteolin-7-O-β-D-glucopyranoside, salicin, p-hydrox...

L'objectif de cette these est d'evaluer les modifications du metabolisme secondaire des p... more L'objectif de cette these est d'evaluer les modifications du metabolisme secondaire des plantes contaminees aux elements trace metalliques (ETM) et leurs consequences sur les communautes bacteriennes rhizospheriques associees incluant des bacteries presentant des phenotypes de MultiDrug Resistance (MDR). Nous nous sommes focalises sur deux contextes de sols exposes aux metaux : la phytoremediation de sites miniers au Vietnam et la reconversion de sols agricoles contamines par la re-deposition atmospherique d'activites metallurgiques en France. Nos resultats ont mis en evidence que la contamination par differents types de metaux (dont Cu et Pb principalement) a conduit a une alteration de la production des metabolites secondaires des racines, tiges et feuilles de la plante hyperaccumulatrice Pteris vittata et que concernant les racines des tendances similaires dans les changements metaboliques ont pu etre observes dans un autre type de contexte de pollution (Zn et Pb plus...

Journal of Chemistry, 2020

In this study, the relationship between heavy metals (HMs) concentrations in soils and several we... more In this study, the relationship between heavy metals (HMs) concentrations in soils and several weeds including Cyclosorus parasiticus, Dicranopteris linearis, Pityrogramma calomelanos, and Pteris vittata in three mining sites (Cam Gia (Thai Nguyen city), Tan Long (Dong Hy district), and Ha Thuong (Dai Tu district)) in Thai Nguyen province, Vietnam, have been investigated. The levels of HMs varied among soil origins and showed the contaminations of As, Cu, and Pb in soil samples collected in Dong Hy and Dai Tu districts. In addition, the HM distribution and cocontamination phenomena in different soils significantly affected the HM residues and transportation abilities into different species as well as tissues. Moreover, based on the analysis of bioaccumulation factor (BF) and translocation factor (TF), C. parasiticus and D. linearis were found potentially for phytoextraction by roots, while P. calomelanos and P. vittata were suitable for hyperaccumulation in shoots and leaves. Conseq...

Molecules

Multi-drug resistance to antibiotics represents a growing challenge in treating infectious diseas... more Multi-drug resistance to antibiotics represents a growing challenge in treating infectious diseases. Outside the hospital, bacteria with the multi-drug resistance (MDR) phenotype have an increased prevalence in anthropized environments, thus implying that chemical stresses, such as metals, hydrocarbons, organic compounds, etc., are the source of such resistance. There is a developing hypothesis regarding the role of metal contamination in terrestrial and aquatic environments as a selective agent in the proliferation of antibiotic resistance caused by the co-selection of antibiotic and metal resistance genes carried by transmissible plasmids and/or associated with transposons. Efflux pumps are also known to be involved in either antibiotic or metal resistance. In order to deal with these situations, microorganisms use an effective strategy that includes a range of expressions based on biochemical and genetic mechanisms. The data from numerous studies suggest that heavy metal contamin...

Antibiotics

During the process of adapting to metal contamination, plants produce secondary metabolites that ... more During the process of adapting to metal contamination, plants produce secondary metabolites that have the potential to modulate multidrug-resistant (MDR) phenotypes; this is achieved by inhibiting the activity of efflux pumps to reduce the minimum inhibitory concentrations (MICs) of antimicrobial substrates. Our study evaluated the effect of secondary metabolites of belowground parts of Pteris vittata L. and Fallopia japonica, two metal-tolerant plants from northern Vietnam, on six antibiotic-resistant Stenotrophomonas maltophilia strains possessing efflux pump resistance mechanisms that were isolated from soil and clinical samples. The chemical composition of aqueous and dichloromethane (DCM) fractions extracted from P. vittata and F. japonica was determined using UHPLC-DAD-ESI/QTOF analysis. The antibacterial and efflux pump inhibitory activities of the four fractions were evaluated for the six strains (K279a, 0366, BurA1, BurE1, PierC1, and 502) using a microdilution assay at fra...

HAL (Le Centre pour la Communication Scientifique Directe), 2015

Environmental Science and Pollution Research

Biomedical Chromatography, 2021

The objective of this work was the development of a detailed, extensive and reliable database of ... more The objective of this work was the development of a detailed, extensive and reliable database of the metabolomes of P. vittata. Using an UPLC-QqQ-MS/MS system and based on the knowledge of retention time and mass spectral characteristics of an in-house collection of authentic standards, we screened for the presence of a large collection of natural compounds. The database represents 359 authenticated metabolites, comprising 220 primary and 139 secondary metabolites (70 flavonoids, 16 phenylpropanoic acid derivatives, 5 coumarins, 2 stilbenoids, 14 benzoic acids, 9 phenols, 20 alkaloids and 3 terpenoids). Comparison of the accumulation of these compounds in two tissues showed that the aerial parts are enriched in flavonols, whereas the subterranean parts were enriched in anthocyanins. The comprehensive database developed here can be highly beneficial in improving the understanding of the chemical basis of plant therapeutic profile by using multivariate analysis, with a particular example of antioxidant activity.

Applied Soil Ecology, 2018

Miscanthus x giganteus is well known for its ability to grow on metal contaminated soils. However... more Miscanthus x giganteus is well known for its ability to grow on metal contaminated soils. However, little is known concerning its metabolic changes including secondary metabolites under metal pressure. These changes might impact the diversity and function of associated bacterial populations. Thus, this study focused on evaluating the modifications of secondary metabolism production of M. x giganteus belowground parts (i.e. roots and rhizomes), and of rhizosphere bacterial communities under diverse contaminated conditions. Samples of M. x giganteus roots and rhizomes were collected from 3 sites exhibiting a gradient of metal pollution and extracted with MeOH:H 2 O. Secondary metabolic profiles of root and rhizome extracts were analyzed by UHPLC/DAD/ESI-QTOF. The structure and diversity of rhizosphere communities were studied using high-throughput sequencing. The results showed out the modification of the secondary metabolic profiles of M. x giganteus belowground parts, when they are grown on diversely contaminated soils. Major increased metabolites were identified as 3-and 5-feruloylquinic acid whereas decreased compound was 4-feruloylquinic acid. Metal contamination also led to a shift in rhizosphere bacterial composition and structure as well as the selection of some opportunistic pathogenic genera such as Pseudomonas or Stenotrophomonas but there was only a weak effect on the bacterial diversity and richness. In the context of a moderate metal contamination in agricultural soil slight changes were seen in the secondary metabolic profiles of M. x giganteus roots and rhizomes and their associated bacterial communities. Whether the metal-induced changes allow plants to recruit beneficial microbes that favor the adaptation process to this stress need to be further investigated.

Environmental science and pollution research international, Jan 31, 2017

Plants adapt to metal stress by modifying their metabolism including the production of secondary ... more Plants adapt to metal stress by modifying their metabolism including the production of secondary metabolites in plant tissues. Such changes may impact the diversity and functions of plant associated microbial communities. Our study aimed to evaluate the influence of metals on the secondary metabolism of plants and the indirect impact on rhizosphere bacterial communities. We then compared the secondary metabolites of the hyperaccumulator Pteris vittata L. collected from a contaminated mining site to a non-contaminated site in Vietnam and identified the discriminant metabolites. Our data showed a significant increase in chlorogenic acid derivatives and A-type procyanidin in plant roots at the contaminated site. We hypothesized that the intensive production of these compounds could be part of the antioxidant defense mechanism in response to metals. In parallel, the structure and diversity of bulk soil and rhizosphere communities was studied using high-throughput sequencing. The results...