The attraction of necrophagous insects, particularly blow flies, to corpses and carrion is of eco... more The attraction of necrophagous insects, particularly blow flies, to corpses and carrion is of ecological, economic, and agricultural importance, although the mechanisms by which it occurs are not well understood. Much of the published research on blow fly attractants has focused on volatiles emitted from carrion surrogates, but little attention has been given to the possibility that blow fly eggs themselves may emit chemical cues that are responsible for conspecific and heterospecific insect attraction. In this study, the headspace volatiles emitted from eggs representing two aggregated oviposition events that were collected 1 mo apart from two species of the Calliphoridae family (Order: Diptera), Lucilia sericata (Meigen), and Phormia regina (Meigen) were analyzed via solid-phase microextraction-facilitated GC-MS. The volatiles’ profiles were found to be consistent between samples representing the same species, but unique between the two species. Over 100 molecules covering a wide ...
Journal of the California Dental Association, 2014
ABSTRACT Objective: Many plant metabolites and structurally similar derivatives have been identif... more ABSTRACT Objective: Many plant metabolites and structurally similar derivatives have been identified as inhibitors of bacterial biofilm formation and quorum sensing (QS). Previously, we have demonstrated biofilm and QS inhibition using modified cysteines, similar to those produced by the tropical plant Petiveria alliacea. In this study we expanded our compound library to examine structure-activity relationships for biofilm and QS inhibition. Method: Using a microplate-based screening approach, we observed the biofilm formation by three indigenous oral Gram-positive bacteria: Streptococcus mutans UA159, Streptococcus sanguis 10556, and Actinomyces oris MG1. Bacteria were grown in the presence of inhibitory compounds and analyzed using fluorescent staining for biomass and via confocal microscopy. Compounds were also tested in a Vibrio harveyi QS reporter which responds to autoinducer-2 (AI-2) signaling (interspecies) but not acyl-homoserine lactone signaling (intraspecies). Reverse transcriptase real-time PCR and global RNA sequencing (RNAseq) were used to study modified genetic expression in S. mutans UA159 in the presence of select compounds from our library. Result: From our 46 compound library, six were capable of inhibiting biofilm formation in all three species tested at a concentration of 1mM. All six compounds are structurally similar to S-ribosyl homocysteine, the precursor for autoinducer-2 biosynthesis. These compounds also reduced bioluminescence in V. harveyi BB170, indicating inhibition of AI-2 based QS. Gene expression analysis showed distinct down-regulation of genes previously related to quorum sensing and/or biofilm formation in S. mutans. Conclusion: The use of plant-inspired cysteine derivatives to inhibit bacterial virulence may serve as a novel tool to improve oral health. We propose that the compounds used in this study may inhibit biofilm formation by interrupting bacterial communication pathways, particularly in AI-2 biosynthetic reactions. Since our library is derived from eukaryotic (plant) origins, this study may provide initial evidence of interkingdom signaling, which has implications for studies of the human microbiome.
Despite advances made in its therapeutic management, human immunodeficiency virus (HIV) infection... more Despite advances made in its therapeutic management, human immunodeficiency virus (HIV) infection has remained an intractable problem, and complete eradication of the virus an unrealized goal. Experience in the clinical application of combination therapy using a variety of reverse transcriptase and protease inhibitors have revealed a number of challenges, in spite of the observed albeit temporary success in reduction of patient viral loads. Problems with current protocols include poor patient compliance, and the presence of latent reservoirs of virus that ultimately result in the appearance of phenotypic resistance. These considerations necessitate continued research and development into alternative strategies to circumvent the aforementioned problems. One approach to minimizing and/or eliminating the appearance of escape mutants and latent viral reservoirs is the targeting of essential and mutationally intolerant enzymes such as the nucleocapsid protein, which contains two highly conserved zinc knuckles. Concerns have been raised regarding the targeting of this protein, since the ubiquitous occurrence of important mammalian zinc finger proteins implies that drug specificity towards the nucleocapsid protein may be difficult to attain. In this review, strong evidence supporting the hypothesis that this protein can be targeted to the exclusion of other cellular zinc finger proteins is presented. The effects of small molecule induced abrogation of nucleocapsid protein mediated activities, as well as efforts to develop nucleocapsid protein inhibitors as antiretrovirals are also discussed.
Background Hemp and marijuana are the two major varieties of Cannabis sativa. While both contain ... more Background Hemp and marijuana are the two major varieties of Cannabis sativa. While both contain Δ9-tetrahydrocannabinol (THC), the primary psychoactive component of C. sativa, they differ in the amount of THC that they contain. Presently, U.S. federal laws stipulate that C. sativa containing greater than 0.3% THC is classified as marijuana, while plant material that contains less than or equal to 0.3% THC is hemp. Current methods to determine THC content are chromatography-based, which requires extensive sample preparation to render the materials into extracts suitable for sample injection, for complete separation and differentiation of THC from all other analytes present. This can create problems for forensic laboratories due to the increased workload associated with the need to analyze and quantify THC in all C. sativa materials. Method The work presented herein combines direct analysis in real time—high-resolution mass spectrometry (DART-HRMS) and advanced chemometrics to differ...
RATIONALE Classified by the UNODC as a top 20 plant of concern, Piper methysticum (also known as ... more RATIONALE Classified by the UNODC as a top 20 plant of concern, Piper methysticum (also known as Kava) is being increasingly abused recreationally for its mind-altering effects. It is of significant forensic relevance to establish methods to rapidly identify and quantify psychoactive compounds, especially those yet to be scheduled as controlled substances and which have exhibited various noteworthy health concerns. METHODS Direct analysis in real time-high resolution mass spectrometry (DART-HRMS) demonstrated the ability to detect a rangeof kavalactones in Piper methysticum derived products and plant material with no sample preparation. In addition, a validated method using calibration curves developed with a deuterated internal standard was used for the quantification of the psychoactive molecule yangonin in various products. RESULTS DART-HRMS detected the protonated masses of six major kavalactones and three flavokavains in 18 commercial Kava products. A method consistent with FDA validation guidelines was established for the quantification of yangonin in the various complex matrices. Implementation of this method, with an LLOQ of 5 mg/mL, enabled successful quantification of yangonin in 16 Kava products. Concentrations for solid products ranged from 2.71 - 8.99 mg/g, while that for liquid products ranged from 1.03 - 4.59 mg/mL. CONCLUSIONS Rapid identification and quantification of psychoactive small molecules in plant material can be accomplished using a validated DART-HRMS protocol. This work illustrates an approach to qualitative and quantitative analyses of a wide variety of complex matrices derived from plants, and demonstrates that the commercially available products analyzed are P. methysticum derived and do contain psychoactive yangonin at quantifiable levels.
Methods for the accomplishment of small-molecule imaging by mass spectrometry are challenged by t... more Methods for the accomplishment of small-molecule imaging by mass spectrometry are challenged by the need for sample pre-treatment steps such as cryo-sectioning, dehydration, chemical fixation, or application of a matrix or solvent, that must be performed to obtain interpretable spatial distribution data. Furthermore, these steps along with requirements of the mass spectrometer such as high vacuum, can severely limit the range of sample types that can be analyzed by this powerful method. Here, we report the development of a laser ablation-direct analysis in real time imaging mass spectrometry approach which couples a 213 nm Nd:YAG solid state UV laser to a direct analysis in real time ion source and high resolution time-of-flight mass spectrometer. This platform enables facile determination of the spatial distribution of small-molecules spanning a range of polarities in a diversity of sample types, and requires no matrix, vacuum, solvent, or complicated sample pre-treatment steps. It...
<p>For both the onion and <i>P. alliacea</i> alliinases, reaction with a cystei... more <p>For both the onion and <i>P. alliacea</i> alliinases, reaction with a cysteine sulfoxide derivative yields a fleeting sulfenic acid, two molecules of which can condense to give thiosulfinates. The thiosulfinates react further to yield a variety of organosulfur compounds. Compounds <b>1−6</b> from garlic have been found to inhibit <i>luxR</i>- and <i>lasR</i>-based QS systems. The <i>P. alliacea</i> alliinase has been shown to have broad substrate specificity and degrade a variety of cysteine sulfoxide derivatives such as compounds <b>7−11</b>.</p
Three γ-glutamyl dipeptides have been isolated from Petiveria alliacea L. roots. These dipeptides... more Three γ-glutamyl dipeptides have been isolated from Petiveria alliacea L. roots. These dipeptides include (SC2RC7)-γ-glutamyl-S-benzylcysteine together with two diastereomeric sulfoxides, namely (SC2RC7RS)- and (SC2RC7RS)-γ-glutamyl-S-benzylcysteine S-oxides (γ-glutamyl-petiveriins A and B, respectively). Their structures and absolute configurations have been determined by NMR, MALDI-HRMS, IR and CD spectroscopy, and confirmed by comparison with authentic compounds obtained by synthesis.
The attraction of necrophagous insects, particularly blow flies, to corpses and carrion is of eco... more The attraction of necrophagous insects, particularly blow flies, to corpses and carrion is of ecological, economic, and agricultural importance, although the mechanisms by which it occurs are not well understood. Much of the published research on blow fly attractants has focused on volatiles emitted from carrion surrogates, but little attention has been given to the possibility that blow fly eggs themselves may emit chemical cues that are responsible for conspecific and heterospecific insect attraction. In this study, the headspace volatiles emitted from eggs representing two aggregated oviposition events that were collected 1 mo apart from two species of the Calliphoridae family (Order: Diptera), Lucilia sericata (Meigen), and Phormia regina (Meigen) were analyzed via solid-phase microextraction-facilitated GC-MS. The volatiles’ profiles were found to be consistent between samples representing the same species, but unique between the two species. Over 100 molecules covering a wide ...
Journal of the California Dental Association, 2014
ABSTRACT Objective: Many plant metabolites and structurally similar derivatives have been identif... more ABSTRACT Objective: Many plant metabolites and structurally similar derivatives have been identified as inhibitors of bacterial biofilm formation and quorum sensing (QS). Previously, we have demonstrated biofilm and QS inhibition using modified cysteines, similar to those produced by the tropical plant Petiveria alliacea. In this study we expanded our compound library to examine structure-activity relationships for biofilm and QS inhibition. Method: Using a microplate-based screening approach, we observed the biofilm formation by three indigenous oral Gram-positive bacteria: Streptococcus mutans UA159, Streptococcus sanguis 10556, and Actinomyces oris MG1. Bacteria were grown in the presence of inhibitory compounds and analyzed using fluorescent staining for biomass and via confocal microscopy. Compounds were also tested in a Vibrio harveyi QS reporter which responds to autoinducer-2 (AI-2) signaling (interspecies) but not acyl-homoserine lactone signaling (intraspecies). Reverse transcriptase real-time PCR and global RNA sequencing (RNAseq) were used to study modified genetic expression in S. mutans UA159 in the presence of select compounds from our library. Result: From our 46 compound library, six were capable of inhibiting biofilm formation in all three species tested at a concentration of 1mM. All six compounds are structurally similar to S-ribosyl homocysteine, the precursor for autoinducer-2 biosynthesis. These compounds also reduced bioluminescence in V. harveyi BB170, indicating inhibition of AI-2 based QS. Gene expression analysis showed distinct down-regulation of genes previously related to quorum sensing and/or biofilm formation in S. mutans. Conclusion: The use of plant-inspired cysteine derivatives to inhibit bacterial virulence may serve as a novel tool to improve oral health. We propose that the compounds used in this study may inhibit biofilm formation by interrupting bacterial communication pathways, particularly in AI-2 biosynthetic reactions. Since our library is derived from eukaryotic (plant) origins, this study may provide initial evidence of interkingdom signaling, which has implications for studies of the human microbiome.
Despite advances made in its therapeutic management, human immunodeficiency virus (HIV) infection... more Despite advances made in its therapeutic management, human immunodeficiency virus (HIV) infection has remained an intractable problem, and complete eradication of the virus an unrealized goal. Experience in the clinical application of combination therapy using a variety of reverse transcriptase and protease inhibitors have revealed a number of challenges, in spite of the observed albeit temporary success in reduction of patient viral loads. Problems with current protocols include poor patient compliance, and the presence of latent reservoirs of virus that ultimately result in the appearance of phenotypic resistance. These considerations necessitate continued research and development into alternative strategies to circumvent the aforementioned problems. One approach to minimizing and/or eliminating the appearance of escape mutants and latent viral reservoirs is the targeting of essential and mutationally intolerant enzymes such as the nucleocapsid protein, which contains two highly conserved zinc knuckles. Concerns have been raised regarding the targeting of this protein, since the ubiquitous occurrence of important mammalian zinc finger proteins implies that drug specificity towards the nucleocapsid protein may be difficult to attain. In this review, strong evidence supporting the hypothesis that this protein can be targeted to the exclusion of other cellular zinc finger proteins is presented. The effects of small molecule induced abrogation of nucleocapsid protein mediated activities, as well as efforts to develop nucleocapsid protein inhibitors as antiretrovirals are also discussed.
Background Hemp and marijuana are the two major varieties of Cannabis sativa. While both contain ... more Background Hemp and marijuana are the two major varieties of Cannabis sativa. While both contain Δ9-tetrahydrocannabinol (THC), the primary psychoactive component of C. sativa, they differ in the amount of THC that they contain. Presently, U.S. federal laws stipulate that C. sativa containing greater than 0.3% THC is classified as marijuana, while plant material that contains less than or equal to 0.3% THC is hemp. Current methods to determine THC content are chromatography-based, which requires extensive sample preparation to render the materials into extracts suitable for sample injection, for complete separation and differentiation of THC from all other analytes present. This can create problems for forensic laboratories due to the increased workload associated with the need to analyze and quantify THC in all C. sativa materials. Method The work presented herein combines direct analysis in real time—high-resolution mass spectrometry (DART-HRMS) and advanced chemometrics to differ...
RATIONALE Classified by the UNODC as a top 20 plant of concern, Piper methysticum (also known as ... more RATIONALE Classified by the UNODC as a top 20 plant of concern, Piper methysticum (also known as Kava) is being increasingly abused recreationally for its mind-altering effects. It is of significant forensic relevance to establish methods to rapidly identify and quantify psychoactive compounds, especially those yet to be scheduled as controlled substances and which have exhibited various noteworthy health concerns. METHODS Direct analysis in real time-high resolution mass spectrometry (DART-HRMS) demonstrated the ability to detect a rangeof kavalactones in Piper methysticum derived products and plant material with no sample preparation. In addition, a validated method using calibration curves developed with a deuterated internal standard was used for the quantification of the psychoactive molecule yangonin in various products. RESULTS DART-HRMS detected the protonated masses of six major kavalactones and three flavokavains in 18 commercial Kava products. A method consistent with FDA validation guidelines was established for the quantification of yangonin in the various complex matrices. Implementation of this method, with an LLOQ of 5 mg/mL, enabled successful quantification of yangonin in 16 Kava products. Concentrations for solid products ranged from 2.71 - 8.99 mg/g, while that for liquid products ranged from 1.03 - 4.59 mg/mL. CONCLUSIONS Rapid identification and quantification of psychoactive small molecules in plant material can be accomplished using a validated DART-HRMS protocol. This work illustrates an approach to qualitative and quantitative analyses of a wide variety of complex matrices derived from plants, and demonstrates that the commercially available products analyzed are P. methysticum derived and do contain psychoactive yangonin at quantifiable levels.
Methods for the accomplishment of small-molecule imaging by mass spectrometry are challenged by t... more Methods for the accomplishment of small-molecule imaging by mass spectrometry are challenged by the need for sample pre-treatment steps such as cryo-sectioning, dehydration, chemical fixation, or application of a matrix or solvent, that must be performed to obtain interpretable spatial distribution data. Furthermore, these steps along with requirements of the mass spectrometer such as high vacuum, can severely limit the range of sample types that can be analyzed by this powerful method. Here, we report the development of a laser ablation-direct analysis in real time imaging mass spectrometry approach which couples a 213 nm Nd:YAG solid state UV laser to a direct analysis in real time ion source and high resolution time-of-flight mass spectrometer. This platform enables facile determination of the spatial distribution of small-molecules spanning a range of polarities in a diversity of sample types, and requires no matrix, vacuum, solvent, or complicated sample pre-treatment steps. It...
<p>For both the onion and <i>P. alliacea</i> alliinases, reaction with a cystei... more <p>For both the onion and <i>P. alliacea</i> alliinases, reaction with a cysteine sulfoxide derivative yields a fleeting sulfenic acid, two molecules of which can condense to give thiosulfinates. The thiosulfinates react further to yield a variety of organosulfur compounds. Compounds <b>1−6</b> from garlic have been found to inhibit <i>luxR</i>- and <i>lasR</i>-based QS systems. The <i>P. alliacea</i> alliinase has been shown to have broad substrate specificity and degrade a variety of cysteine sulfoxide derivatives such as compounds <b>7−11</b>.</p
Three γ-glutamyl dipeptides have been isolated from Petiveria alliacea L. roots. These dipeptides... more Three γ-glutamyl dipeptides have been isolated from Petiveria alliacea L. roots. These dipeptides include (SC2RC7)-γ-glutamyl-S-benzylcysteine together with two diastereomeric sulfoxides, namely (SC2RC7RS)- and (SC2RC7RS)-γ-glutamyl-S-benzylcysteine S-oxides (γ-glutamyl-petiveriins A and B, respectively). Their structures and absolute configurations have been determined by NMR, MALDI-HRMS, IR and CD spectroscopy, and confirmed by comparison with authentic compounds obtained by synthesis.
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Papers by Rabi Musah