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Three new compounds, i.e. stenophyllols A-C (1-3), were isolated from the rhizome of Boesenbergia stenophylla. The structures were determined by spectroscopic analysis (UV, IR, NMR and HRESIMS). In-vitro neuroblastoma cell viability assay showed stenophyllol A (1) was able to reduce the N2A cell viability to 20% within 24 h.
Phoebe Sussana Primus; Muhammad Hazran Ismail; Nabila Elyana Adnan; Carol Hsin-Yi Wu; Chao-Lin Kao; Yeun-Mun Choo. Stenophyllols A-C, new compounds from Boesenbergia stenophylla. Journal of Asian Natural Products Research 2021, 1 -7.
AMA StylePhoebe Sussana Primus, Muhammad Hazran Ismail, Nabila Elyana Adnan, Carol Hsin-Yi Wu, Chao-Lin Kao, Yeun-Mun Choo. Stenophyllols A-C, new compounds from Boesenbergia stenophylla. Journal of Asian Natural Products Research. 2021; ():1-7.
Chicago/Turabian StylePhoebe Sussana Primus; Muhammad Hazran Ismail; Nabila Elyana Adnan; Carol Hsin-Yi Wu; Chao-Lin Kao; Yeun-Mun Choo. 2021. "Stenophyllols A-C, new compounds from Boesenbergia stenophylla." Journal of Asian Natural Products Research , no. : 1-7.
A novel mass spectrometry detection technique based on a multi-period and multi- experiment (MRM-EPI-MRM3) with library matching in a single run for fast and rapid screening and identification of amphetamine type stimulants (ATS) related drugs in whole blood, urine and dried blood stain was developed and validated. The ATS-related drugs analyzed in this study include ephedrine, pseudoephedrine, amphetamine, methamphetamine, MDMA (3,4-Methylenedioxymethamphetamine), MDA (3,4-Methylenedioxyamphetamine), MDEA (3,4-Methylenedioxy-N-ethylamphetamine) and phentermine. The relative standard deviation for inter and intraday was less than 15% while recoveries ranged from 80% to 120% for all three matrices, i.e., whole blood, urine and dried blood stain. All compounds gave library matching percentage of more than 85% based on the purity. This method was proven to be simple and robust, and provide high confident results complemented with library matching confirmation.
Fathiah A Zubaidi; Yeun Mun Choo; Guan-Huat Tan; Hamimah Abd Hamid; Yap Ken Choy. A Novel Liquid Chromatography Tandem Mass Spectrometry Technique using Multi-Period-Multi-Experiment of MRM-EPI-MRM3 with Library Matching for Simultaneous Determination of Amphetamine Type Stimulants Related Drugs in Whole Blood, Urine and Dried Blood Stain (DBS)—Application to Forensic Toxicology Cases in Malaysia. Journal of Analytical Toxicology 2019, 43, 528 -535.
AMA StyleFathiah A Zubaidi, Yeun Mun Choo, Guan-Huat Tan, Hamimah Abd Hamid, Yap Ken Choy. A Novel Liquid Chromatography Tandem Mass Spectrometry Technique using Multi-Period-Multi-Experiment of MRM-EPI-MRM3 with Library Matching for Simultaneous Determination of Amphetamine Type Stimulants Related Drugs in Whole Blood, Urine and Dried Blood Stain (DBS)—Application to Forensic Toxicology Cases in Malaysia. Journal of Analytical Toxicology. 2019; 43 (7):528-535.
Chicago/Turabian StyleFathiah A Zubaidi; Yeun Mun Choo; Guan-Huat Tan; Hamimah Abd Hamid; Yap Ken Choy. 2019. "A Novel Liquid Chromatography Tandem Mass Spectrometry Technique using Multi-Period-Multi-Experiment of MRM-EPI-MRM3 with Library Matching for Simultaneous Determination of Amphetamine Type Stimulants Related Drugs in Whole Blood, Urine and Dried Blood Stain (DBS)—Application to Forensic Toxicology Cases in Malaysia." Journal of Analytical Toxicology 43, no. 7: 528-535.
Mycotoxins are common food contaminants which cause poisoning and severe health risks to humans and animals. The present study applied chemometric approach in liquid chromatography-tandem mass spectrometry (LC-MS/MS) optimization for simultaneous determination of mycotoxins, i.e., aflatoxins B1, B2, G1, and G2, and ochratoxin A. The validated quick, easy, cheap, effective, rugged, and safe (QuEChERS)-LC-MS/MS method was used to study the occurrence of mycotoxins in 120 food matrices. The recovery ranges from 81.94% to 101.67% with relative standard deviation (RSD) lesser than 11%. Through the developed method, aflatoxins were detected in raisin, pistachio, peanut, wheat flour, spice, and chili samples with concentration ranges from 0.45 to 16.93 µg/kg. Trace concentration of ochratoxin A was found in wheat flour and peanut samples which ranged from 1.2 to 3.53 µg/kg. Some of the tested food samples contained mycotoxins of above the European legal maximum limit.
Ali Mohamed Ali Alsharif; Yeun-Mun Choo; Guan-Huat Tan. Detection of Five Mycotoxins in Different Food Matrices in the Malaysian Market by Using Validated Liquid Chromatography Electrospray Ionization Triple Quadrupole Mass Spectrometry. Toxins 2019, 11, 196 .
AMA StyleAli Mohamed Ali Alsharif, Yeun-Mun Choo, Guan-Huat Tan. Detection of Five Mycotoxins in Different Food Matrices in the Malaysian Market by Using Validated Liquid Chromatography Electrospray Ionization Triple Quadrupole Mass Spectrometry. Toxins. 2019; 11 (4):196.
Chicago/Turabian StyleAli Mohamed Ali Alsharif; Yeun-Mun Choo; Guan-Huat Tan. 2019. "Detection of Five Mycotoxins in Different Food Matrices in the Malaysian Market by Using Validated Liquid Chromatography Electrospray Ionization Triple Quadrupole Mass Spectrometry." Toxins 11, no. 4: 196.
A modified hollow-fiber-supported dispersive liquid-liquid microextraction (HF-DLLME) method was developed for the determination of aflatoxins and ochratoxin A in food samples. The various parameters affecting the efficiency of extraction, such as pH, salt addition, extraction time, stirring rate, desorption time, type and volume of extractant and disperser solvents were carefully studied and optimized using two step strategies. The linearity of the evaluated results was 0.1 to 30 μg L−1 for aflatoxins and 0.1 to 20 μg L−1 for ochratoxin A, with regression coefficients (R2) exceeding 0.9990. The precision was satisfactory with relative standard deviation values less than 11%. The method accuracy was within the recommended range from 70% to 120% and analyte accuracy between 83% and 101%. The limits of detection and quantification were in the range from 0.04 to 0.06 μg L−1 and 0.08 to 0.13 μg L−1, respectively, for multi-aflatoxins, and 0.02 to 0.04 µg L−1 and 0.08 to 0.10 µg L−1, respectively, for ochratoxin A. The developed method was successfully applied for the determination of mycotoxins in food samples.
Ali Mohamed Ali Alsharif; Yeun-Mun Choo; Guan Huat Tan; Lukman Bola Abdulra’Uf. Determination of Mycotoxins Using Hollow Fiber Dispersive Liquid–Liquid–Microextraction (HF-DLLME) Prior to High-Performance Liquid Chromatography – Tandem Mass Spectrometry (HPLC - MS/MS). Analytical Letters 2019, 52, 1976 -1990.
AMA StyleAli Mohamed Ali Alsharif, Yeun-Mun Choo, Guan Huat Tan, Lukman Bola Abdulra’Uf. Determination of Mycotoxins Using Hollow Fiber Dispersive Liquid–Liquid–Microextraction (HF-DLLME) Prior to High-Performance Liquid Chromatography – Tandem Mass Spectrometry (HPLC - MS/MS). Analytical Letters. 2019; 52 (12):1976-1990.
Chicago/Turabian StyleAli Mohamed Ali Alsharif; Yeun-Mun Choo; Guan Huat Tan; Lukman Bola Abdulra’Uf. 2019. "Determination of Mycotoxins Using Hollow Fiber Dispersive Liquid–Liquid–Microextraction (HF-DLLME) Prior to High-Performance Liquid Chromatography – Tandem Mass Spectrometry (HPLC - MS/MS)." Analytical Letters 52, no. 12: 1976-1990.
Methamphetamine (MA) and phentermine (PTM) are critical isomeric compounds that often coexist in biological specimen in toxicology cases which have similar nominal mass. The dependency of high-resolution mass spectrometer and special chiral stationary phase column for separation of isomeric compound impedes screening throughput especially in meeting high sampling demand. In the absence of such equipment for identification, we introduce the flow injection analysis (FIA)-MRM3 technique and demonstrated its capabilities for quick identification of both isomeric compounds without liquid chromatography (LC) separation through the addition of selectivity criteria in the MRM3 mode. 20 to 100 ng/mL of MA and PTM, respectively, in whole blood sample (WBS) and dried blood stain (DBS) were used to develop the method for the identification and relative quantification. Twenty whole blood samples which were reported positive of the drugs were randomly selected and were individually stained onto the Flinders Technology Associates (FTA) card for DBS study. The peaks from the two isomeric compounds were successfully discerned for all the tested specimens using the FIA-MRM3 spectrometry technique. The limit of detection (LOD) and limit of quantification (LOQ) for MA and PTM were comparable to normal liquid chromatography-tandem mass spectrometry runs at 2.23 and 2.07 ng/mL, respectively, for WBS (n = 30). For DBS, the LOD and LOQ were 3.40 and 2.86 ng/mL, respectively. The accuracy and inter-day precision for DBS and WBS were in the range of 99.97–111.19% and 7.17–9.55%, respectively. These results demonstrated that the technique is highly adoptable in the screening of isomeric compounds of similar masses in a simple and rapid analysis.
Fathiah A Zubaidi; Yeun-Mun Choo; Guan-Huat Tan; P Myron; Cs Cornelia. High-throughput flow injection analysis-MRM3 (FIA-MRM3) spectrometry for alternative fast screening of the isomeric methamphetamine and phentermine in blood for forensic toxicology cases in Malaysia. Toxicology Research and Application 2019, 3, 1 .
AMA StyleFathiah A Zubaidi, Yeun-Mun Choo, Guan-Huat Tan, P Myron, Cs Cornelia. High-throughput flow injection analysis-MRM3 (FIA-MRM3) spectrometry for alternative fast screening of the isomeric methamphetamine and phentermine in blood for forensic toxicology cases in Malaysia. Toxicology Research and Application. 2019; 3 ():1.
Chicago/Turabian StyleFathiah A Zubaidi; Yeun-Mun Choo; Guan-Huat Tan; P Myron; Cs Cornelia. 2019. "High-throughput flow injection analysis-MRM3 (FIA-MRM3) spectrometry for alternative fast screening of the isomeric methamphetamine and phentermine in blood for forensic toxicology cases in Malaysia." Toxicology Research and Application 3, no. : 1.
Nabila Elyana Adnan; Nur Atiqah Mohd Nasuha; Zanariah Abdullah; Yeun-Mun Choo; Hairul Anuar Tajuddin. Isolation and Photophysical Properties of Di- and Tri-substituted Natural Anthraquinones from Malaysian Morinda citrifolia. Sains Malaysiana 2018, 47, 903 -908.
AMA StyleNabila Elyana Adnan, Nur Atiqah Mohd Nasuha, Zanariah Abdullah, Yeun-Mun Choo, Hairul Anuar Tajuddin. Isolation and Photophysical Properties of Di- and Tri-substituted Natural Anthraquinones from Malaysian Morinda citrifolia. Sains Malaysiana. 2018; 47 (5):903-908.
Chicago/Turabian StyleNabila Elyana Adnan; Nur Atiqah Mohd Nasuha; Zanariah Abdullah; Yeun-Mun Choo; Hairul Anuar Tajuddin. 2018. "Isolation and Photophysical Properties of Di- and Tri-substituted Natural Anthraquinones from Malaysian Morinda citrifolia." Sains Malaysiana 47, no. 5: 903-908.
Siti Rabeah Fadzil; Ann-Chee Yap; Yeun-Mun Choo. A New Cyclopentylidene and Other Chemical Constituents from Malaysian Crotalaria pallida. Sains Malaysiana 2017, 46, 1581 -1586.
AMA StyleSiti Rabeah Fadzil, Ann-Chee Yap, Yeun-Mun Choo. A New Cyclopentylidene and Other Chemical Constituents from Malaysian Crotalaria pallida. Sains Malaysiana. 2017; 46 (9):1581-1586.
Chicago/Turabian StyleSiti Rabeah Fadzil; Ann-Chee Yap; Yeun-Mun Choo. 2017. "A New Cyclopentylidene and Other Chemical Constituents from Malaysian Crotalaria pallida." Sains Malaysiana 46, no. 9: 1581-1586.
Enterobacter cloacae is a highly pathogenic Gram-negative proteobacterium which is responsible for a wide array of infections. In the present study, the fermentation culture of E. cloacae has yielded one new oxolane compound, Rimboxo (1) in addition to three known compounds, i.e. Maculosine (2), phenylacetic acid (3) and methyl myristate (4). These compounds were isolated and characterised using extensive chromatographic and spectroscopic methods, and were subjected to cytotoxicity evaluations.
Ann-Chee Yap; Kok-Gan Chan; Kae-Shin Sim; Yeun-Mun Choo. A new oxolane fromEnterobacter cloacae. Natural Product Research 2015, 30, 783 -788.
AMA StyleAnn-Chee Yap, Kok-Gan Chan, Kae-Shin Sim, Yeun-Mun Choo. A new oxolane fromEnterobacter cloacae. Natural Product Research. 2015; 30 (7):783-788.
Chicago/Turabian StyleAnn-Chee Yap; Kok-Gan Chan; Kae-Shin Sim; Yeun-Mun Choo. 2015. "A new oxolane fromEnterobacter cloacae." Natural Product Research 30, no. 7: 783-788.
Minoru Isobe; Atsushi Nishida; Yeun-Mun Choo; Noorsaadah Abd. Rahman; Poonsakdi Ploypradith; Somsak Ruchirawat; Guo-Qiang Lin; Ang Li; Zhu-Jun Yao; Biing-Jiun Uang; Chun-Chen Liao; Pauline Chiu; Byeong Moon Kim; Teck Peng Loh. The Last and Next Decades of the Asian Core Program on Cutting-Edge Organic Chemistry in Asia. Chemistry - An Asian Journal 2015, 10, 790 -804.
AMA StyleMinoru Isobe, Atsushi Nishida, Yeun-Mun Choo, Noorsaadah Abd. Rahman, Poonsakdi Ploypradith, Somsak Ruchirawat, Guo-Qiang Lin, Ang Li, Zhu-Jun Yao, Biing-Jiun Uang, Chun-Chen Liao, Pauline Chiu, Byeong Moon Kim, Teck Peng Loh. The Last and Next Decades of the Asian Core Program on Cutting-Edge Organic Chemistry in Asia. Chemistry - An Asian Journal. 2015; 10 (4):790-804.
Chicago/Turabian StyleMinoru Isobe; Atsushi Nishida; Yeun-Mun Choo; Noorsaadah Abd. Rahman; Poonsakdi Ploypradith; Somsak Ruchirawat; Guo-Qiang Lin; Ang Li; Zhu-Jun Yao; Biing-Jiun Uang; Chun-Chen Liao; Pauline Chiu; Byeong Moon Kim; Teck Peng Loh. 2015. "The Last and Next Decades of the Asian Core Program on Cutting-Edge Organic Chemistry in Asia." Chemistry - An Asian Journal 10, no. 4: 790-804.
Ann-Chee Yap; Wuen-Yew Teoh; Kok-Gan Chan; Kae-Shin Sim; Yeun-Mun Choo. A new oxathiolane from Enterobacter cloacae. Natural Product Research 2014, 29, 722 -726.
AMA StyleAnn-Chee Yap, Wuen-Yew Teoh, Kok-Gan Chan, Kae-Shin Sim, Yeun-Mun Choo. A new oxathiolane from Enterobacter cloacae. Natural Product Research. 2014; 29 (8):722-726.
Chicago/Turabian StyleAnn-Chee Yap; Wuen-Yew Teoh; Kok-Gan Chan; Kae-Shin Sim; Yeun-Mun Choo. 2014. "A new oxathiolane from Enterobacter cloacae." Natural Product Research 29, no. 8: 722-726.
Homocysteine and methylmalonic acid are important biomarkers for diseases associated with an impaired central nervous system (CNS). A new chemoassay utilizing coumarin-based fluorescent probe 1 to detect the levels of homocysteine is successfully implemented using Parkinson's disease (PD) patients' blood serum. In addition, a rapid identification of homocysteine and methylmalonic acid levels in blood serum of PD patients was also performed using the liquid chromatography-mass spectrometry (LC-MS). The results obtained from both analyses were in agreement. The new chemoassay utilizing coumarin-based fluorescent probe 1 offers a cost- and time-effective method to identify the biomarkers in CNS patients.
Ann-Chee Yap; Ummi Affah Mahamad; Shen-Yang Lim; Hae-Jo Kim; Yeun-Mun Choo. A Coumarin-Based Fluorescent Probe as a Central Nervous System Disease Biomarker. Sensors 2014, 14, 21140 -21150.
AMA StyleAnn-Chee Yap, Ummi Affah Mahamad, Shen-Yang Lim, Hae-Jo Kim, Yeun-Mun Choo. A Coumarin-Based Fluorescent Probe as a Central Nervous System Disease Biomarker. Sensors. 2014; 14 (11):21140-21150.
Chicago/Turabian StyleAnn-Chee Yap; Ummi Affah Mahamad; Shen-Yang Lim; Hae-Jo Kim; Yeun-Mun Choo. 2014. "A Coumarin-Based Fluorescent Probe as a Central Nervous System Disease Biomarker." Sensors 14, no. 11: 21140-21150.
Bacterial cell-to-cell communication (quorum sensing) refers to the regulation of bacterial gene expression in response to changes in microbial population density. Quorum sensing bacteria produce, release and respond to chemical signal molecules called autoinducers. Bacteria use two types of autoinducers, namely autoinducer-1 (AI-1) and autoinducer-2 (AI-2) where the former are N-acylhomoserine lactones and the latter is a product of the luxS gene. Most of the reported literatures show that the majority of oral bacteria use AI-2 for quorum sensing but rarely the AI-1 system. Here we report the isolation of Pseudomonas putida strain T2-2 from the oral cavity. Using high resolution mass spectrometry, it is shown that this isolate produced N-octanoylhomoserine lactone (C8-HSL) and N-dodecanoylhomoserine lactone (C12-HSL) molecules. This is the first report of the finding of quorum sensing of P. putida strain T2-2 isolated from the human tongue surface and their quorum sensing molecules were identified.
Jian-Woon Chen; Shenyang Chin; Kok Keng Tee; Wai-Fong Yin; Yeun Mun Choo; Kok-Gan Chan. N-acyl Homoserine Lactone-Producing Pseudomonas putida Strain T2-2 from Human Tongue Surface. Sensors 2013, 13, 13192 -13203.
AMA StyleJian-Woon Chen, Shenyang Chin, Kok Keng Tee, Wai-Fong Yin, Yeun Mun Choo, Kok-Gan Chan. N-acyl Homoserine Lactone-Producing Pseudomonas putida Strain T2-2 from Human Tongue Surface. Sensors. 2013; 13 (10):13192-13203.
Chicago/Turabian StyleJian-Woon Chen; Shenyang Chin; Kok Keng Tee; Wai-Fong Yin; Yeun Mun Choo; Kok-Gan Chan. 2013. "N-acyl Homoserine Lactone-Producing Pseudomonas putida Strain T2-2 from Human Tongue Surface." Sensors 13, no. 10: 13192-13203.
Takumi Yamaguchi; Yukiko Kamiya; Yeun Mun Choo; Sayoko Yamamoto; Koichi Kato. Terminal Spin Labeling of a High-mannose-type Oligosaccharide for Quantitative NMR Analysis of Its Dynamic Conformation. Chemistry Letters 2013, 42, 544 -546.
AMA StyleTakumi Yamaguchi, Yukiko Kamiya, Yeun Mun Choo, Sayoko Yamamoto, Koichi Kato. Terminal Spin Labeling of a High-mannose-type Oligosaccharide for Quantitative NMR Analysis of Its Dynamic Conformation. Chemistry Letters. 2013; 42 (5):544-546.
Chicago/Turabian StyleTakumi Yamaguchi; Yukiko Kamiya; Yeun Mun Choo; Sayoko Yamamoto; Koichi Kato. 2013. "Terminal Spin Labeling of a High-mannose-type Oligosaccharide for Quantitative NMR Analysis of Its Dynamic Conformation." Chemistry Letters 42, no. 5: 544-546.
Ann-Chee Yap; Yeun-Mun Choo. Phytochemical Studies of Malaysian Crotalaria Mucronata. The Open Conference Proceedings Journal 2013, 4, 143 -143.
AMA StyleAnn-Chee Yap, Yeun-Mun Choo. Phytochemical Studies of Malaysian Crotalaria Mucronata. The Open Conference Proceedings Journal. 2013; 4 (1):143-143.
Chicago/Turabian StyleAnn-Chee Yap; Yeun-Mun Choo. 2013. "Phytochemical Studies of Malaysian Crotalaria Mucronata." The Open Conference Proceedings Journal 4, no. 1: 143-143.
Nortina Shahrizaila; Ummi Affah Mahamad; Ann-Chee Yap; Yeun-Mun Choo; Connie Marras; Shen-Yang Lim. Is chronic levodopa therapy associated with distal symmetric polyneuropathy in Parkinson's disease? Parkinsonism & Related Disorders 2013, 19, 391 -393.
AMA StyleNortina Shahrizaila, Ummi Affah Mahamad, Ann-Chee Yap, Yeun-Mun Choo, Connie Marras, Shen-Yang Lim. Is chronic levodopa therapy associated with distal symmetric polyneuropathy in Parkinson's disease? Parkinsonism & Related Disorders. 2013; 19 (3):391-393.
Chicago/Turabian StyleNortina Shahrizaila; Ummi Affah Mahamad; Ann-Chee Yap; Yeun-Mun Choo; Connie Marras; Shen-Yang Lim. 2013. "Is chronic levodopa therapy associated with distal symmetric polyneuropathy in Parkinson's disease?" Parkinsonism & Related Disorders 19, no. 3: 391-393.
We report the production and degradation of quorum sensing N-acyl-homoserine lactones by bacteria isolated from Malaysian montane forest soil. Phylogenetic analysis indicated that these isolates clustered closely to the genera of Arthrobacter, Bacillus and Pseudomonas. Quorum quenching activity was detected in six isolates of these three genera by using a series of bioassays and rapid resolution liquid chromatography analysis. Biosensor screening and high resolution liquid chromatography-mass spectrometry analysis revealed the production of N-dodecanoyl-L-homoserine lactone (C12-HSL) by Pseudomonas frederiksbergensis (isolate BT9). In addition to degradation of a wide range of N-acyl-homoserine lactones, Arthrobacter and Pseudomonas spp. also degraded p-coumaroyl-homoserine lactone. To the best of our knowledge, this is the first documentation of Arthrobacter and Pseudomonas spp. capable of degrading p-coumaroyl-homoserine lactone and the production of C12-HSL by P. frederiksbergensis.
Teik-Min Chong; Chong-Lek Koh; Choon-Kook Sam; Yeun-Mun Choo; Wai-Fong Yin; Kok-Gan Chan. Characterization of Quorum Sensing and Quorum Quenching Soil Bacteria Isolated from Malaysian Tropical Montane Forest. Sensors 2012, 12, 4846 -4859.
AMA StyleTeik-Min Chong, Chong-Lek Koh, Choon-Kook Sam, Yeun-Mun Choo, Wai-Fong Yin, Kok-Gan Chan. Characterization of Quorum Sensing and Quorum Quenching Soil Bacteria Isolated from Malaysian Tropical Montane Forest. Sensors. 2012; 12 (4):4846-4859.
Chicago/Turabian StyleTeik-Min Chong; Chong-Lek Koh; Choon-Kook Sam; Yeun-Mun Choo; Wai-Fong Yin; Kok-Gan Chan. 2012. "Characterization of Quorum Sensing and Quorum Quenching Soil Bacteria Isolated from Malaysian Tropical Montane Forest." Sensors 12, no. 4: 4846-4859.
A chemically defined medium called KGm medium was used to isolate from a sample of sea water a bacterial strain, MW3A, capable of using N-3-oxohexanoyl-l-homoserine lactone as the sole carbon source. MW3A was clustered closely to Pseudomonas aeruginosa by 16S ribosomal DNA sequence analysis. It degraded both N-acylhomoserine lactones (AHLs) with a 3-oxo group substitution and, less preferably, AHLs with unsubstituted groups at C3 position in the acyl side chain, as determined by Rapid Resolution Liquid Chromatography. Its quiP and pvdQ homologue gene sequences showed high similarities to those of known acylases. Spent supernatant of MW3A harvested at 8-h post inoculation was shown to contain long-chain AHLs when assayed with the biosensor Escherichia coli [pSB1075], and specifically N-dodecanoyl-l-homoserine lactone and N-3-oxotetradecanoyl-l-homoserine lactone by high resolution mass spectrometry. Hence, we report here a novel marine P. aeruginosa strain MW3A possessing both quorum-quenching and quorum-sensing properties.
Cheng-Siang Wong; Wai-Fong Yin; Yeun Mun Choo; Choon-Kook Sam; Chong Lek Koh; Kok-Gan Chan. Coexistence of quorum-quenching and quorum-sensing in tropical marine Pseudomonas aeruginosa strain MW3A. World Journal of Microbiology and Biotechnology 2011, 28, 453 -461.
AMA StyleCheng-Siang Wong, Wai-Fong Yin, Yeun Mun Choo, Choon-Kook Sam, Chong Lek Koh, Kok-Gan Chan. Coexistence of quorum-quenching and quorum-sensing in tropical marine Pseudomonas aeruginosa strain MW3A. World Journal of Microbiology and Biotechnology. 2011; 28 (2):453-461.
Chicago/Turabian StyleCheng-Siang Wong; Wai-Fong Yin; Yeun Mun Choo; Choon-Kook Sam; Chong Lek Koh; Kok-Gan Chan. 2011. "Coexistence of quorum-quenching and quorum-sensing in tropical marine Pseudomonas aeruginosa strain MW3A." World Journal of Microbiology and Biotechnology 28, no. 2: 453-461.
Three new indole alkaloids (1-3), named grandilodines A-C, and five known ones were obtained from the Malayan Kopsia grandifolia. The structures were established using NMR and MS analyses and, in the case of 1 and 2, were confirmed by X-ray diffraction analyses. Alkaloids 1, 3, and lapidilectine B (8) were found to reverse multidrug resistance in vincristine-resistant KB cells.
Wai-Sum Yap; Chew-Yan Gan; Yun-Yee Low; Yeun-Mun Choo; Tadahiro Etoh; Masahiko Hayashi; Kanki Komiyama; Toh-Seok Kam. Grandilodines A−C, Biologically Active Indole Alkaloids fromKopsia grandifolia. Journal of Natural Products 2011, 74, 1309 -1312.
AMA StyleWai-Sum Yap, Chew-Yan Gan, Yun-Yee Low, Yeun-Mun Choo, Tadahiro Etoh, Masahiko Hayashi, Kanki Komiyama, Toh-Seok Kam. Grandilodines A−C, Biologically Active Indole Alkaloids fromKopsia grandifolia. Journal of Natural Products. 2011; 74 (5):1309-1312.
Chicago/Turabian StyleWai-Sum Yap; Chew-Yan Gan; Yun-Yee Low; Yeun-Mun Choo; Tadahiro Etoh; Masahiko Hayashi; Kanki Komiyama; Toh-Seok Kam. 2011. "Grandilodines A−C, Biologically Active Indole Alkaloids fromKopsia grandifolia." Journal of Natural Products 74, no. 5: 1309-1312.
A total of 25 alkaloids were isolated from the leaf and stem-bark extracts of Alstonia spatulata, of which five are new alkaloids of the strychnan type (alstolucines A-E, 1-5) and the other, a new alkaloid of the secoangustilobine A type (alstolobine A, 6). The structures of these alkaloids were established using NMR and MS analysis and, in the case of alstolucine B (2), also confirmed by X-ray diffraction analysis. A reinvestigation of the stereochemical assignment of scholaricine (13) by NMR and X-ray analyses indicated that the configuration at C-20 required revision. Alkaloids 1, 2, 6, 7, 9, 10, and 13 reversed multidrug resistance in vincristine-resistant KB cells.
Shin-Jowl Tan; Yun Yee Low; Yeun Mun Choo; Zanariah Abdullah; Tadahiro Etoh; Masahiko Hayashi; Kanki Komiyama; Toh-Seok Kam. Strychnan and Secoangustilobine A Type Alkaloids fromAlstonia spatulata.Revision of the C-20 Configuration of Scholaricine. Journal of Natural Products 2010, 73, 1891 -1897.
AMA StyleShin-Jowl Tan, Yun Yee Low, Yeun Mun Choo, Zanariah Abdullah, Tadahiro Etoh, Masahiko Hayashi, Kanki Komiyama, Toh-Seok Kam. Strychnan and Secoangustilobine A Type Alkaloids fromAlstonia spatulata.Revision of the C-20 Configuration of Scholaricine. Journal of Natural Products. 2010; 73 (11):1891-1897.
Chicago/Turabian StyleShin-Jowl Tan; Yun Yee Low; Yeun Mun Choo; Zanariah Abdullah; Tadahiro Etoh; Masahiko Hayashi; Kanki Komiyama; Toh-Seok Kam. 2010. "Strychnan and Secoangustilobine A Type Alkaloids fromAlstonia spatulata.Revision of the C-20 Configuration of Scholaricine." Journal of Natural Products 73, no. 11: 1891-1897.
Three unusual natural products, viz., alstopirocine, a macroline alkaloid incorporating a substituted pyrrole moiety, pleiomaltinine, an alkaloid–pyrone adduct, and pleiomalicine, an alkaloid–carbamic acid adduct, were isolated from the Malayan Alstonia angustifolia. The alkaloid moiety in alstopirocine was alstomicine while that in pleiomaltinine and pleiomalicine was pleiocarpamine. The structures were determined by spectroscopic methods and in the case of pleiomaltinine, confirmed by X-ray diffraction analysis. Possible biogenetic pathways to these unusual compounds are presented.
Shin-Jowl Tan; Yeun Mun Choo; Noel F. Thomas; Ward T. Robinson; Kanki Komiyama; Toh-Seok Kam. Unusual indole alkaloid–pyrrole, –pyrone, and –carbamic acid adducts from Alstonia angustifolia. Tetrahedron 2010, 66, 7799 -7806.
AMA StyleShin-Jowl Tan, Yeun Mun Choo, Noel F. Thomas, Ward T. Robinson, Kanki Komiyama, Toh-Seok Kam. Unusual indole alkaloid–pyrrole, –pyrone, and –carbamic acid adducts from Alstonia angustifolia. Tetrahedron. 2010; 66 (39):7799-7806.
Chicago/Turabian StyleShin-Jowl Tan; Yeun Mun Choo; Noel F. Thomas; Ward T. Robinson; Kanki Komiyama; Toh-Seok Kam. 2010. "Unusual indole alkaloid–pyrrole, –pyrone, and –carbamic acid adducts from Alstonia angustifolia." Tetrahedron 66, no. 39: 7799-7806.