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Identification of sildenafil, tadalafil and vardenafil by gas chromatography-mass spectrometry on short capillary column

Man CN, Nor NM, Lajis R, Harn GL

J Chromatogr A, 2009 Nov 20;1216(47):8426-30.
PMID: 19853256 DOI: 10.1016/j.chroma.2009.10.016

Sildenafil and its analogues (tadalafil and vardenafil) are phosphodiesterase type 5 inhibitors used in the treatment of male erectile dysfunction. Some dietary supplements, herbal preparations and food products which claim to enhance male sexual function have been found to be adulterated with these drugs. In this study, a gas chromatograph-mass spectrometer (GC-MS) assay was developed for identification of the drugs. In addition to good and short chromatographic separation that can be achieved within 6 min by using a short 10 m capillary column, no prior sample clean-up before GC-MS analysis was required, thus making this assay a cost saving and rapid method. Furthermore, the assay is specific as the identification of sildenafil, tadalafil and vardenafil were done by detection of molecular ions; m/z 474, 389 and 488, [corrected] respectively, and several other characteristic ions resulted from the mass fragmentation of individual molecules. Using our currently developed assay, sildenafil and its analogues were successfully identified in food and herbal matrices.
Determination of hair nicotine by gas chromatography-mass spectrometry

Man CN, Ismail S, Harn GL, Lajis R, Awang R

J Chromatogr B Analyt Technol Biomed Life Sci, 2009 Jan 15;877(3):339-42.
PMID: 19109080 DOI: 10.1016/j.jchromb.2008.12.014

Hair nicotine is a known biomarker for monitoring long-term environmental tobacco smoke (ETS) exposure and smoking status. In general, hair nicotine assay involves alkaline digestion, extraction and instrumental analysis. The gas chromatography-mass spectrometry (GC-MS) assay currently developed has shown to be of high throughput with average approximately 100 hair samples being extracted and analyzed per day. This was achieved through simplified extraction procedure and shortened GC analysis time. The extraction was improved by using small volume (0.4 mL) of organic solvent that does not require further evaporation and salting steps prior to GC-MS analysis. Furthermore, the amount of hair utilized in the extraction was very little (5 mg) while the sensitivity and selectivity of the assay is equal, if not better than other established methods. The linearity of the assay (r(2)>0.995), limit of quantitation (0.04 ng/mg hair), within- and between-assays accuracies and precisions (<11.4%) and mean recovery (92.6%) were within the acceptable range.
Screening of tetrodotoxin in puffers using gas chromatography-mass spectrometry

Man CN, Noor NM, Harn GL, Lajis R, Mohamad S

J Chromatogr A, 2010 Nov 19;1217(47):7455-9.
PMID: 20950812 DOI: 10.1016/j.chroma.2010.09.064

Tetrodotoxin (TTX), a toxic compound found in some puffers can cause death to humans through consumption. We have developed a simplified method for the screening of TTX in puffers using GC-MS. A puffer tissue of 0.5g was treated with 5mL of 0.1% acetic acid, followed by alkaline hydrolysis, LLE or liquid-liquid extraction and N-methyl-N-TMS-trifluoroacetamide derivatization. The developed method used only a small sample and solvent, simplified LLE and derivatization procedures and short chromatographic analysis (8.2min). All of these contribute to cost-saving, enhanced sample throughput and high sensitivity of the screening assay. The developed method was validated and proved to be within the acceptable range.
Vimentin protein is a factor for decreasing breast cancer cell proliferation co-culture with human bone marrow-derived mesenchymal stem cells pre-treated with thiazolidinedione solutions

Kwok LS, Yian SS, Ismael LQ, Bee YTG, Harn GL, Yin KB

Mol Biol Rep, 2024 Feb 21;51(1):317.
PMID: 38381204 DOI: 10.1007/s11033-024-09269-z

BACKGROUND: Our previous study investigated the levels of soluble growth factors in the conditioned media of bone marrow-derived mesenchymal stem cells (BMSCs) pre-treated with thiazolidinedione solutions. The present study aimed to investigate the complex intracellular proteins extracted from BMSCs pre-treated with pioglitazone and/or rosiglitazone using proteomics.
METHODS: The proliferative effect of the identified protein on MCF-7 cells that interacted non-adhesively with BMSCs pre-treated with pioglitazone and/or rosiglitazone was evaluated using cell culture inserts and conditioned media. The mRNA expression of proliferation and lipid accumulation markers was also evaluated in the interacted MCF-7 cells by reverse transcription-quantitative PCR. Finally, the correlation between the identified protein and fibroblast growth factor 4 (FGF-4) protein in the conditioned media of the pre-treated BMSCs was evaluated by ELISA.
RESULTS: The present study identified vimentin as the specific protein among the complex intracellular proteins that likely plays a role in MCF-7 cell proliferation when the breast cancer cells interacted non-adhesively with BMSCs pre-treated with a combination of pioglitazone and rosiglitazone. The inhibition of this protein promoted the proliferation of MCF-7 cells when the breast cancer cells interacted with pre-treated BMSCs. Gene expression analysis indicated that pre-treatment of BMSCs with a combination of pioglitazone and rosiglitazone decreased the mRNA expression of Ki67 and proliferating cell nuclear antigen in MCF-7 cells. The pre-treatment did not induce mRNA expression of PPARγ, which is a sign of lipid accumulation. The level of vimentin protein was also associated with the FGF-4 protein expression level in the conditioned media of the pre-treated BMSCs. Bioinformatics analysis revealed that vimentin regulated the expression of FGF-4 through its interaction with SRY-box 2 and POU class 5 homeobox 1.
CONCLUSIONS: The present study identified a novel intracellular protein that may represent the promising target in pre-treated BMSCs to decrease the proliferation of breast cancer MCF-7 cells for human health and wellness.
Correlation between urinary nicotine, cotinine and self-reported smoking status among educated young adults

Man CN, Fathelrahman AI, Harn GL, Lajis R, Samin AS, Omar M, et al.

Environ Toxicol Pharmacol, 2009 Jul;28(1):92-6.
PMID: 21783987 DOI: 10.1016/j.etap.2009.03.003

The objective of this study was to correlate, differentiate and validate the self-reported smoking status of educated young adults with urinary biomarkers (i.e. nicotine and cotinine). Freshmen students were recruited on voluntary basis. They filled-up self-administered questionnaire and their urine samples were collected for analysis. The urinary nicotine (UN) and cotinine (UC) were measured by gas chromatograph-mass spectrometry. Smokers, non-smokers and ex-smokers were found to be both significantly correlated and different in their UN and UC levels. UC level of 25ng/ml was the optimal cut-off to differentiate smokers from non-smokers. Using this cut-off value, the prevalence of smoking among the students was found to be higher (15.4%) than the self-reported data (14.3%). UC is useful in validating individual recent smoking history and the cut-off could serve as a marker for assessing the clinical impact of smoking and environmental tobacco smoke (ETS) exposure on human health.
Study site: university health centre, Universiti SainsMalaysia (USM), Pulau Pinang, Malaysia