MyMedR

Fulltext Evaluation of selected biological capacities of Baeckea frutescens

Navanesan S, Wahab NA, Manickam S, Sim KS

BMC Complement Altern Med, 2015;15:186.

PMID: 26081250 DOI: 10.1186/s12906-015-0712-6

Baeckea frutescens is a natural remedy recorded to be used in curing various health conditions. In Peninsular Malaysia, B. frutescens is found on the mountain tops, quartz ridge and sandy coasts. To our knowledge, there is only limited published literature on B. frutescens.

A new oxolane from Enterobacter cloacae

Yap AC, Chan KG, Sim KS, Choo YM

Nat Prod Res, 2016 Apr;30(7):783-8.

PMID: 26252083 DOI: 10.1080/14786419.2015.1065492

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.

Thiosemicarbazone Derivative Induces in vitro Apoptosis in Metastatic PC-3 Cells via Activation of Mitochondrial Pathway

Sinniah SK, Tan KW, Ng SW, Sim KS

Anticancer Agents Med Chem, 2017;17(5):741-753.

PMID: 27671302 DOI: 10.2174/1871520616666160926110929

BACKGROUND: Thiosemicarbazone (TSC) is a Schiff base that has been receiving considerable attention owing to its promising biological implication and remarkable pharmacological properties. The most promising drug candidate of this class would be Triapine (3-aminopyridine-2-carboxaldehyde thiosemicarbazone) which has entered phase II clinical trials as a potent anti-cancer chemotherapeutic agent.

OBJECTIVE: The current research aimed to synthesize several Schiff base ligands from (3-formyl-4-hydroxyphenyl) methyltriphenylphosphonium (T). Additionally, the current research aimed to study the growth inhibitory effect of triphenylphosphonium containing thiosemicarbazone derivatives on PC-3 cells by deciphering the mechanisms involved in cell death.

METHOD: The compounds were characterized by various spectroscopic methods (infrared spectra, 1H NMR, 13C NMR, HRESIMS and X-ray crystallography) and the results were in conformity with the structure of the targeted compounds. Growth inhibitory effect of the compounds were performed against six human cell lines.

RESULTS: DM(tsc)T displayed most potent activity against PC-3 cells with IC50 value of 2.64 ± 0.33 μM, surpassing that of the positive control cisplatin (5.47 ± 0.06 μM). There were marked morphological changes observed in DM(tsc)T treated cells stained with acridine orange and ethidium bromide which were indicative of cell apoptosis. Treatment with DM(tsc)T showed that the cell cycle is arrested in the G0/G1 phase after 72 hours. Mitochondrial membrane potential loss was observed in cells treated with DM(tsc)T, indicating the apoptosis could be due to mitochondria mediated pathway.

CONCLUSION: This study indicates that DM(tsc)T would serve as a lead scaffold for rational anticancer agent development.

Improvement to the scanning electron microscope image adaptive Canny optimization colorization by pseudo-mapping

Lo TY, Sim KS, Tso CP, Nia ME

Scanning, 2014 Sep-Oct;36(5):530-9.

PMID: 25139061 DOI: 10.1002/sca.21152

An improvement to the previously proposed adaptive Canny optimization technique for scanning electron microscope image colorization is reported. The additional feature, called pseudo-mapping technique, is that the grayscale markings are temporarily mapped to a set of pre-defined pseudo-color map as a mean to instill color information for grayscale colors in chrominance channels. This allows the presence of grayscale markings to be identified; hence optimization colorization of grayscale colors is made possible. This additional feature enhances the flexibility of scanning electron microscope image colorization by providing wider range of possible color enhancement. Furthermore, the nature of this technique also allows users to adjust the luminance intensities of selected region from the original image within certain extent.

Reducing charging effects in scanning electron microscope images by Rayleigh contrast stretching method (RCS)

Wan Ismail WZ, Sim KS, Tso CP, Ting HY

Scanning, 2011 Jul-Aug;33(4):233-51.

PMID: 21611953 DOI: 10.1002/sca.20237

To reduce undesirable charging effects in scanning electron microscope images, Rayleigh contrast stretching is developed and employed. First, re-scaling is performed on the input image histograms with Rayleigh algorithm. Then, contrast stretching or contrast adjustment is implemented to improve the images while reducing the contrast charging artifacts. This technique has been compared to some existing histogram equalization (HE) extension techniques: recursive sub-image HE, contrast stretching dynamic HE, multipeak HE and recursive mean separate HE. Other post processing methods, such as wavelet approach, spatial filtering, and exponential contrast stretching, are compared as well. Overall, the proposed method produces better image compensation in reducing charging artifacts.

Local dynamic range compensation for scanning electron microscope imaging system by sub-blocking multiple peak HE with convolution

Sim KS, Teh V, Tey YC, Kho TK

Scanning, 2016 Nov;38(6):492-501.

PMID: 26618303 DOI: 10.1002/sca.21285

This paper introduces new development technique to improve the Scanning Electron Microscope (SEM) image quality and we name it as sub-blocking multiple peak histogram equalization (SUB-B-MPHE) with convolution operator. By using this new proposed technique, it shows that the new modified MPHE performs better than original MPHE. In addition, the sub-blocking method consists of convolution operator which can help to remove the blocking effect for SEM images after applying this new developed technique. Hence, by using the convolution operator, it effectively removes the blocking effect by properly distributing the suitable pixel value for the whole image. Overall, the SUB-B-MPHE with convolution outperforms the rest of methods. SCANNING 38:492-501, 2016. © 2015 Wiley Periodicals, Inc.

Fulltext Whole-Genome Sequence of Endophytic Plant Growth-Promoting Escherichia coli USML2

Tharek M, Sim KS, Khairuddin D, Ghazali AH, Najimudin N

Genome Announc, 2017 May 11;5(19).

PMID: 28495774 DOI: 10.1128/genomeA.00305-17

Escherichia coli strain USML2 was originally isolated from the inner leaf tissues of surface-sterilized phytopathogenic-free oil palm (Elaeis guineensis Jacq.). We present here the whole-genome sequence of this plant-endophytic strain. The genome consists of a single circular chromosome of 4,502,758 bp, 4,315 predicted coding sequences, and a G+C content of 50.8%.

Aspidofractinine and Eburnane Alkaloids from a North Borneo Kopsia. Ring-Contracted, Additional Ring-Fused, and Paucidactine-Type Aspidofractinine Alkaloids from K. pauciflora

Yap WS, Gan CY, Sim KS, Lim SH, Low YY, Kam TS

J Nat Prod, 2016 Jan 22;79(1):230-9.

PMID: 26717050 DOI: 10.1021/acs.jnatprod.5b00992

Eleven new indole alkaloids (1-11) comprising seven aspidofractinine and four eburnane alkaloids, were isolated from the stem-bark extract of Kopsia pauciflora occurring in Malaysian Borneo. The aspidofractinine alkaloids include a ring-contracted, an additional ring-fused, a paucidactine regioisomer, two paucidactine, and one kopsine alkaloid. The structures of several of these alkaloids were also confirmed by X-ray diffraction analyses. The bisindole alkaloids isolated, norpleiomutine and kopsoffinol, showed in vitro growth inhibitory activity against human PC-3, HCT-116, MCF-7, and A549 cells and moderate effects in reversing multidrug-resistance in vincristine-resistant human KB cells.

A new oxathiolane from Enterobacter cloacae

Yap AC, Teoh WY, Chan KG, Sim KS, Choo YM

Nat Prod Res, 2015;29(8):722-6.

PMID: 25427277 DOI: 10.1080/14786419.2014.983507

Enterobacter cloacae is a versatile bacterial species inhabiting a wide variety of niches and is capable of metabolising a wide variety of substances as energy resources. The fermentation culture of this bacterial species has successfully yielded one new compound, Rimboxa (1) and three known compounds, i.e. indole-3-carboxaldehyde (2), indole-3-acetic acid (3) and 3,4-di-t-butylaniline (4). Rimboxa (1) is shown to possess the 1,2-oxathiolane core structure. 3,4-Di-t-butylaniline (4) is isolated for the first time from a natural resource. These compounds were isolated and characterised using extensive chromatographic and spectroscopic methods, and were subjected to cytotoxicity evaluations.

Phytochemical investigation of Gynura bicolor leaves and cytotoxicity evaluation of the chemical constituents against HCT 116 cells

Teoh WY, Tan HP, Ling SK, Abdul Wahab N, Sim KS

Nat Prod Res, 2016;30(4):448-51.

PMID: 25738869 DOI: 10.1080/14786419.2015.1017726

Gynura bicolor (Compositae) is a popular vegetable in Asia and believed to confer a wide range of benefits including anti-cancer. Our previous findings showed that the ethyl acetate extract of G. bicolor possessed cytotoxicity and induced apoptotic and necrotic cell death in human colon carcinoma cells (HCT 116). A combination of column chromatography had been used to purify chemical constituents from the ethyl acetate and water extract of G. bicolor leaves. Eight chemical constituents 5-p-trans-coumaroylquinic acid (I), 4-hydroxybenzoic acid (II), rutin (III), kampferol-3-O-rutinoside (IV), 3,5-dicaffeoylquinic acid (V), kampferol-3-O-glucoside (VI), guanosine (VII) and chlorogenic acid (VIII) were isolated from G. bicolor grown in Malaysia. To our best knowledge, all chemical constituents were isolated for the first time from G. bicolor leaves except rutin (III). 3,5-dicaffeoylquinic acid (V), guanosine (VII) and chlorogenic acid (VIII) demonstrated selective cytotoxicity (selective index>3) against HCT 116 cancer cells compared to CCD-18Co human normal colon cells.

Corynanthean, eburnan, secoleuconoxine, and pauciflorine alkaloids from Kopsia pauciflora

Gan CY, Yoganathan K, Sim KS, Low YY, Lim SH, Kam TS

Phytochemistry, 2014 Dec;108:234-42.

PMID: 25442910 DOI: 10.1016/j.phytochem.2014.09.014

Eleven indole alkaloids, comprising four corynanthean, two eburnane, one aspidofractinine, one secoleuconoxine, one andranginine, and two pauciflorine type alkaloids were isolated from the stem-bark and leaf extracts of Kopsia pauciflora. Their structures were determined using NMR and MS analyses. The catharinensine type alkaloid kopsirensine B and the secoleuconoxine alkaloid arboloscine A showed moderate to weak activity in reversing MDR in vincristine-resistant KB cells. The alkaloid content was markedly different compared to that of a sample from Malaysian Borneo.

Cytotoxic vobasine, tacaman, and corynanthe-tryptamine bisindole alkaloids from Tabernaemontana and structure revision of tronoharine

Sim DS, Chong KW, Nge CE, Low YY, Sim KS, Kam TS

J Nat Prod, 2014 Nov 26;77(11):2504-12.

PMID: 25333996 DOI: 10.1021/np500589u

Seven new indole alkaloids (1-7) comprising four vobasine, two tacaman, and one corynanthe-tryptamine bisindole alkaloid were isolated from the stem-bark extract of a Malayan Tabernaemontana. Two of the new vobasine alkaloids (1, 3), as well as 16-epivobasine (15) and 16-epivobasenal (17), showed appreciable cytotoxicity toward KB cells (IC50 ca. 5 μg/mL). The structure of the known Tabernaemontana alkaloid tronoharine (8) was revised based on newly acquired NMR data, as well as X-ray diffraction analysis.

Oxidized derivatives of macroline, sarpagine, and pleiocarpamine alkaloids from Alstonia angustifolia

Tan SJ, Lim JL, Low YY, Sim KS, Lim SH, Kam TS

J Nat Prod, 2014 Sep 26;77(9):2068-80.

PMID: 25211145 DOI: 10.1021/np500439u

A total of 20 new indole alkaloids comprising mainly oxidized derivatives of macroline- (including alstofonidine, a macroline indole incorporating a butyrolactone ring-F), pleiocarpamine-, and sarpagine-type alkaloids were isolated from the bark and leaf extracts of Alstonia angustifolia. The structures and relative configurations of these alkaloids were determined using NMR and MS analyses and in some instances confirmed by X-ray diffraction analyses. Alkaloids 3, 7, 35, and 41 showed moderate to weak activity, while 21 showed strong activity in reversing multidrug resistance in vincristine-resistant KB cells.

Fulltext Cytotoxic activity of Alpinia murdochii Ridl.: A mountain ginger species from Peninsular Malaysia

Sim KS, Ibrahim H, Malek SN, Syamsir DR, Awang K

Pharmacogn Mag, 2014 Jan;10(37):70-2.

PMID: 24695515 DOI: 10.4103/0973-1296.126666

Alpinia murdochii (Zingiberaceae) is a wild ginger species restricted to mountain areas of Peninsular Malaysia. Due to rapid development and deforestation activities, this species is becoming rare. This is the first report of the cytotoxic activity of A. murdochii.

Breast cancer detection from MR images through an auto-probing discrete Fourier transform system

Sim KS, Chia FK, Nia ME, Tso CP, Chong AK, Abbas SF, et al.

Comput Biol Med, 2014 Jun;49:46-59.

PMID: 24736203 DOI: 10.1016/j.compbiomed.2014.03.003

A computer-aided detection auto-probing (CADAP) system is presented for detecting breast lesions using dynamic contrast enhanced magnetic resonance imaging, through a spatial-based discrete Fourier transform. The stand-alone CADAP system reduces noise, refines region of interest (ROI) automatically, and detects the breast lesion with minimal false positive detection. The lesions are then classified and colourised according to their characteristics, whether benign, suspicious or malignant. To enhance the visualisation, the entire analysed ROI is constructed into a 3-D image, so that the user can diagnose based on multiple views on the ROI. The proposed method has been applied to 101 sets of digital images, and the results compared with the biopsy results done by radiologists. The proposed scheme is able to identify breast cancer regions accurately and efficiently.

Copper complexes with phosphonium containing hydrazone ligand: topoisomerase inhibition and cytotoxicity study

Chew ST, Lo KM, Lee SK, Heng MP, Teoh WY, Sim KS, et al.

Eur J Med Chem, 2014 Apr 9;76:397-407.

PMID: 24602785 DOI: 10.1016/j.ejmech.2014.02.049

Four new copper(II) complexes containing phosphonium substituted hydrazone (L) with the formulations [CuL]Cl(3), [Cu(phen)L]Cl(4), [Cu(bpy)L]Cl(5), [Cu(dbpy)L]Cl(6), (where L = doubly deprotonated hydrazone; phen = 1,10'-phenanthroline; bpy = 2,2'-bipyridine; dbpy = 5,5'-dimethyl-2,2'-bipyridine) have been synthesized. The compounds were characterized by elemental analysis, spectroscopic methods and in the case of crystalline products by X-ray crystallography. The cytotoxicity and topoisomerase I (topo I) inhibition activities of these compounds were studied. It is noteworthy that the addition of N,N-ligands to the copper(II) complex lead to the enhancement in the cytotoxicity of the compounds, especially against human prostate adenocarcinoma cell line (PC-3). Complex 4 exhibits the highest activity against PC-3 with the IC₅₀ value of 3.2 μΜ. The complexes can also inhibit topo I through the binding to DNA and the enzyme.

Macroline, akuammiline, sarpagine, and ajmaline alkaloids from Alstonia macrophylla

Lim SH, Low YY, Sinniah SK, Yong KT, Sim KS, Kam TS

Phytochemistry, 2014 Feb;98:204-15.

PMID: 24342109 DOI: 10.1016/j.phytochem.2013.11.014

A total of seventeen alkaloids, comprising six macroline (including alstofolinine A, a macroline indole incorporating a butyrolactone ring-E), two ajmaline, one sarpagine, and eight akuammiline alkaloids, were isolated from the stem-bark and leaf extracts of the Malayan Alstonia macrophylla. The structure and relative configurations of these alkaloids were established using NMR, MS and in several instances, confirmed by X-ray diffraction analysis. Six of these alkaloids were effective in reversing multidrug-resistance (MDR) in vincristine-resistant KB cells.

Fulltext Phenolic content, antioxidant effect and cytotoxic activity of Leea indica leaves

Reddy NS, Navanesan S, Sinniah SK, Wahab NA, Sim KS

BMC Complement Altern Med, 2012;12:128.

PMID: 22898370 DOI: 10.1186/1472-6882-12-128

The leaves of Leea indica (Vitaceae), commonly known as 'Huo Tong Shu' in Malaysia, have been traditionally used as natural remedy in folk medicine by the locals. The current study reports the outcome of antioxidant and cytotoxic investigation of L. indica leaves. To the best of our knowledge, this is the first report of L. indica leaf crude ethanol and its fractionated extracts (hexane, ethyl acetate and water) for evaluation of total phenolic content, antioxidant effect and cytotoxic activity against colon cancer cell lines.

Fulltext Reducing scanning electron microscope charging by using exponential contrast stretching technique on post-processing images

Sim KS, Tan YY, Lai MA, Tso CP, Lim WK

J Microsc, 2010 Apr 1;238(1):44-56.

PMID: 20384837 DOI: 10.1111/j.1365-2818.2009.03328.x

An exponential contrast stretching (ECS) technique is developed to reduce the charging effects on scanning electron microscope images. Compared to some of the conventional histogram equalization methods, such as bi-histogram equalization and recursive mean-separate histogram equalization, the proposed ECS method yields better image compensation. Diode sample chips with insulating and conductive surfaces are used as test samples to evaluate the efficiency of the developed algorithm. The algorithm is implemented in software with a frame grabber card, forming the front-end video capture element.

Fulltext Phytochemical and cytotoxic investigations of Alpinia mutica rhizomes

Malek SN, Phang CW, Ibrahim H, Norhanom AW, Sim KS

Molecules, 2011 Jan 14;16(1):583-9.

PMID: 21240148 DOI: 10.3390/molecules16010583

The methanol and fractionated extracts (hexane, ethyl acetate and water) of Alpinia mutica (Zingiberaceae) rhizomes were investigated for their cytotoxic effect against six human carcinoma cell lines, namely KB, MCF7, A549, Caski, HCT116, HT29 and non-human fibroblast cell line (MRC 5) using an in vitro cytotoxicity assay. The ethyl acetate extract possessed high inhibitory effect against KB, MCF7 and Caski cells (IC₅₀ values of 9.4, 19.7 and 19.8 µg/mL, respectively). Flavokawin B (1), 5,6-dehydrokawain (2), pinostrobin chalcone (3) and alpinetin (4), isolated from the active ethyl acetate extract were also evaluated for their cytotoxic activity. Of these, pinostrobin chalcone (3) and alpinetin (4) were isolated from this plant for the first time. Pinostrobin chalcone (3) displayed very remarkable cytotoxic activity against the tested human cancer cells, such as KB, MCF7 and Caski cells (IC₅₀ values of 6.2, 7.3 and 7.7 µg/mL, respectively). This is the first report of the cytotoxic activity of Alpinia mutica.

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