Displaying publications 1 - 20 of 90 in total

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  1. Genome-wide association study identifies five new susceptibility loci for primary angle closure glaucoma
    Khor CC, Do T, Jia H, Nakano M, George R, Abu-Amero K, et al.
    Nat Genet, 2016 May;48(5):556-62.
    PMID: 27064256 DOI: 10.1038/ng.3540
    Primary angle closure glaucoma (PACG) is a major cause of blindness worldwide. We conducted a genome-wide association study (GWAS) followed by replication in a combined total of 10,503 PACG cases and 29,567 controls drawn from 24 countries across Asia, Australia, Europe, North America, and South America. We observed significant evidence of disease association at five new genetic loci upon meta-analysis of all patient collections. These loci are at EPDR1 rs3816415 (odds ratio (OR) = 1.24, P = 5.94 × 10(-15)), CHAT rs1258267 (OR = 1.22, P = 2.85 × 10(-16)), GLIS3 rs736893 (OR = 1.18, P = 1.43 × 10(-14)), FERMT2 rs7494379 (OR = 1.14, P = 3.43 × 10(-11)), and DPM2-FAM102A rs3739821 (OR = 1.15, P = 8.32 × 10(-12)). We also confirmed significant association at three previously described loci (P < 5 × 10(-8) for each sentinel SNP at PLEKHA7, COL11A1, and PCMTD1-ST18), providing new insights into the biology of PACG.
  2. Fulltext Genome-wide association analyses identify three new susceptibility loci for primary angle closure glaucoma
    Vithana EN, Khor CC, Qiao C, Nongpiur ME, George R, Chen LJ, et al.
    Nat Genet, 2012 Oct;44(10):1142-1146.
    PMID: 22922875 DOI: 10.1038/ng.2390
    Primary angle closure glaucoma (PACG) is a major cause of blindness worldwide. We conducted a genome-wide association study including 1,854 PACG cases and 9,608 controls across 5 sample collections in Asia. Replication experiments were conducted in 1,917 PACG cases and 8,943 controls collected from a further 6 sample collections. We report significant associations at three new loci: rs11024102 in PLEKHA7 (per-allele odds ratio (OR)=1.22; P=5.33×10(-12)), rs3753841 in COL11A1 (per-allele OR=1.20; P=9.22×10(-10)) and rs1015213 located between PCMTD1 and ST18 on chromosome 8q (per-allele OR=1.50; P=3.29×10(-9)). Our findings, accumulated across these independent worldwide collections, suggest possible mechanisms explaining the pathogenesis of PACG.
  3. Fulltext Genetic risk of extranodal natural killer T-cell lymphoma: a genome-wide association study
    Li Z, Xia Y, Feng LN, Chen JR, Li HM, Cui J, et al.
    Lancet Oncol, 2016 Sep;17(9):1240-7.
    PMID: 27470079 DOI: 10.1016/S1470-2045(16)30148-6
    BACKGROUND: Extranodal natural killer T-cell lymphoma (NKTCL), nasal type, is a rare and aggressive malignancy that occurs predominantly in Asian and Latin American populations. Although Epstein-Barr virus infection is a known risk factor, other risk factors and the pathogenesis of NKTCL are not well understood. We aimed to identify common genetic variants affecting individual risk of NKTCL.

    METHODS: We did a genome-wide association study of 189 patients with extranodal NKTCL, nasal type (WHO classification criteria; cases) and 957 controls from Guangdong province, southern China. We validated our findings in four independent case-control series, including 75 cases from Guangdong province and 296 controls from Hong Kong, 65 cases and 983 controls from Guangdong province, 125 cases and 1110 controls from Beijing (northern China), and 60 cases and 2476 controls from Singapore. We used imputation and conditional logistic regression analyses to fine-map the associations. We also did a meta-analysis of the replication series and of the entire dataset.

    FINDINGS: Associations exceeding the genome-wide significance threshold (p<5 × 10(-8)) were seen at 51 single-nucleotide polymorphisms (SNPs) mapping to the class II MHC region on chromosome 6, with rs9277378 (located in HLA-DPB1) having the strongest association with NKTCL susceptibility (p=4·21 × 10(-19), odds ratio [OR] 1·84 [95% CI 1·61-2·11] in meta-analysis of entire dataset). Imputation-based fine-mapping across the class II MHC region suggests that four aminoacid residues (Gly84-Gly85-Pro86-Met87) in near-complete linkage disequilibrium at the edge of the peptide-binding groove of HLA-DPB1 could account for most of the association between the rs9277378*A risk allele and NKTCL susceptibility (OR 2·38, p value for haplotype 2·32 × 10(-14)). This association is distinct from MHC associations with Epstein-Barr virus infection.

    INTERPRETATION: To our knowledge, this is the first time that a genetic variant conferring an NKTCL risk is noted at genome-wide significance. This finding underlines the importance of HLA-DP antigen presentation in the pathogenesis of NKTCL.

    FUNDING: Top-Notch Young Talents Program of China, Special Support Program of Guangdong, Specialized Research Fund for the Doctoral Program of Higher Education (20110171120099), Program for New Century Excellent Talents in University (NCET-11-0529), National Medical Research Council of Singapore (TCR12DEC005), Tanoto Foundation Professorship in Medical Oncology, New Century Foundation Limited, Ling Foundation, Singapore National Cancer Centre Research Fund, and the US National Institutes of Health (1R01AR062886, 5U01GM092691-04, and 1R01AR063759-01A1).

  4. Fulltext Deep whole-genome sequencing of 100 southeast Asian Malays
    Wong LP, Ong RT, Poh WT, Liu X, Chen P, Li R, et al.
    Am J Hum Genet, 2013 Jan 10;92(1):52-66.
    PMID: 23290073 DOI: 10.1016/j.ajhg.2012.12.005
    Whole-genome sequencing across multiple samples in a population provides an unprecedented opportunity for comprehensively characterizing the polymorphic variants in the population. Although the 1000 Genomes Project (1KGP) has offered brief insights into the value of population-level sequencing, the low coverage has compromised the ability to confidently detect rare and low-frequency variants. In addition, the composition of populations in the 1KGP is not complete, despite the fact that the study design has been extended to more than 2,500 samples from more than 20 population groups. The Malays are one of the Austronesian groups predominantly present in Southeast Asia and Oceania, and the Singapore Sequencing Malay Project (SSMP) aims to perform deep whole-genome sequencing of 100 healthy Malays. By sequencing at a minimum of 30× coverage, we have illustrated the higher sensitivity at detecting low-frequency and rare variants and the ability to investigate the presence of hotspots of functional mutations. Compared to the low-pass sequencing in the 1KGP, the deeper coverage allows more functional variants to be identified for each person. A comparison of the fidelity of genotype imputation of Malays indicated that a population-specific reference panel, such as the SSMP, outperforms a cosmopolitan panel with larger number of individuals for common SNPs. For lower-frequency (<5%) markers, a larger number of individuals might have to be whole-genome sequenced so that the accuracy currently afforded by the 1KGP can be achieved. The SSMP data are expected to be the benchmark for evaluating the value of deep population-level sequencing versus low-pass sequencing, especially in populations that are poorly represented in population-genetics studies.
  5. Quinoline, Indole, and Isogranatanine Alkaloids from Malayan Leuconotis eugeniifolia
    Tan YS, Ng MP, Tan CH, Tang WK, Sim KS, Yong KT, et al.
    J Nat Prod, 2024 Feb 23;87(2):286-296.
    PMID: 38284153 DOI: 10.1021/acs.jnatprod.3c00960
    Nine new alkaloids, eugeniinalines A-H (1-8) and (+)-eburnamenine N-oxide (9), comprising one quinoline, six indole, and two isogranatanine alkaloids, were isolated from the stem-bark extract of the Malayan Leuconotis eugeniifolia. The structures and absolute configurations of these alkaloids were established based on the analysis of the spectroscopic data, GIAO NMR calculations, DP4+ probability analysis, TDDFT-ECD method, and X-ray diffraction analysis. Eugeniinaline A (1) represents a new pentacyclic quinoline alkaloid with a 6/6/5/6/7 ring system. Eugeniinaline G (7) and its seco-derivative, eugeniinaline H (8), were the first isogranatanine alkaloids isolated as natural products. The known alkaloids leucolusine (10) and melokhanine A (11) were found to be the same compound, based on comparison of the spectroscopic data of both compounds, with the absolute configuration of (7R, 20R, 21S). Eugeniinalines A and G (1 and 7) showed cytotoxic activity against the HT-29 cancer cell line with IC50 values of 7.1 and 7.2 μM, respectively.
  6. Antimicrobial and Antiproliferative Effects of Zingiberaceae Oils: A Natural Solution for Oral Health
    Amil MA, Rahman SNSA, Yap LF, Razak FA, Bakri MM, Salem LSO, et al.
    Chem Biodivers, 2024 Mar;21(3):e202301836.
    PMID: 38253795 DOI: 10.1002/cbdv.202301836
    Essential oils have been recognised for their potential benefits in oral care. The aim of this study was to evaluate the antibacterial and antiproliferative activity of essential oils derived from four Zingiberaceae species. A combination of GC/MS and GC-FID was employed to analyse these essential oils. The results showed that β-myrcene (79.77 %) followed by ethyl-cinnamate (40.14 %), β-curcumene (34.90 %), and alloaromadendrene (25.15 %) as the primary constituents of Curcuma mangga, Curcuma xanthorrhiza, Kaempferia galanga and Curcuma aeruginosa, respectively. The Zingiberaceae oils were tested for their antibacterial activity against oral bacteria using the disc diffusion test. Curcuma xanthorrhiza oil showed the largest inhibition zones against Streptococcus mitis (19.50±2.22 mm) and Streptococcus sanguinis (15.04±3.05 mm). Similarly, Curcuma mangga oil exhibited significant antibacterial activity against Streptococcus mutans (12.55±0.45 mm) and mixed oral bacteria (15.03±3.82 mm). Furthermore, the MTT viability assay revealed moderate inhibitory activity of these essential oils against H103 and ORL-204 oral cancer cells. The study findings demonstrate that Curcuma xanthorrhiza and Curcuma mangga essential oils have potent antibacterial properties, suggesting their potential use as natural alternatives to synthetic antibacterial agents in oral care products. However, further investigations are necessary to fully explore their therapeutic applications.
  7. Biologically active vallesamine, strychnan, and rhazinilam alkaloids from Alstonia: Pneumatophorine, a nor-secovallesamine with unusual incorporation of a 3-ethylpyridine moiety
    Lim JL, Sim KS, Yong KT, Loong BJ, Ting KN, Lim SH, et al.
    Phytochemistry, 2015 Sep;117:317-24.
    PMID: 26125941 DOI: 10.1016/j.phytochem.2015.06.024
    Four alkaloids comprising two vallesamine, one strychnan, and one pyranopyridine alkaloid, in addition to 32 other known alkaloids were isolated from two Malayan Alstonia species, Alstonia pneumatophora and Alstonia rostrata. The structures of these alkaloids were determined using NMR and MS analyses, and in one instance, confirmed by X-ray diffraction analysis. The nor-6,7-secovallesamine alkaloid, pneumatophorine, is notable for an unusual incorporation of a 3-ethylpyridine moiety in a monoterpenoid indole. The rhazinilam-type alkaloids (rhazinicine, nor-rhazinicine, rhazinal, and rhazinilam) showed strong cytotoxicity toward human KB, HCT-116, MDA-MB-231, and MRC-5 cells, while pneumatophorine, the uleine alkaloid undulifoline, and the strychnan alkaloids, N4-demethylalstogustine and echitamidine, induced concentration dependent relaxation in phenylephrine-precontracted rat aortic rings.
  8. Macroline-Sarpagine Bisindole Alkaloids with Antiproliferative Activity from Alstonia penangiana
    Yeap JS, Saad HM, Tan CH, Sim KS, Lim SH, Low YY, et al.
    J Nat Prod, 2019 11 22;82(11):3121-3132.
    PMID: 31642315 DOI: 10.1021/acs.jnatprod.9b00712
    A methanol extract of the stem bark of the Malayan Alstonia penangiana provided seven new bisindole alkaloids, comprising six macroline-sarpagine alkaloids (angustilongines E-K, 1-6) and one macroline-pleiocarpamine bisindole alkaloid (angustilongine L, 7). Analysis of the spectroscopic data (NMR and MS) of these compounds led to the proposed structures of these alkaloids. The macroline-sarpagine alkaloids (1-6) showed in vitro growth inhibitory activity against a panel of human cancer cell lines, inclusive of KB, vincristine-resistant KB, PC-3, LNCaP, MCF7, MDA-MB-231, HT-29, HCT 116, and A549 cells (IC50 values: 0.02-9.0 μM).
  9. Surgical site infection and development of antimicrobial sutures: a review
    Chua RAHW, Lim SK, Chee CF, Chin SP, Kiew LV, Sim KS, et al.
    Eur Rev Med Pharmacol Sci, 2022 Feb;26(3):828-845.
    PMID: 35179749 DOI: 10.26355/eurrev_202202_27991
    Sutures are used to facilitate wound healing and play an important role in ensuring the success of surgical interventions in healthcare facilities. Suture-associated surgical site infection (SSI) may develop when bacterial contaminants colonize the suture surface and establish biofilms that are highly resistant to antibiotic treatment. The outcome of SSI affects postoperative care, leading to high rates of morbidity and mortality, prolonged hospitalization, and increased financial burden. Antimicrobial sutures coated with antiseptics such as triclosan and chlorhexidine have been used to minimize the occurrence of SSI. However, as the efficacy of antiseptic-based sutures may be affected due to the emergence of resistant strains, new approaches for the development of alternative antimicrobial sutures are necessary. This review provides an update and outlook of various approaches in the design and development of antimicrobial sutures. Attaining a zero SSI rate will be possible with the advancement in suturing technology and implementation of good infection control practice in clinical settings.
  10. Antiproliferative and Microtubule-stabilizing Activities of Two Iboga-vobasine Bisindoles Alkaloids from Tabernaemontana corymbosa in Colorectal Adenocarcinoma HT-29 Cells
    Tan CH, Sim DSY, Lim SH, Mohd Mohidin TB, Mohan G, Low YY, et al.
    Planta Med, 2022 Nov;88(14):1325-1340.
    PMID: 35100653 DOI: 10.1055/a-1755-5605
    Two iboga-vobasine bisindoles, 16'-decarbomethoxyvoacamine (1: ) and its 19,20-dihydro derivative, 16'-decarbomethoxydihydrovoacamine (2: ) from Tabernaemontana corymbosa exhibited potent cytotoxicity against the human colorectal adenocarcinoma HT-29 cells in our previous studies. Bisindoles 1: and 2: selectively inhibited the growth of HT-29 cells without significant cytotoxicity to normal human colon fibroblasts CCD-18Co. Treatment with bisindoles 1: and 2: suppressed the formation of HT-29 colonies via G0/G1 cell cycle arrest and induction of mitochondrial apoptosis. Owing to its higher antiproliferative activity, bisindole 2: was chosen for the subsequent studies. Bisindole 2: inhibited the formation of HT-29 spheroids (tumor-like cell aggregates) in 3D experiments in a dose-dependent manner, while an in vitro tubulin polymerization assay and molecular docking analysis showed that bisindole 2: is a microtubule-stabilizing agent which is predicted to bind at the β-tubulin subunit at the taxol-binding site. The binding resulted in the generation of ROS, which consequently activated the oxidative stress-related cell cycle arrest and apoptotic pathways, viz., JNK/p38, p21Cip1/Chk1, and p21Cip1/Rb/E2F, as shown by microarray profiling.
  11. Size-dependent effect of cystine/citric acid-capped confeito-like gold nanoparticles on cellular uptake and photothermal cancer therapy
    Saw WS, Ujihara M, Chong WY, Voon SH, Imae T, Kiew LV, et al.
    Colloids Surf B Biointerfaces, 2018 Jan 01;161:365-374.
    PMID: 29101882 DOI: 10.1016/j.colsurfb.2017.10.064
    Physiochemical changes, including size, are known to affect gold nanoparticle cellular internalization and treatment efficacy. Here, we report the effect of four sizes of cystine/citric acid-coated confeito-like gold nanoparticles (confeito-AuNPs) (30, 60, 80 and 100nm) on cellular uptake, intracellular localization and photothermal anticancer treatment efficiency in MDA-MB231 breast cancer cells. Cellular uptake is size dependent with the smallest size of confeito-AuNPs (30nm) having the highest cellular internalization via clathrin- and caveolae-mediated endocytosis. However, the other three sizes (60, 80 and 100nm) utilize clathrin-mediated endocytosis for cellular uptake. The intracellular localization of confeito-AuNPs is related to their endocytosis mechanism, where all sizes of confeito-AuNPs were localized highly in the lysosome and mitochondria, while confeito-AuNPs (30nm) gave the highest localization in the endoplasmic reticulum. Similarly, a size-dependent trend was also observed in in vitro photothermal treatment experiments, with the smallest confeito-AuNPs (30nm) giving the highest cell killing rate, whereas the largest size of confeito-AuNPs (100nm) displayed the lowest photothermal efficacy. Its desirable physicochemical characteristics, biocompatible nature and better photothermal efficacy will form the basis for further development of multifunctional confeito-AuNP-based nanotherapeutic applications.
  12. Structural insights and cytotoxicity evaluation of benz[e]indole pyrazolyl-substituted amides
    Ramle AQ, Chan NNMY, Ng MP, Tan CH, Sim KS, Tiekink ERT, et al.
    Mol Divers, 2023 Jun 06.
    PMID: 37278911 DOI: 10.1007/s11030-023-10662-2
    Five new compounds of benz[e]indole pyrazolyl-substituted amides (2a-e) were synthesised in low to good yields via the direct amide-coupling reaction between a pyrazolyl derivative containing a carboxylic acid and several amine substrates. The molecular structures were determined by various spectroscopic methods, such as NMR (1H, 13C and 19F), FT-IR and high-resolution mass spectrometry (HRMS). X-ray crystallographic analysis on the 4-fluorobenzyl derivative (2d) reveals the amide-O atom to reside to the opposite side of the molecule to the pyrazolyl-N and pyrrolyl-N atoms; in the molecular packing, helical chains feature amide-N‒H⋯N(pyrrolyl) hydrogen bonds. Density-functional theory (DFT) at the geometry-optimisation B3LYP/6-31G(d) level on the full series shows general agreement with the experimental structures. While the LUMO in each case is spread over the benz[e]indole pyrazolyl moiety, the HOMO spreads over the halogenated benzo-substituted amide moieties or is localised near the benz[e]indole pyrazolyl moieties. The MTT assay showed that 2e, exhibited the highest toxicity against a human colorectal carcinoma (HCT 116 cell line) without appreciable toxicity towards the normal human colon fibroblast (CCD-18Co cell line). Based on molecular docking calculations, the probable cytotoxic mechanism of 2e is through the DNA minor groove binding.
  13. Discovery of indoleninyl-pyrazolo[3,4-b]pyridines as potent chemotherapeutic agents against colorectal cancer cells
    Basir NH, Ramle AQ, Ng MP, Tan CH, Tiekink ERT, Sim KS, et al.
    Bioorg Chem, 2024 May;146:107256.
    PMID: 38460334 DOI: 10.1016/j.bioorg.2024.107256
    A new series of indolenines decorated with pyrazolo[3,4-b]pyridines were designed and synthesized in up to 96% yield from the acid-catalyzed cyclocondensation of 1,3-dialdehydes with 3-aminopyrazoles. X-ray crystallography on a representative derivative, 5n, revealed two close to planar conformations whereby the N-atom of the pyridyl residue was syn or anti to the pyrrole-N atom in the two independent molecules of the asymmetric unit. The computational and DNA binding data suggest that 5n is a strong DNA intercalator with the results in agreement with its potent cytotoxicity against two colorectal cancer cell lines (HCT 116 and HT-29). In contrast to doxorubicin, compounds 5k-o have higher druggability (compliance to more criteria stated in Lipinski's rule of five and Veber's rule), higher bioavailability, and better medicinal chemistry properties, indicative of their potential application as chemotherapeutical agents.
  14. 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.
  15. 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.
  16. 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.
  17. 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.
  18. 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.
  19. 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.
  20. 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.
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