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Iridoids from Rothmannia macrophylla

Ling SK, Tanaka T, Kouno I

J Nat Prod, 2001 Jun;64(6):796-8.
PMID: 11421747

A new iridoid glucoside with an ether linkage between C-3 and C-10 and a novel nonglycosidic iridoid with an ether linkage between C-3 and C-6 and a lactonic linkage at C-1, named macrophylloside (1) and macrophyllide (2), respectively, were isolated from the leaves of Rothmannia macrophylla, along with six known iridoids. Their structures were established by NMR and MS spectroscopies.
Medicinal plants used for treating female diseases in Malaysia--a review

Ling SK, Ng LT

Am J Chin Med, 1998;26(2):211-22.
PMID: 9799973 DOI: 10.1142/S0192415X98000269

A survey of plants used in Malaysia for treating female diseases was made by consulting books, journals and traditional healers. In this report on the survey, forty-four plants are described. Information on plant parts used, methods of preparation and administration, and other usages of plants are given for each species.
A new diglycosyl megastigmane from Carallia brachiata

Ling SK, Takashima T, Tanaka T, Fujioka T, Mihashi K, Kouno I

Fitoterapia, 2004 Dec;75(7-8):785-8.
PMID: 15567266

A new megastigmane diglycoside was isolated from the leaves of Carallia brachiata. The structure was determined by spectroscopic methods as 3-hydroxy-5,6-epoxy-beta-ionol -3-O-beta-apiofuranosyl-(1-->6)-beta-glucopyranoside (1). Additionally, 29 known compounds consisting of two megastigmanes, one 1,2-dithiolane derivative, seven aromatic compounds, five condensed tannins, 12 flavonoids, and two glyceroglycolipids were isolated and identified.
New cyanogenic and alkyl glycoside constituents from Phyllagathis rotundifolia

Ling SK, Tanaka T, Kouno I

J Nat Prod, 2002 Feb;65(2):131-5.
PMID: 11858743

Methanolic extracts of the leaves, stems, and roots of Phyllagathis rotundifolia collected in Malaysia yielded seven galloylated cyanogenic glucosides based on prunasin, with six of these being new compounds, prunasin 2',6'-di-O-gallate (3), prunasin 3',6'-di-O-gallate (4), prunasin 4',6'-di-O-gallate (5), prunasin 2',3',6'-tri-O-gallate (6), prunasin 3',4',6'-tri-O-gallate (7), and prunasin 2',3',4',6'-tetra-O-gallate (8). Also obtained was a new alkyl glycoside, oct-1-en-3-yl alpha-arabinofuranosyl-(1-->6)-beta-glucopyranoside (9). For compounds 3-8, the galloyl groups were individually linked to the sugar moieties via ester bonds. All new structures were established on the basis of NMR and MS spectroscopic studies. In addition, prunasin (1), gallic acid and its methyl ester, beta-glucogallin, 3,6-di-O-galloyl-D-glucose, 1,2,3,6-tetra-O-galloyl-beta-D-glucose, strictinin, 6-O-galloyl-2,3-O-(S)-hexahydroxydiphenoyl-D-glucose, praecoxin B, and pterocarinin C were isolated and identified. The isolation of 1 and its galloyl derivatives (3-8) from a Melastomataceous plant are described for the first time.
Antifungal Compound Isolated from Catharanthus roseus L. (Pink) for Biological Control of Root Rot Rubber Diseases

Zahari R, Halimoon N, Ahmad MF, Ling SK

Int J Anal Chem, 2018;2018:8150610.
PMID: 29692811 DOI: 10.1155/2018/8150610

Rigidoporus microporus, Ganoderma philippii, and Phellinus noxius are root rot rubber diseases and these fungi should be kept under control with environmentally safe compounds from the plant sources. Thus, an antifungal compound isolated from Catharanthus roseus was screened for its effectiveness in controlling the growth of these fungi. The antifungal compound isolated from C. roseus extract was determined through thin layer chromatography (TLC) and nuclear magnetic resonance (NMR) analysis. Each C. roseus of the DCM extracts was marked as CRD1, CRD2, CRD3, CRD4, CRD5, CRD6, and CRD7, respectively. TLC results showed that all of the C. roseus extracts peaked with red colour at Rf = 0.61 at 366 nm wavelength, except for CRD7. The CRD4 extract was found to be the most effective against R. microporus and G. philippii with inhibition zones of 3.5 and 1.9 mm, respectively, compared to that of other extracts. These extracts, however, were not effective against P. noxius. The CRD4 extract contained ursolic acid that was detected by NMR analysis and the compound could be developed as a biocontrol agent for controlling R. microporus and G. philippii. Moreover, little or no research has been done to study the effectiveness of C. roseus in controlling these fungi.
Effects of iridoids on lipoxygenase and hyaluronidase activities and their activation by beta-glucosidase in the presence of amino acids

Ling SK, Tanaka T, Kouno I

Biol Pharm Bull, 2003 Mar;26(3):352-6.
PMID: 12612446

Enzyme inhibitory activities of 14 iridoids previously obtained from two Malaysian medicinal plants, Saprosma scortechinii and Rothmannia macrophylla, were evaluated in vitro using soybean lipoxygenase and bovine testis hyaluronidase. Most of the iridoids, including asperulosidic acid, paederosidic acid, and an epimeric mixture of gardenogenins A and B, did not show any effect on the enzyme activities, except for the bis-iridoids, which inhibited the lipoxygenase activity with their IC(50) values of approximately 1.3 times that of a known inhibitor, fisetin. Structural modification of asperulosidic acid and paederosidic acid through enzymatic hydrolysis by beta-glucosidase resulted in their inhibition towards the enzyme activities, and these activities were enhanced by the presence of some amino acids (lysine, leucine or glutamic acid) or ammonium acetate. Mixtures of gardenogenins A and B; isomers of non-glucosidic iridoids, incubated with amino acid or ammonium acetate did not show any inhibitory effect on the enzyme activities during the 6 h incubation period, except for lysine where spontaneous reaction between the iridoids and amino acid resulted in the inhibition of lipoxygenase activity. The results from these biomimetic reactions suggested that the iridoid aglycons and the intermediates formed by these reactive species could inhibit the enzyme activities, and thus substantiate previous reports that the formation of iridoidal aglycons is a prerequisite for the iridoid glycosides to demonstrate some of the biological activities. In addition, the results also indicated that it is worthwhile to further explore these intermediates as potential anti-inflammatory agents.
Platelet-activating factor (PAF) receptor binding antagonist activity of the methanol extracts and isolated flavonoids from Chromolaena odorata (L.) King and Robinson

Ling SK, Pisar MM, Man S

Biol Pharm Bull, 2007 Jun;30(6):1150-2.
PMID: 17541171

The leaf, stem and root extracts of Chromolaena odorata were evaluated for their effect on platelet-activating factor (PAF) receptor binding on rabbit platelets using 3H-PAF as a ligand. The leaf extract demonstrated high PAF receptor binding inhibitory activity of 79.2+/-2.1% at 18.2 microg/ml. A total of eleven flavonoids were subsequently isolated from the active leaf extract and evaluated for their effects on PAF receptor binding. Eight of the flavonoids exhibited >50% inhibition on the binding activity at 18.2 microg/ml. These flavonoids were identified as eriodictyol 7,4'-dimethyl ether, quercetin 7,4'-methyl ether, naringenin 4'-methyl ether, kaempferol 4'-methyl ether, kaempferol 3-O-rutinoside, taxifolin 4'-methyl ether, taxifolin 7-methyl ether and quercetin 4'-methyl ether. Their IC50 values ranged from 19.5 to 62.1 microM.
Fulltext Bioassay-Guided Isolation of Cytotoxic Cycloartane Triterpenoid Glycosides from the Traditionally Used Medicinal Plant Leea indica

Wong YH, Abdul Kadir H, Ling SK

Evid Based Complement Alternat Med, 2012;2012:164689.
PMID: 22203865 DOI: 10.1155/2012/164689

Leea indica is a medicinal plant used traditionally to cure cancer. In this study, the cytotoxic compounds of L. indica were isolated using bioassay-guided approach. Two cycloartane triterpenoid glycosides, mollic acid arabinoside (MAA) and mollic acid xyloside (MAX), were firstly isolated from L. indica. They inhibited the growth of Ca Ski cervical cancer cells with IC(50) of 19.21 μM (MAA) and 33.33 μM (MAX). MRC5 normal cell line was used to calculate selectivity index. MAA and MAX were about 8 and 4 times more cytotoxic to Ca Ski cells compared to MRC5. The cytotoxicity of MAA was characterized by both cytostatic and cytocidal effects. MAA decreased the expression of proliferative cell nuclear antigen, increased sub-G1 cells, and arrested cells in S and G2/M phases. This study provides the evidence for the ethnomedicinal use of L. indica and paves the way for future mechanism studies on the anticancer effects of MAA.
Fulltext Antiproliferative activity of Vallaris glabra Kuntze (Apocynaceae)

Wong SK, Lim YY, Ling SK, Chiang Chan EW

Pharmacogn Mag, 2014 Apr;10(Suppl 2):S232-9.
PMID: 24991097 DOI: 10.4103/0973-1296.133238

Our earlier study on the antiproliferative (APF) activity of leaf extracts of ten Apocynaceae species showed that leaves of Vallaris glabra possessed strong and broad-spectrum properties.
Bioassay-guided isolation of neuroprotective compounds from Loranthus parasiticus against H₂O₂-induced oxidative damage in NG108-15 cells

Wong DZ, Kadir HA, Ling SK

J Ethnopharmacol, 2012 Jan 6;139(1):256-64.
PMID: 22107836 DOI: 10.1016/j.jep.2011.11.010

A parasite plant, Loranthus parasiticus (Loranthaceae), which is generally known as benalu teh (in Malay), Sang Ji Sheng (in Chinese), and baso-kisei (in Japan) distributed in south and southwest part of China, has been used as a folk medicine for the treatment of schizophrenia in southwest China. Loranthus parasiticus has various uses in folk and traditional medicines for bone, brain, kidney, liver, expels wind-damp, and prevents miscarriage.
Fulltext Caffeoylquinic acids in leaves of selected Apocynaceae species: Their isolation and content

Wong SK, Lim YY, Ling SK, Chan EW

Pharmacognosy Res, 2014 Jan;6(1):67-72.
PMID: 24497746 DOI: 10.4103/0974-8490.122921

Three compounds isolated from the methanol (MeOH) leaf extract of Vallaris glabra (Apocynaceae) were those of caffeoylquinic acids (CQAs). This prompted a quantitative analysis of their contents in leaves of V. glabra in comparison with those of five other Apocynaceae species (Alstonia angustiloba, Dyera costulata, Kopsia fruticosa, Nerium oleander, and Plumeria obtusa), including flowers of Lonicera japonica (Japanese honeysuckle), the commercial source of chlorogenic acid (CGA).
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.
Neuroprotective activity of galloylated cyanogenic glucosides and hydrolysable tannins isolated from leaves of Phyllagathis rotundifolia

Tan HP, Wong DZ, Ling SK, Chuah CH, Kadir HA

Fitoterapia, 2012 Jan;83(1):223-9.
PMID: 22093753 DOI: 10.1016/j.fitote.2011.10.019

The galloylated cyanogenic glucosides based on prunasin (1-7), gallotannins (8-14), ellagitannins (15-17), ellagic acid derivatives (18, 19) and gallic acid (20) isolated from the leaves of Phyllagathis rotundifolia (Melastomataceae) were investigated for their neuroprotective activity against hydrogen peroxide (H(2)O(2))-induced oxidative damage in NG108-15 hybridoma cell line. Among these compounds, the gallotannins and ellagitannins exhibited remarkable neuroprotective activities against oxidative damage in vitro as compared to galloylated cyanogenic glucosides and ellagic acid derivatives in a dose-dependent manner. They could be explored further as potential natural neuroprotectors in various remedies of neurodegenerative diseases.
Sulfur-containing bis-iridoid glucosides and iridoid glucosides from Saprosmas cortechinii

Ling SK, Komorita A, Tanaka T, Fujioka T, Mihashi K, Kouno I

J Nat Prod, 2002 May;65(5):656-60.
PMID: 12027736

Six new sulfur-containing bis-iridoid glucosides, saprosmosides A-F (1-6), were isolated from the leaves of Saprosma scortechinii. From the stems of this same plant, two new iridoid glucosides, 3,4-dihydro-3-methoxypaederoside (8) and 10-O-benzoyldeacetylasperulosidic acid (12), were isolated. Their structures were elucidated by means of chemical, NMR, and mass spectroscopic methods. Additionally, 11 known iridoid glucosides were isolated and characterized as deacetylasperuloside, asperuloside, paederoside (7), deacetylasperulosidic acid (9), scandoside, asperulosidic acid, 10-acetylscandoside, paederosidic acid (10), 6-epi-paederosidic acid (11), methylpaederosidate, and monotropein. The structures of the new bis-iridoid glucosides were formed by intermolecular esterification between the glucose and carboxyl groups of three monomeric iridoid glucosides (7, 9, and 10).
Fulltext Hydroxychavicol, a polyphenol from Piper betle leaf extract, induces cell cycle arrest and apoptosis in TP53-resistant HT-29 colon cancer cells

Rajedadram A, Pin KY, Ling SK, Yan SW, Looi ML

J Zhejiang Univ Sci B, 2021 Feb 15;22(2):112-122.
PMID: 33615752 DOI: 10.1631/jzus.B2000446

This study aims to elucidate the antiproliferative mechanism of hydroxychavicol (HC). Its effects on cell cycle, apoptosis, and the expression of c-Jun N-terminal kinase (JNK) and P38 mitogen-activated protein kinase (MAPK) in HT-29 colon cancer cells were investigated. HC was isolated from Piper betle leaf (PBL) and verified by high-performance liquid chromatography (HPLC), nuclear magnetic resonance (NMR), and gas chromatography-mass spectrometry (GC-MS). The cytotoxic effects of the standard drug 5-fluorouracil (5-FU), PBL water extract, and HC on HT-29 cells were measured after 24, 48, and 72 h of treatment. Cell cycle and apoptosis modulation by 5-FU and HC treatments were investigated up to 30 h. Changes in phosphorylated JNK (pJNK) and P38 (pP38) MAPK expression were observed up to 18 h. The half maximal inhibitory concentration (IC50) values of HC (30 μg/mL) and PBL water extract (380 μg/mL) were achieved at 24 h, whereas the IC50 of 5-FU (50 μmol/L) was obtained at 72 h. Cell cycle arrest at the G0/G1 phase in HC-treated cells was observed from 12 h onwards. Higher apoptotic cell death in HC-treated cells compared to 5-FU-treated cells (P<0.05) was observed. High expression of pJNK and pP38 MAPK was observed at 12 h in HC-treated cells, but not in 5-FU-treated HT-29 cells (P<0.05). It is concluded that HC induces cell cycle arrest and apoptosis of HT-29 cells, with these actions possibly mediated by JNK and P38 MAPK.
Iridoids and anthraquinones from the Malaysian medicinal plant, Saprosma scortechinii (Rubiaceae)

Ling SK, Komorita A, Tanaka T, Fujioka T, Mihashi K, Kouno I

Chem Pharm Bull (Tokyo), 2002 Aug;50(8):1035-40.
PMID: 12192133

A further investigation of the leaves and stems of Saprosma scortechinii afforded 13 compounds, of which 10 are new compounds. These were elucidated as the bis-iridoid glucosides, saprosmosides G (1) and H (2), the iridoid glucoside, 6-O-epi-acetylscandoside (3), and the anthraquinones, 1-methoxy-3-hydroxy-2-carbomethoxy-9,10-anthraquinone (4), 1-methoxy-3-hydroxy-2-carbomethoxy-9,10-anthraquinone 3-O-beta-primeveroside (5), 1,3-dihydroxy-2-carbomethoxy-9,10-anthraquinone 3-O-beta-primeveroside (6), 1,3,6-trihydroxy-2-methoxymethyl-9,10-anthraquinone (7), 1-methoxy-3,6-dihydroxy-2-hydroxymethyl-9,10-anthraquinone (8), 1,3,6-trihydroxy-2-hydroxymethyl-9,10-anthraquinone 3-O-beta-primeveroside (9), and 3,6-dihydroxy-2-hydroxymethyl-9,10-anthraquinone (10). Structure assignments for all compounds were established by means of mass and NMR spectroscopies, chemical methods, and comparison with published data. The new anthraquinones were derivatives of munjistin and lucidin.
Phytosterols isolated from Clinacanthus nutans induce immunosuppressive activity in murine cells

Le CF, Kailaivasan TH, Chow SC, Abdullah Z, Ling SK, Fang CM

Int Immunopharmacol, 2017 Mar;44:203-210.
PMID: 28119186 DOI: 10.1016/j.intimp.2017.01.013

Clinacanthus nutans (Burm. f.) Lindau is a traditional medicinal plant belonging to the Acanthaceae family. Its therapeutic potentials have been increasingly documented particularly the antiviral activity against Herpes Simplex Virus (HSV), anti-cancer, anti-oxidant, anti-inflammatory and immunomodulatory activities. However, majority of these studies used crude or fractionated extracts and not much is known about individual compounds from these extracts and their biological activities. In the present study, we have isolated four compounds (CN1, CN2, CN3 and CN4) from the hexane fractions of C. nutans leaves. Using NMR spectroscopic analysis, these compounds were identified to be shaftoside (CN1), stigmasterol (CN2), β-sitosterol (CN3) and a triterpenoid lupeol (CN4). To determine the immunosuppressive potential of these compounds, their effects on mitogens induced T and B lymphocyte proliferation and the secretion of helper T cell cytokines were examined. Among the four compounds, stigmasterol (CN2) and β-sitosterol (CN3) were shown to readily inhibit T cell proliferation mediated by Concanavalin A (ConA). However, only β-sitosterol (CN3) and not stigmasterol (CN2) blocks the secretion of T helper 2 (Th2) cytokines (IL-4 and IL-10). Both compounds have no effect on the secretion of Th1 cytokines (IL-2 and IFN-γ), suggesting that β-sitosterol treatment selectively suppresses Th2 activity and promotes a Th1 bias. CN3 was also found to significantly reduce the proliferation of both T helper cells (CD4(+)CD25(+)) and cytotoxic T cells (CD8(+)CD25(+)) following T cell activation induced by ConA. These results suggested that phytosterols isolated from C. nutans possess immunomodulatory effects with potential development as immunotherapeutics.
Systematic analysis of in vitro photo-cytotoxic activity in extracts from terrestrial plants in Peninsula Malaysia for photodynamic therapy

Ong CY, Ling SK, Ali RM, Chee CF, Samah ZA, Ho AS, et al.

J. Photochem. Photobiol. B, Biol., 2009 Sep 4;96(3):216-22.
PMID: 19647445 DOI: 10.1016/j.jphotobiol.2009.06.009

One hundred and fifty-five extracts from 93 terrestrial species of plants in Peninsula Malaysia were screened for in vitro photo-cytotoxic activity by means of a cell viability test using a human leukaemia cell-line HL60. These plants which can be classified into 43 plant families are diverse in their type of vegetation and their natural habitat in the wild, and may therefore harbour equally diverse metabolites with potential pharmaceutical properties. Of these, 29 plants, namely three from each of the Clusiaceae, Leguminosae, Rutaceae and Verbenaceae families, two from the Piperaceae family and the remaining 15 are from Acanthaceae, Apocynaceae, Bignoniaceae, Celastraceae, Chrysobalanaceae, Irvingiaceae, Lauraceae, Lythraceae, Malvaceae, Meliaceae, Moraceae, Myristicaceae, Myrsinaceae, Olacaceae and Sapindaceae. Hibiscus cannabinus (Malvaceae), Ficus deltoidea (Moraceae), Maranthes corymbosa (Chrysobalanaceae), Micromelum sp., Micromelum minutum and Citrus hystrix (Rutaceae), Cryptocarya griffithiana (Lauraceae), Litchi chinensis (Sapindaceae), Scorodocarpus bornensis (Olacaceae), Kokoona reflexa (Celastraceae), Irvingia malayana (Irvingiaceae), Knema curtisii (Myristicaceae), Dysoxylum sericeum (Meliaceae), Garcinia atroviridis, Garcinia mangostana and Calophyllum inophyllum (Clusiaceae), Ervatamia hirta (Apocynaceae), Cassia alata, Entada phaseoloides and Leucaena leucocephala (Leguminosae), Oroxylum indicum (Bignoniaceae), Peronema canescens,Vitex pubescens and Premna odorata (Verbenaceae), Piper mucronatum and Piper sp. (Piperaceae), Ardisia crenata (Myrsinaceae), Lawsonia inermis (Lythraceae), Strobilanthes sp. (Acanthaceae) were able to reduce the in vitro cell viability by more than 50% when exposed to 9.6J/cm(2) of a broad spectrum light when tested at a concentration of 20 microg/mL. Six of these active extracts were further fractionated and bio-assayed to yield four photosensitisers, all of which are based on the pheophorbide-a and -b core structures. Our results suggest that the main photosensitisers from terrestrial plants are likely based on the cyclic tetrapyrrole structure and photosensitisers with other structures, if present, are present in minor amounts or are not as active as those with the cyclic tetrapyrrole structure.
Fulltext Psychological Health of Surgeons in a Time of COVID-19: A Global Survey

Tan YQ, Wang Z, Yap QV, Chan YH, Ho RC, Hamid ARAH, et al.

Ann Surg, 2023 Jan 01;277(1):50-56.
PMID: 33491983 DOI: 10.1097/SLA.0000000000004775

OBJECTIVE: To assess the degree of psychological impact among surgical providers during the COVID-19 pandemic.
SUMMARY OF BACKGROUND DATA: The COVID-19 pandemic has extensively impacted global healthcare systems. We hypothesized that the degree of psychological impact would be higher for surgical providers deployed for COVID-19 work, certain surgical specialties, and for those who knew of someone diagnosed with, or who died, of COVID-19.
METHODS: We conducted a global web-based survey to investigate the psychological impact of COVID-19. The primary outcomes were the depression anxiety stress scale-21 and Impact of Event Scale-Revised scores.
RESULTS: A total of 4283 participants from 101 countries responded. 32.8%, 30.8%, 25.9%, and 24.0% screened positive for depression, anxiety, stress, and PTSD respectively. Respondents who knew someone who died of COVID-19 were more likely to screen positive for depression, anxiety, stress, and PTSD (OR 1.3, 1.6, 1.4, 1.7 respectively, all P < 0.05). Respondents who knew of someone diagnosed with COVID-19 were more likely to screen positive for depression, stress, and PTSD (OR 1.2, 1.2, and 1.3 respectively, all P < 0.05). Surgical specialties that operated in the head and neck region had higher psychological distress among its surgeons. Deployment for COVID- 19-related work was not associated with increased psychological distress.
CONCLUSIONS: The COVID-19 pandemic may have a mental health legacy outlasting its course. The long-term impact of this ongoing traumatic event underscores the importance of longitudinal mental health care for healthcare personnel, with particular attention to those who know of someone diagnosed with, or who died of COVID-19.

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