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Denzil R Beukes - One of the best experts on this subject based on the ideXlab platform.
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plaxenone a and b cytotoxic halogenated monoterpenes from the south african red seaweed Plocamium maxillosum
Phytochemistry Letters, 2019Co-Authors: John J Bolton, Michael G Knott, Edith Antunes, Joanne De La Mare, Adrienne L Edkins, Angel Zhang, Martin J Stillman, Denzil R BeukesAbstract:Abstract The endemic South African red seaweed Plocamium maxillosum (Poiret) Lamouroux produces two unusual isomeric dichlorinated cyclohexenone monoterpenes, plaxenone A and B (1 and 2). The structures of the isolated compounds were determined from spectroscopic data and their absolute configuration was determined by comparison of the experimental and calculated ECD spectra. Compounds 1 and 2 inhibit the growth of MDA-MB-231 breast cancer cells.
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identification and in vitro anti esophageal cancer activity of a series of halogenated monoterpenes isolated from the south african seaweeds Plocamium suhrii and Plocamium cornutum
Phytochemistry, 2011Co-Authors: Edith Antunes, Anthonia F Afolayan, John J Bolton, Michael G Knott, Maynard T Chiwakata, Jameel Fakee, Catherine E Whibley, Denver T Hendricks, Denzil R BeukesAbstract:Five known (1, 2, 4, 6 and 7) halogenated monoterpenes together with 1Z,3R∗,4S∗,5E,7Z)-1-bromo-3,4,8-trichloro-7-(dichloromethyl)-3-methylocta-1,5,7-triene (3) and (3R∗,4S∗)-3,4,6,7-tetrachloro-3,7-dimethyl-octen-1-ene (5) were isolated from the red macroalga Plocamium suhrii and their structures deduced from their spectroscopic data. The seven compounds from P. suhrii together with five related compounds from Plocamium cornutum have been evaluated for their cytotoxic effects on an esophageal cancer cell line (WHCO1). Compounds 1–6 showed greater cytotoxicity in this assay as compared to the known anticancer drug cisplatin.
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antiplasmodial halogenated monoterpenes from the marine red alga Plocamium cornutum
Phytochemistry, 2009Co-Authors: Anthonia F Afolayan, Maryssa G A Mann, Carmen Lategan, Pete Smith, John J Bolton, Denzil R BeukesAbstract:In our continuing search for antimalarial leads from South African marine organisms we have examined the antiplasmodial organic extracts of the endemic marine red alga Plocamium cornutum (Turner) Harvey. Two new and three known halogenated monoterpenes were isolated and their structures determined by standard spectroscopic techniques. The 3,7-dimethyl-3,4-dichloro-octa-1,5,7-triene skeleton is common to all five compounds. Interestingly, compounds bearing the 7-dichloromethyl substituent showed significantly higher antiplasmodial activity toward a chloroquine sensitive strain of Plasmodium falciparum.
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halogenated monoterpene aldehydes from the south african marine alga Plocamium corallorhiza
Journal of Natural Products, 2007Co-Authors: Maryssa G A Mann, John J Bolton, Edith Antunes, Catherine E Whibley, Denver T Hendricks, Henry Mkwananzi, Denzil R BeukesAbstract:Four new halogenated monoterpene aldehydes (1−4) have been isolated from the South African marine red alga Plocamium corallorhiza, along with the known compounds 4,6-dibromo-1,1-dichloro-3,7-dimethyl-2E,7-octadiene (5) and 1,4,8-tribromo-3,7-dichloro-3,7-dimethyl-1E,5E-octadiene (10). The structures of the new compounds were determined by interpretation of their spectroscopic data and synthesis and mass spectrometric analysis of their pentafluorobenzyloxime (PFBO) derivatives.
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plocoralides a c polyhalogenated monoterpenes from the marine alga Plocamium corallorhiza
Phytochemistry, 2005Co-Authors: Michael G Knott, John J Bolton, Denver T Hendricks, Henry Mkwananzi, Catherine E Arendse, Denzil R BeukesAbstract:Abstract Three new polyhalogenated monoterpenes, plocoralides A–C ( 1 – 3 ) along with three known compounds ( 4 – 6 ) have been isolated from the organic extract of the red alga P. corallorhiza . Structures of the new compounds were characterized as 4,8-dibromo-1,1-dichloro-3,7-dimethyl-2 E ,6 E -octadiene ( 1 ), 4,6-dibromo-1,1-dichloro-3,7-dimethyl-2 E ,7-octadiene ( 2 ) and 4,8-dibromo-1,1,7-trichloro-3,7-dimethyl-2 E ,5 Z -octadiene ( 3 ) on the basis of one- and two-dimensional NMR spectroscopic data and MS analyses. Compounds 2 – 6 show moderate cytotoxicity toward esophageal cancer cells.
John J Bolton - One of the best experts on this subject based on the ideXlab platform.
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plaxenone a and b cytotoxic halogenated monoterpenes from the south african red seaweed Plocamium maxillosum
Phytochemistry Letters, 2019Co-Authors: John J Bolton, Michael G Knott, Edith Antunes, Joanne De La Mare, Adrienne L Edkins, Angel Zhang, Martin J Stillman, Denzil R BeukesAbstract:Abstract The endemic South African red seaweed Plocamium maxillosum (Poiret) Lamouroux produces two unusual isomeric dichlorinated cyclohexenone monoterpenes, plaxenone A and B (1 and 2). The structures of the isolated compounds were determined from spectroscopic data and their absolute configuration was determined by comparison of the experimental and calculated ECD spectra. Compounds 1 and 2 inhibit the growth of MDA-MB-231 breast cancer cells.
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identification and in vitro anti esophageal cancer activity of a series of halogenated monoterpenes isolated from the south african seaweeds Plocamium suhrii and Plocamium cornutum
Phytochemistry, 2011Co-Authors: Edith Antunes, Anthonia F Afolayan, John J Bolton, Michael G Knott, Maynard T Chiwakata, Jameel Fakee, Catherine E Whibley, Denver T Hendricks, Denzil R BeukesAbstract:Five known (1, 2, 4, 6 and 7) halogenated monoterpenes together with 1Z,3R∗,4S∗,5E,7Z)-1-bromo-3,4,8-trichloro-7-(dichloromethyl)-3-methylocta-1,5,7-triene (3) and (3R∗,4S∗)-3,4,6,7-tetrachloro-3,7-dimethyl-octen-1-ene (5) were isolated from the red macroalga Plocamium suhrii and their structures deduced from their spectroscopic data. The seven compounds from P. suhrii together with five related compounds from Plocamium cornutum have been evaluated for their cytotoxic effects on an esophageal cancer cell line (WHCO1). Compounds 1–6 showed greater cytotoxicity in this assay as compared to the known anticancer drug cisplatin.
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antiplasmodial halogenated monoterpenes from the marine red alga Plocamium cornutum
Phytochemistry, 2009Co-Authors: Anthonia F Afolayan, Maryssa G A Mann, Carmen Lategan, Pete Smith, John J Bolton, Denzil R BeukesAbstract:In our continuing search for antimalarial leads from South African marine organisms we have examined the antiplasmodial organic extracts of the endemic marine red alga Plocamium cornutum (Turner) Harvey. Two new and three known halogenated monoterpenes were isolated and their structures determined by standard spectroscopic techniques. The 3,7-dimethyl-3,4-dichloro-octa-1,5,7-triene skeleton is common to all five compounds. Interestingly, compounds bearing the 7-dichloromethyl substituent showed significantly higher antiplasmodial activity toward a chloroquine sensitive strain of Plasmodium falciparum.
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halogenated monoterpene aldehydes from the south african marine alga Plocamium corallorhiza
Journal of Natural Products, 2007Co-Authors: Maryssa G A Mann, John J Bolton, Edith Antunes, Catherine E Whibley, Denver T Hendricks, Henry Mkwananzi, Denzil R BeukesAbstract:Four new halogenated monoterpene aldehydes (1−4) have been isolated from the South African marine red alga Plocamium corallorhiza, along with the known compounds 4,6-dibromo-1,1-dichloro-3,7-dimethyl-2E,7-octadiene (5) and 1,4,8-tribromo-3,7-dichloro-3,7-dimethyl-1E,5E-octadiene (10). The structures of the new compounds were determined by interpretation of their spectroscopic data and synthesis and mass spectrometric analysis of their pentafluorobenzyloxime (PFBO) derivatives.
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plocoralides a c polyhalogenated monoterpenes from the marine alga Plocamium corallorhiza
Phytochemistry, 2005Co-Authors: Michael G Knott, John J Bolton, Denver T Hendricks, Henry Mkwananzi, Catherine E Arendse, Denzil R BeukesAbstract:Abstract Three new polyhalogenated monoterpenes, plocoralides A–C ( 1 – 3 ) along with three known compounds ( 4 – 6 ) have been isolated from the organic extract of the red alga P. corallorhiza . Structures of the new compounds were characterized as 4,8-dibromo-1,1-dichloro-3,7-dimethyl-2 E ,6 E -octadiene ( 1 ), 4,6-dibromo-1,1-dichloro-3,7-dimethyl-2 E ,7-octadiene ( 2 ) and 4,8-dibromo-1,1,7-trichloro-3,7-dimethyl-2 E ,5 Z -octadiene ( 3 ) on the basis of one- and two-dimensional NMR spectroscopic data and MS analyses. Compounds 2 – 6 show moderate cytotoxicity toward esophageal cancer cells.
Michael G Knott - One of the best experts on this subject based on the ideXlab platform.
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halogenated monoterpenes from namibian Plocamium rigidum accurate quantification and chemotaxonomic relevance
South African Journal of Botany, 2020Co-Authors: Stefan Louw, Lineekela Kandjengo, Jonathan Ortmann, Michael G KnottAbstract:Abstract Recently, a Namibian Plocamium specimen that shares the characteristics of both P. suhrii and P. rigidum was described in terms of the chemistry of its secondary metabolite constituents. Three variants or forms of this species with similarities and subtle differences in terms of morphology were found in the intertidal zone of Henties Bay, Namibia. Without DNA analysis, there is a degree of uncertainty regarding which Plocamium species these samples belong to. However, tentative morphological identification of the samples suggests P. rigidum. Hence, detailed chemical profiles of these variants were investigated in order to determine if their chemical compositions are in agreement with their morphological and taxonomic similarities and differences. Twelve halogenated monoterpenes previously identified in Namibian Plocamium species were mostly found to be present in the crude MeOH/DCM extracts of the three variants in this study. The major compound, 1E,3R,4S,5E,7Z-1-bromo-3,4,8-trichloro-7-(dichloromethyl)-3-methylocta-1,5,7-triene, was previously identified as the major metabolite of P. suhrii, the Namibian Plocamium species and also mostly likely P. rigidum. Gas chromatography with flame ionisation detection (GC-FID) was used for the accurate determination of the absolute and relative quantities of the twelve metabolites in the extracts. This data revealed that two of the variants were chemically similar, while the quantities of the metabolites present in the remaining variant showed large variations. In particular, significant variations in the concentration of the major metabolite was observed in the latter variant. However, the relative abundance of this metabolite in the former variants was almost 90%, which is consistent with what was previously reported and hence these two variants most probably belong to the same Namibian Plocamium rigidum species. Hence it was concluded that the remaining sample could be an intraspecies variant, or even another species of Plocamium.
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plaxenone a and b cytotoxic halogenated monoterpenes from the south african red seaweed Plocamium maxillosum
Phytochemistry Letters, 2019Co-Authors: John J Bolton, Michael G Knott, Edith Antunes, Joanne De La Mare, Adrienne L Edkins, Angel Zhang, Martin J Stillman, Denzil R BeukesAbstract:Abstract The endemic South African red seaweed Plocamium maxillosum (Poiret) Lamouroux produces two unusual isomeric dichlorinated cyclohexenone monoterpenes, plaxenone A and B (1 and 2). The structures of the isolated compounds were determined from spectroscopic data and their absolute configuration was determined by comparison of the experimental and calculated ECD spectra. Compounds 1 and 2 inhibit the growth of MDA-MB-231 breast cancer cells.
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in vitro antimicrobial activities of Plocamium rigidum and Plocamium cornutum from the namibian coast line
African Journal of Pharmacy and Pharmacology, 2018Co-Authors: Anthony Ishola, Michael G Knott, Jane M MisihairabgwiAbstract:The aim of this study was to determine suitable extraction solvents for antimicrobial compounds and the antimicrobial activity of two algal species, Plocamium cornutum and Plocamium rigidum collected from the coastline of Namibia. Samples were collected at low tide from the intertidal area of the coastline at Luderitz and Henties Bay. The samples were collected about 5 to 10 cm under water by hand and placed in a sealable polythene bag and refrigerated at -20°C. Dried algae extracts were reconstituted in distilled water, hexane, dichloromethane, ethanol, methanol and chloroform, respectively and tested in vitro for antimicrobial activity using the Kirby Bauer disc diffusion method against 12 pathogens (Escherichia coli, Staphylococcus aureus, Staphylococcus saprophyticus, Pseudomonas aeruginosa, Streptococcus pyogenes, Proteus mirabilis, Listeria monocytogenes, Shigella sonnei, Salmonella species, Enterococcus faecalis, Candida albicans and Staphylococcus epidermidis). Screening confirmed that water extracts showed no activity against all the pathogens as the extracts were insoluble in water. The Plocamium extracts in the remaining solvents showed varying degrees of antimicrobial activity. Both dichloromethane and methanol extracts reconstituted in chloroform showed the greatest activity amongst the five different solvents that were used. Ampicillin (10 µg/ml) showed no antimicrobial activity against S. epidermidis whilst a zone of inhibition of 6.26±0.07 mm was recorded for 10 µg/ml of P. cornutum extract reconstituted in chloroform. An ethanolic extract of P. rigidum showed a zone of inhibition of 6.35±0.25 mm against L. monocytogenes while the standard ampicillin had no activity. Extracts of P. rigidum in ethanol and P. cornutum in chloroform are evidently potential lead candidate antibiotics in vitro against L. monocytogenes and S. epidermidis, respectively. Key words: Antimicrobial activity, Plocamium cornutum, Plocamium rigidum, Listeria monocytogenes.
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antioxidant activity of a halogenated monoterpene isolated from a namibian marine algal Plocamium species
Journal of Food Science and Technology-mysore, 2017Co-Authors: Christ W Shapumba, Michael G Knott, Petrina T KapewangoloAbstract:The antioxidant potential of various marine natural products is well documented. The aim of this study was to evaluate the antioxidant potential of a rare halogenated monoterpene, namely; 1E,3R,4S,5E,7Z-1-bromo-3,4,8-trichloro-7-(dichloromethyl)-3-methylocta-1,5,7-triene (1) for the first time. This compound was isolated from a Namibian red algal Plocamium species. The antioxidant activity of the compound was evaluated using a series of antioxidant assays, namely; 2,2-diphenyl-1-picryl-hydrazyl radical (DPPH), reducing power, nitric oxide (NO) and hydrogen peroxide (H2O2). The compound demonstrated remarkable DPPH, NO and H2O2 scavenging activities with IC50 values of 0.05 ± 0.01, 4.18 ± 0.22 and 5.58 ± 1.11 mM, respectively. The reducing power of the compound increased with an increase in concentration. These results were compared to the absorbance of ascorbic acid, which was used as a standard control in all the antioxidant assays. The results strongly suggest that compound 1 is a promising antioxidant agent with potential commercial applications.
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gas chromatography mass spectrometry gc ms combined with retention index prediction for the rapid identification of halogenated monoterpenes from a namibian Plocamium species
Natural Product Communications, 2017Co-Authors: Stefan Louw, Lineekela Kandjengo, Michael G KnottAbstract:Plocamiun species collected from the Namibian coast display morphological features similar to those of both P. rigidum and P. suhrii which makes identification of these species a difficult task. It has been reported that the major secondary metabolites found in various Plocamium species are unique to each species [1]. In this study GC-MS combined with a retention index (RI) prediction strategy was used for the rapid identification of halogenated monoterpenes characteristic of a particular Namibian Plocatnium species. The RIs of the metabolites were matched with the predicted RIs of halogenated monoterpenes for which similar MS data have been reported for the same species of Plocamium. Based on the identification of the major secondary metabolite, IE,3R,4S,5E,7Z- 1-bromo-3;4,8- trichloro-7-(dichloromethyl)-3-methylocta-1,5,7-triene [2], it was proposed that these Namibian samples are closely related to that of P. suhrii. From. this, it was determined that the proposed P. suhrii specimens collected in Namibia contain four additional metabolites (with molecular formulae C₁₀H₁₆Br₂C₂, C₁₀H₁₁BrCI₄, C₁₀H₉BrCl₆ and an unknown compound) previously not reported in P. suhrii species. In addition, a compound previously identified in South African P. suhrii was not present in the Namibian Plocamium specimens.
Gary W Saunders - One of the best experts on this subject based on the ideXlab platform.
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a new taxonomic interpretation of the type of Plocamium cartilagineum plocamiales florideophyceae and its consequences
European Journal of Phycology, 2011Co-Authors: Javier Cremades, Rodolfo Barreiro, Isabel Maneiro, Gary W SaundersAbstract:A detailed study of the type specimen of Plocamium cartilagineum and other original material of European species of Plocamium revealed that the nomenclatural reorganization proposed by Saunders & Lehmkuhl in 2005 must be revised. The main consequences of the new interpretation are: (1) the use of Plocamium lyngbyanum to name their molecular entity EUR1 (previously considered to be equivalent to P. cartilagineum s.s.); and (2) adopting P. cartilagineum for their molecular entity EUR2, which renders P. subtile Kutzing a taxonomic synonym. Using a combination of morphological, anatomical and molecular information (barcoding), we conclude that the colour and consistency of the thallus, the number of ramuli per series, the morphology and arrangement of the tetrasporangial stichidia, the length of the tetrasporangia, and the type of habitat are the most reliable characters of classical taxonomy for discriminating between the species of Plocamium occurring in northern Europe.
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molecular divergence and morphological diversity among four cryptic species of Plocamium plocamiales florideophyceae in northern europe
European Journal of Phycology, 2005Co-Authors: Gary W Saunders, Virginia K LehmkuhlAbstract:The Plocamiaceae currently includes two genera: the free-living Plocamium and the adelphoparasite, Plocamiocolax. Plocamium includes ca. 40 species that are widely distributed throughout the world's oceans. Most species are clearly defined anatomically and biogeographically; however, the type species Plocamium cartilagineum (type locality: considered northern Europe) is an exception. Although reportedly cosmopolitan in distribution, our investigations unequivocally indicate that there is substantial genetic diversity among isolates from different geographic locations and that there are at least eight divergent cryptic species currently included in P. cartilagineum. In this investigation we focused on populations of P. cartilagineum from northern Europe. We used a combination of molecular and morphological characters in order to establish boundaries between four cryptic species in this geographical area. Our molecular results not only resolve these four entities as distinct, but also indicate that they are...
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96 recognizing cryptic species investigations into the molecular relatedness and morphological diversity of the species of the red algal genus Plocamium plocamiales florideophyceae
Journal of Phycology, 2003Co-Authors: K V Lehmkuhl, Gary W SaundersAbstract:Small-subunit ribosomal DNA (SSU) sequences used in combination with anatomical and morphological data have supported elevation of the Plocamiaceae to ordinal status. The Plocamiales currently includes two genera: the free-living Plocamium Lamouroux; and the adelphoparasite, Plocamiocolax Setchell. Plocamium includes upwards of 40 species, which are widely distributed throughout the world's oceans. Most species are clearly defined anatomically and biogeographically. In this regard the type species, P. cartilagineum (L.) Dixon (type locality: reportedly Northern Europe), is an exception. Plocamium cartilagineum is considered cosmopolitan in distribution, with individuals varying in size, and in the number and habit of ramuli in their alternating series. We have sequenced the large-subunit ribosomal DNA (LSU) for representatives of P. cartilagineum from France, Ireland, Norway and Scotland as well as isolates from Australia and the North Pacific. These data indicate that many cryptic species, four within Europe itself, are currently included within the concept of P. cartilagineum. We present molecular, biogeographical, ecological, and morphological/anatomical data characterizing these European forms and provide taxonomic revisions that reflect this diversity within P. cartilagineum.
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small subunit rrna gene sequences from representatives of selected families of the gigartinales and rhodymeniales rhodophyta 1 evidence for the plocamiales ord nov
Botany, 1994Co-Authors: Gary W Saunders, G T KraftAbstract:Nucleotide sequences of the nuclear, small-subunit (SSU) ribosomal RNAs, as inferred from polymerase chain reaction (PCR)-amplified products, are presented for Areschougia congesta (Turner) J. Agardh (Solieriaceae), Dasyphloea insignis Montagne (Dumontiaceae), Sarcothalia crassifolia (C. Agardh) Edyvane & Womersley (Gigartinaceae), Nizymenia australis Sonder (Nizymeniaceae), Phacelocarpus peperocarpos (Poiret) Wynne, Ardre & Silva (Phacelocarpaceae), Plocamiocolax pulvinata Setchell, Plocamium angustum (J. Agardh) J.D. Hooker, Plocamium cartilagineum (Linnaeus) Dixon (Plocamiaceae), Rhodymenia linearis J. Agardh (Rhodymeniaceae), and Sphaerococcus coronopifolius Stackhouse (Sphaerococcaceae). Phylogenetic analyses of the SSU sequences between the Plocamiaceae and members of the Sphaerococcaceae, Phacelocarpaceae, and Nizymeniaceae, with which the Plocamiaceae has been associated historically, show SSU differences of between 87 and 105 nucleotides and do not indicate a close relationship. A review of anato...
Anthonia F Afolayan - One of the best experts on this subject based on the ideXlab platform.
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identification and in vitro anti esophageal cancer activity of a series of halogenated monoterpenes isolated from the south african seaweeds Plocamium suhrii and Plocamium cornutum
Phytochemistry, 2011Co-Authors: Edith Antunes, Anthonia F Afolayan, John J Bolton, Michael G Knott, Maynard T Chiwakata, Jameel Fakee, Catherine E Whibley, Denver T Hendricks, Denzil R BeukesAbstract:Five known (1, 2, 4, 6 and 7) halogenated monoterpenes together with 1Z,3R∗,4S∗,5E,7Z)-1-bromo-3,4,8-trichloro-7-(dichloromethyl)-3-methylocta-1,5,7-triene (3) and (3R∗,4S∗)-3,4,6,7-tetrachloro-3,7-dimethyl-octen-1-ene (5) were isolated from the red macroalga Plocamium suhrii and their structures deduced from their spectroscopic data. The seven compounds from P. suhrii together with five related compounds from Plocamium cornutum have been evaluated for their cytotoxic effects on an esophageal cancer cell line (WHCO1). Compounds 1–6 showed greater cytotoxicity in this assay as compared to the known anticancer drug cisplatin.
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antiplasmodial halogenated monoterpenes from the marine red alga Plocamium cornutum
Phytochemistry, 2009Co-Authors: Anthonia F Afolayan, Maryssa G A Mann, Carmen Lategan, Pete Smith, John J Bolton, Denzil R BeukesAbstract:In our continuing search for antimalarial leads from South African marine organisms we have examined the antiplasmodial organic extracts of the endemic marine red alga Plocamium cornutum (Turner) Harvey. Two new and three known halogenated monoterpenes were isolated and their structures determined by standard spectroscopic techniques. The 3,7-dimethyl-3,4-dichloro-octa-1,5,7-triene skeleton is common to all five compounds. Interestingly, compounds bearing the 7-dichloromethyl substituent showed significantly higher antiplasmodial activity toward a chloroquine sensitive strain of Plasmodium falciparum.
