Diaa Youssef | King AbdulAziz University (KAU) Jeddah, Saudi Arabia (original) (raw)
Papers by Diaa Youssef
Zeitschrift für Naturforschung C, 2016
Two new antimicrobial fatty acid esters, penicilloitins A and B (1 and 2), along with α-cyclopiaz... more Two new antimicrobial fatty acid esters, penicilloitins A and B (1 and 2), along with α-cyclopiazonic acid (3), tryptamine (4) and indole-3-carbaldehyde (5), were isolated from mycelial extracts and the culture broth of a marine endophytic Penicillium species and their structures established by spectroscopic techniques including 1D (1H NMR and 13C NMR) and 2D NMR (COSY, multiplicity-edited HSQC, and HMBC) as well as HRESIMS. Of these compounds, 1, 3 and 4 displayed modest antimicrobial activity.
Marine Drugs
Cyanobacteria ascribed to the genus Lyngbya (Family Oscillatoriaceae) represent a potential thera... more Cyanobacteria ascribed to the genus Lyngbya (Family Oscillatoriaceae) represent a potential therapeutic gold mine of chemically and biologically diverse natural products that exhibit a wide array of biological properties. Phylogenetic analyses have established the Lyngbya ‘morpho-type’ as a highly polyphyletic group and have resulted in taxonomic revision and description of an additional six new cyanobacterial genera in the same family to date. Among the most prolific marine cyanobacterial producers of biologically active compounds are the species Moorena producens (previously L. majuscula, then Moorea producens), M. bouillonii (previously L. bouillonii), and L. confervoides. Over the years, compounding evidence from in vitro and in vivo studies in support of the significant pharmaceutical potential of ‘Lyngbya’-derived natural products has made the Lyngbya morphotype a significant target for biomedical research and novel drug leads development. This comprehensive review covers comp...
Marine Drugs
Marine natural products (MNPs) continue to be in the spotlight in the global drug discovery endea... more Marine natural products (MNPs) continue to be in the spotlight in the global drug discovery endeavor. Currently, more than 32,000 structurally diverse secondary metabolites from marine sources have been isolated, making MNPs a vital source for researchers to look for novel drug candidates. The marine-derived psammaplysins possess the rare and unique 1,6-dioxa-2-azaspiro [4.6] undecane backbone and are represented by 44 compounds in the literature, mostly from sponges of the order Verongiida. Compounds with 1,6-dioxa-2-azaspiro [4.6] undecane moiety exist in the literature under five names, including psammaplysins, ceratinamides, frondoplysins, ceratinadins, and psammaceratins. These compounds displayed significant biological properties including growth inhibitory, antimalarial, antifouling, protein tyrosine phosphatase inhibition, antiviral, immunosuppressive, and antioxidant effects. In this review, a comprehensive literature survey covering natural occurrence of the psammaplysins ...
Bulletin of Pharmaceutical Sciences. Assiut, 2005
Bioassay-guided fractionation and purification of the ethanolic extract of the fresh flowers of H... more Bioassay-guided fractionation and purification of the ethanolic extract of the fresh flowers of Hippeastrum vittatum (Amaryllidaceae) cultivated in Egypt yielded three compounds viz. caffeic acid (1), dihydrocaffeic acid methyl ester (2), together with the polyhydroxylated alkaloid pancratistatin (3). The structures of the isolated compounds were determined on the basis of extensive 1D (1 H and 13 C) and 2D (COSY, HMQC, and HMBC) NMR studies, and mass spectral measurements. The cytotoxic activity of compounds 1-3 is presented and discussed.
Phytochemistry Letters, 2012
Records of Pharmaceutical and Biomedical Sciences, 2017
The diversity of the symbiotic fungi associated with two Red Sea sponges of the genus Hyrtios (H.... more The diversity of the symbiotic fungi associated with two Red Sea sponges of the genus Hyrtios (H. erecta and H. erectus) was investigated. A total of 20 isolates were purified from these sponges. Using the morphological properties, 10 fungal strains were identified to the genus level from each sponge. Strains isolated from H. erecta were identified to the species level using the Internal Transcribed Spacer ITS-rDNA sequences. Most of the identified fungal strains belong to the genera Penicillium and Aspergillus. The antibacterial activities of organic extracts of these fungi were investigated against three pathogenic microbes including E. coli, S. aureus and C. albicans. All of the fungal extracts displayed moderate to high levels of antimicrobial activities against the three pathogens. Several fungal strains of the genera Penicillium and Aspergillus displayed strong antibacterial activities provide potential for future investigation of these strains to identify the bioactive leads in these fungal extracts.
Plants, 2022
Regarding our growing interest in identifying biologically active leads from Amaryllidaceous plan... more Regarding our growing interest in identifying biologically active leads from Amaryllidaceous plants, the flowers of Pancratium maritimum L. (Amaryllidaceae) were investigated. Purification of the cytotoxic fractions of the alcoholic extract of the flowers gave a new glycoside, 3-[4-(β-D-glucopyranosyloxy)phenyl]-2-(Z)-propenoic acid methyl ester (1), together with the previously reported compounds 3-methoxy-4-(β-D-glucopyranosyloxy)benzoic acid methyl ester (2), 3-(4-methoxyphenyl)propan-1-ol-1-O-β-D-glucopyranoside (3), (E)-3-(4-hydroxyphenyl)acrylic acid methyl ester (4), caffeic acid (5), dihydrocaffeic acid methyl ester (6), and pancratistatin (7). Interestingly, compounds 1 and 2 are phenolic-O-glycosides, while the glucose moiety in 3 is attached to the propanol side chain. This is the first report about the existence of 1–6 in the genus Pancratium. Further, glycosides 1–3 from the Amaryllidaceae family are reported on here for the first time. The structures of 1–7 were determ...
Our previous studies showed that several sipholane triterpenes, sipholenol A, sipholenone E, siph... more Our previous studies showed that several sipholane triterpenes, sipholenol A, sipholenone E, sipholenol L and siphonellinol D, have potent reversal effect for multidrug resistance (MDR) in cancer cells that overexpressed P-glycoprotein (P-gp/ABCB1). Through comparison of cytotoxicity towards sensitive and multi-drug resistant cell lines, we identified that the semisynthetic esters sipholenol A-4-O-acetate and sipholenol A-4-O-isonicotinate potently reversed P-gp-mediated MDR but had no effect on
Natural product sciences, 2007
Investigation of the chloroform soluble fraction of the red alga Liagora farinosa, collected from... more Investigation of the chloroform soluble fraction of the red alga Liagora farinosa, collected from Hurghada at the Red Sea resulted in the isolation of three compounds; a nucleoside (thymidine) and two glycosides (methyl--D-xylopyranoside and glycerol-2--D-glucopyranoside). The structures of the isolated compounds were established on the basis of different spectroscopic techniques as well as comparison with the previously published data. This is the first report for the isolation of the three compounds fron red algae; moreover, the compounds were examined for their antioxidant activity and showed variable activity.
Biomolecules, 2020
The world's oceans have been shown to be rich habitats with great biodiversity and chemical e... more The world's oceans have been shown to be rich habitats with great biodiversity and chemical entities with proven bioactivities related to cancer, inflammation, epilepsy, the immunomodulatory system, microbial and parasitic infections, and many others [...].
Bulletin of Pharmaceutical Sciences. Assiut, 2003
Bioactive-guided fractionation and purification of the ethyl acetate fraction of an ethanolic ext... more Bioactive-guided fractionation and purification of the ethyl acetate fraction of an ethanolic extract of fresh flowers of Pancratium maritimum (Amaryllidaceae) cultivated in Egypt yielded an alkaloid, pancratistatin (1), together with 3caffeoylquinic acid methyl ester (2). Their structures were determined on the basis of extensive 1D (1 H and 13 C) and 2D (COSY, HMQC, HMBC, and NOESY) NMR studies and high-resolution mass spectral measurements. Both compounds showed potent cytotoxic activity against HeLa cells and moderate anti-tuberculosis activity against Mycobacterium tuberculosis H37Rv. This is the first report of pancratistatin in Pancratium maritimum and the first report of 3-caffeoylquinic acid methyl ester in the family Amaryllidaceae.
Revista Brasileira de Farmacognosia, 2016
In the course of our ongoing effort to identify bioactive compounds from marine-derived fungi, th... more In the course of our ongoing effort to identify bioactive compounds from marine-derived fungi, the marine fungus, Penicillium species was isolated from the Red Sea tunicate, Didemnum species. Two new cerebrosides, penicillosides A and B were isolated from the marine-derived fungus, Penicillium species using different chromatographic methods. Their structures were established by different spectroscopic data including 1D (1 H NMR and 13 C NMR) and 2D NMR (COSY, HSQC, and HMBC) studies as well as highresolution mass spectral data. Penicilloside A displayed antifungal activity against Candida albicans while penicilloside B illustrated antibacterial activities against Staphylococcus aureus and Escherichia coli in the agar diffusion assay. Additionally, both compounds showed weak activity against HeLa cells.
Biochemical and Biophysical Research Communications, 2002
Multidrug resistance (MDR) cells can be sensitized to anticancer drugs when treated concomitantly... more Multidrug resistance (MDR) cells can be sensitized to anticancer drugs when treated concomitantly with chemosensitizers. In this study, chemosensitizing effects of 5,6,7,3′,4′-pentamethoxyflavone (sinensetin) and its analogs were investigated with respect to in vitro efficacy and structure–activity relationship. Sinensetin reversed the resistance of P-glycoprotein (Pgp)-overexpressing AML-2/D100 to vincristine in a concentration-dependent manner. Chemosensitizing effect of sinensetin was 10- and 18-fold higher
Marine Drugs
Investigation of the cytotoxic fractions of the ethyl acetate extract of the fermentation broth o... more Investigation of the cytotoxic fractions of the ethyl acetate extract of the fermentation broth of the tunicate-derived Aspergillus sp. DY001 afforded two new dipeptides, asperopiperazines A and B (1 and 2), along with the previously reported compounds (+)-citreoisocoumarin (3) and (−)-6,8-di-O-methylcitreoisocoumarin (4). Analyses of the 1D and 2D NMR spectroscopic data of the compounds supported their structural assignments. Asperopiperazine A (1) is a cyclic dipeptide of leucine and phenylalanine moieties, which are substituted with an N-methyl and an N-acetyl group, respectively. On the other hand, asperopiperazine B (2) is a cyclic dipeptide of proline and phenylalanine moieties with a hydroxyl group at C-2 of the proline part. The absolute configuration of the amino acid moieties in 1 and 2 were determined by Marfey’s analyses and DFT NMR chemical shift calculations, leading to their assignment as cyclo(l-NMe-Leu-l-NAc-Phe) and cyclo(d-6-OH-Pro-l-Phe), respectively. Asperopipe...
Marine Drugs, 2015
In the course of our continuing efforts to identify bioactive secondary metabolites from Red Sea ... more In the course of our continuing efforts to identify bioactive secondary metabolites from Red Sea marine invertebrates, we have investigated the sponge Hemimycale arabica. The antimicrobial fraction of an organic extract of the sponge afforded two new hydantoin alkaloids, hemimycalins A and B (2 and 3), together with the previously reported compound (Z)-5-(4-hydroxybenzylidene)imidazolidine-2,4-dione (1). The structures of the compounds were determined by extensive 1D and 2D NMR (COSY, HSQC and HMBC) studies and high-resolution mass spectral determinations. Hemimycalins A (2) and B (3) represent the first examples of the natural N-alkylated hydantoins from the sponge Hemimycale arabica. Compounds 1-3 displayed variable antimicrobial activities against E. coli, S. aureus, and C. albicans. In addition, compound 1 displayed moderate antiproliferative activity against the human cervical carcinoma (HeLa) cell line. These findings provide further insight into the chemical diversity as well as the biological activity of this class of compounds.
Records of Natural Products, 2016
Calotroposide S (1), a new oxypregnane oligoglycoside has been isolated from the n-butanol fracti... more Calotroposide S (1), a new oxypregnane oligoglycoside has been isolated from the n-butanol fraction of Calotropis procera (Ait) R. Br. root bark. The structure of 1 was assigned based on various spectroscopic analyses. Calotroposide S (1) possesses the 12-O-benzoylisolineolon aglycone moiety with eight sugar residues attached to C-3 of the aglycone. It showed potent anti-proliferative activity towards PC-3 prostate cancer, A549 non-small cell lung cancer (NSCLC), and U373 glioblastoma (GBM) cell lines with IC50 0.18, 0.2, and 0.06 μM, respectively compared with cisplatin and carboplatin.
Marine Drugs
In the course of our continuing efforts to identify bioactive secondary metabolites from Red Sea ... more In the course of our continuing efforts to identify bioactive secondary metabolites from Red Sea marine sponges, we have investigated the sponge Hemimycale sp. The cytotoxic fraction of the organic extract of the sponge afforded three new compounds, hemimycalins C–E (1–3). Their structural assignments were obtained via analyses of their one- and two-dimensional NMR spectra and HRESI mass spectrometry. Hemimycalin C was found to differ from the reported hydantoin compounds in the configuration of the olefinic moiety at C-5–C-6, while hemimycalins D and E were found to contain an 2-iminoimidazolidin-4-one moiety instead of the hydantoin moiety in previously reported compounds from the sponge. Hemimycalins C–E showed significant antimicrobial activity against Escherichia coli and Candida albicans and cytotoxic effects against colorectal carcinoma (HCT 116) and the triple-negative breast cancer (MDA-MB-231) cells.
![Research paper thumbnail of Magnificines A and B, Antimicrobial Marine Alkaloids Featuring a Tetrahydrooxazolo[3,2-a]azepine-2,5(3H,6H)-dione Backbone from the Red Sea Sponge Negombata magnifica](https://attachments.academia-assets.com/78280422/thumbnails/1.jpg)
](Investigation of the Red Sea sponge Negombata magnifica gave two novel alkaloids, magnificines A ... more Investigation of the Red Sea sponge Negombata magnifica gave two novel alkaloids, magnificines A and B (1 and 2) and a new β-ionone derivative, (±)-negombaionone (3), together with the known latrunculin B (4) and 16-epi-latrunculin B (5). The analysis of the NMR and HRESIMS spectra supported the planar structures and the relative configurations of the compounds. The absolute configurations of magnificines A and B were determined by the analysis of the predicted and experimental ECD spectra. Magnificines A and B possess a previously unreported tetrahydrooxazolo[3,2-a]azepine-2,5(3H,6H)-dione backbone and represent the first natural compounds in this class. (±)-Negombaionone is the first β-ionone of a sponge origin. Compounds 1-3 displayed selective activity against Escherichia coli in a disk diffusion assay with inhibition zones up to 22 mm at a concentration of 50 µg/disc and with MIC values down to 8.0 µM. Latrunculin B and 16-epi-latrunculin B inhibited the growth of HeLa cells wi...
Marine Drugs
During an investigation of the chemistry of the Red Sea Verongiid sponge Pseudoceratina arabica, ... more During an investigation of the chemistry of the Red Sea Verongiid sponge Pseudoceratina arabica, we discovered a small molecule, pseudoceratonic acid (1), along with the new moloka’iamine derivatives, ceratinines N (2), O (3), and the previously reported compounds moloka’iamine (4), hydroxymoloka’iamine (5) and ceratinamine (6). The structural assignments of 1–6 were accomplished by interpretation of their NMR and HRESIMS spectral data. Pseudoceratonic acid possesses a dibrominated hydrazine-derived functional group not found in any reported chemical compound. Pseudoceratonic acid selectively inhibited the growth of E. coli and S. aureus, while ceratinine N selectively inhibited C. albicans. Further, ceratinine N showed potent cytotoxic effects against the triple-negative breast cancer, colorectal carcinoma, and human cervical carcinoma cell lines down to 2.1 µM.
Marine Drugs
Bioassay-guided partition of the extract of the Red Sea sponge Pseudoceratina arabica and HPLC pu... more Bioassay-guided partition of the extract of the Red Sea sponge Pseudoceratina arabica and HPLC purification of the active fraction gave a psammaplysin dimer, psammaceratin A (1), along with psammaplysin A (2). The dimer comprises two units of psammaplysin A (2) connected via the terminal amines with an unprecedented (2Z,3Z)-2,3-bis(aminomethylene)succinamide moiety, and it represents the first dimer to be identified among the psammaplysin family. Data from 1D- and 2D-NMR and HRMS supported the chemical structures of the compounds. Psammaceratin A (1) and psammaplysin A (2) exhibited significant growth inhibition of HCT 116, HeLa, and MBA-MB-231 cells down to 3.1 μM.
Zeitschrift für Naturforschung C, 2016
Two new antimicrobial fatty acid esters, penicilloitins A and B (1 and 2), along with α-cyclopiaz... more Two new antimicrobial fatty acid esters, penicilloitins A and B (1 and 2), along with α-cyclopiazonic acid (3), tryptamine (4) and indole-3-carbaldehyde (5), were isolated from mycelial extracts and the culture broth of a marine endophytic Penicillium species and their structures established by spectroscopic techniques including 1D (1H NMR and 13C NMR) and 2D NMR (COSY, multiplicity-edited HSQC, and HMBC) as well as HRESIMS. Of these compounds, 1, 3 and 4 displayed modest antimicrobial activity.
Marine Drugs
Cyanobacteria ascribed to the genus Lyngbya (Family Oscillatoriaceae) represent a potential thera... more Cyanobacteria ascribed to the genus Lyngbya (Family Oscillatoriaceae) represent a potential therapeutic gold mine of chemically and biologically diverse natural products that exhibit a wide array of biological properties. Phylogenetic analyses have established the Lyngbya ‘morpho-type’ as a highly polyphyletic group and have resulted in taxonomic revision and description of an additional six new cyanobacterial genera in the same family to date. Among the most prolific marine cyanobacterial producers of biologically active compounds are the species Moorena producens (previously L. majuscula, then Moorea producens), M. bouillonii (previously L. bouillonii), and L. confervoides. Over the years, compounding evidence from in vitro and in vivo studies in support of the significant pharmaceutical potential of ‘Lyngbya’-derived natural products has made the Lyngbya morphotype a significant target for biomedical research and novel drug leads development. This comprehensive review covers comp...
Marine Drugs
Marine natural products (MNPs) continue to be in the spotlight in the global drug discovery endea... more Marine natural products (MNPs) continue to be in the spotlight in the global drug discovery endeavor. Currently, more than 32,000 structurally diverse secondary metabolites from marine sources have been isolated, making MNPs a vital source for researchers to look for novel drug candidates. The marine-derived psammaplysins possess the rare and unique 1,6-dioxa-2-azaspiro [4.6] undecane backbone and are represented by 44 compounds in the literature, mostly from sponges of the order Verongiida. Compounds with 1,6-dioxa-2-azaspiro [4.6] undecane moiety exist in the literature under five names, including psammaplysins, ceratinamides, frondoplysins, ceratinadins, and psammaceratins. These compounds displayed significant biological properties including growth inhibitory, antimalarial, antifouling, protein tyrosine phosphatase inhibition, antiviral, immunosuppressive, and antioxidant effects. In this review, a comprehensive literature survey covering natural occurrence of the psammaplysins ...
Bulletin of Pharmaceutical Sciences. Assiut, 2005
Bioassay-guided fractionation and purification of the ethanolic extract of the fresh flowers of H... more Bioassay-guided fractionation and purification of the ethanolic extract of the fresh flowers of Hippeastrum vittatum (Amaryllidaceae) cultivated in Egypt yielded three compounds viz. caffeic acid (1), dihydrocaffeic acid methyl ester (2), together with the polyhydroxylated alkaloid pancratistatin (3). The structures of the isolated compounds were determined on the basis of extensive 1D (1 H and 13 C) and 2D (COSY, HMQC, and HMBC) NMR studies, and mass spectral measurements. The cytotoxic activity of compounds 1-3 is presented and discussed.
Phytochemistry Letters, 2012
Records of Pharmaceutical and Biomedical Sciences, 2017
The diversity of the symbiotic fungi associated with two Red Sea sponges of the genus Hyrtios (H.... more The diversity of the symbiotic fungi associated with two Red Sea sponges of the genus Hyrtios (H. erecta and H. erectus) was investigated. A total of 20 isolates were purified from these sponges. Using the morphological properties, 10 fungal strains were identified to the genus level from each sponge. Strains isolated from H. erecta were identified to the species level using the Internal Transcribed Spacer ITS-rDNA sequences. Most of the identified fungal strains belong to the genera Penicillium and Aspergillus. The antibacterial activities of organic extracts of these fungi were investigated against three pathogenic microbes including E. coli, S. aureus and C. albicans. All of the fungal extracts displayed moderate to high levels of antimicrobial activities against the three pathogens. Several fungal strains of the genera Penicillium and Aspergillus displayed strong antibacterial activities provide potential for future investigation of these strains to identify the bioactive leads in these fungal extracts.
Plants, 2022
Regarding our growing interest in identifying biologically active leads from Amaryllidaceous plan... more Regarding our growing interest in identifying biologically active leads from Amaryllidaceous plants, the flowers of Pancratium maritimum L. (Amaryllidaceae) were investigated. Purification of the cytotoxic fractions of the alcoholic extract of the flowers gave a new glycoside, 3-[4-(β-D-glucopyranosyloxy)phenyl]-2-(Z)-propenoic acid methyl ester (1), together with the previously reported compounds 3-methoxy-4-(β-D-glucopyranosyloxy)benzoic acid methyl ester (2), 3-(4-methoxyphenyl)propan-1-ol-1-O-β-D-glucopyranoside (3), (E)-3-(4-hydroxyphenyl)acrylic acid methyl ester (4), caffeic acid (5), dihydrocaffeic acid methyl ester (6), and pancratistatin (7). Interestingly, compounds 1 and 2 are phenolic-O-glycosides, while the glucose moiety in 3 is attached to the propanol side chain. This is the first report about the existence of 1–6 in the genus Pancratium. Further, glycosides 1–3 from the Amaryllidaceae family are reported on here for the first time. The structures of 1–7 were determ...
Our previous studies showed that several sipholane triterpenes, sipholenol A, sipholenone E, siph... more Our previous studies showed that several sipholane triterpenes, sipholenol A, sipholenone E, sipholenol L and siphonellinol D, have potent reversal effect for multidrug resistance (MDR) in cancer cells that overexpressed P-glycoprotein (P-gp/ABCB1). Through comparison of cytotoxicity towards sensitive and multi-drug resistant cell lines, we identified that the semisynthetic esters sipholenol A-4-O-acetate and sipholenol A-4-O-isonicotinate potently reversed P-gp-mediated MDR but had no effect on
Natural product sciences, 2007
Investigation of the chloroform soluble fraction of the red alga Liagora farinosa, collected from... more Investigation of the chloroform soluble fraction of the red alga Liagora farinosa, collected from Hurghada at the Red Sea resulted in the isolation of three compounds; a nucleoside (thymidine) and two glycosides (methyl--D-xylopyranoside and glycerol-2--D-glucopyranoside). The structures of the isolated compounds were established on the basis of different spectroscopic techniques as well as comparison with the previously published data. This is the first report for the isolation of the three compounds fron red algae; moreover, the compounds were examined for their antioxidant activity and showed variable activity.
Biomolecules, 2020
The world's oceans have been shown to be rich habitats with great biodiversity and chemical e... more The world's oceans have been shown to be rich habitats with great biodiversity and chemical entities with proven bioactivities related to cancer, inflammation, epilepsy, the immunomodulatory system, microbial and parasitic infections, and many others [...].
Bulletin of Pharmaceutical Sciences. Assiut, 2003
Bioactive-guided fractionation and purification of the ethyl acetate fraction of an ethanolic ext... more Bioactive-guided fractionation and purification of the ethyl acetate fraction of an ethanolic extract of fresh flowers of Pancratium maritimum (Amaryllidaceae) cultivated in Egypt yielded an alkaloid, pancratistatin (1), together with 3caffeoylquinic acid methyl ester (2). Their structures were determined on the basis of extensive 1D (1 H and 13 C) and 2D (COSY, HMQC, HMBC, and NOESY) NMR studies and high-resolution mass spectral measurements. Both compounds showed potent cytotoxic activity against HeLa cells and moderate anti-tuberculosis activity against Mycobacterium tuberculosis H37Rv. This is the first report of pancratistatin in Pancratium maritimum and the first report of 3-caffeoylquinic acid methyl ester in the family Amaryllidaceae.
Revista Brasileira de Farmacognosia, 2016
In the course of our ongoing effort to identify bioactive compounds from marine-derived fungi, th... more In the course of our ongoing effort to identify bioactive compounds from marine-derived fungi, the marine fungus, Penicillium species was isolated from the Red Sea tunicate, Didemnum species. Two new cerebrosides, penicillosides A and B were isolated from the marine-derived fungus, Penicillium species using different chromatographic methods. Their structures were established by different spectroscopic data including 1D (1 H NMR and 13 C NMR) and 2D NMR (COSY, HSQC, and HMBC) studies as well as highresolution mass spectral data. Penicilloside A displayed antifungal activity against Candida albicans while penicilloside B illustrated antibacterial activities against Staphylococcus aureus and Escherichia coli in the agar diffusion assay. Additionally, both compounds showed weak activity against HeLa cells.
Biochemical and Biophysical Research Communications, 2002
Multidrug resistance (MDR) cells can be sensitized to anticancer drugs when treated concomitantly... more Multidrug resistance (MDR) cells can be sensitized to anticancer drugs when treated concomitantly with chemosensitizers. In this study, chemosensitizing effects of 5,6,7,3′,4′-pentamethoxyflavone (sinensetin) and its analogs were investigated with respect to in vitro efficacy and structure–activity relationship. Sinensetin reversed the resistance of P-glycoprotein (Pgp)-overexpressing AML-2/D100 to vincristine in a concentration-dependent manner. Chemosensitizing effect of sinensetin was 10- and 18-fold higher
Marine Drugs
Investigation of the cytotoxic fractions of the ethyl acetate extract of the fermentation broth o... more Investigation of the cytotoxic fractions of the ethyl acetate extract of the fermentation broth of the tunicate-derived Aspergillus sp. DY001 afforded two new dipeptides, asperopiperazines A and B (1 and 2), along with the previously reported compounds (+)-citreoisocoumarin (3) and (−)-6,8-di-O-methylcitreoisocoumarin (4). Analyses of the 1D and 2D NMR spectroscopic data of the compounds supported their structural assignments. Asperopiperazine A (1) is a cyclic dipeptide of leucine and phenylalanine moieties, which are substituted with an N-methyl and an N-acetyl group, respectively. On the other hand, asperopiperazine B (2) is a cyclic dipeptide of proline and phenylalanine moieties with a hydroxyl group at C-2 of the proline part. The absolute configuration of the amino acid moieties in 1 and 2 were determined by Marfey’s analyses and DFT NMR chemical shift calculations, leading to their assignment as cyclo(l-NMe-Leu-l-NAc-Phe) and cyclo(d-6-OH-Pro-l-Phe), respectively. Asperopipe...
Marine Drugs, 2015
In the course of our continuing efforts to identify bioactive secondary metabolites from Red Sea ... more In the course of our continuing efforts to identify bioactive secondary metabolites from Red Sea marine invertebrates, we have investigated the sponge Hemimycale arabica. The antimicrobial fraction of an organic extract of the sponge afforded two new hydantoin alkaloids, hemimycalins A and B (2 and 3), together with the previously reported compound (Z)-5-(4-hydroxybenzylidene)imidazolidine-2,4-dione (1). The structures of the compounds were determined by extensive 1D and 2D NMR (COSY, HSQC and HMBC) studies and high-resolution mass spectral determinations. Hemimycalins A (2) and B (3) represent the first examples of the natural N-alkylated hydantoins from the sponge Hemimycale arabica. Compounds 1-3 displayed variable antimicrobial activities against E. coli, S. aureus, and C. albicans. In addition, compound 1 displayed moderate antiproliferative activity against the human cervical carcinoma (HeLa) cell line. These findings provide further insight into the chemical diversity as well as the biological activity of this class of compounds.
Records of Natural Products, 2016
Calotroposide S (1), a new oxypregnane oligoglycoside has been isolated from the n-butanol fracti... more Calotroposide S (1), a new oxypregnane oligoglycoside has been isolated from the n-butanol fraction of Calotropis procera (Ait) R. Br. root bark. The structure of 1 was assigned based on various spectroscopic analyses. Calotroposide S (1) possesses the 12-O-benzoylisolineolon aglycone moiety with eight sugar residues attached to C-3 of the aglycone. It showed potent anti-proliferative activity towards PC-3 prostate cancer, A549 non-small cell lung cancer (NSCLC), and U373 glioblastoma (GBM) cell lines with IC50 0.18, 0.2, and 0.06 μM, respectively compared with cisplatin and carboplatin.
Marine Drugs
In the course of our continuing efforts to identify bioactive secondary metabolites from Red Sea ... more In the course of our continuing efforts to identify bioactive secondary metabolites from Red Sea marine sponges, we have investigated the sponge Hemimycale sp. The cytotoxic fraction of the organic extract of the sponge afforded three new compounds, hemimycalins C–E (1–3). Their structural assignments were obtained via analyses of their one- and two-dimensional NMR spectra and HRESI mass spectrometry. Hemimycalin C was found to differ from the reported hydantoin compounds in the configuration of the olefinic moiety at C-5–C-6, while hemimycalins D and E were found to contain an 2-iminoimidazolidin-4-one moiety instead of the hydantoin moiety in previously reported compounds from the sponge. Hemimycalins C–E showed significant antimicrobial activity against Escherichia coli and Candida albicans and cytotoxic effects against colorectal carcinoma (HCT 116) and the triple-negative breast cancer (MDA-MB-231) cells.
Investigation of the Red Sea sponge Negombata magnifica gave two novel alkaloids, magnificines A ... more Investigation of the Red Sea sponge Negombata magnifica gave two novel alkaloids, magnificines A and B (1 and 2) and a new β-ionone derivative, (±)-negombaionone (3), together with the known latrunculin B (4) and 16-epi-latrunculin B (5). The analysis of the NMR and HRESIMS spectra supported the planar structures and the relative configurations of the compounds. The absolute configurations of magnificines A and B were determined by the analysis of the predicted and experimental ECD spectra. Magnificines A and B possess a previously unreported tetrahydrooxazolo[3,2-a]azepine-2,5(3H,6H)-dione backbone and represent the first natural compounds in this class. (±)-Negombaionone is the first β-ionone of a sponge origin. Compounds 1-3 displayed selective activity against Escherichia coli in a disk diffusion assay with inhibition zones up to 22 mm at a concentration of 50 µg/disc and with MIC values down to 8.0 µM. Latrunculin B and 16-epi-latrunculin B inhibited the growth of HeLa cells wi...
Marine Drugs
During an investigation of the chemistry of the Red Sea Verongiid sponge Pseudoceratina arabica, ... more During an investigation of the chemistry of the Red Sea Verongiid sponge Pseudoceratina arabica, we discovered a small molecule, pseudoceratonic acid (1), along with the new moloka’iamine derivatives, ceratinines N (2), O (3), and the previously reported compounds moloka’iamine (4), hydroxymoloka’iamine (5) and ceratinamine (6). The structural assignments of 1–6 were accomplished by interpretation of their NMR and HRESIMS spectral data. Pseudoceratonic acid possesses a dibrominated hydrazine-derived functional group not found in any reported chemical compound. Pseudoceratonic acid selectively inhibited the growth of E. coli and S. aureus, while ceratinine N selectively inhibited C. albicans. Further, ceratinine N showed potent cytotoxic effects against the triple-negative breast cancer, colorectal carcinoma, and human cervical carcinoma cell lines down to 2.1 µM.
Marine Drugs
Bioassay-guided partition of the extract of the Red Sea sponge Pseudoceratina arabica and HPLC pu... more Bioassay-guided partition of the extract of the Red Sea sponge Pseudoceratina arabica and HPLC purification of the active fraction gave a psammaplysin dimer, psammaceratin A (1), along with psammaplysin A (2). The dimer comprises two units of psammaplysin A (2) connected via the terminal amines with an unprecedented (2Z,3Z)-2,3-bis(aminomethylene)succinamide moiety, and it represents the first dimer to be identified among the psammaplysin family. Data from 1D- and 2D-NMR and HRMS supported the chemical structures of the compounds. Psammaceratin A (1) and psammaplysin A (2) exhibited significant growth inhibition of HCT 116, HeLa, and MBA-MB-231 cells down to 3.1 μM.