Mohamed Shaaban

Essramycin : A First Triazolopyrimidine Antibiotic Isolated from Nature

In the course of our screening program for new bio-active compounds, a novel triazolopyrimidine antibiotic, essramycin (1), was obtained from the culture broth of the marine Streptomyces sp., isolate Merv8102. Structure 1 was established by intensive NMR studies and by mass spectra. The compound is antibacterially active with MIC of 2 to 8 μg/ml against Gram-positive and Gram-negative bacteria, while it showed no antifungal activity. The fermentation and isolation, as well as the structure elucidation and biological activity of 1 are described.

Mansouramycins A-D, cytotoxic isoquinolinequinones from a marine streptomycete.

Chemical screening of the ethyl acetate extract from the marine-derived Streptomyces sp. isolate Mei37 resulted in five isoquinolinequinones, four new derivatives, mansouramycin A-D (1, 3-5), and the known 3-methyl-7-(methylamino)-5,8-isoquinolinedione (2). Their structures were elucidated by NMR and MS techniques and by comparison with related compounds. Cytotoxicity profiling of the mansouramycins in a panel of up to 36 tumor cell lines indicated significant cytotoxicity of several derivatives, with pronounced selectivity for non-small cell lung cancer, breast cancer, melanoma, and prostate cancer cells.

Bioactive Secondary Metabolites from a New Terrestrial Streptomyces sp. TN262

During our search for Streptomyces spp. as new producers of bioactive secondary metabolites, the ethyl acetate extract of the new terrestrial Streptomyces isolate TN262 delivered eight antimicrobially active compounds. They were identified as 1-acetyl-β-carboline (1), tryptophol (2), cineromycin B (3), 2,3-dihydrocineromycin B (4), cyclo-(tyrosylprolyl) (5), 3-(hydroxyacetyl)-indole (6), brevianamide F (7), and cis-cyclo-(l-prolyl-l-leucyl) (8). Three further metabolites were detected in the unpolar fractions using GC–MS and tentatively assigned as benzophenone (9), N-butyl-benzenesulfonamide (10), and hexanedioic acid-bis-(2-ethylhexyl) ester (11). This last compound is known as plasticizer derivatives, but it has never been described from natural sources. In this article, we describe the identification of the new Streptomyces sp. isolate TN262 using its cultural characteristics, the nucleotide sequence of the corresponding 16S rRNA gene and the phylogenetic analysis, followed by optimization, large-scale fermentation, isolation of the bioactive constituents, and determination of their structures. The biological activity of compounds (2), (3), (4), and those of the unpolar fractions was addressed as well.

New bioactive compounds from Aloe hijazensis

The chemical constituents and biological activities of leaves and roots of Aloe hijazensis, collected in Saudi Arabia, are reported here for the first time. Twenty-two compounds were obtained, among them eight hydroxyquinones: aloe-emodin (1), emodin (2), chrysophanol (3), aloesaponarin II 3-methyl ether (4), ziganein (5), ziganein-5-methyl ether (6a), aloesaponarin I (7) and chrysophanein (8), the dihydro-isocoumarin feralolide (9), 4,7-dichloro-quinoline (10), the triterpene lupeol (11), the anthrone aloin (12), three aloenin derivatives, aloenin (13) ethylidene-aloenin (14), and aloenin B (15), four flavonoids, quercetin (16), kaempferol (17) cosmosiin (18) and isovitexin (19), and cinnamic acid (20) and two further analogues, caffeic acid (21) and ferulic acid (22). While 15 of the isolated compounds were found in the leaves, 12 were isolated from roots of the plant. Compounds 6a and 10 are reported as new natural constituents, while the compounds 4, 5, 8, and 18 are reported here for the first time from Aloe spp. The structures of the compounds were deduced by intensive studies of their UV, NMR, MS data and by comparison with related structures. The biological activity of plant extracts was studied against various microbial strains, and potent anti-bacterial and anti-fungal activities were found.

Phenolic dimers and an indole alkaloid from Campylospermum flavum (Ochnaceae)

From the leaves and stem bark of Campylospermum flavum (Ochnaceae), three compounds, namely 4‴-O-methylagathisflavone, flavumchalcone, and flavumindole have been isolated together with 10 known compounds, including three flavonoids, two biflavonoids, two alkaloids, two nitrile glucosides, and glucopyranosyl-β-sistosterol. The structures of these compounds and their relative configurations were established by 1D and 2D NMR experiments. The methanolic crude extracts of leaves and stem bark of C. flavum and compounds displayed a significant cytotoxicity towards Artemia salina larvae.

Seven naphtho-γ-pyrones from the marine-derived fungus Alternaria alternata: structure elucidation and biological properties.

Eight bioactive pyrone derivatives were identified from the culture of Alternaria alternata strain D2006, isolated from the marine soft coral Denderonephthya hemprichi, which was selected as its profound antimicrobial activities. The compounds were assigned as pyrophen (1), rubrofusarin B (2), fonsecin (3), and fonsecin B (5) beside to the four dimeric naphtho-γ-pyrones; aurasperone A (6), aurasperone B (7), aurasperone C (8), and aurasperone F (9). Structures of the isolated compounds were identified on the basis of 1D and 2D NMR spectroscopy and mass (EI, ESI, HRESI) data, and by comparison with the literature. Configuration of the four dimeric naphtho-γ-pyrones 6-9 was analyzed by CD spectra, exhibiting an identical stereochemistry.

Chemical composition and biological activity of ripe pumpkin fruits (Cucurbita pepo L.) cultivated in Egyptian habitats.

The chemical composition and biological activity of three parts (rind, flesh and seeds) of pumpkin fruits (Cucurbita pepo L.) cultivated in Egypt were studied. Chemical analysis of fibre, protein, β-carotene, carbohydrates, minerals and fatty acids present in the rind, flesh, seeds and defatted seeds meal was conducted. Chemical, GC-MS and biological assays of organic extracts of the main fruit parts, rind and flesh established their unique constituents. Chromatographic purification of the extracts afforded triglyceride fatty acid mixture (1), tetrahydro-thiophene (2), linoleic acid (3), calotropoleanly ester (4), cholesterol (5) and 13(18)-oleanen-3-ol (6). GC-MS analysis of the extracts unpolar fraction revealed the existence of dodecane and tetradecane. Structures of the isolated compounds (1–6) were confirmed by NMR and EI-MS spectrometry. Antimicrobial, antiviral and antitumour activities of the fruit parts were discussed. The promising combined extract of rind and flesh was biologically studied for microbial and cytotoxic activities in comparison with the whole isolated components.

Phytochemical investigation and biological studies of Bombax malabaricum flowers

In this study, extracts of the flowers of the folk medicinal plant Bombax malabaricum DC were biologically and chemically screened. Chemical constituents in the n-hexane fraction from the flowers of B. malabaricum DC were investigated using gas–liquid chromatography (GLC) analysis, affording 14 compounds, including cholesterol, stigmasterol, campesterol and α-amyrin, while the residual 10 compounds are hydrocarbons. GLC analysis of the fatty acid (FA) esters established the majority abundance of the saturated FA over their unsaturated analogues. The polar methanol fraction afforded seven flavones: vicenin 2 (1), linarin (2), saponarin (3), cosmetin (4), isovitexin (5), xanthomicrol (6) and apigenin (7). Structures 1–7 were established by intensive studies of various spectral data (H-NMR, mass spectroscopy and UV) and comparison with authentic samples. Compounds 1–7 are described here for the first time from this plant. Extracts of n-hexane and methanol exhibited significant antioxidant and antimicrobial activities.

Hurgadacin: A new steroid from Sinularia polydactyla

Hurgadacin (1), a 24,25-bishomo-26-methylenecholesterol was isolated from the soft coral Sinularia polydactyla, collected from the Red Sea, near Hurghada at the Egyptian coast. The new steroid 1 was isolated together with the closely related polyhydroxy steroids 24-methylenecholestane-3β,5α,6β-triol (2) and 24-methylenecholestane-1α,3β,5α,6β,11α-pentol (3), in addition to the sesquiterpene lactiflorenol (4) and the trinorcarotenolide acetate peridinin (5), The structures of the isolated compounds were confirmed by intensive studies of their 1D and 2D NMR spectra and mass data. The antimicrobial and cytotoxic activities of the soft coral extract and the corresponding constituents were evaluated against diverse pathogenic microorganisms and brine shrimps, respectively.

Pachydictyols B and C: new diterpenes from Dictyota dichotoma Hudson.

Two new diterpenoids, pachydictyol B (1a/1b) and C (2), were isolated from the dichloromethane extract of the marine brown alga, Dictyota dichotoma, collected from the Red Sea coast of Egypt, along with the known metabolites, pachydictyol A (3a), dictyol E (4), cis-africanan-1α-ol (5a), fucosterol (6), tetrahydrothiophen-1,1-dioxide and poly-β-hydroxybutyric acid. GC-MS analysis of the nonpolar fractions also indicated the presence of β-bourbonene and nonanal, along with three hydrocarbons and five fatty acids or their simple derivatives, respectively. GC-MS analysis of the unsaponifiable algal petroleum ether extract revealed the presence of a further eight compounds, among them 2,2,6,7-tetramethyl-10-oxatricyclo[4.3.0.1(1,7)]decan-5-one (7), N-(4-bromo-n-butyl)-piperidin-2-one (8) and tert-hexadecanethiol. Structures 1–6 were assigned by 1D and 2D NMR, mass spectra (EI, CI, HREI and HRESI) and by comparison with data from related structures. The crude algal extract was potently active against the breast carcinoma tumor cell line, MCF7 (IC50 = 0.6 µg mL−1); pachydictyol B (1a) and dictyol E (4) showed weak antimicrobial properties, and the other compounds were inactive. Pachydictyols B (1a) and C (2) demonstrated a weak and unselective cytotoxicity against twelve human tumor cell lines with a mean IC50 of >30.0 µM.