Kamel H. Shaker

Triterpenoid saponins from Zygophyllum species

Abstract From the roots of Zygophyllum coccineum and the aerial parts of Z. album and Z. dumosum, the new triterpenoid saponin 3-O-[β-d-2-O-sulphonylquinovopyranosyl]-quinovic acid -27-O-[β- d -glucopyranosyl ] ester (zygophyloside F) has been isolated. The known saponins, 3-O-[β- d -quinovopyranosyl ]- quinovic acid 27-O-[β- d -glucopyranosyl ] ester and 3-O-[β- d -quinovopyranosyl ]- quinovic acid, were isolated from the aerial parts of Z. dumosum. The structures were determined primarily on the basis of NMR spectroscopy. The assignment of the NMR signals were performed by means of 1H1H COSY −45°, HMQC, HMBC and TOCSY experiments.

Environmental stresses of field growth allow cinnamyl alcohol dehydrogenase-deficient Nicotiana attenuata plants to compensate for their structural deficiencies

The organized lignocellulosic assemblies of cell walls provide the structural integrity required for the large statures of terrestrial plants. Silencing two CINNAMYL ALCOHOL DEHYDROGENASE (CAD) genes in Nicotiana attenuata produced plants (ir-CAD) with thin, red-pigmented stems, low CAD and sinapyl alcohol dehydrogenase activity, low lignin contents, and rubbery, structurally unstable stems when grown in the glasshouse (GH). However, when planted into their native desert habitat, ir-CAD plants produced robust stems that survived wind storms as well as the wild-type plants. Despite efficient silencing of NaCAD transcripts and enzymatic activity, field-grown ir-CAD plants had delayed and restricted spread of red stem pigmentation, a color change reflecting blocked lignification by CAD silencing, and attained wild-type-comparable total lignin contents. The rubbery GH phenotype was largely restored when field-grown ir-CAD plants were protected from wind, herbivore attack, and ultraviolet B exposure and grown in restricted rooting volumes; conversely, it was lost when ir-CAD plants were experimentally exposed to wind, ultraviolet B, and grown in large pots in growth chambers. Transcript and liquid chromatography-electrospray ionization-time-of-flight analysis revealed that these environmental stresses enhanced the accumulation of various phenylpropanoids in stems of field-grown plants; gas chromatography-mass spectrometry and nuclear magnetic resonance analysis revealed that the lignin of field-grown ir-CAD plants had GH-grown comparable levels of sinapaldehyde and syringaldehyde cross-linked into their lignins. Additionally, field-grown ir-CAD plants had short, thick stems with normal xylem element traits, which collectively enabled field-grown ir-CAD plants to compensate for the structural deficiencies associated with CAD silencing. Environmental stresses play an essential role in regulating lignin biosynthesis in lignin-deficient plants.

Cembranoid diterpenes and a briarane diterpene from corals

Two new cembrane diterpenes (+)-polydactylide (1) and (+)-7α,8β-dihydroxydeepoxysarcophine (2) together with (+)-sarcophine (3) and (+)-sarcophytoxide (4) have been isolated from the soft coral Sinularia polydactyla. The new cembrane diterpene (−)-7β-hydroxy-8α-methoxydeepoxysarcophine (5) has been obtained from the soft coral Sarcophyton trocheliophorum and the known briarane diterpene briaexcavatolide W (6) from the gorgonian coral Briareum sp. The structures were determined primarily by NMR spectroscopy. The assignment of NMR signals was performed by means of 1H–1H COSY, ROESY, HMQC and HMBC experiments.

Bioactive Metabolites from the Sponge Suberea sp.

Two new brominated compounds, subereaphenol K (2) and 2‐(3,5‐dibromo‐1‐ethoxy‐4‐oxocyclohexa‐2,5‐dien‐1‐yl)acetamide (3), together with subereaphenol B (methyl 2‐(2,4‐dibromo‐3,6‐dihydroxyphenyl)acetate; 1) with a revised structure, and five dibromotyrosine‐derived metabolites, 4–8, were isolated from the sponge Suberea sp. and characterized by 1D‐ and 2D‐NMR spectroscopic and HR‐MS spectrometric data. Compounds 1, 2, 6, and 8 exhibited various weak or moderate bioactivities, including antimicrobial and cytotoxic activities. Furthermore, compounds 1 and 2 inhibited human recombinant phosphodiesterase 4 (PDE4) with IC50 values of 2 μM, whereas compounds 6 and 8 were less active.

Flavone Composition and Antihypercholesterolemic and Antihyperglycemic Activities of Chrysanthemum coronarium L.

Five flavones were isolated from Chrysanthemum coronarium L., four of which were isolated for the first time from the genus Chrysanthemum. Two were the flavonoid aglycones 5,7- dihydroxy-3,6,4’-trimethoxyflavone (1) and scutellarin-6,7-dimethyl ether (2). A new flavonoid glycoside, apigenin-7-O-[2’’(6’’’-O-b-ß-acetylglucopyranosyl)]-6’’-O-acetylglucopyranoside (3), along with two known ones, i. e. apigenin-7-O-(2’’-O-b-ß-glucopyranosyl)-b-ß-glucopyranoside (4) and 6-methoxy quercetin-7-O-b-ß-glucopyranoside (5), were identified. Structures were elucidated by NMR and MS. The therapeutic value of petroleum ether, ethyl acetate, and methanol extracts, respectively, in rats suffering from hypercholesterolemia - as a consequence of high-fat diet - and hyperglycemia - as a consequence of hypercholesterolemia and low doses of streptozotocin - was investigated through determination of biochemical markers and histopathology. The ethyl acetate and methanol extracts showed remarkable results, followed by the petroleum ether extract

Phaseoloidin, a Homogentisic Acid Glucoside from Nicotiana Attenuata Trichomes, Contributes to the Plant’s Resistance against Lepidopteran Herbivores

Plant trichomes are known for their capability to produce and store secondary metabolites that protect plants from biotic and abiotic stresses. 1H NMR studies on intact individual trichomes located on the leaf surface of Nicotiana attenuata revealed the presence of two major secondary metabolites: nicotine, the signature metabolite of the genus, and phaseoloidin, a homogentisic acid glucoside. This glucoside was reported originally from the seeds of Entada phaseoloides, and this is the first report of its occurrence in a Solanaceous plant. Artificial diet feeding bioassays with Manduca sexta and Spodoptera littoralis larvae, two important herbivores of N. attenuata, revealed that the ingestion of phaseoloidin negatively influenced caterpillar performance. This effect was more pronounced for the generalist, S. littoralis, than for the specialists, M. sexta.

Beetles Do It Differently : Two Stereodivergent Cyclisation Modes in Iridoid-Producing Leaf-Beetle Larvae

Larvae of the Chrysomelina species Phaedon cochleariae, Hydrothassa marginella, Phratora vulgatissima, Gastrophysa viridula, Gastrophysa atrocyanea, Gastrophysa cyanea and Gastrophysa polygoni produce the iridoid chrysomelidial (1) to defend themselves against predators. Feeding experiments with a deuterated precursor ([2H5]8‐hydroxygeraniol 9) and in vitro isotope exchange experiments with defensive secretion in 2H2O revealed differences in the cyclisation of the ultimate precursor 8‐oxogeranial (8) to 1, between members of the genus Gastrophysa and all other species. In P. cochleariae, H. marginella and P. vulgatissima 1 is most likely produced by a Rauhut–Currier‐type cyclisation via a “transoid dienamine”, with loss of a single deuterium atom from C(4) of the precursor. In contrast, members of the genus Gastrophysa cyclise 8 via a “cisoid dienamine” intermediate, with exchange of all three deuterium atoms from the methyl group at C(3). To study whether the different cyclisation modes influence the stereochemistry of 1, the absolute configuration of 1 of the larvae was determined by GC‐MS on a chiral column. In accordance with literature (J. Meinwald, T. H. Jones, J. Am. Chem. Soc. 1978, 100, 1883 and N. Shimizu, R. Yakumaru, T. Sakata, S. Shimano, Y. Kuwahara, J. Chem. Ecol. 2012, 38, 29), we found (5S,8S)‐chrysomelidial (1) in H. marginella and P. vulgatissima, but P. cochleariae and all investigated members of the genus Gastrophysa synthesise (5R,8R)‐chrysomelidial (1).

Sulfonated Triterpenoid Saponins from Fagonia indica

Abstract Two new triterpenoid saponins, 3-O-{[ β-ᴅ-4-O-sulfonylglucopyranosyl-(1→3)]-α-ʟ-ara-binopyranosyl}-ursolic acid -28-O-[β-ᴅ-glucopyranosyl] ester (indicasaponin C) and 3-O-{[β-ᴅ-4-O-sulfonylglucopyranosyl-(1→3)]-[β-ᴅ-xylopyranosyl-(1→2)]-α-ʟ-arabinopyranosyl}-ursolic acid -28-O-[β-ᴅ-glucopyranosyl] ester (indicasaponin D) have been isolated from Fagonia indica. The structures were determined primarily by NMR spectroscopy. The assignment of NMR signals was performed by means of 1H -1H COSY, NOESY, ROESY, TOCSY, HMQC and HMBC experiments.

Phenolic glucosides from Hasseltia floribunda.

The leaves of Hasseltia floribunda were examined for their chemical constituents. Twelve phenolic glucosides, namely three hydroxycyclohexenyl acyl glucosides, four acylated salicortin derivatives, and five coumaroyl salicin derivatives, were isolated along with eight known phenolic glycosides, six known flavones, and two known sesquiterpenoid cyclohexenone derivatives. The structures of the isolated compounds were elucidated by NMR spectroscopic and HRMS spectrometric methods and by comparing analytical data with those of related structures.

Cross-Reactivity of Schistosoma mansoni-Fasciola gigantica Influenced by Saponins

The aim of the present work was to investigate the Schistosoma mansoni and Fasciola gigantica cross-reactivity between adult worms and egg homogenates of the parasites. Immunoprophylactic effects of crude Schistosoma mansoni worms and egg antigens mixed with or without saponins extracted from Atriplex nummularia were studied followed by challenge with 80 cercariae of Schistosoma mansoni. Our results showed that post 1st immunization with schistosome egg antigens (SEA) there was a significant change (P ≈ 0.05) in the IgM levels against Fasciola egg homogenate (FgEH) without saponins. Post 2nd immunization with SEA mixed with saponins the levels of IgM increased significantly (P ≈ 0.05) against Fasciola worm homogenate (FgWH) as compared with a non-immunized group. Post 2nd immunization the level of IgG was significantly elevated (P ≈ 0.05) by SEA mixed with saponins against FgWH. Post 2nd immunizations with SEA mixed with saponins showed a signifi cant change (P ≈ 0.05) in IgG levels against FgEH. These results clearly demonstrated that there is a cross-reactivity between Schistosoma mansoni eggs and Fasciola gigantica worms and eggs. Saponins were found to be immunostimulatory adjuvants in our study