Mohamed S. Kamel

Elicitation of secondary metabolism in actinomycetes

Genomic sequence data have revealed the presence of a large fraction of putatively silent biosynthetic gene clusters in the genomes of actinomycetes that encode for secondary metabolites, which are not detected under standard fermentation conditions. This review focuses on the effects of biological (co-cultivation), chemical, as well as molecular elicitation on secondary metabolism in actinomycetes. Our review covers the literature until June 2014 and exemplifies the diversity of natural products that have been recovered by such approaches from the phylum Actinobacteria.

Iridoid and megastigmane glycosides from Phlomis aurea

From the leaves of Phlomis aurea, two new iridoids of unique structures named 3-epiphlomurin (1) and phlomurin (2), a new megastigmane glucoside phlomuroside (3) and a new benzyl alcohol glycoside having the structure benzyl alcohol-O-beta-xylopyranosyl-(1-->2)-beta-glucopyranoside (4) have been isolated together with four known iridoids auroside, lamiide, 8-epiloganin and ipolamiide, two known phenolic glycosides acteoside (verbascoside) and syringin, one known phenylethanoid glycoside 2-phenylethyl-O-beta-xylopyranosyl-(1-->2)-beta-glucopyranoside, one known lignan liriodendrin and three known flavonoids chrysoeriol-7-O-beta-glucopyranoside, acacetin-7-O-beta-glucopyranoside and luteolin-7-O-beta-glucopyranoside. The structures of the isolated compounds were verified by means of mass spectrometry (MS) and nuclear magnetic resonance (NMR) spectral analyses.

Lignan glycosides from stems of Salvadora persica

Abstract From stems of Salvadora persica , five glycosides were isolated. Two are new and identified as sodium 1- O -benzyl-β- d -glucopyranoside-2-sulphate (salvadoside) and 5,5′-dimethoxylariciresinol 4,4′bis- O -β- d -glucopyranoside (salvadoraside), in addition to syringin, liriodendrin and sitosterol 3- O -glucopyranoside. This represents the first report of syringin and lignan glycosides from the family Salvadoraceae.

Benzoxazinoid glucosides from Acanthus ilicifolius

From the aerial parts of Acanthus ilicifolius, two benzoxazinoid glucosides, 7-chloro-(2R)-2-O-beta-D-glucopyranosyl-2H-1,4-benzoxazin-3(4H)-one and (2R)-2-O-beta-D-glucopyranosyl-5-hydroxy-2H-1,4-benzoxazin-3(4H)-one have been isolated, together with six known compounds. The structural elucidations were based on the analyses of spectroscopic data.

A furostanol saponin from fruits of Balanites aegyptiaca

A new furostanol saponin was isolated from the mesocarp of Balanites aegyptiaca fruits and identified as 26-O-beta-D-glucopyranosyl-(25R)-furost-5-ene-3,22,26-triol 3-O-[[alpha-L-rhamnopyranosyl-(1-->2)]-[beta-D-xylopyranosyl-(1-->2)]-be ta- D-xylopyranosyl-(1-->2)]-beta-D-xylopyranoside (balanitesin).

Monoterpene and pregnane glucosides from Solenostemma argel.

From the aerial parts of Solenostemma argel, two monoterpene glucosides have been isolated and identified as 6,7-dihydroxy-dihydrolinalool 3-O-beta-glucopyranoside and 6,7-dihydroxy-dihydrolinalool 7-O-beta-glucopyranoside. A pregnane glucoside was also isolated and assigned as pregn-5-ene-3,14-beta-dihydroxy-7,20-dione 3-O-beta-glucopyranoside together with the known compounds benzyl alcohol O-beta-apiofuranosyl-(1-->6)-beta-glucopyranoside, 2-phenylethyl O-alpha-arabinopyranosyl-(1-->6)-beta-glucopyranoside, astragalin and kaempferol-3-O-alpha-rhamnopyranosyl-(1-->2)-beta-glucopyranoside.

Monoterpene glucosides from Origanum syriacum

From the aerial parts of Origanum syriacum, three new monoterpene glucosides thymoquinol 2,5-O-beta-diglucopyranoside (3), carvacrol 2-O-beta-glucopyranosyl-(1-->2)-beta-glucopyranoside (4) and p-menth-1-ene-3,4-diol 4-O-beta-glucopyranoside (5) together with two known monoterpene glucosides thymoquinol 2-O-beta-glucopyranoside (1), thymoquinol 5-O-beta-glucopyranoside (2) have been isolated. The structures of the isolated compounds were verified by means of MS and NMR spectral analyses.

Pregnane glycosides from fruits of Balanites aegyptiaca

From the mesocarp of Balanites aegyptiaca fruits, two pregnane glycosides were isolated. One is new and identified as pregn-5-ene-3 beta,16 beta,20(R)-triol 3-O-(2,6-di-O-alpha-L-rhamnopyranosyl)-beta-D-glucopyranoside (balagyptin), while the other is known and assigned as pregn-5-ene-3 beta,16 beta,20(R)-triol 3-O-beta-D-glucopyranoside.

Acylated phenolic glycosides from Solenostemma argel

From the aerial parts of Solenostemma argel, four new acylated phenolic glycosides sinapyl alcohol 9-O-feruloyl-4-O-alpha-rhamnopyranosyl-(1-->2)-beta-glucopyranoside, solargin I (1), sinapyl alcohol 9-O-caffeoyl-4-O-alpha-rhamnopyranosyl-(1-->2)-beta-glucopyranoside, solargin II (2), sinapyl alcohol 9-O-feruloyl-4-O-alpha-rhamnopyranosyl-(1-->2)-alpha-rhamnopyranosyl-(1-->2)-beta-glucopyranoside, solargin III (3) and sinapyl alcohol 9-O-caffeoyl-4-O-alpha-rhamnopyranosyl-(1-->2)-alpha-rhamnopyranosyl-(1-->2)-beta-glucopyranoside, solargin IV (4) have been isolated. The structures of the isolated compounds were verified by means of MS and NMR spectral analyses.

Cardiac glycosides from Cryptostegia grandiflora.

From the leaves of Cryptostegia grandiflora, four new cardiac glycosides oleandrigenin 3-O-beta-glucopyranosyl-(1-->4)-beta-cymaropyranosyl-(1-->4)-beta-digitoxopyranoside, cryptostigmin I, oleandrigenin 3-O-beta-glucopyranosyl-(1-->4)-alpha-rhamnopyranoside, cryptostigmin II, 16-propionylgitoxigenin 3-O-beta-glucopyranosyl-(1-->4)-alpha-rhamnopyranoside, cryptostigmin III and oleandrigenin 3-O-beta-glucopyranosyl-(1-->6)-beta-glucopyranosyl-(1-->4)-beta-cymaropyranosyl-(1-->4)-beta-digitoxopyranoside, cryptostigmin IV have been isolated together with two known cardenolides subalpinosid and 16-O-acetyl-digitalinum verum. The structures of the isolated compounds were verified by means of MS and NMR spectral analyses.