Ahmed F. Halim

Chemical Constituents of the Essential Oils of Origanum syriacum and Stachys aegyptiaca

AbstractThe Essential Leaf Oils Of Origanum Syriacum Var. Aegyptiacum and Stachys Aegyptiaca (Lamiaceae), Were Prepared By Hydrodistillation and Studied By Cgc and Gc-Ms. Among The 28 Compounds Identified In The Oil Of Origanum, Up To 83% Consists Of The Antiseptic and Flavoring Agent Carvacrol. In Addition, Carvacrol Methyl Ether and Carvacryl Acetate Are Present In Minute Amounts. The Monoterpene Hydrocarbon Fraction Accounts For Nearly 12% Of The Oil Of Which P-Cymene, γ-Terpinene, Myrceneand A-Thujene Are The Major Components. The Sesquiterpene Compounds and The Monoterpene Alcohols Occur In Rather Insignificant Concentrations.The Oil Of Stachys Aegyptiaca Consists Mainly Of 14 Monoterpene Hydrocarbons (75%), 4 Oxygenated Monoterpenes (1.1%) and 7 Sesquiterpene Hydrocarbons (17%). The Dominant Compound Is Ot-Pinene.

Pregnane glycosides from Caralluma retrospiciens

Two pregnane ester glycosides were isolated and identified from the alcohol extract of the aerial parts of Caralluma retrospiciens. Their structures were established as 12 beta-benzoyloxy-20-isovaleroyloxy-8 beta,14 beta-dihydroxypregnane-3-O -[beta-D-glucopyranosyl-(1-->6)-beta-D-glucopyranosyl -(1-->4)-beta-D-(3-O-methyl-6-deoxy)-galactopyranoside] (caretroside A) and the bioside 12 beta-benzoyloxy-8 beta,14 beta-dihydroxypregn-20-one-3-O-[beta -D-oleandropyranosyl-(1-->4)-beta-D-cymaropyranoside]. They were characterized through physical and chemical methods in addition to standard spectroscopic techniques especially 2D NMR (COSY, HMQC and HMBC). This is the first report of the isolation of these compounds from a natural source.

ANTHRAQUINONES FROM GALIUM SINAICUM

Abstract The new anthraquinones, 7-methylanthragallol 1,3-dimethyl ether, 7-methyl-anthragallol 2-methyl ether, 6-methylanthragallol 3-methyl ether, 8-hydroxyanthragallol 2,3-dimethyl ether, 7-formylanthragallol 1,3-dimethyl ether, copareolatin 5,7-dimethyl ether, copareolatin 6,7-dimethyl ether, 6-methoxylucidin ω-ethyl ether and 6-hydroxyxanthopurpurin, as well as a novel bianthraquinone, bisinaiquinone [10,2′-bi(9-hydroxy-3-methyl-1,4-anthraquinonyl)] were isolated from the roots of Galium sinaicum . Their structures were established by spectroscopic techniques including 2D-NMR. In addition, eight known anthraquinones were also isolated and fully characterized.

Cytotoxic triterpenes from Cleome africana

Eighteen dammarane-type triterpenes were obtained from the whole plant of Cleome africana by means of cytotoxic bioassay-directed fractionation. Twelve of them were novel compounds whose structures were elucidated by various spectroscopic methods.

Flavonol glycosides from Nitraria retusa.

The new flavonol trioside, isorhamnetin 3-O-4Rham-galactosylrobinobioside and five known flavonol glycosides, isorhamnetin 3-robinobioside, isorhamnetin 3-rutinoside, isorhamnetin 3-galactoside, isorhamnetin 3-glucoside and free isorhamnetin were isolated from the leaves and young stems of Nitraria retusa and characterized by UV and NMR spectroscopy. Isorhamnetin 3-xylosylrobinobioside was also tentatively identified.

Cytotoxic hydroazulene diterpenes from the brown alga Dictyota dichotoma.

Two new hydroazulenoid (prenyl guaiane) diterpenes, dictyone acetate (2) and 3,4-epoxy 13-hydroxy pachydictyol A (4) were isolated from the petroleum ether fraction of the alcoholic extract of the brown alga, Dictyota dichotoma (Hudson) Lamouroux, which was collected from the Red Sea coasts at Hurgada, Egypt, together with three known ones, pachydictyol A (1), dictyone (3) and 11-hydroxypachydictyol A (dictyol E) (5). In addition, the steroidal compound, stigmasta-5,(E)-24(28)-dien-3-β-ol (fucosterol) (6) was also isolated. The structures of the isolated compounds have been determined on the basis of spectroscopic evidences as well as physical and chemical correlation with known compounds. Compounds 1, 2, 3 and 5 showed moderate cytotoxic activity

(+)-12α-hydroxylupanine, a lupin alkaloid from Lygos raetam

Abstract A new lupin alkaloid, (+)-12α-hydroxylupanine, was isolated from the aerial part of Lygos raetam , together with six known alkaloids: (+)-retamine, (+)-sparteine, (−)-lupanine, (−)-anagyrine, (−)-cytisine and (−)- N -methylcytisine. The structure of the new alkaloid including absolute configuration was determined by spectroscopic methods and by its chemical transformation to (+)-retamine.

Anthraquinones from the polar fractions of Galium sinaicum

The new anthraquinones, 6,7-dimethoxy xanthopurpurin, 6-hydroxy-7-methoxy rubiadin, 5-hydroxy-6-hydroxymethyl anthragallol 1, 3-dimethyl ether, 7-carboxy anthragallol 1,3-dimethyl ether, anthragallol 1-methyl ether 3-O-beta-D-glucopyranoside, anthragallol 1-methyl ether 3-O-rutinoside, anthragallol 3-O-rutinoside and alizarin 1-methyl ether 2-O-primeveroside were isolated from the CH2Cl2 and n-BuOH extracts of Galium sinaicum roots and their structures were established by various spectroscopic techniques. In addition, two known anthraquinones were also isolated and fully characterized.

Pregnane glycosides from Stapelia variegata.

Eleven new pregnane ester glycosides have been isolated from the aerial parts of Stapelia variegata. Eight of the recognized compounds were established to possess the same trioside moiety, viz. 3-O-[3-O-methyl-6-deoxy-beta-D-allopyranosyl-(1-4)-beta-D- cymaropyranosyl-(1-4)-beta-D-cymaropyranoside]. These compounds were identified as: stavaroside A: 12-O-beta-angeloyl-20-O-benzoyl sarcostin; stavaroside B: 12-O-beta-angeloyl-20-O-tigloyl sarcostin; stavaroside C: 11 alpha-acetoxy 2 beta-benzoxy-3 beta,8 beta, 14 beta-trihydroxy-pregn-5-ene-20-one; stavaroside D: 11 alpha-acetoxy- 12 beta-tigloxy-3 beta,8 beta,14 beta-trihydroxy-pregn-5-ene-20-one; stavaroside E: 12-O-beta-benzoyl sarcostin; stavaroside F: 11 alpha-acetoxy-12 beta-acetoxy-3 beta,8 beta,14 beta-trihydroxy-pregn-5- ene-20-one; stavaroside G: 12-O-beta,20-O-diacetyl sarcostin and stavaroside H: 3 beta, 8 beta, 11 alpha, 12 beta, 14 beta-pentahydroxy-pregn-5- ene-20-one. The other three compounds were shown to possess the same tetraside sugar moiety, viz. 3-O-[beta-D-glucopyranosyl- (1-4)-3-O-methyl-6-deoxy-beta-D-allopyranosyl-(1-4)-beta-D-cymaropyra nosyl- (1-4)-beta-D-cymaropyranoside]. These compounds were identified as: stavaroside I: 1 alpha, 12 beta-angeloxy and benzoxy-3 beta,8 beta,14 beta-trihydroxy- pregn-5-ene-20-one; stavaroside J: 11 alpha-acetoxy-12 beta-benzoxy-3 beta, 8 beta,14 beta-trihydroxy-pregn-5-ene-20-one and stavaroside K: 11 alpha-acetoxy-12 beta-tigloxy-3 beta,8 beta,14 beta-trihydroxy-pregn-5-ene- 20-one. The structural elucidation of the isolated compounds was aided significantly on the basis of the chemical and spectral evidence. The decisive assignments of the ester positions were based on the Inverse Detected-Heteronuclear Multiple Bond Connectivity (HMBC) experiments.

Diterpenes and a flavone from Leucas neufliseana

Abstract Three labdane-type diterpenes; 3-oxo-marrubiin and a mixture of two related C-15 epimeric diterpenes based on 9α,13α,15,16-bisepoxy-15-hydroxy-3-oxo-labdan-6β, 19-olide, in addition to the acylated flavone apigenin 7- O -[6″- O -( p -hydroxy- trans -cinnamoyl)glucoside] were isolated and identified from the aerial parts of Leucas neufliseana . Their structures were established through physical and chemical methods in addition to standard spectroscopic techniques. This is the first report of the isolation of the two epimeric diterpenes from a natural source.