Abdallah A. Omar

Phytochemical investigation and antimicrobial activity of Psidium guajava L. leaves.

Psidium guajava L. leaves were subjected to extraction, fractionation and isolation of the flavonoidal compounds. Five flavonoidal compounds were isolated which are quercetin, quercetin-3-O-α-L-arabinofuranoside, quercetin-3-O-β-D-arabinopyranoside, quercetin-3-O-β-D-glucoside and quercetin-3-O-β-D-galactoside. Quercetin-3-O-β-D-arabinopyranoside was isolated for the first time from the leaves. Fractions together with the isolates were tested for their antimicrobial activity. The antimicrobial studies showed good activities for the extracts and the isolated compounds.

Guaiane sesquiterpenes from Teucrium leucocladum

Abstract Three guaiane derivatives have been isolated from the aerial parts of Teucrium leucocladum . Their structures [1α,5β-guai-10(14)-ene-4β,6β-diol (teucladiol), 1α,5β-guaiane-4β,6β,10α-triol (teuclatriol) and 1α,5β-guaiane-4β,6β,10β-triol (10-epiteuclatriol)] were established by 1 H and 13 C NMR spectroscopic studies and by comparison with closely related compounds. In addition, the already known neo -clerodane diterpene montanin C has also been isolated from the same source.

Terpenes and flavonoids from an Egyptian collection of Cleome droserifolia.

Four new sesquiterpene derivatives have been isolated from the aerial parts of Cleome droserifolia. Their structures were established as 6-di(7-hydroxy, 1, 5-epoxy germacrane) (2), 4(15)-guaiane-6-ol (3), 7α-germacra-1(10), 4(15)-diene-5β, 6α-diol (4) and 4,7,8-eudesma-triol (5). In addition, a new dolabellane diterpene derivative with the naturally rare peroxy function was identified as methyl ester of 2,18-O-diacetyl-16-O-(3-hydroxy-3-methylglutaryl)-7-hydroperoxydolabella-3,8(17)diene-2,16,18 triol (7). Two known flavonoid derivatives, pinocembrin (6) and quercetin-3-glucoside,7-rhamnoside (1) were isolated from the same source. Structures were established by spectroscopic data.

Two neo-clerodane diterpenoids containing an unusual 2,6-dioxabicyclo[2.2.1]heptane structural moiety

Abstract Two new diterpenoids, teucrolivins G and H, have been isolated from the aerial parts of Teucrium oliverianum (Labiatae). The structures of teucrolivin G [6α,19-diacetoxy-4α,18;15,16-diepoxy-3-oxo-neo-cleroda-13(16), 14-dien-12,8β,10β-acetal, 1] and teucrolivin H [19-acetoxy-4α,18;15, 16-diepoxy-6α-hydroxy-3-oxo-neo-cleroda-13(16),14-dien-12,8β,10β-acetal, 2] were established mainly by spectroscopic means, including an X-ray diffraction analysis of the former (1). Compounds 1 and 2 possess an unusual 2,6-dioxabicyclo [2.2.1] heptane structural moiety which, to the best of our knowledge, has now been found for the first time in natural products.

Teucrolivins D–F, neo-clerodane derivatives from Teucrium oliverianum

Abstract Three new neo-clerodane diterpenoids, teucrolivins D–F, have been isolated from the aerial parts of Teucrium oliverianum. Their structures, 3β,7β,19-triacetoxy-4α,18;15,16-diepoxy-6α-hydroxy-neo-cleroda-13(16),14-diene (teucrolivin D), 3β,19-diacetoxy-4α,18;15,16-diepoxy-6α-hydroxy-neo-cleroda-13(16),14-dien-7-one (teucrolivin E) and 6α,19-diacetoxy-4α,18-epoxy-3-oxo-13,14,15,16-tetranor-neo-clerodan-12,10β-olide teucrolivin F), were established by spectroscopic means.

Erythroxan diterpenes and flavonoids from Fagonia bruguieri

Abstract Aerial parts of Fagonia bruguieri afforded two new erythroxan-type diterpenes: 15,16-dihydroxy-7-oxo- cis-ent -erythrox-3-ene (fagonone) and 16- O -acetylfagonone. The structures were determined by spectroscopic methods and a single crystal X-ray diffraction study on 16- O -acetylfagonone. Five known substituted 8-methoxyflavones were also identified. This is the first reported occurrence of diterpenes in the family Zygophyllaceae and the first known ent -erythroxane.

Erythroxan diterpenes from Fagonia species

Abstract Aerial parts of Fagonia bruguieri afforded a new erythroxan-type diterpene: 15,16-dihydroxy-7-β-hydroxy- cis-ent -erythrox-3-ene (7-β-hydroxyfagonene). Aerial parts of F. glutinosa yielded a series of additional new related erythroxans, most based upon a 15,16-dihydroxy- cis -ent-erythrox-3-ene structure, trivially named fagonene. These isolations extend the recently discovered presence of diterpenes in the Zygophyllaceae and provide additional examples in the ent -erythroxane diterpene series.

Guaianolides from Cynara sibthorpiana

Abstract The aqueous extract of the leaves of Cynara sibthorpiana afforded a terpenoid alcohol vomifoliol (= blumenol A) and three guaianolide sesquiterpene lactones, namely the cytotoxic zaluzanin-C, solstitalin and a new guaianolide named as sibthorpine.

The Protective Effect of Egyptian Withania somnifera Against AlzeheimerâÂÂs

Withania somnifera popularly known as ashwaganda or Indian Ginseng is a well known plant in India. Furthermore, it is a common plant in Egypt. The objective of this study is to evaluate the effectiveness of the extracts of different parts of the plant in the protection against oxidative stress and its therapeutic potential in the treatment of Alzheimer’s. All the tested extracts showed significant anticholinesterase activity, with the highest activity produced by the ripe fruit extract, significant nitric oxide scavenging activity, strong haemolysis protection as well as strong antioxidant activity. Unlike the Indian plant that is reputed for the medicinal use of its roots, the results of the present study also suggest that both the fruits and leaves of Egyptian plant have promising activities. Withanolide S isolated from its leaves extract, could be regarded as an interesting drug candidate for treatment of Alzheimer’s as it showed strong in vitro acetylcholinesterase (AChE) inhibitory activity with IC50 value of 0.00035 μM, strong haemolysis protection and antiinflammatory activities. Molecular docking studies was carried out in order to explore its exact mechanism of action.

Validated thin-layer chromatographic method for the identification and monitoring of the effect of the extraction method on the yield and phytochemical constituents of Egyptian Withania somnifera leaves

A sensitive, reliable, simple and rapid thin-layer chromatographic method has been developed for routine analysis of withanolide S content for the purpose of quality control assessment of chemotype III of Withania somnifera. The new method was used first to compare the accumulation of withanolide S in different parts of the plant, which was found to be the highest in the leaves extract (0.21% w/w). Second, to investigate different extraction parameters that improve the extraction efficiency of withanolides from the leaves using conventional and ultrasound-assisted extraction methods. The extraction efficiency was expressed via total withanolide content and withanolide S content.