Abeer Moawad

Flavonoids of Calligonum polygonoides and their cytotoxicity

Abstract Context Calligonum polygonoides L. subsp. comosum L’ Hér. (Polygonaceae), locally known as “arta”, is a slow-growing small leafless desert shrub. Objective Isolation, structure elucidation and evaluation of cytotoxic activity of flavonoids from C. polygonoides aerial parts. Materials and methods Flavonoids in the hydroalcoholic extract of the of C. polygonoides were isolated and purified using column chromatography and preparative HPLC. The structures of the isolated flavonoids were elucidated on the basis of spectroscopic data including 2D NMR techniques. The cytotoxic activity of the isolated flavonoids (6.25, 25, 50 and 100 μg/mL) was evaluated against liver HepG2 and breast MCF-7 cancer cell lines using sulphorhodamine-B assay. Results A new flavonoid, kaempferol-3-O-β-D-(6″-n-butyl glucuronide) (1), and 13 known flavonoids, quercetin 3-O-β-D-(6″-n-butyl glucuronide) (2), kaempferol-3-O-β-D-(6″-methyl glucuronide) (3), quercetin-3-O-β-D-(6″-methyl glucuronide) (4), quercetin-3-O-glucuronide (5), kaempferol-3-O-glucuronide (6), quercetin-3-O-α-rhamnopyranoside (7), astragalin (8), quercetin-3-O-glucopyranoside (9), taxifolin (10), (+)-catechin (11), dehydrodicatechin A (12), quercetin (13), and kaempferol (14), were isolated from the aerial parts of C. polygonoides. Quercetin showed significant cytotoxic activity against HepG2 and MCF-7 cell lines with IC50 values of 4.88 and 0.87 μg/mL, respectively. Structure–activity relationships were analyzed by comparing IC50 values of several pairs of flavonoids differing in one structural element. Discussion and conclusion The activity against breast cancer cell lines decreased by glycosylation at C-3. The presence of 2,3-double bond in ring C, carbonyl group at C-4 and 3’,4’-dihydroxy substituents in ring B are essential structural requirements for the cytotoxic activity against breast cancer cells.

Synthesis of new 1-(4-methane(amino)sulfonylphenyl)-5-(4-substituted-aminomethylphenyl)-3-trifluoromethyl-1H-pyrazoles: A search for novel nitric oxide donor anti-inflammatory agents

A group of 1-(4-methane(amino)sulfonylphenyl)-5-(4-substituted-aminomethylphenyl)-3-trifluoromethyl-1H-pyrazoles (12a-f) was synthesized and evaluated as anti-inflammatory agents. While all the compounds (20mg/kg) showed significant anti-inflammatory activity after 3h of inflammation induction (69-89%) as compared to celecoxib (80%), 1-(4-methanesulfonylphenyl)-5-(4-methylaminomethylphenyl)-3-trifluoromethyl-1H-pyrazole (12 a) was found to be the most effective one (89%). The synthesis of model hybrid nitric oxide donor N-diazen-1-ium-1,2-diolate derivatives of 1-(4-methanesulfonylphenyl)-5-(4-substituted-aminomethylphenyl)-3-trifluoromethyl-1H-pyrazoles (10a-f) requires further investigation since the reaction of N-(4-(1-(4-(methylsulfonyl)phenyl)-3-(trifluoromethyl)-1H-pyrazol-5-yl)benzyl)ethanamine (12 b) or 1-(4-(1-(4-(methylsulfonyl)phenyl)-3-(trifluoromethyl)-1H-pyrazol-5-yl)benzyl)piperazine (12c) with nitric oxide furnished N-nitroso derivatives (13 and 14), respectively, rather than the desired N-diazen-1-ium-1,2-diolate derivatives (10b and 10 c).

Biologically-guided isolation of leishmanicidal secondary metabolites from Euphorbia peplus L.

Leishmaniasis is a worldwide health problem, highly endemic in developing countries. Moreover, the severe side effects and the reported drug resistance make it an urgent need to search for effective drugs that can replace or supplement those currently used. In a research program designed to investigate the antileishmanial activity of plants collected from the Egyptian flora, twenty extracts from fifteen plants growing in Egypt have been investigated for in vitro leishmanicidal activity against Leishmania donovani promastigotes. Among the tested extracts, the methanol extract of Euphorbia peplus aerial parts exhibited a significant antileishmanial activity as it produced 100% inhibition of growth with activity similar to amphotericin B. The total extract was subjected to liquid-liquid fractionation using solvents of different polarities, followed by testing the antileishmanial activity of the successive fractions. Phytochemical exploration of the active n-hexane fraction (which produced 75% inhibition of growth) led to isolation of four compounds: simiarenol (1), 1-hexacosanol (2), β-sitosterol (3), and β-sitosterol-3-O-glucoside (4) from the biologically active sub-fractions. Structure elucidation was aided by 1D and 2D NMR techniques. In conclusion, E. peplus plant has many non-polar secondary metabolites that can be used as drug leads for treatment of leishmaniasis.

Two new dihydroamentoflavone glycosides from Cycas revoluta

Phytochemical investigation of the ethyl acetate extract of Cycas revoluta Thunb. leaflets afforded five compounds including two new dihydroamentoflavone glucosides, (2S)-I-(2,3)-dihydro-I-7-O-β-d-glucopyranosylamentoflavone (1) and (2S)-I-(2,3)-dihydro-I-7,II-7-di-O-β-d-glucopyranosylamentoflavone (2), in addition to the known compounds prunin (3), vitexin-2″-rhamnoside (4) and protocatechuic acid (5). Compounds (3) and (4) being reported for the first time in this plant. The structures of these compounds were established by the detailed analysis of their spectroscopic data, mainly 1D NMR, 2D NMR, CD and HR-MSD-TOF. The ethyl acetate extract showed weak cytotoxicity against HepG2 (IC50 = 207.6 μg/mL) and RAW 264.2 cells (IC50 = 160.8 μg/mL). Compound 4 showed significant activity towards Leishmania donavani (IC50 = 13.8 μM, IC90 = 34.6 μM). The isolated compounds showed weak antimicrobial activity (IC50>10 μg/mL).

Chemotaxonomic and biosynthetic relationships between flavonolignans produced by Silybum marianum populations

Flavonolignans constitute an important class of plant secondary metabolites formed by oxidative coupling of one flavonoid and one phenylpropanoid moiety. The standardized flavonolignan-rich extract prepared from the fruits of Silybum marianum is known as silymarin and has long been used medicinally, prominently as an antihepatotoxic and as a chemopreventive agent. Principal component analysis of the variation in flavonolignan content in S. marianum samples collected from different locations in Egypt revealed biosynthetic relationships between the flavonolignans. Silybin A, silybin B, and silychristin are positively correlated as are silydianin, isosilychristin, and isosilybin B. The detection of silyamandin in the extracts of S. marianum correlates with isosilychristin and silydianin content. The positive correlation between silydianin, isosilychristin, and silyamandin was demonstrated using quantitative 1H nuclear magnetic resonance spectroscopy (qHNMR). These correlations can be interpreted as evidence for the involvement of a flavonoid radical in the biosynthesis of the flavonolignans in S. marianum. The predominance of silybins A & B over isosilybin A & B in the silybin-rich samples is discussed in light of the relative stabilities of their respective radical flavonoid biosynthetic intermediates.