Asmaa I. Owis

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.

The fatty acid-rich fraction of Eruca sativa (rocket salad) leaf extract exerts antidiabetic effects in cultured skeletal muscle, adipocytes and liver cells

Abstract Context: Eruca sativa Mill. (Brassicaceae), commonly known as rocket salad, is a popular leafy-green vegetable with many health benefits. Objective: To evaluate the antidiabetic activities of this plant in major insulin-responsive tissues. Materials and methods: Five E. sativa leaf extracts of varying polarity were prepared (aqueous extract, 70% and 95% ethanol extracts, the n-hexane-soluble fraction of the 95% ethanol extract (ES3) and the defatted 95% ethanol extract). Eruca sativa extracts were investigated through a variety of cell-based in vitro bioassays for antidiabetic activities in C2C12 skeletal muscle cells, H4IIE hepatocytes and 3T3-L1 adipocytes. Guided by the results of these bioassays, ES3 was fractionated into the saponifiable (SM) and the unspaonifiable (USM) fractions. Glucose uptake was measured using [3H]-deoxy-glucose, while the effects on hepatic glucose-6-phosphatase (G6Pase) and adipogenesis were assessed using Wako AutoKit Glucose and AdipoRed assays, respectively. Results: ES3 and its SM fraction significantly stimulated glucose uptake with EC50 values of 8.0 and 5.8 μg/mL, respectively. Both extracts significantly inhibited G6Pase activity (IC50 values of 4.8 and 9.3 μg/mL, respectively). Moreover, ES3 and SM showed significant adipogenic activities with EC50 of 4.3 and 6.1 μg/mL, respectively. Fatty acid content of SM was identified by GC-MS. trans-Vaccenic and palmitoleic acids were the major unsaturated fatty acids, while palmitic and azelaic acids were the main saturated fatty acids. Discussion and conclusion: These findings indicate that ES3 and its fatty acid-rich fraction exhibit antidiabetic activities in insulin-responsive cell lines and may hence prove useful for the treatment of type 2 diabetes.

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.

Elicitation of phenolics from the micropropagated endangered medicinal plant Calligonum polygonoides L. (Polygonoaceae)

Background: Calligonum polygonoides L. subsp. comosum (L′Hér.) Sosk. is a plant species belonging to family Polygonaceae. Susceptibility to threaten, presence of various chemical constituents, and many medicinal effects reported for this plant in addition to rareness of in vitro culture studies have fuelled the need for its micropropagation and phytochemical investigations of the produced cultures. Objectives: To employ in vitro culture technique for ex situ conservation of C. polygonoides, using the fruit as an explant; establish callus and cell suspension cultures from in vitro germinated plantlets; investigate the production of phenolics through callus, redifferentiated shoot, and cell suspension cultures; attempt to enhance cell capacity to accumulate phenolics using salicylic acid and yeast extract and provide a brief demonstration of biosynthetic pathway leading to phenolic production. Materials and Methods: Modified Murashige and Skoog media supplemented with growth hormones such as kinetin, 1-naphthaleneacetic acid, 6-benzylaminopurine, and indole-3-acetic acid were used to establish callus, redifferentiated shoots, and cell suspension cultures. Elicitation of cell suspension culture was performed using salicylic acid and yeast extracts. A reversed phase-high performance liquid chromatography method for determination of phenolic content in the aforementioned cultures was developed. Results: The unorganized callus and cell suspension cultures contained fewer amounts of phenolic compounds than redifferentiated shoots. Elicitation produced massive quantitative reprogramming of phenolic content. Conclusion: The present study offers an alternative and renewable source for this valuable natural plant, provide a chance to improve secondary metabolite yield and serve as a useful tool for studying the biosynthesis of these compounds and its regulation in plant cells. Abbreviation used: H 2 O 2: Hydrogen peroxide, Kin: Kinetin, NAA: Naphthaleneacetic acid, BAP: 6-benzylaminopurine, IAA: Indole-3-acetic acid, HPLC: High-performance liquid chromatography.

Protective effect of Cordia boissieri A. DC. (Boraginaceae) on metabolic syndrome

Article history: Received on: 01/02/2016 Revised on: 06/03/2016 Accepted on: 22/04/2016 Available online: 30/08/2016 Increased fructose ingestion has been linked to obesity, hyperglycemia, dyslipidemia, and hypertension associated with metabolic syndrome. Cordia boissieri A. DC. (Boraginaceae) is a slow growing beautiful plant, used traditionally as herbal remedy by diabetic Hispanic women in the Southwestern USA. The present study aimed to elucidate the toxicity and the possible protective effect of ethyl acetate extract of C. boissieri leaves on metabolic syndrome. Three groups of rats were fed on fructose-enriched diet for 14 weeks. One group served as fructose-enriched diet control, while the remaining groups were treated with metformin (10 mg/kg/day) and ethyl acetate extract (200 mg/kg/day) during the last 4 weeks. A fourth group was fed on normal laboratory diet. At the end of the experiment, blood samples were withdrawn for the estimation of metabolic syndrome-related markers and liver samples were subjected to histopathological and immunohistochemical examination. Induction of metabolic syndrome using fructose enriched diet was associated with increased weight gain coupled with elevated levels of blood glucose, insulin, uric acid, urea, creatinine, total cholesterol, triglycerides, malondialdehyde (MDA), nitric oxide and tumor necrosis factor in addition to, decreased level of glutathione (GSH). Four-weeks oral administration of ethyl acetate extract attenuated most of the changes associated with metabolic syndrome as marked by improved insulin sensitivity, glucose tolerance, kidney function, lipid profiles and reduced oxidative stress and inflammation. The present study provides evidence of the potential protective effect of C. boissieri against metabolic syndrome.

Identification and Quantification of the Major Constituents in Egyptian Carob Extract by Liquid Chromatography-Electrospray Ionization-Tandem Mass Spectrometry.

Background: Carob - Ceratonia siliqua L., commonly known as St Johns-bread or locust bean, family Fabaceae - is one of the most useful native Mediterranean trees. There is no data about the chromatography methods performed by high performance liquid chromatography (HPLC) for determining polyphenols in Egyptian carob pods. Objective: To establish a sensitive and specific liquid chromatography–electrospray ionization (ESI)-tandem mass spectrometry (MSn) methodology for the identification of the major constituents in Egyptian carob extract. Materials and Methods: HPLC with diode array detector and ESI-mass spectrometry (MS) was developed for the identification and quantification of phenolic acids, flavonoid glycosides, and aglycones in the methanolic extract of Egyptian C. siliqua. The MS and MSn data together with HPLC retention time of phenolic components allowed structural characterization of these compounds. Peak integration of ions in the MS scans had been used in the quantification technique. Results: A total of 36 compounds were tentatively identified. Twenty-six compounds were identified in the negative mode corresponding to 85.4% of plant dry weight, while ten compounds were identified in the positive mode representing 16.1% of plant dry weight, with the prevalence of flavonoids (75.4% of plant dry weight) predominantly represented by two methylapigenin-O-pentoside isomers (20.9 and 13.7% of plant dry weight). Conclusion: The identification of various compounds present in carob pods opens a new door to an increased understanding of the different health benefits brought about by the consumption of carob and its products.

Citrus Polymethoxyflavones: Biofunctional Molecules of Therapeutic Interest

Abstract Polymethoxyflavones (PMFs) are group of flavonoids exist almost exclusively in the genus citrus, especially in the peels. The natural occurrence, chemical structures, in addition to various medicinal effects reported for these compounds have attracted the attention of many researchers who consider PMFs as a molecular target. PMFs have shown many biological activities such as anticancer, antiinflammatory, antiallergic, antimutagenic, antiatherosclerosis, hypoglycemic, antioxidant, and neuroprotective effects. The chemical structure of the members of this group is similar yet different and plays an important role in their biological properties. Several techniques have been recently developed for extraction, isolation, and identification of PMFs. Multidimensional preparative liquid chromatographic system coupled with a photodiode array detector, and a single quadrupole mass spectrometer was developed for purification, nanoliquid chromatography system coupled with an electron ionization mass spectrometer was developed for characterization while high-performance liquid chromatography coupled with electrochemistry detection was developed for simultaneous determination of PMFs. A series of PMFs were synthesized through dehydrogenation, O-methylation, glycoside hydrolysis, dimethyldioxirane oxidation, and regioselective demethylation, starting from abundant and inexpensive natural sources. New synthetic route for PMFs was developed such as CuBr-catalyzed and microwave-assisted aromatic nucleophilic substitution of bromide by methoxy group. PMFs alone or in combination with other drugs represent promising candidates to develop new therapies or improve the existing ones. This chapter looks at the structures of PMFs in relation with its pharmacological properties, recent development in their extraction, isolation, identification, analytical, and synthetic methods.

Monoamine oxidases inhibitors from Colvillea racemosa: Isolation, biological evaluation, and computational study

Bioassay-guided fractionation and chemical investigation of Colvillea racemosa stems led to identification of two new α, β-dihydroxydihydrochalcones, colveol A (1) and colveol B (2) along with fifteen known compounds. The structures were elucidated via interpretation of spectroscopic data. The absolute configurations of the dihydrochalcones 1 and 2 were assigned by a combination of chemical modification and electronic circular dichroism data. The isolated compounds were evaluated for their inhibition activity toward recombinant human monoamine oxidases (rhMAO-A and -B). Compound 1 demonstrated preferential inhibition against hMAO-A isoenzyme (IC50 0.62μM, SIA/B 0.02) while S-naringenin (13) and isoliquiritigein (15) demonstrated preferential hMAO-B inhibition (IC50 0.27 and 0.51μM, SIA/B 31.77 and 44.69, respectively). Fisetin (11) showed inhibition against hMAO-A with IC50 value of 4.62μM and no inhibitory activity toward hMAO-B up to 100μM. Molecular docking studies for the most active compounds were conducted to demonstrate the putative binding modes. It suggested that 1 interacts with Gln215, Ala111, Phe352, and Phe208 amino acid residues which have a role in the orientation and stabilization of the inhibitor binding to hMAO-A, while S-naringenin (13) occupies both entrance and substrate cavities and interacts with Tyr326, a critical residue in inhibitor recognition in hMAO-B.