Browsing by Author "Omar Bakr, Riham"

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Characterization of the bioactive constituents of Nymphaea alba rhizomes and evaluation of anti-biofilm as well as antioxidant and cytotoxic properties
(Journal of Medicinal Plants Research, 2016) Omar Bakr, Riham; Wasfi, Reham; Swilam, Noha; Ezz Sallam, Ibrahim
Anti-biofilm represents an urge to face drug resistance. Nymphaea alba L. flowers and rhizomes have been traditionally used in Ayurvedic medicine for dyspepsia, enteritis, diarrhea and as an antiseptic. This study was designed to identify the main constituents of Nymphaea alba L. rhizomes and their antibiofilm activity. 70% aqueous ethanolic extract (AEE) of N. alba rhizomes was analyzed by liquid chromatography, high resolution, mass spectrometry (LC-HRMS) for its phytoconstituents in the positive and negative modes in addition to column chromatographic separation. Sixty-four phenolic compounds were identified for the first time in N. alba rhizomes. Hydrolysable tannins represent the majority with identification of galloyl hexoside derivative, hexahydroxydiphenic (HHDP) derivatives, glycosylated phenolic acids and glycosylated flavonoids. Five phenolics have been isolated and identified as gallic acid and its methyl and ethyl ester in addition to ellagic acid and pentagalloyl glucose. Minimum inhibitory concentrations (MIC) and anti-biofilm activity for the extract and the major isolated compounds were determined. Radical scavenging activity using 2.2Di (4-tert-octylphenyl)-1- picryl-hydrazyl (DPPH) assay as well as cytotoxic activity using 3-(4, 5-dimethyl thiazol-2-yl)-2, 5- diphenyl tetrazolium bromide (MTT) assay have also been evaluated. MIC of N. alba rhizomes against Staphylococcus aureus was 0.25 mg/mL compared with 0.1 mg/mL for methyl gallate. The best reduction in biofilm formation (84.9%) as well as the best radical scavenging (IC50 3 µg/mL) and cytotoxic (IC50 9.61 ± 0.3 µg/mL) activities were observed with methyl gallate. This is the first study for in-depth characterization of phenolic compounds in N. alba rhizomes revealing it as a valuable source of phenolic compounds and promising anti-biofilm forming agent of natural origin.
A Comprehensive Review of the Aizoaceae Family: Phytochemical, and Biological Studies
(Bentham Science Publishers, 2020-02) Omar Bakr, Riham
The Aizoaceae “ice plant” family, is one of the neglected plant family despites of its promising phytoconstituents. It includes approximately 135 genera and 2499 succulent species distributed throughout the tropics and subtropics worldwide. Many of the species in this family have a long history in traditional medicine, and many phytochemical and biological studies have attempted to confirm the folk uses of these plants. This review gathers all the available information concerning this family offering an in-depth search for all published papers, websites, and proceedings for the identified compounds besides their biological activities. More than one hundred eighty compounds belonging to different classes have been identified and found responsible for a wide range of therapeutic activity including, antioxidant, anti-inflammatory, anti-hepatotoxic, anticancer and antimicrobial activities revealing Aizoaceae species as very promising candidates for all phytochemical and biological studies.
Phenolic content, radical scavenging activity and cytotoxicity of Tamarix nilotica (Ehrenb.) bunge growing in Egypt
(Journal of Pharmacognosy and Phytotherapy, 2013) Omar Bakr, Riham; Abd El-Aziz El Raey, Mohamed; Seif Ashour, Rehab
The radical scavenging activity using 1,1-diphenyl, 2-picrylhydrazyl (DPPH) and cytotoxicity using sulphorhodamine B (SRB) assay of the aqueous methanolic extract of Tamarix nilotica (Ehrenb.) Bunge (Tamaricaceae) flowers and its subextracts (CHCl3, EtOAC and Pet.ether) were evaluated. Total phenolic and flavonoid contents were estimated using colorimetric assays. Ethyl acetate (EtOAc) showed the highest free radical scavenging activity with inhibitory concentration (IC50) 7.25 ± 0.86 µg/ml in addition to potential cytotoxic effect on liver cell carcinoma (Huh-7) (IC50 49.1 ± 0.96 µg/ml) whereas effect on lung cell carcinoma (A-549) was much lower (IC50: 137.9 ± 1.85 µg/ml). EtOAc had the highest flavonoid content (1.75 ± 1.5 mg/g QE) compared to other subextracts. These results indicated that ethyl acetate fraction contains bioactive compounds worthy of more sophisticated studies as free radical scavenger and cytotoxic agent.
Phenolic profile of Centaurea aegyptiaca L. growing in Egypt and its cytotoxic and antiviral activities
(African Ethnomedicines Network (Nigeria), 2016) Omar Bakr, Riham; Abd El Halim Mohamed, Shaza; Ayoub, Nahla
Background: Centaurea aegyptiaca L (Asteraceae), is one of the most attractive plants growing wildly in Sinai, and is not well investigated for its phytochemical constituents. This study represents the first in-depth characterization of the phenolic profile of the aerial parts of C. aegyptiaca methanolic extract utilizing liquid chromatography (LC) combined with electrospray ionization (ESI) tandem mass spectrometry (MS/MS). Material and Methods: Phenolic profile was researched utilizing LC-HRESI-MS-MS. Assessment of cytotoxic activity against four human cancer cell lines (Hep-G2; hepatocellular carcinoma cells, MCF-7; breast adenocarcinoma cells, and HCT-116; colon carcinoma and HELA; cervical carcinoma cells) was performed using 3-[4,5-dimethylthiazole-2-yl]-2,5-diphenyltetrazolium bromide (MTT) assay. Antiviral activity was surveyed utilizing cytopathic effect inhibition assay. Results: A total of sixty-one compounds were tentatively distinguished (twenty-one phenolic acids and their derivatives, thirty-one flavonols and nine flavones) in the negative and positive modes. Centaurea aegyptiaca demonstrated outstanding results against Hep-G2, MCF-7, HCT-116 and HELA cell lines with IC50 of 12.1, 30.9, 11.7 and 19.5 µg/mL respectively compared and doxorubicin as a reference drug. Weak antiviral activity was seen against hepatitis A virus (HAV) and no impact against herpes simplex virus type 1 (HSV 1). Conclusion: This study provides a better understanding of the chemistry of C. aegyptiaca that announces itself as a promising cytotoxic agent.
Phenolics of Achillea fragrantissima growing in Egypt and its cytotoxic activity
(Journal of Medicinal Plant Research, 2014) Omar Bakr, Riham; Khedr Arafa, Reem; Mohamed Al-Abd, Ahmed; Mohamed Elshishtawy, Hisham
Achillea fragrantissima Sch. Bip. (Asteraceae) has been reputed in folk medicine of the Arabia region and Egypt for the treatment of many diseases. Air dried aerial parts of A. fragrantissima were extracted with 70% aqueous ethanol and fractionated with petroleum ether, dichloromethane, n-butanol and ethyl acetate fractions. Among them, dichloromethane showed the highest activity and was subjected to separation and purification by various chromatographic techniques. Five flavones and one phenolic acid were isolated and identified as acerosin (1), cirsimaritin (2), cirsiliol (3), luteolin (4), apigenin (5) and caffeic acid (6), respectively. Acerosin, the flavone of higher concentration isolated for the first time in genus Achillea, showed promising cytotoxic and radical scavenging activity. Molecular modeling of acerosin indicated its ability to bind in a co-crystallized ligand-like manner with kinase enzyme (FAK), namely with Cys502, alongside extra binding interactions with Glu430, Lys454 and Asp564. Total protein profiling of A. fragrantissima DNA was performed using polyacrylamide gel electrophoresis (PAGE) for characterization of plant where the total number of bands recovered was 4.
Phytochemical and pharmacological screening of seeds and fruits pulp of Cucurbita moschata duchesne cultivated in Egypt
(International Journal of Pharmacognosy and Phytochemistry, 2014) Z.H. Eleiwa, Naglaa; Omar Bakr, Riham; A. Mohamed, Shaza
Family Cucurbitaceae is one of the most important families known for its edible fruits. It was, therefore, deemed of interest to carry out phytochemical and pharmacological studies on one of its species which is Cucurbita moschata Duchesne as one of widely used edible plants. Phytochemical screening of its seeds and fruits pulp revealed the presence of carbohydrates, saponins and steroids in considerable amounts in both of them. GLC analysis for lipoidal content of seeds revealed that lauric acid was the major saturated fatty acid while oleic and linoleic acids were the major unsaturated fatty acids. Vitamin A and E were estimated using RP-HPLC analysis. The highest vitamin E concentration was found in the petroleum ether extract (PEE) of the seeds while the highest vitamin A concentration was observed in 70% aqueous methanolic extract (AME) of seeds. Pharmacological investigation revealed that, AME of Cucurbita moschata Duchesne seeds and fruits pulp have favorable anti-inflammatory activities without notable ulcerogenic effect; that usually associated the antiinflammatory drugs; based on their antioxidant properties. Moreover, there are remarkable analgesic and antidepressant activities recorded for AME of its seeds.
Tecoma stans: Alkaloid profile and antimicrobial activity
(Wolters Kluwer--Medknow Publications, 2019) Omar Bakr, Riham; Abdelaziz Ali Fayed, Marwa; Alaraby Salem, Mohammad; Samir Hussein, Ahmed
Aim: Tecoma stans (L.) Kunth is a promising species in the trumpet creeper family Bignoniaceae. This study aimed at showing the antibacterial and antifungal potentials of T. stans methanolic leaf extract (TSME) correlated to its phytoconstituents. Materials and Methods: The antimicrobial potential of TSME was evaluated using agar diffusion method. The main alkaloids were separated on silica gel column and identified using nuclear magnetic resonance spectral analysis. Molecular docking was performed for the isolated compounds against MurD ligase, penicillin-binding protein, and dihydropteroate synthase enzyme to rationalize the observed antibacterial effect. Results and Discussion: TSME showed significant antibacterial effect against all tested microorganisms with comparable minimum inhibitory concentration (MIC) to the ampicillin and gentamicin with MIC values ranging between 0.98 and 1.95 µg/mL, in addition to a promising antifungal effect when compared to amphotericin with MIC values 3.9 and 15.63 µg/mL for Aspergillus flavus and Candida albicans, respectively. Several alkaloids were separated, purified, and identified as tecostanine, 4-OH tecomanine, 5-hydroxyskytanthine, and tecomanine, which were previously isolated from T. stans. The docking study showed that the alkaloids bind in a similar fashion to the co-crystallized ligands of the crystal structures of MurD ligase. The binding poses and scores in the case of penicillin-binding protein and dihydropteroate synthase did not match the co-crystallized ligands in their crystal structures. The in silico results suggest an antibacterial mechanism that involves the inhibition of MurD ligase. Conclusion: T. stans alkaloids could represent the basic skeleton for a powerful antimicrobial agent.