الفهرس 
AbstractOnly 14 pages are availabe for public view
 |  | from | 308 |  |  |
| | | from | 308 | | |
Abstract
The present study includes the following:
Part I: Phytochemical screening, GC-MS analysis and biological activity of some macroalgae from the Egyptian Red Sea revealed that:
• The brown macroalgae exhibited the highest cytotoxic activity against HepG-2 and MCF-7 cell lines followed by the green macroalgae.
• Also the brown macroalga Hydroclathrus clathratus exhibited the highest antimicrobial activity followed by the red alga Galaxaura elongata.
• The four algae contain flavonoids, carbohydrates, terpenoids, saponins, steroids and phlorotannins.
• Absence of alkaloids from Hydroclathrus clathratus, but they were present in the other three algae.
• Hexadecanoic acid, was the most abundant component (15.07%) in macroalgae.
Part II: Phytochemical investigation and biological activities of Cystoseira trinodis
• The hexane fraction of Cystoseira trinodis exhibited the highest cytotoxic activity against HepG-2 and MCF-7 cell lines, followed by the crude extract,
• The crude extract and fractions showed moderate inhibition against some of the tested microorganisms, especially the butanol fraction exhibited the maximum inhibition zone against Salmonella typhimurium.
• GC-MS analysis of the fractions showed that the most abundant compound in hexane fraction was hexadecanoic acid (33.06%).
• The main compound of dichloromethane fraction was (-)-(1R)-methyl1-hydroxy-4-methoxy-2-oxocyclopent-3-ene-carboxylate (13.98%).
• The main compound of ethyl acetate fraction were benzene acetic acid (8.55%).
• The main compound of butanol fraction were diisooctyl phthalate (17.79%).
• The major component of aqueous fraction was hexadecanoic acid (21.75%).
• Phytochemical analysis of the hexane and dichloromethane fractions led to isolation of nine compounds, octacosanoic acid (1), glyceryl trilinoleate (2), oleic acid (3), and the epimeric mixture of saringosterols (4,5), β-sitosterol (6), glycoglycerolipid (7) and a mixture of kjellmanianone and loliolide (8,9) eight of them were isolated for the first time.
• The isolated compounds were tested for their cytotoxicity against HepG-2 cell lines and kjellmanianone and loliolide mixture exhibited significant cytotoxic activity (IC50 7.27±0.72 µg/ml).
• Molecular docking analysis confirmed that most of the studied compounds especially compounds 8 and 9 strongly interact with TPK and VEGFR-2 with highest binding energies supported that the high cytotoxicity of these compounds against human hepatocellular cancer in the experimental part.
• Molecular properties descriptors, bioactivity score and ADMET analysis confirmed that most of the studied compounds especially compounds 8 and 9 exhibit significant biological activities and have a better chance to be developed as drug leads.
• The bioactivity scores of all studied compounds showed that compounds 8 and 9 exhibit significant biological activities, while compounds 4 and 5 show moderately biological activities.
• DFT calculations confirmed that the interaction between compounds 8, 9 and cytosine formed stable complexes with high binding energies and charge-transfer energies in gas and water phases.
• Part III: Phytochemical investigation and biological activities of Hydroclathrus clathratus and Caulerpa serrulata revealed that:
• The crude extract (70%MeOH) exhibited the highest cytotoxic effect against both HepG-2 and MCF-7 cells with IC50 value of (24.8± 1.1 and 26.6± 1.2 µg/ml) respectively followed by the ethyl acetate fraction, hexane fraction, and finally butanol fraction.
• The crude extract and the all fractions inhibited the growth of Escherichia coli with varying degrees, but they did not showe any inhibition against Aspergillus fumigatus and Candida albicans.
• The ethyl acetate and hexane fractions of Hydroclathrus clathratus showed inhibition against the most tested microbes.
• GC-MS analysis showed that the predominant compound in the all fractions was hexadecanoic acid, methyl ester with 31.24%, 64.98% and 63.90% in the the ethyl acetate, hexane and butanol fractions respectively.
• Three compounds have been isolated from the ethyl acetate and butanol mixture of Hydroclathrus clathratus by fractionation on a series of silica gel columns. The compounds were identified as oleic acid (1), 24-methylene cholesterol (2) and hexadecanoic acid (3).
• 24-methylene cholesterol (2) exhibited significant activity against HepG-2 cell lines (IC50 4.83±0.2 µg/ml).
• The bisindole alkaloid caulerpin was isolated from Caulerpa serrulata.
• Caulerpin exhibited cytotoxic effect against HepG-2 cell lines (IC50 102 ± 3.4 µg/ml).
Part IV: Evaluation of the antiviral activity of the all isolated compounds from Cystoseira trinodis, Hydroclathrus clathratus and Caulerpa serrulata against COVID-19 by in silico approaches
1. The inhibitory effect of the isolated compounds against SARS-CoV-2 main protease insights from molecular docking analysis and molecular dynamic simulation revealed that:
• The Homology modeling and sequence alignment of 2019-nCov main protease showed that SARS-CoV and SARS-CoV-2-3CLpro share remarkable 96.00 % sequence alignment among all other human coronaviruses.
• The crystal structure of SARS-CoV-2-3CLpro (PDB ID: 6LU7) is highly similar to its SARS-CoV sister (PDB ID: 3TNT) at high resolution with 1.59 Å.
• The molecular docking analysis revealed that bioactive caulerpin has the highest binding affinity against all studied receptors with compared to other studied compounds and the antiviral drugs.
• The ADMET properites strongly provide the ability of most of all studied compounds to act as a drug, except compound 7.
• Molecular dynamic simulation confirmed the stability of caulerpin-6LU7 receptor in the presence of explicit water solvent at 10 ns.
• Lower RMSD value of the caulerpin in the complex with 6LU7indicates its stability and provided a suitable basis for our study.
• The RMSF plot for the complex indicates that binding caulerpin to the receptor was stable and had no major effect on the flexibility of the protein throughout the simulations.
• The bioactive caulerpin molecule was able to maintain strong interaction with the binding pocket of 6LU7 throughout the simulation period and this confirmed the efficacy of the caulerpin molecule against SARS-CoV-2 main protease.
2. Destabilizing the structural integrity of COVID-19 by caulerpin and its derivatives along with some antiviral drugs: An in silico approaches for a combination therapy revealed that:
• The molecular docking analysis revealed that most of all caulerpin derivatives can act as 6VYB and 6LU7 inhibitors especially compounds 7, 10 and 19.
• Inserting of NH2, Halogen and vinyl groups can increase the binding affinity of caulerpin toward 6VYB and 6LU7. While, inserting alkyl group decease the binding affinity of caulerpin toward 6VYB and 6LU7. So, we can modify the inhibitory effect of caulerpin against 6VYB and 6LU7 by inserting NH2, Halogen and vinyl groups.
• The ADMET properites strongly provide the ability of most of all studied compounds to act as a drug, except compounds 3, 5 and 9.
• Molecular properties descriptors and Prediction of bioactivity score confirmed that compounds 7, 10, and 19 did not violate any of the Lipinski’s rule of five and exhibit significant biological activities.
• RMSD of the receptor-ligands complexes of both receptors has maintained the stability at around 2 Å and RMSD of three drugs complexed with the protein are in the favorable range of within 1.2 Å and has remained stable during the simulations.
• RMSF indicated that binding of combination therapy of simeprevir and the two candidate compounds to the receptors was stable and had no major effect on the flexibility of the protein throughout the simulations.
• The backbone atoms of the complex and free receptor show similar RMSF, indicating the stability of the combination therapy between the studied compounds and simeprevir inside 6LU7 and 6VYB receptors.
• The combination of caulerpin derivatives and simeprevir are highly effective against SARS-CoV-2 protease, and these drugs can be explored further for drug repurposing against the successful inhibition of COVID-19.