M’hamed Ali Hamza

Semi-synthesis of new antimicrobial esters from the natural oleanolic and maslinic acids

In this article, we report an effective procedure for the selective isolation of oleanolic acid 1 and maslinic acid 2 (3.4 and 8.5mg/g DW, respectively) from pomace olive (Olea europaea L.) using an ultrasonic bath, and the synthesis of a series of new triterpenic acid esters. The compounds were characterized by their spectral data and were evaluated for their antimicrobial activity. Among the compounds tested, those having sulfur and chlorine atoms were found to be antibacterial. They showed activity against two Gram-positive bacteria Staphylococcus aureus and Enterococcus faecalis and two Gram-negative bacteria Escherichia coli and Pseudomonas aeruginosa (MICs within a range of 5-25μg/mL). The fungus Penicillium italicum was found to be the most sensitive to both sulfur derivatives: (3β)-3-((thiophene-2-carbonyl)oxy)-olean-12-en-28-oic acid (1a) (IZ=22mm) and (2α,3β-2,3-bis((thiophene-2-carbonyl)oxy)olean-12-en-28-oic acid (2a) (IZ=24mm).

New septanoside and 20-hydroxyecdysone septanoside derivative from Atriplex portulacoides roots with preliminary biological activities.

The phytochemical investigation of a Tunisian plant Atriplex portulacoides (Chenopodiaceae) led to the isolation of two new compounds designated as portulasoid (2) and septanoecdysone (3) along with the known 20-hydroxyecdysone (20HE) (1). Their chemical structures were elucidated on the basis of extensive spectroscopic methods including ES-HRMS, 1D and 2D-NMR. The isolated compounds were finally tested for their antioxidant activity by using DPPH, ABTS(+), Fe(3+) and catalase assays and also for their antibacterial and anticholinesterase activities.

New antioxidant bibenzyl derivative and isoflavonoid from the Tunisian Salsola tetrandra Folsk

Two new phytochemical compounds, Tetranins A and B, 1-(3,5′-dihydroxy-4′-méthoxyphenyl)-2-phenylethanol 1 and 5,2′-dihydroxy-5′-methoxy-6,7-methylenedioxy-isoflavone 2, were isolated from the EtOAc extract of Salsola tetrandra roots. They exhibited a significant antioxidant effect in 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical and 2,2′-azinobis (3-ethylbenzothiazoline-6-sulphonic acid (ABTS) assays. Their structures were elucidated by extensive spectroscopic methods including 1-D-(1H and 13C) and 2-D-NMR experiments (CHcorr, HMBC, 1H-1H COSY and NOESY) as well as high-resolution ES-MS and they were found to be quite active as antioxidants in the DPPH and ABTS assays.

Synthesis and antimicrobial activity of novel coumarin derivatives from 4-methylumbelliferone

AbstractConsidering the potential interest of heterocyclic compounds, the aim of the present study is to synthesize new coumarin derivatives, to provide their full chemical characterization and to evaluate their antimicrobial activities. The reaction of ethyl 2-(4-methyl-2-oxo-2H-chromen-7-yloxy) acetate 2 with sodium hydroxide afforded the corresponding 2-(2-oxo-4-methyl-2H-chromen-7-yloxy) acetic acid 3 which was esterified using a series of alcohols in the presence of iodine to yield a new series of coumarin esters 4a–j. On the other hand, treatment of the key intermediate 2 with an aqueous solution of hydrazine in ethanol at reflux gave the corresponding hydrazide 5 which further converted into coumarin derivatives 6a–f and 7a–c by condensation with a series of aromatic aldehydes and cyclic anhydrides, respectively. The synthesized compounds were completely characterized by 1H NMR, 13C NMR, IR and HRMS. The antibacterial and antifungal activities of the new synthesized compounds were evaluated using the disc diffusion method and seemed to be significant.

Synthesis of New Phosphonate Derivatives of Naphtho[2,1-b[Pyran]3,2-e][1,2,4]Triazolo [1,5-c]Pyrimidines

Abstract The synthesis of new naphthopyranotriazolopyrimidines phosphonates 4a–i in good yields (74%–93%) has been accomplished via Michaelis–Arbusov rearrangement by the reaction of trialkyl phosphite with naphthopyranotriazolopyrimidines chloride 3a–e, which were obtained from α-functionalized iminoethers 1 in two steps. The synthesized compounds 4a–i were completely characterized by IR, 1H, 13C, and 31P NMR and HRMS. Supplemental materials are available for this article. Go to the publishers online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file. GRAPHICAL ABSTRACT

Isolation and Structure Elucidation of Secondary Metabolites from the Roots of the Tunisian Convolvulus dorycnium

A phytochemical investigation of the roots of Convolvulus dorycnium led to the isolation of a new phenolic metabolite methyl 3-(3-caffeoyl-1,2-dihydroxycyclobutyl)-3-hydroxypropanoate (1) named convoldorine and the previously known dorycnic acid (2), chlorogenic acid (3), scopolin (4) and scopolitin (5). Their structures were elucidated on the basis of spectroscopic evidence, including 1D and 2D NMR experiments and by comparison with authentic samples.