Amin Abedini

Bioactivity-guided identification of antimicrobial metabolites in Alnus glutinosa bark and optimization of oregonin purification by Centrifugal Partition Chromatography

Barks from conifers and broadleaved trees constitute abundant wastes generated from wood harvesting and logging activities. Extracts of such residues obtained from Alnus trees have been reported as interesting resources with potent antibacterial activities. The present study aims to determine the antimicrobial activity of a crude methanol extract prepared from the bark of Alnus glutinosa against a panel of 22 bacteria and yeasts and to optimize a purification method enabling the high production of the most active substances. Fractionation of the crude extract was performed by Centrifugal Partition Chromatography (CPC) using a three-phase solvent system composed of n-heptane, methyl-ter-butyl ether, acetonitrile and water. The major known compounds contained in the fractions produced by CPC were chemically profiled by (13)C NMR dereplication, resulting in the unambiguous identification of oregonin, hirsutanonol, betulinic acid, and alusenone 1a. The antibacterial evaluation of the fractions by bioautography on Staphylococcus aureus revealed that oregonin, in addition to being the major metabolite of the crude extract (∼32% w/w), was the most active with an antibacterial inhibitory effect comparable to antibiotics. The purification of oregonin was optimized at the laboratory-scale by CPC. A single injection of 3.7g of crude extract resulted in a recovery of 72% (850mg) of the available oregonin at purity higher than 94%.

Two new bis-iridoids isolated from Scabiosa stellata and their antibacterial, antioxidant, anti-tyrosinase and cytotoxic activities

This study presents the chemical profile investigation of a 70% ethanol extract obtained from Scabiosa stellata, a medicinal herbaceous traditionally used to treat heel cracks. A 13C NMR-based dereplication methodology was firstly applied on centrifugal partition chromatography-generated fractions in order to quickly identify the major compounds of the extract. The dereplication process was then completed by semi-preparative high-performance liquid chromatography in order to identify unknown or minor compounds. Two new bis-iridoids, namely 7-O-caffeoyl-sylvestroside I (1) and 7-O-(p-coumaroyl)-sylvestroside I (2), together with ten known compounds (3-12) were isolated. Their structures were elucidated by spectroscopic methods including NMR and HR-ESI-MS. The antibacterial, anti-tyrosinase and DPPH radical scavenging activities of the crude extract, fractions, and isolated compounds were evaluated. A significant antibacterial activity was observed for nine isolated compounds, particularly 1 and 2 which yielded MIC values of 31.2μg/mL against Enterococcus faecalis and 62.5μg/mL against Staphylococcus epidermidis. The cytotoxic activity of these new bis-iridoids was evaluated on a fibrosarcoma cell line (HT1080) and only compound 1 exhibited a moderate cytotoxic activity (IC50 35.9μg/mL).

Chemical composition, antioxidant and antibacterial activities of Tamarix balansae J. Gay aerial parts

Abstract A previously undescribed phenolic sulphate ester, potassium 34-dihydroxy-3-methoxybenzoic acid methyl ester-5-sulphate (1), along with nine known flavonoids, kaempferol-3-O-potassium sulphate-4′,7-dimethyl ether (2), kaempferol-4′,7-dimethyl ether (3), rhamnocitrin-3-O-potassium sulphate (4), rhamnocitrin (5), kaempferol (6), quercetin (7), afzelin (8), quercetin-3-O-α-l-rhamnopyranoside (9) and luteolin-3′-O-potassium sulphate (10) were isolated from the aerial parts of Tamarix balansae. Structures elucidation was performed by comprehensive 1D and 2D NMR analyses, mass spectrometry and by comparison with literature data. The antibacterial assay against Enterococcus faecalis, Staphylococcus aureus, Staphylococcus epidermidis, Escherichia coli and Pseudomonas aeruginosa bacteria showed a good activity for 2, 3, 7 and 9, with MICs ranging from 62.5 to 250 μg/mL. The abilities of these compounds to scavenge the DPPH were evaluated. Compounds 1, 7, 9 and 10 exhibited a good antiradical activity potential with IC50 values ranging from 3.0 to 115.5 μg/mL, compared with ascorbic acid (IC50 7.4 μg/mL) which was used as positive control.

Abietane diterpenes from the cones of Abies numidica de Lannoy ex Carrière (Pinaceae) and in vitro evaluation of their antimicrobial properties

Abstract Eight known abietane diterpenes (1–8) were isolated for the first time from Abies numidica cones (Pinaceae). The structures of all compounds were established by means of 1D and 2D NMR, and UV spectral analyses. The hydromethanolic extract of A. numidica cones was tested for its antimicrobial activity against 17 gram-positive and gram-negative bacteria and against five yeasts by the use of liquid and solid medium and bioautography methods. The best antimicrobial activity was found against gram-positive bacteria (MIC ≤ 0.3 mg/mL) Bacillus subtilis, Enterococcus faecalis ATCC 1034, Staphylococcus aureus 8325.4, S. aureus CIP 53.154, Micrococcus luteus and Listeria innocua and against Candida yeasts. The determination of MIC’s of isolated products showed a high activity of compounds 4 and 6 against S. aureus, L. innocua (MIC = 62.5 μg/mL) and E. faecalis (MIC = 125 μg/mL).

Antibacterial, antioxidant and cytotoxic activities of triterpenes and flavonoids from the aerial parts of Salvia barrelieri Etl.

Abstract From the aerial parts of Salvia barrelieri Etl. (Lamiaceae), 12 compounds including a new triterpene, 3β-acetoxy-olean-18-ene-2α-ol, were isolated. Their structures were established by the combination analyses of spectroscopy including 1D-, 2D-NMR and HRESIMS and in comparison with the reported data in the literature. The antibacterial activity of these compounds was evaluated by bioautography on Staphylococcus aureus followed by the determination of MIC values by serial dilution technique against five bacteria. Three compounds were active against Enterococcus faecalis, S. aureus, Staphylococcus epidermidis, Escherichia coli and Pseudomonas aeruginosa (MIC 15.1 to 125 μg/mL). Two compounds showed moderate DPPH radical scavenging activity (IC50 79.1 and 21.2 μg/mL). These compounds did not show significant tyrosinase inhibitory activities (IC50> 1.5 mg/mL). Their cytotoxic activity was evaluated against promyelocytic leukaemia (HL60), human erythromyeloblastoid leukaemia (K562) and fibrosarcoma (HT1080) cell lines and four compounds exhibited a moderate cytotoxic activity (IC50 28.75 to 85.0 μM).

Chemical constituents of Genista numidica Spach aerial parts and their antimicrobial, antioxidant and antityrosinase activities

Abstract A previously undescribed triterpenoid saponin, 3-O-[α-l-rhamnopyranosyl-(1→2)-{β-d-glucopyranosyl-(1→6)-}β-d-galactopyranosyl-(1→2)-β-d-glucuronopyranosyl]-sophoradiol (1), in addition to twenty-nine known constituents (2–30) were isolated from the aerial parts of Genista numidica Spach. Structures elucidation was performed by comprehensive 1D- and 2D-NMR analyses and HRESIMS. The extracts, fractions and isolated compounds were evaluated for their antibacterial, antioxidant and tyrosinase inhibitory activities. The experimental findings indicated that genistin (16), isosalipurpol (27), and koaburaside (29) have moderate to low antibacterial activity against E. faecalis, S. aureus, S. epidermidis and P. aeruginosa bacteria with MICs ranging from 31.2 to 125 μg/mL. Compounds 19 and 27 exhibited a good antiradical activity potential (IC50 11.8 and 11.1 μg/mL, respectively). Only compounds 23, 27 and 28 exhibited low inhibitory effect against mushroom tyrosinase (IC50 from 90.2 to 225.6 μg/mL).