Plant-Assisted Synthesis of Ag-Based Nanoparticles on Cotton: Antimicrobial and Cytotoxicity Studies.

The syntheses of Ag-based nanoparticles (NPs) with the assistance of plant extracts have been shown to be environmentally benign and cost-effective alternatives to conventional chemical syntheses. This study discusses the application of Paliurus spina-christi, Juglans regia, Humulus lupulus, and Sambucus nigra leaf extracts for in situ synthesis of Ag-based NPs on cotton fabric modified with citric acid. The presence of NPs with an average size ranging from 57 to 99 nm on the fiber surface was confirmed by FESEM. XPS analysis indicated that metallic (Ag0) and/or ionic silver (Ag2O and AgO) appeared on the surface of the modified cotton. The chemical composition, size, shape, and amounts of synthesized NPs were strongly dependent on the applied plant extract. All fabricated nanocomposites exhibited excellent antifungal activity against yeast Candida albicans. Antibacterial activity was significantly stronger against Gram-positive bacteria Staphylococcus aureus than Gram-negative bacteria Escherichia coli. In addition, 99% of silver was retained on the samples after 24 h of contact with physiological saline solution, implying a high stability of nanoparticles. Cytotoxic activity towards HaCaT and MRC5 cells was only observed for the sample synthetized in the presence of H. lupulus extract. Excellent antimicrobial activity and non-cytotoxicity make the developed composites efficient candidates for medicinal applications.

Chemo- and biocatalytic esterification of marchantin A and cytotoxic activity of ester derivatives.

Chemical and biocatalytic synthesis of seven previously undescribed marchantin A ester derivatives has been presented. Chemical synthesis afforded three peresterified bisbibenzyl products (TE1-TE3), while enzymatic method, using lipase, produced regioselective monoester derivatives (ME1-ME4). The antiproliferative activities of all prepared derivatives of marchantin A were tested on MRC-5 healthy human lung fibroblast, A549 human lung cancer, and MDA-MB-231 human breast cancer cell lines. All tested esters were less cytotoxic in comparison to marchantin A, but they also exhibited lower cytotoxicity against healthy cells. Monoesters displayed higher cytotoxic activities than the corresponding peresterified products, presumably due to the presence of free catechol group. Monohexanoyl ester ME3 displayed the same IC50 like marchantin A against MDA-MB-231 cells, but the selectivity was higher. In this way, regioselective enzymatic monoesterification enhanced selectivity of marchantin A. ME3 was also the most active among all derivatives against lung cancer cells A549 with the slightly lower activity and selectivity in comparison to marchantin A.

Diarylheptanoids from Alnus viridis ssp. viridis and Alnus glutinosa: Modulation of Quorum Sensing Activity in Pseudomonas aeruginosa.

Diarylheptanoids from the barks of Alnus viridis ssp. viridis (green alder) and Alnus glutinosa (black alder) were explored for anti-quorum sensing activity. Chemicals with anti-quorum sensing activity have recently been examined for antimicrobial applications. The anti-quorum sensing activity of the selected diarylheptanoids was determined using two biosensors, namely Pseudomonas aeruginosa PAO1 and Chromobacterium violaceum CV026. Although all of the investigated compounds negatively influenced the motility of P. aeruginosa PAO1, four were able to inhibit biofilm formation of this human opportunistic pathogen for 40-70 %. Three of the diarylheptanoids (3, 4, and 5) negatively influenced the biosynthesis of pyocyanin, which is under the control of quorum sensing. Platyphyllenone (7) and hirsutenone (5) were able to inhibit the biosynthesis of violacein in C. violaceum CV026, with 5 being able to inhibit the synthesis of both biopigments. Only one of the tested diarylheptanoids (1) was shown to significantly decrease the production of acyl homoserine lactones (AHL) in P. aeruginosa PAO1, more specifically, production of the long chain N-(3-oxododecanoyl)-l-HSL. On the other side, four diarylheptanoids (2-5) significantly reduced the synthesis of 2-alkyl-4-quinolones, part of the P. aeruginosa quinolone-mediated signaling system. To properly assess therapeutic potential of these compounds, their in vitro antiproliferative effect on normal human lung fibroblasts was determined, with doses affecting cell proliferation between 10 and 100 µg/mL. This study confirms that the barks of green and black alders are rich source of phytochemicals with a wide range of biological activities that could further be exploited as natural agents against bacterial contaminations and infections.

Cytotoxic effect of Reseda lutea L.: A case of forgotten remedy.

ETHNOPHARMACOLOGICAL RELEVANCE: Reseda lutea L. (Resedaceae) or Wild Mignonette is a widely distributed plant species. Pliny the Elder (AD 23-AD 79), a Roman scholar and naturalist, reported the use of R. lutea for reducing tumors in his Historia naturalis. Accounts of the beneficial effects of R. lutea in tumor treatment could also be found in the works of later authors, such as Étienne François Geoffroy (1672-1731) and Samuel Frederick Gray (1766-1828). However, to date no in vivo or in vitro evidence exists in support of the alleged tumor healing properties of R. lutea. MATERIALS AND METHODS: The composition of autolysates obtained from different organs (root, flower and fruit) of R. lutea was investigated by GC and GC-MS analyses and IR, 1D and 2D NMR spectroscopy. These analyses led to the discovery of a new compound isolated in pure form from the flower autolysate. Autolysates and their major constituents were submitted to MTT-dye reduction cytotoxic assay on human A375 (melanoma) and MRC5 (fibroblast) cell lines. Mechanism of the cytotoxic effects was studied by cell cycle analysis and Annexin V assay. RESULTS: Benzyl isothiocyanate and 2-(α-l-rhamnopyranosyloxy)benzyl isothiocyanate were identified as the major constituents of the root and flower autolysates, respectively (the later represents a new natural product). These compounds showed significant antiproliferative effects against both cell lines, which could also explain the observed high cytotoxic activity of the tested autolysates. Cell cycle analysis revealed apoptosis as the probable mechanism of cell death. CONCLUSIONS: Tumor healing properties attributed to R. lutea in the pre-modern texts were substantiated by the herein obtained results. Two isothiocyanates were found to be the major carriers of the observed activity. Although there was a relatively low differential effect of the plant metabolites on transformed and non-transformed cell lines, one can argue that the noted strong cytotoxicity provides first evidence that could explain the long forgotten use of this particular species.

Toxic essential oils. Part III: identification and biological activity of new allylmethoxyphenyl esters from a Chamomile species (Anthemis segetalis Ten.).

To determine the exact structure of previously tentatively identified minor essential-oil constituents of a Chamomile species (Antemis segetalis Ten. (Asteraceae)), we have synthesized a small combinatorial library of 54 regioisomeric allylmethoxyphenyl pentanoates and 2-pentenoates (49 completely new compounds). GC-MS in combination with 1D- and 2D-NMR analyses of the library compounds provided unambiguous data that led to a straightforward identification of the mentioned A. segetalis constituents as eugenyl angelate, 2-methylbutanoate and 3-methylbutanoate (0.21, 0.22, and 0.13 mg/100 g of fresh plant material, respectively). To assess the safety and potential beneficial pharmacological uses of these naturally occurring esters and several other library compounds (these were tested to provide relevant data for a SAR (structure-activity relationship) analysis), we have studied the effect of these compounds in several models of toxicity (acute toxicity against Artemia salina, cytotoxicity against two cell lines (fibroblast and melanoma)), as well as their acetylcholinesterase inhibitory and antibacterial activities. Anthemis segetalis constituents showed low to moderate activity in all tests. The obtained results suggest that the intake of these compounds in naturally available amounts, on their own, would probably not represent a risk to human health but the possible adverse interactions with the plant matrix should not be neglected.