Acanthamoebae are opportunistic pathogens causing serious human infections, including granulomatous amoebic encephalitis (GAE) and Acanthamoeba keratitis (AK). The treatment of those infections is limited and difficult to date. Recent research demonstrated high antimicrobial activity of phosphonium amphiphilic salts. In the present work we aimed to investigate the anti-Acanthamoeba effect of a series of 16 phosphonium salts. The structure of these synthesized cationic amphiphiles was modified in both the polar and nonpolar parts of the surfactant molecule. The compounds have different alkyl chain lengths (C12 - C18) and different numbers of methyl and phenyl groups (0 - 3) attached to the quaternary phosphorus atom. The following basic physicochemical properties of the compounds were determined: critical micelle concentration (cmc), the surface tension value at the cmc and the surface area per surfactant head group. The cmc values, which express the degree of lipophilicity of compounds, were correlated with biological activities. The effects of phosphonium salts on trophozoites of Acanthamoeba quina and Acanthamoeba hatchetti (both strains of genotype T4) and human erythrocytes were studied. The highest trophocidal activity was recorded for the compound C16P(Me)2PhBr with the minimal trophocidal concentration (MTC) of 7.8 μM for the A. quina strain and 15.6 μM for the A. hatchetti strain, after 24 h. Its activity was comparable or higher than the activity of drugs currently used in the treatment of Acanthamoeba keratitis. Therefore, this compound is a promising candidate in the fight against infections caused by Acanthamoeba.

The micellization behavior of urea-based cationic gemini surfactants was investigated using small-angle neutron scattering (SANS) with multi-model form factor analysis. A homologous series of surfactants with urea group included in the hydrophobic tail and polymethylene spacers consisting of two to ten methylene units was analyzed using three form factor models: a core–shell ellipsoid and two variants of homogeneous ellipsoids. The results from all models show a consistent trend of the micelle structures, confirming that the spacer length critically influences micellar geometry, aggregation number, and hydration. The surfactant with four CH2 groups in the spacer formed the largest micelles with the highest aggregation number, while longer spacers led to progressively smaller, more compact aggregates. The shell hydration—quantified as the volume fraction of heavy water within the hydrophilic region—decreased systematically with increasing spacer length due to enhanced hydrophobicity of the headgroup-spacer region. Intermicellar interactions, modeled as screened Coulomb interaction using the rescaled mean spherical approximation (RMSA), revealed the strongest electrostatic repulsion for the case of four methylene groups in the spacer, corresponding to the highest micellar charge and largest interparticle spacing. The observed spacer-dependent trends were robust across all modeling approaches, demonstrating that the spacer length serves as a key structural determinant of self-assembly in this type of urea-based gemini systems. These findings provide insight into the design of gemini surfactants with tailored aggregation behavior for applications in drug delivery, nanostructure templating, and solubilization technologies.

For decades, silver nanoparticles (AgNPs) continue to act as the object of interest of scientific community as well as industry, creating a variety of application opportunities in different areas such as pharmacy and medicine, catalysis, textile industry, sensors, and many others. Due to their strong antimicrobial and cytotoxic effect they form a broad basis for applications in medicine and healthcare. The present study describes the synthesis and functionalization of AgNPs by a series of cationic gemini surfactants with variable length of polymethylene spacer and the presence of urea groups in each of their alkyl chains. Investigations of physical parameters of functionalized AgNPs are represented by the UV-VIS spectral analysis, the determination of particle size and shape using dynamic light scattering and scanning electron microscopy, and the zeta potential measurements as a function of urea gemini surfactant structure. The biological function of functionalized AgNPs is represented by their antimicrobial activity determination against various types of pathogens. The presence of urea groups in surfactant molecular structure alters the physical parameters as well as biological activity of surfactant capped AgNPs due to their non-covalent bonding ability and flexibility control of the surfactant capping layer. As the results indicate, AgNPs functionalized with urea gemini surfactants showed the size in the range 58–144 nm and a positive zeta potential from +41 to +64 mV due to the presence of positive charge of surface-active cations on AgNPs surface. Investigations of AgNPs antimicrobial effect against Gram-negative, Gram-positive pathogens and yeast showed a complex behavior which depends on the urea gemini surfactant spacer length. The study provides a good basis for the development of silver nanoparticle systems with potent antibacterial properties.

Mesoporous silica nanoparticles have been synthesized through sol–gel synthesis in basic conditions. Gemini surfactants having urea in the headgroups were used as pore-forming agents. The effect of the spacer length of the surfactant on the particle morphology was studied on the sub-micrometer and nanometer scales using nitrogen porosimetry, small-angle X-ray scattering (SAXS), ultra-small-angle neutron scattering, and scanning and transmission electron microscopy (SEM, TEM). Depending on the spacer, spherical and/or cylindrical nanoparticles formed in different proportions, as revealed by statistical analysis of SEM micrographs. All prepared materials showed the hexagonal pore structure characteristic of the MCM-41 molecular sieves, with the exception of the sample prepared using the gemini surfactant with the shortest spacer length. The influence of the spacer length on the lattice parameter of the pore network, as well as the average size of the ordered domains, has been assessed by SAXS and TEM. Detailed analysis of the TEM images revealed a spread of the lattice parameter in a range of 10–20%. The broadening of the diffraction peaks was shown to be due to the combination of the effects of the finite domain size and the variance of the lattice parameter across the crystalline domains. The structural differences between the silica gels synthesized with the different surfactants were related to the variation of the micelle morphologies, reported in previous light scattering and small-angle scattering experiments. No connection could be revealed between the micelle shape and size and the pore sizes, showing that surfactants with a broad range of spacer lengths can equally well be used for the preparation of MCM-41 materials.

Mesoporous silica sieves have been prepared through sol-gel synthesis using diester gemini surfactants as pore templates, aiming to obtain new materials with potential use for water remediation. A series of mesoporous spherical silica particles of submicron size have been prepared in an alkali-catalyzed reaction, using a tetraethyl orthosilicate precursor and bis-quaternary ammonium gemini surfactants with diester spacers of varied lengths as pore-forming agents. The effect of the spacer length on the particle morphology was studied using nitrogen porosimetry, small-angle X-ray scattering (SAXS), ultra-small-angle neutron scattering, scanning, and transmission electron microscopy (SEM, TEM). The results revealed that for all spacer lengths, a long-range hexagonal pore ordering developed in the materials. The silica particles were nearly spherical, with sizes below 1 micrometer, and a weak dependence of the mean particle size on the spacer length could be observed. The template removal procedure had a strong influence on the porosity: calcination caused a moderate shrinkage of the pores while retaining the hexagonal structure, whereas treatment with acidified ethanol resulted in only partial removal of the surfactants; however, the hexagonal structure was severely destroyed. The applicability of the obtained calcined materials as adsorbents for heavy metal ions from water was studied with the example of Pb(II). A high sorption capacity of 110 mg/g was obtained in batch experiments, at pH 5 and 4 h contact time.

Bacterial resistance to antibiotics in use represents a critical threat to public health. The treatment of nosocomial, often life-threatening infections is often challenging and requires the search for new antibacterial compounds. In this study a series of phosphonium salts derived from bis(bibenzyl) isoperrottetin A were studied. Bis(bibenzyls) are compounds unique for liverworts. Phosphonium salts were prepared by an eight-step synthesis. The key steps in its preparation were the Ullmann reaction and the Wittig reaction. Ten phosphonium salts were prepared. Isoperrottetin A and its phosphonium salts were tested for antibacterial activity. Some of the compounds exhibit significant biological activity. Most of the prepared derivatives are more potent than the original isoperrottetin A. Compounds were evaluated for the antibacterial activity against selected Gram-positive bacteria such as Staphylococcus aureus, methicillin sensitive and resistant, Enterococcus faecalis and vancomycin sensitive and resistant and Gram-negative bacteria such as Escherichia coli, Pseudomonas aeruginosa, and Klebsiella pneumoniae. Mycobacterium smegmatis and Mycobacterium marinum belonging to the genus Mycobacterium were also tested. Besides antibacterial activity, the compounds inhibit cell breathing and show cytotoxic activity against melanoma cells, retinal and epithelial cells. The results of antibacterial tests showed that the most effective compound is 5,5',5'',5'''-[1,7(1),4,5(1,3)-tetrabenzenaoctaphane-13,44,56,83-tetrayltetrakis(oxy)]tetrakis(5-oxo-P,P,P-triphenylpentane-1-phosphonium) tetrabromide (4P). The values of minimum bactericidal concentration (MBC) against S. aureus methicillin sensitive and resistant and E. faecalis vancomycin sensitive and resistant were < 1 µM. At the same time, the compound does not involve damaging the cell wall, as is known for cationic amphiphilic compounds, and showed favorable safety profiles at MBC values. These findings highlight the potential of compounds found in liverworts as active agents against sensitive and resistant bacterial strains. Chemical modification of bis(bibenzyls) with a phosphonium cation is promising in preparation of potent microbicidal compounds.

Since the last decade, silver nanoparticles (AgNPs) continue to attract interest of both academia and industry due to their peculiar physical, chemical, and optical properties. In the field of pharmaceutical applications, they are efficient carriers in the processes of controlled drug release, improve the drug’s bioavailability, act as efficient antimicrobial agents and provide other biological functions conveyed at the nanometric scale. The known issue hampering further development of applications of AgNPs is their instability in aqueous environment. The present study utilizes two series of cationic bisammonium gemini surfactants with two dodecyl chains and a biodegradable spacer containing two amide or ester groups for the stabilization of AgNPs. The presence of nanosilver in the dispersions was confirmed by UV-VIS plasmon resonance spectra. Stability of AgNPs was characterized by zeta potential measurements proving that amide and ester gemini surfactant series are able to effectively stabilize AgNPs. The particles size analysis utilizing dynamic light scattering and scanning electron microscopy showed that AgNPs stabilized with flexible ester-based gemini surfactants have their size smaller than those capped with amide-containing gemini surfactants. Antimicrobial and anti-inflammatory activity determination as well as cytotoxicity experiments with gemini surfactant stabilized AgNPs showed a complex dependence of biological activity of AgNPs on the molecular structure of stabilizing agents.

Caffeic acid (CA) is one of the most abundant natural compounds present in plants and has a broad spectrum of beneficial pharmacological activities. However, in some cases, synthetic derivation of original molecules can expand their scope. This study focuses on the synthesis of caffeic acid phosphanium derivatives with the ambition of increasing their biological activities. Four caffeic acid phosphanium salts (CAPs) were synthesized and tested for their cytotoxic, antibacterial, antifungal, and amoebicidal activity in vitro, with the aim of identifying the best area for their medicinal use. CAPs exhibited significantly stronger cytotoxic activity against tested cell lines (HeLa, HCT116, MDA-MB-231 MCF-7, A2058, PANC-1, Jurkat) in comparison to caffeic acid. Focusing on Jurkat cells (human leukemic T cell lymphoma), the IC50 value of CAPs ranged from 0.9 to 8.5 μM while IC50 of CA was >300 μM. Antimicrobial testing also confirmed significantly higher activity of CAPs against selected microbes in comparison to CA, especially for Gram-positive bacteria (MIC 13–57 μM) and the yeast Candida albicans (MIC 13–57 μM). The anti-Acanthamoeba activity was studied against two pathogenic Acanthamoeba strains. In the case of A. lugdunensis, all CAPs revealed a stronger inhibitory effect (EC50 74–3125 μM) than CA (>105 µM), while in A. quina strain, the higher inhibition was observed for three derivatives (EC50 44–291 μM). The newly synthesized quaternary phosphanium salts of caffeic acid exhibited selective antitumor action and appeared to be promising antimicrobial agents for topical application, as well as potential molecules for further research.

Triterpene saponin fractions were extracted from Hedera helix , and in-depth analysis of their physicochemical properties was conducted. Hederasaponin B and hederacoside C were extracted from Hedera helix leaves, and their purification was carried out using reverse phase column chromatography with a modified method, providing an affordable alternative to HPLC. Structurally, hederacoside C differs from hederasaponin B only by the presence of a hydroxyl group at the carbon 23 of the aglycon. The critical micelle concentration (cmc) measurement confirmed hydrophilic nature of hederacoside C that led to a higher cmc value compared to hederasaponin B and alpha-hederin. Therefore, the cmc value of hederasaponin B is nearly an order of magnitude lower compared to hederacoside C. Additionally, the study of the surface tension revealed that the more lipophilic alpha-hederin displayed a greater surface tension value (γ cmc = 39.8 mN·m −1 ) compared to hederasaponin B and hederacoside C. Measurements of the surface tension dependence on the concentration in water were enabled to determine the area corresponding to a single saponin molecule at the water/air phase interface (A cmc ). Notably, structural changes had negligible effects, as Acmc values remained practically identical. Particle size determination further indicated that hederacoside C forms only micelles compared to the remaining substances that showed signs of vesicles formation. Alpha-hederin, as the only measured molecule capable of ionization, showed a negative zeta potential.

Synthesis, aggregation parameters and antimicrobial activity of novel cationic gemini surfactants with two amide groups in gemini spacer structure and a variable number of carbon atoms in alkyl tails ranging from 12 to 15 are reported. The critical micelle concentration of gemini surfactants was determined using surface tension and electrical conductivity methods. The cmc values were found in the range 0.83 to 0.06 mM. The interfacial area, micelle ionisation degree and the Gibbs free energy per molecule and alkyl chain were calculated from the surface tension and conductivity curves. Particle size analysis using the dynamic light scattering method confirmed the formation of small spherical micelles 6–7 nm large in size for gemini surfactants with 12 and 13 carbon atoms in the alkyl chain. A large size above 50 nm was found for the aggregates composed of long-chain gemini molecules with 14 and 15 carbon atoms. The zeta potential of gemini surfactants shows a continuous increase with the increasing alkyl chain length. Micelle aggregation number of gemini surfactants correlates well with the hydrodynamic size data. Small aggregation number values were found for short-chain gemini molecules with 12 and 13 carbon atoms in the alkyl chain. Long-chain gemini molecules with 14 and 15 carbon atoms exhibit aggregate growth represented by an increase in the aggregation number values while maintaining the spherical or spheroidal shape of micelles. The investigations of antimicrobial activity against Gram-positive bacteria, Gram-negative bacteria and yeast indicate the increasing antimicrobial efficiency towards the short-chain surfactant with 12 carbon atoms in the alkyl chain. A possible cut-off effect presence is proposed to explain the dependence of antimicrobial activity on the surfactant alkyl tail length.

Gold nanoparticles were prepared by the method of chemical reduction utilising sodium borohydride as reducing agent and stabilised with bisammonium gemini surfactants with variable length of poly-methylene spacer. Physico-chemical investigations indicated the presence of plasmon resonance peaks in the wavelength range 507-544 nm for all investigated Au nanodispersions. The nanoparticle size anal-ysis shows the relationship between the size of gold nanoparticles and the spacer length of stabilising gemini molecules. The strong aggregation tendency of gemini surfactants with short polymethylene spacer composed of 2-4 methylene units in aqueous solutions may be responsible for the formation of clusters of gold nanoparticles which results in the observed large hydrodynamic size of nanoparticle clus-ters at the surfactants concentrations below the CMC. At higher surfactant-to-gold molar ratio values, clusters disintegration occurs and the decrease in size of the nanoparticles is observed. The shape of gold nanoparticles was found to be spherical and polyhedral, as evidenced by the SEM images. The size values varied between 30-60 nm and 10-15 nm for AuNPs capped with gemini molecules with short and medium/long spacer, respectively. Gold nanoparticles are strongly positively charged, with positive zeta potential values being in the interval +44 to +90 mV in the whole analysed region of molar ratio values and surfactant spacer length. The biological experiments indicate a dependence of biological activity of gold nanoparticles on the structural parameter (spacer length) of stabilising gemini molecules. Both cyto-toxicity and anti-inflammatory activity of gold nanoparticles were found to increase with the increasing gemini spacer length up to 12 methylene groups in the spacer.(c) 2022 Elsevier B.V. All rights reserved.

Phosphorus-containing heterocyclic cationic surfactants alkyldimethylphenylphospholium bromides with the alkyl chain length 14 to 18 carbon atoms were used for the stabilization of silver nanodispersions. Zeta potential of silver nanodispersions ranges from +35 to +70 mV, which indicates the formation of stable silver nanoparticles (AgNPs). Long-chain heptadecyl and octadecyl homologs of the surfactants series provided the most intensive stabilizing effect to AgNPs, resulting in high positive zeta potential values and smaller diameter of AgNPs in the range 50–60 nm. A comparison with non-heterocyclic alkyltrimethylphosphonium surfactants of the same alkyl chain length showed better stability and more positive zeta potential values for silver nanodispersions stabilized with heterocyclic phospholium surfactants. Investigations of biological activity of phospholium-capped AgNPs are represented by the studies of antimicrobial activity and cytotoxicity. While cytotoxicity results revealed an increased level of HepG2 cell growth inhibition as compared with the cytotoxicity level of silver-free surfactant solutions, no enhanced antimicrobial action of phospholium-capped AgNPs against microbial pathogens was observed. The comparison of cytotoxicity of AgNPs stabilized with various non-heterocyclic ammonium and phosphonium surfactants shows that AgNPs capped with heterocyclic alkyldimethylphenylphospholium and non-heterocyclic triphenyl-substituted phosphonium surfactants have the highest cytotoxicity among silver nanodispersions stabilized by the series of ammonium and phosphonium surfactants.

Amoebae of the genus Acanthamoeba are worldwide distributed causative agents of serious human infections such as granulomatous amoebic encephalitis (GAE) and Acanthamoeba keratitis (AK). To date, treatment of these infections is non-uniform and frequently unsuccessful. Recently, the phosphonium salts were studied for their high levels of antimicrobial activity. This work was aimed to investigate the cytotoxic effect of metronidazole and two phosphonium salts (PS1, PS2) on two clinical Acanthamoeba isolates. The isolates showed distinctly higher susceptibility to both phosphonium salts than to metronidazole. The highest susceptibility was noted to PS1 after 48 h of incubation. Metronidazole derivate PS2 showed higher susceptibility than metronidazole. The values of EC50 of PS2 were approximately twenty times lower than EC50 of metronidazole for Acanthamoeba lugdunensis strain and sixteen times lower for Acanthamoeba quina strain after 48 h. Although the therapeutic effect of metronidazole in Acanthamoeba infections is usually insufficient, its derivatisation can result in a significantly higher amoebicidal effect. Cytomorphological changes of trophozoites after exposure to tested compounds included rounding up of the cells, damage of membrane integrity, presence of pathological protrusions, elongation of the cells or pseudocyst-like stages. Obtained results indicate possible therapeutic potential of studied phosphonium salts.

A series of alkylphosphocholines with foscarnet moiety was synthesized. The structure of these zwitterionic amphiphiles was modified in both polar and non-polar parts of surfactant molecule. Investigations of physicochemical properties are represented by the determination of critical micelle concentration, the surface tension value at the cmc and the surface area per surfactant head group utilising surface tension measurements. Hydrodynamic diameter of surfactant micelles was determined using the dynamic light scattering technique. Alkylphosphocholines exhibit significant cytotoxic, anticandidal (Candida albicans) and antiamoebal (Acanthamoeba spp. T4 genotype) activity. The relationship between the structure, physicochemical properties and biological activity of the tested compounds revealed that lipophilicity has a significant influence on biological activity of the investigated surfactants. More lipophilic alkylphosphocholines with octadecyl chains show cytotoxic activity against cancer cells which is higher than that of the compounds with shorter alkyl chains. The opposite situation was observed in case of anticandidal and antiamoebal activity of these surfactants. The most active compounds were found to have pentadecyl chains. The foscarnet analogue of miltefosine C15-PFA-C showed the highest anticandidal activity. The minimum value of anticandidal activity of this compound is 1,4 μM thus representing the highest anticandidal activity found within the group of alkylphosphocholines.

A series of phosphonium amphiphilic compounds was synthesized. Cationic parts of molecules contain triphenylphosphonium moieties. Lipophilic parts of compounds are represented by straight alkyl chain or the alkyl chains which are ornamented by benzyl or metronidazole. The physicochemical properties of phosphonium amphiphilic compounds were investigated by the measurements of surface tension and conductivity. The critical micelle concentration (cmc), the surface tension value at the cmc (gamma(cmc)), the surface area at the surface saturation per head group (A(cmc)) were determined. The lowest cmc value was determined for phosphonium salts with straight dodecyl alkyl chain. Its value was 1.5 x 10(-3)mol dm(-3). Surface tension at the cmc decreases with the addition of bulky moieties (benzyl, radical from metronidazol) at the end of alkyl chains. Biological activities of compounds were studied on human erythrocytes and strains ofAcanthamoeba lugdunensisandAcanthamoeba quina. Dodecyltriphenylphosphonium bromide showed the highest activity againstAcanthamoeba. To the best of our knowledge, it is the first compound of the group of phosphonium amphiphiles, which exhibited high activity againstAcanthamoeba. The determined structure-activity relationship indicated nonspecific trophocidal and hemolytic activity that depends on physicochemical properties of the studied compounds.

In present paper, a series of 2-/3-alkoxyphenylcarbamic acid derivatives 5a 5d containing 4 ́-(pyrimidin-2 ́-yl)piperazin-1 ́-yl fragment were synthesized and isolated as salts with hydrochloric acid. Chemical structures of prepared intermediates and final compounds were confirmed by IR, 1H NMR, and 13C NMR spectral data. In addition, target molecules 5a 5d were characterized by MS as well as elemental analyses readouts. Prepared basic carbamates 5aB 5dB were investigated to consider some of their drug-like parameters known as Lipinski Rule of Five, i.e. molecular weight (<500), predicted values of log P for octan-1-ol/water system by applying Moriguchi prediction method ( 4.15) or by using Leo ́s prediction approach ( 5), number of hydrogen bond donors ( 5), number of hydrogen bond acceptors ( 10), number of rotable bonds ( 10) and, finally, the values of topological polar surface area ( 140 Å2). Given compounds have entirely met the criteria formulated above. Assuming their delivery by oral route and absorption by passive mechanisms, evaluated molecules would be able to show good oral bioavailability. The salts 5a 5d were in vitro screened for the activity against virulent Mycobacterium tuberculosis CNCTC My. 331/88 (identical with H37Rv and ATCC 2794) and some of potentially pathogenic strains, i.e. M. avium CNCTC My. 330/80 (identical with ATCC 25291), M. kansasii CNCTC My. 235/80 (identical with ATCC 12478) and clinical isolate of M. kansasii 6509/96, respectively, by the dilution-micromethod using isoniazide and ethambutol as standard drugs. Following estimated values of minimum inhibitory concentration, current research suggested that the presence of 3-alkoxy side chain attached to phenylcarbamoyloxy fragment as well as relatively -electron rich aromatic system(s) within basic compartment would be favorable in terms of the activity against M. tuberculosis H37Rv.

Cationic gemini surfactants with polymethylene spacer and linear alkyl chains containing an even number of carbon atoms have been extensively studied in the recent past, with the emphasis put on the determination of their aggregation behaviour in aqueous solution and their biological properties. However, the information on the aggregation of branched gemini surfactants with an odd number of carbon atoms in their alkyl chains is only sparsely reported in the literature. To help cover this gap in the research of cationic gemini surfactants, a series of branched bisammonium cationic gemini surfactants with an odd number of carbon atoms in alkyl chains (tridecane-2-yl chains) and a polymethylene spacer with a variable length ranging from 3 to 12 carbon atoms have been synthesized and investigated. Critical micelle concentration, which was determined by three methods, was found to be in the order 10-4 mol/L. A comparison of the obtained data of the novel series of tridecyl chain geminis with those of gemini surfactants with dodecyl chains and an identical spacer structure revealed that structural differences between both series of gemini surfactants result in different aggregation and surface properties for surfactants with 6 and 8 methylene groups in the spacer (N,N'-bis(tridecane-2-yl)-N,N,N',N'-tetramethylhexane-1,6-diaminium dibromide and N,N'-bis(tridecane-2-yl)-N,N,N',N'-tetramethyloctane-1,8-diaminium dibromide) with the cmc values 8.2 × 10-4 mol/L and 6.5 × 10-4 mol/L, respectively, as determined by surface tension measurements. Particle size analysis showed the formation of small stable spherical micelles in the interval between 2.8 and 5 nm and with zeta potential around +50 mV, which are independent of surfactant concentration and increase with the increasing spacer length. Microbicidal activity of 13-s-13 gemini surfactants was found to be efficient against Gram-positive, Gram-negative bacteria and yeast.

: Self-assembly properties of cationic gemini surfactants with biodegradable amide or ester groups in the spacer were investigated utilising time-resolved fluorescence quenching, dynamic light scattering and zeta potential measurements. A correlation between aggregation parameters such as micelle aggregation number, micelle size and zeta potential with the structure of gemini molecules was made. For gemini molecules with medium spacer lengths, micelle aggregation number does not change much with the surfactant concentration. When the spacer is extended, a stronger aggregation tendency is observed for gemini surfactant molecules with two ester groups in the spacer and the aggregation number increases. The assumption of stronger aggregation of ester-based gemini molecules at larger spacer number values is also documented by measurements of the size and zeta potential of ester-based micelles. The explanation of the difference in aggregation ability of amide-based and ester-based gemini molecules is related to the structural features of gemini molecules, notably to the larger flexibility and denser arrangement of ester-based gemini molecules in a micelle. To support this assumption, optimised 3D models of the studied gemini molecules were constructed. Correspondingly, the calculations show smaller size and interfacial area for ester-based gemini conformers.

This paper deals with the analysis of antioxidant activities of polyphenolic compounds by TLC-DPPH method. Polyphenolic compounds are represented by lichen acids (depsides, benzyldepsides, depsidones, dibenzofuranes and antraquinones) and dihydrostilbenoids, macrocyclic dimeric dihydrostilbenoids, flavonoids occurring in liverworts. The highest antioxidant activity was observed in the case of 3-hydroxyphysodic acid from Hypogymnia physodes, marchantin A and flavonoids from Marchantia polymorpha. The assessment of the TLC-DPPH method shows that it is suitable for an easy and fast analysis of the antioxidant potential of the polyphenolic compounds occurring in the thalus of lichens and liverworts. The filter paper modification of this method is also discussed.