Emerging investigator series: determination of biphasic core-shell droplet properties using aerosol optical tweezers

We present a new algorithm for the analysis of whispering gallery modes (WGMs) found in the cavity enhanced Raman spectra retrieved from optically tweezed droplets. Our algorithm improves the computational scaling when analyzing core-shell droplets (i.e. phase-separated or biphasic droplets) in the aerosol optical tweezers (AOT), making it computationally practical to analyze spectra collected at a few Hz over hours-long experiments. This enables the determination of the size and refractive index of both the core and shell phases with high accuracy, at 0.5 Hz time resolution. Phase-separated core-shell droplets are common morphologies in a wide variety of biophysical, colloidal, and aerosolized chemical systems, and have recently become a major focus in understanding the atmospheric chemistry of particulate matter. Our new approach reduces the number of parameters directly searched for, decreasing computational demands. We assess the accuracy of the diameters and refractive indices retrieved from a homogeneous or core-shell droplet. We demonstrate the performance of the new algorithm using experimental data from a droplet of aqueous glycerol coated by squalane. We demonstrate that a shell formation causes adjacent WGMs to split from each other in their wavenumber position through the addition of a secondary organic aerosol shell around a NaCl(aq) droplet. Our new algorithm paves the way for more in-depth physiochemical experiments into liquid-liquid phase separation and their consequences for interfacial chemistry-a topic with growing experimental needs for understanding the dynamics and chemistry of atmospheric aerosol particles, and in biochemical systems.

Two new convenient syntheses of 14C-squalene from turbinaric acid

Carbon-14 labeled (6E,10E,14E,18E)-2,6,10,15,19,23-hexamethyltetracosa-2,6,10,14,18,22-hexaene, also known as squalene, was synthesized as a tool for pharmacokinetic studies. Two simple and efficient labeling approaches were developed to give [2-¹⁴ C]-squalene and [3-¹⁴ C]-squalene from a halogenated precursor derived from turbinaric acid. They were obtained in 13.5% radiochemical yield in 6 steps and in 38% radiochemical yield in 3 steps respectively from carbon-14 labeled potassium cyanide with a radiochemical purity higher than 98% in both cases.

Biophysical characterization of asolectin-squalene liposomes

Liposomes are shell nanoparticles able to embed hydrophobic molecules into their lipid layers to be released to cells. In pharmaceutical sciences, liposomes remain the delivery system with the highest biocompatibility, stability, loading characteristics, tunable physicochemical properties. Squalene is a natural, water insoluble, lipid, abundant in olive oil and shark liver. Studies in vitro and in animal models suggest protective and inhibitory effects of squalene against cancer. To study its effect on cells, and to overcome its insolubility in water, we have designed and produced large unilamellar liposomes containing different quantities of this terpene (0%, 2.8%, 5% w/w). Liposomes have been characterized by different biophysical techniques. Size-exclusion and affinity chromatography showed a unimodal size distribution and confirmed the squalene loaded dose. Laurdan fluorescence evidenced the changes in the hydration of the external layer of liposomes as a function of squalene concentration. Dynamic light scattering and small angle X-ray scattering revealed squalene induced structural differences in the hydrodynamic radius distribution and in the bilayer thickness respectively. Finally, preliminary experiments on the effects of liposome-delivered squalene on tumor and non-tumor cell lines showed time- and dose-dependent cytotoxic effects on LAN5 tumor cells and no effect on NIH-3T3 normal cells.

Marine Longilenes, Oxasqualenoids with Ser-Thr Protein Phosphatase 2A Inhibition Activity

The red seaweed Laurencia viridis is a rich source of oxygenated secondary metabolites that were derived from squalene. We report here the structures of three novel compounds, (+)-longilene peroxide (1), longilene (2), and (+)-prelongilene (3) that were isolated from this alga, in addition to other substances, 4 and 5, resulting from their acid-mediated degradation. The effect of compounds 1 and 3 against Ser-Thr protein phosphatase type 2A (PP2A) was evaluated, showing that (+)-longilene peroxide (1) inhibited PP2A (IC₅₀ 11.3 μM). In order to explain the interaction between PP2A and compounds 1 and 3, molecular docking simulations onto the PP2A enzyme-binding region were used.

Pandemrix® vaccination is not associated with increased risk of islet autoimmunity or type 1 diabetes in the TEDDY study children

AIMS/HYPOTHESIS

During the A/H1N1 2009 (A/California/04/2009) pandemic, mass vaccination with a squalene-containing vaccine, Pandemrix®, was performed in Sweden and Finland. The vaccination was found to cause narcolepsy in children and young adults with the HLA-DQ 6.2 haplotype. The aim of this study was to investigate if exposure to Pandemrix® similarly increased the risk of islet autoimmunity or type 1 diabetes.

METHODS

In The Environmental Determinants of Diabetes in the Young (TEDDY) study, children are followed prospectively for the development of islet autoimmunity and type 1 diabetes. In October 2009, when the mass vaccination began, 3401 children at risk for islet autoimmunity and type 1 diabetes were followed in Sweden and Finland. Vaccinations were recorded and autoantibodies against insulin, GAD65 and insulinoma-associated protein 2 were ascertained quarterly before the age of 4 years and semi-annually thereafter.

RESULTS

By 5 August 2010, 2413 of the 3401 (71%) children observed as at risk for an islet autoantibody or type 1 diabetes on 1 October 2009 had been vaccinated with Pandemrix®. By 31 July 2016, 232 children had at least one islet autoantibody before 10 years of age, 148 had multiple islet autoantibodies and 96 had developed type 1 diabetes. The risk of islet autoimmunity was not increased among vaccinated children. The HR (95% CI) for the appearance of at least one islet autoantibody was 0.75 (0.55, 1.03), at least two autoantibodies was 0.85 (0.57, 1.26) and type 1 diabetes was 0.67 (0.42, 1.07). In Finland, but not in Sweden, vaccinated children had a lower risk of islet autoimmunity (0.47 [0.29, 0.75]), multiple autoantibodies (0.50 [0.28, 0.90]) and type 1 diabetes (0.38 [0.20, 0.72]) compared with those who did not receive Pandemrix®. The analyses were adjusted for confounding factors.

CONCLUSIONS/INTERPRETATION

Children with an increased genetic risk for type 1 diabetes who received the Pandemrix® vaccine during the A/H1N1 2009 pandemic had no increased risk of islet autoimmunity, multiple islet autoantibodies or type 1 diabetes. In Finland, the vaccine was associated with a reduced risk of islet autoimmunity and type 1 diabetes.

Biomimetic Platinum-Promoted Polyene Polycyclizations: Influence of Alkene Substitution and Pre-cyclization Conformations

Results of kinetic experiments and quantum chemical computations on a series of platinum-promoted polycyclization reactions are described. Analyses of these results reveal a reactivity model that reaches beyond the energetics of the cascade itself, incorporating an ensemble of pre-cyclization conformations of the platinum-alkene reactant complex, only a subset of which are productive for bi- (or larger) cyclization and lead to products. Similarities and differences between this scenario, including reaction coordinates for polycyclization, for platinum- and enzyme-promoted polycyclization reactions are highlighted.

Circulating Lipoproteins: A Trojan Horse Guiding Squalenoylated Drugs to LDL-Accumulating Cancer Cells

Selective delivery of anticancer drugs to rapidly growing cancer cells can be achieved by taking advantage of their high receptor-mediated uptake of low-density lipoproteins (LDLs). Indeed, we have recently discovered that nanoparticles made of the squalene derivative of the anticancer agent gemcitabine (SQGem) strongly interacted with the LDLs in the human blood. In the present study, we showed both in vitro and in vivo that such interaction led to the preferential accumulation of SQGem in cancer cells (MDA-MB-231) with high LDL receptor expression. As a result, an improved pharmacological activity has been observed in MDA-MB-231 tumor-bearing mice, an experimental model with a low sensitivity to gemcitabine. Accordingly, we proved that the use of squalene moieties not only induced the gemcitabine insertion into lipoproteins, but that it could also be exploited to indirectly target cancer cells in vivo.

Phytochemical Analysis of a Cytotoxic Fraction of Quassia silvestris using LC-HR-ESI-MSn

INTRODUCTION

The genus Quassia is a promising source of secondary metabolites with biological potential including antimalarial and cytotoxic activities. Limited data are available on the phytochemistry and pharmacology of Quassia silvestris Cheek & Jongkind, a Cameroonian medicinal plant used to treat various ailments.

OBJECTIVES

To carry out the bioassay-guided fractionation and LC-HR-ESI-MS analyses of the leaves extract from Q. silvestris; to purify the active fractions and isolate the major compounds using different chromatographic and spectroscopic methods. The obtained compounds will be evaluated for their biological activity.

MATERIAL AND METHODS

Following the cytotoxic screening and LC-HR-ESI-MS profiling of fractions obtained from partition of the methanolic extract of Q. silvestris leaves, the CH₂ Cl₂ -soluble fraction which exhibited the highest cytotoxicity was retained for further investigations.

RESULTS

Sixteen squalene-derived metabolites were identified with oxasqualenoid derivatives being the most predominant. Among the isolates, structure elucidation of two new oxasqualenoids quassiols E (1) and F (2), were achieved by NMR (one-dimensional (1D) and two-dimensional (2D)) and MS methods. The newly characterised compounds 1 and 2, together with the known tetraol (3) and 3-oxo-oleanoic acid (16) displayed moderate cytotoxicity.

CONCLUSION

The identification and structural characterisation of highly oxidised squalene derived metabolites from this plant may provide important insight data for further pharmacological investigations. The LC-HR-ESI-MSⁿ method reported here could be developed as a rapid and efficient tool for the analyses of structurally related compounds in the genera Quassia, Simarouba, and Eurycoma of the subfamily Simarouboideae. Copyright © 2016 John Wiley & Sons, Ltd.

Isolation and Characterization of Cyclic C33 Botryococcenes and a Trimethylsqualene Isomer from Botryococcus braunii Race B

Three cyclic C₃₃ botryococcenes and one new trimethylsqualene isomer were isolated from the B race, Showa (Berkeley) strain of Botryococcus braunii, which is known to produce large amounts of isoprenoid hydrocarbons ranging in carbon number from 30 to 34. Their purity was determined by GC-MS, and structures were characterized by 1D and 2D NMR. One of these molecules, cyclic C₃₃-1 botryococcene (5), has an unusual connection of a methylenecyclohexane ring to the molecule backbone not seen before in botryococcenes. This report further adds to our knowledge of the wide range of isoprenoid hydrocarbon structures produced by B. braunii.

Regioselectivity and Reaction Mechanism of Ru-Catalyzed Hydrogenolysis of Squalane and Model Alkanes

The dependence of the C-C hydrogenolysis activity on reaction parameters and the structure of the substrate alkanes was investigated for Ru/CeO₂ catalyst with very small (dispersion: H/Ru=0.89) Ru particles. The substrate concentration and reaction temperature did not have a significant effect on the selectivity pattern, except that methane production was promoted at high temperatures. However, the hydrogen pressure had a marked effect on the selectivity pattern. C_tertiary -C bond dissociation, terminal C_secondary -C_primary bond dissociation, and fragmentation to form excess methane had negative reaction order with respect to hydrogen partial pressure, whereas C_secondary -C_secondary bond dissociation had an approximately zero reaction order. Therefore, a high hydrogen pressure is essential for the regioselective hydrogenolysis of C_secondary -C_secondary bonds in squalane. Ru/SiO₂ catalyst with larger Ru particles showed similar changes in the product distribution during the change in hydrogen pressure. The reaction mechanism for each type of C-C bond dissociation is proposed based on reactivity trends and DFT calculations. The proposed intermediate species for the internal C_secondary -C_secondary dissociation, terminal C_secondary -C_primary dissociation, and C_tertiary -C dissociation is alkyls, alkylidynes, and alkenes, respectively.

A botanically derived skin surface lipid mimetic based on the composition of healthy 22-year-old females

INTRODUCTION

Skin surface lipids (SSLs) greatly affect the skin physiology and are thought to be involved in skin processes such as thermoregulation, bacterial colonization, and barrier function and maintenance. SSLs are primarily composed of fatty acids, triglycerides, cholesterol, steryl esters, wax esters, and squalene. The objective of this research was to evaluate and better understand the SSL composition and variation in an age- and sex-controlled population, and create an appropriate botanically derived mimetic.

METHODS

SSL samples taken from the foreheads of 59 healthy, 22-year-old females were analyzed by gas chromatography mass spectrometry (GC-MS). Using botanically derived raw materials from Macadamia integrifolia, Simmondsia chinensis, and Olea europaea, a mimetic was engineered via a series of esterification reactions and lipid components quantitated with GC-MS. The glyceride and wax ester components were produced by the interesterification of M. integrifolia and S. chinensis under specified conditions. The steryl ester component was produced by the esterification of the fatty acids of M. integrifolia and phytosterols under similar conditions.

RESULTS

The following major classes of lipids were found and quantified by percent composition: glycerides, free fatty acids, squalene, wax esters, steryl esters, and cholesterol. The variability between subjects for each component was minimal; however, the greatest variation was seen for free fatty acids and cholesterol. Correlations among the components were calculated and found to be statistically or directionally significant with few exceptions. The esterification reactions of jojoba, macadamia, and tall oils, along with a precise addition of squalene derived from O. europaea, produced a suitable SSL mimetic. When applied to delipidized skin, the mimetic helped restore barrier function, increased skin hydration, and increased skin elasticity and firmness in aged skin.

DISCUSSION

The present research indicates that, overall, the SSL composition is quite consistent in a controlled population of 22-year-old females. Furthermore, there were strong correlations between the SSL components among subjects, with the exception of squalene and steryl esters. This was expected due to the fact that of the six major SSL components, steryl esters and squalene also showed higher variation over time for each individual. The variation in free fatty acids may be attributable to the potential differences in the microflora of the subjects. The variation in this study's results, as compared to previously published work, could indicate that the collection methods, geographic location, gender, and age specificity contribute to the distribution or collection of different lipid components on the skin surface. Since the excretion of sebum is known to decrease in females after 40 years of age, the proposed mimetic could be a beneficial supplement to human SSLs in aged skin, as well as in skin where the stratum corneum is defective, by aiding in the restoration of barrier function, while increasing skin hydration, elasticity, and firmness.

Biosynthetic Approaches to Squalene Production: The Case of Yeast

Squalene is a precursor in the eukaryotic sterol biosynthesis. It is a valuable compound with several human health-related applications. Since the traditional natural resources of squalene are limited, alternatives for the production of squalene on industrial scale have been intensively explored during past years. The yeast Saccharomyces cerevisiae represents an attractive option due to elaborated techniques of genetic and metabolic engineering that can be applied to improve squalene yields. We discuss in this chapter some theoretical aspects of genetic manipulations of the ergosterol biosynthesis pathway aimed at increased squalene production and describe analytical methods for squalene purification and determination of its content in yeast cells.

Kinetics and Products from Heterogeneous Oxidation of Squalene with Ozone

Motivated by the importance of the heterogeneous chemistry of squalene contained within skin oil to indoor air chemistry, the surface reaction of squalene with gas-phase ozone has been investigated. Using direct analysis in real time mass spectrometry (DART-MS) to monitor squalene, the reactive uptake coefficients were determined to be (4.3 ± 2.2) × 10^-4 and (4.0 ± 2.2) × 10^-4 for ozone mixing ratios (MR_O3) of 50 and 25 ppb, respectively, on squalene films deposited on glass surfaces. At an MR_O3 of 25 ppb, the lifetime for oxidation was the same as that in an indoor office with an MR_O3 between 22 and 32 ppb, suggesting that O₃ was the dominant oxidant in this indoor setting. While the heterogeneous kinetics of squalene and O₃ were independent of relative humidity (RH), the RH significantly affected the reaction products. Under dry conditions (<5% RH), in addition to several products between m/z 300 and 350, the major condensed-phase end products were levulinic acid (LLA) and succinic acid (SCA). Under humid conditions (50% RH), the major end products were 4-oxopentanal, 4-oxobutanoic acid, and LLA. The molar yields of LLA and SCA were quantified as 230 ± 43% and 110 ± 31%, respectively, under dry conditions and 91 ± 15% and <5%, respectively, at 50% RH. Moreover, high-molecular weight (molecular weight of >450 Da) products were observed under dry conditions with indications that LLA was involved in their formation. The mechanism of squalene oxidation is discussed in light of these observations, with indications of an important role played by Criegee intermediates.

Multifunctional oxidosqualene cyclases and cytochrome P450 involved in the biosynthesis of apple fruit triterpenic acids

Apple (Malus × domestica) accumulates bioactive ursane-, oleanane-, and lupane-type triterpenes in its fruit cuticle, but their biosynthetic pathway is still poorly understood. We used a homology-based approach to identify and functionally characterize two new oxidosqualene cyclases (MdOSC4 and MdOSC5) and one cytochrome P450 (CYP716A175). The gene expression patterns of these enzymes and of previously described oxidosqualene cyclases were further studied in 20 apple cultivars with contrasting triterpene profiles. MdOSC4 encodes a multifunctional oxidosqualene cyclase producing an oleanane-type triterpene, putatively identified as germanicol, as well as β-amyrin and lupeol, in the proportion 82 : 14 : 4. MdOSC5 cyclizes 2,3-oxidosqualene into lupeol and β-amyrin at a ratio of 95 : 5. CYP716A175 catalyses the C-28 oxidation of α-amyrin, β-amyrin, lupeol and germanicol, producing ursolic acid, oleanolic acid, betulinic acid, and putatively morolic acid. The gene expression of MdOSC1 was linked to the concentrations of ursolic and oleanolic acid, whereas the expression of MdOSC5 was correlated with the concentrations of betulinic acid and its caffeate derivatives. Two new multifuntional triterpene synthases as well as a multifunctional triterpene C-28 oxidase were identified in Malus × domestica. This study also suggests that MdOSC1 and MdOSC5 are key genes in apple fruit triterpene biosynthesis.

Interactions between Phospholipids and Organic Phases: Insights into Lipoproteins and Nanoemulsions

The adsorption of phosphatidylcholines (PCs), dissolved in squalene or squalane as an organic phase, was studied at the interface with water. Using profile analysis tensiometry, the equilibrium adsorption isotherms, minimum molecular interfacial areas, and solubility limits were derived. For squalene, differences in PC solubility and interfacial adsorption were found, depending on PC saturation. Compared to saturated PCs, unsaturated PCs showed a 3-fold-lower interfacial density but up to a 28-fold-higher critical aggregation concentration (CAC). In addition, the solubility limit of unsaturated PC in squalene and in its saturated form squalane diverged by a factor of 739. These findings provided evidence for steric repulsion or π-π interactions of π bonds in both solvent and solute or both effects acting complementarily. In squalane, low solubilities but high interfacial densities were found for all investigated PCs. Changes in fatty acid chain lengths showed that the influence of the increases in entropy and enthalpy on solubility is much smaller than solvent/solute interactions. Oxidation products of squalene lowered the interfacial tension, but increasing concentrations of PC expelled them from the interface. The CAC of saturated PC was increased by oxidation products of squalene whereas that of unsaturated PCs was not. Our findings indicate that the oxidation of triglycerides in lipoprotein cores can lead to increased solubility of saturated phospholipids covering the lipoproteins, contributing to destabilization, coalescence, and terminally the formation of atherosclerotic plaques. The consideration of solvent/solute interactions in molecular modeling may contribute to the interfacial tension and the corresponding kinetic or thermodynamic stability of lipoproteins. Measured areas per molecule prove that PCs form monolayers of different interfacial densities at the squalene/water interface but multilayers at the squalane/water interface. These findings showed that combinations of solvent or solute saturation affect the outcome for nanoemulsions forming either expanded or condensed monolayers or multilayers.

Engineering Triterpene and Methylated Triterpene Production in Plants Provides Biochemical and Physiological Insights into Terpene Metabolism

Linear, branch-chained triterpenes, including squalene (C30), botryococcene (C30), and their methylated derivatives (C31-C37), generated by the green alga Botryococcus braunii race B have received significant attention because of their utility as chemical and biofuel feedstocks. However, the slow growth habit of B. braunii makes it impractical as a production system. In this study, we evaluated the potential of generating high levels of botryococcene in tobacco (Nicotiana tabacum) plants by diverting carbon flux from the cytosolic mevalonate pathway or the plastidic methylerythritol phosphate pathway by the targeted overexpression of an avian farnesyl diphosphate synthase along with two versions of botryococcene synthases. Up to 544 µg g(-1) fresh weight of botryococcene was achieved when this metabolism was directed to the chloroplasts, which is approximately 90 times greater than that accumulating in plants engineered for cytosolic production. To test if methylated triterpenes could be produced in tobacco, we also engineered triterpene methyltransferases (TMTs) from B. braunii into wild-type plants and transgenic lines selected for high-level triterpene accumulation. Up to 91% of the total triterpene contents could be converted to methylated forms (C31 and C32) by cotargeting the TMTs and triterpene biosynthesis to the chloroplasts, whereas only 4% to 14% of total triterpenes were methylated when this metabolism was directed to the cytoplasm. When the TMTs were overexpressed in the cytoplasm of wild-type plants, up to 72% of the total squalene was methylated, and total triterpene (C30+C31+C32) content was elevated 7-fold. Altogether, these results point to innate mechanisms controlling metabolite fluxes, including a homeostatic role for squalene.

Atmospheric Oxidation of Squalene: Molecular Study Using COBRA Modeling and High-Resolution Mass Spectrometry

Squalene is a major component of skin and plant surface lipids and is known to be present at high concentrations in indoor dust. Its high reactivity toward ozone makes it an important ozone sink and a natural protectant against atmospheric oxidizing agents. While the volatile products of squalene ozonolysis are known, the condensed-phase products have not been characterized. We present an analysis of condensed-phase products resulting from an extensive oxidation of squalene by ozone probed by electrospray ionization (ESI) high-resolution mass spectrometry (HR-MS). A complex distribution of nearly 1300 peaks assignable to molecular formulas is observed in direct infusion positive ion mode ESI mass spectra. The distribution of peaks in the mass spectra suggests that there are extensive cross-coupling reactions between hydroxy-carbonyl products of squalene ozonolysis. To get additional insights into the mechanism, we apply a Computational Brewing Application (COBRA) to simulate the oxidation of squalene in the presence of ozone, and compare predicted results with those observed by the HR-MS experiments. The system predicts over one billion molecular structures between 0 and 1450 Da, which correspond to about 27 000 distinct elemental formulas. Over 83% of the squalene oxidation products inferred from the mass spectrometry data are matched by the simulation. The simulation indicates a prevalence of peroxy groups, with hydroxyl and ether groups being the second-most important O-containing functional groups formed during squalene oxidation. These highly oxidized products of squalene ozonolysis may accumulate on indoor dust and surfaces and contribute to their redox capacity.

Insecticidal activity of Jatropha curcas extracts against housefly, Musca domestica

The hexane and ether extracts of leaves, bark and roots of Jatropha curcas were screened for their toxicity against different developmental stages of housefly. The larvicidal, pupicidal and adulticidal activities were analysed at various concentrations (0.78-7.86 mg/cm(2)) of hexane and ether extracts. The lethal concentration values (LC50) of hexane extract of J. curcas leaves were 3.0 and 0.27 mg/cm(2) for adult and larval stages of housefly, respectively, after 48 h. Similarly, the ether extract of leaf showed the LC50 of 2.20 and 4.53 mg/cm(2) for adult and larval stages of housefly. Least toxicity was observed with hexane root extract of J. curcas with LC50 values of 14.18 and 14.26 mg/cm(2) for adult and larvae of housefly, respectively, after 48 h. The variation in LC50 against housefly pupae was found to be 8.88-13.10 mg/cm(2) at various J. curcas extract concentrations. The GC-MS analysis of J. curcas leaf extract revealed the presence of trans-phytol (60.81 %), squalene (28.58 %), phytol (2.52 %) and nonadecanone (1.06 %) as major components that could be attributed for insecticidal activity of J. curcas extracts.

[Analysis of meibum by gas chromatography-mass spectrometry]

OBJECTIVE

To analyze and identify the meibum from healthy individuals and patients with meibomian gland dysfunction (MGD) by gas chromatography-mass spectrometry (GC-MS).

METHODS

Case-control study. The meibum from twenty healthy persons and nineteen MGD patients was separated and analyzed by GC-MS. GC conditions were: column: DB-5 MS (30 m × 0.25 mm × 0.25 µm) capillary column, carrier gas: He, flow rate: 1.0 ml/min, injection amount: 1 ml. MS conditions were: MS ionization mode: EI, electron impact source electron energy: 70 eV, ion source temperature: 200 °C, electron multiplier voltage of 1.10 kV, solvent delay time: 1.00 min, scanning mode: San, scanning range m/z 20-500 aum. The components of meibum were identified by El mass fragmentation and the standard substance in the database. The relative content of the components was calculated by the method of chromatographic peak area normalization.

RESULTS

In the 39 samples that were analyzed by GC-MS, 102 chromatography peaks were separated, and 23 compounds were identified, including 3 alkanes, 4 alkenes, 2 alcohols, 1 aromatic hydrocarbon, 7 esters, 4 fatty acids, 1 amide, and 1 phenol. However, there was no corresponding physical mass library information in the remaining 79 GC peaks, and no identification could be performed. The relative concentration level of palmitic acid, stearic acid, and squalene in the MGD group was significantly lower than that in the healthy controls (U = -2.086, -2.027, -2.866, P < 0.05).

CONCLUSIONS

Meibum has a wide variety of components, the structures are complex, and the components in different individuals vary greatly. Palmitic acid, stearic acid, and squalene levels were significantly decreased in MGD patients compared to the healthy group, suggesting that MGD is related to changes of the meibum components.

Probing the Evaporation Dynamics of Mixed SOA/Squalane Particles Using Size-Resolved Composition and Single-Particle Measurements

An analysis of the formation and evaporation of mixed-particles containing squalane (a surrogate for hydrophobic primary organic aerosol, POA) and secondary organic aerosol (SOA) is presented. In these experiments, one material (D62-squalane or SOA from α-pinene + O3) was prepared first to serve as surface area for condensation of the other, forming the mixed-particles. The mixed-particles were then subjected to a heating-ramp from 22 to 44 °C. We were able to determine that (1) almost all of the SOA mass is comprised of material less volatile than D62-squalane; (2) AMS collection efficiency in these mixed-particle systems can be parametrized as a function of the relative mass fraction of the components; and (3) the vast majority of D62-squalane is able to evaporate from the mixed particles, and does so on the same time scale regardless of the order of preparation. We also performed two-population mixing experiments to directly test whether D62-squalane and SOA from α-pinene + O3 form a single solution or two separate phases. We find that these two OA types are immiscible, which informs our inference of the morphology of the mixed-particles. If the morphology is core-shell and dictated by the order of preparation, these data indicate that squalane is able to diffuse relatively quickly through the SOA shell, implying that there are no major diffusion limitations.

P450s and UGTs: Key Players in the Structural Diversity of Triterpenoid Saponins

The recent spread of next-generation sequencing techniques has facilitated transcriptome analyses of non-model plants. As a result, many of the genes encoding enzymes related to the production of specialized metabolites have been identified. Compounds derived from 2,3-oxidosqualene (the common precursor of sterols, steroids and triterpenoids), a linear compound of 30 carbon atoms produced through the mevalonate pathway, are called triterpenes. These include essential sterols, which are structural components of biomembranes; steroids such as the plant hormones, brassinolides and the toxin in potatoes, solanine; as well as the structurally diverse triterpenoids. Triterpenoids containing one or more sugar moieties attached to triterpenoid aglycones are called triterpenoid saponins. Triterpenoid saponins have been shown to have various medicinal properties, such as anti-inflammatory, anticancerogenic and antiviral effects. This review summarizes the recent progress in gene discovery and elucidates the biochemical functions of biosynthetic enzymes in triterpenoid saponin biosynthesis. Special focus is placed on key players in generating the structural diversity of triterpenoid saponins, cytochrome P450 monooxygenases (P450s) and the UDP-dependent glycosyltransferases (UGTs). Perspectives on further gene discovery and the use of biosynthetic genes for the microbial production of plant-derived triterpenoid saponins are also discussed.

Characterization of the 2,3-Oxidosqualene Cyclase Gene from Antrodia cinnamomea and Enhancement of Cytotoxic Triterpenoid Compound Production

Antrodia cinnamomea is a scarce, epiphyte, host-specific, brown-rot fungus that produces diverse bioactive compounds with potent biological activity. Natural wild-type fruiting bodies of A. cinnamomea are rare and highly valued, but their artificial culture poses challenges. Triterpenoids are a group of secondary metabolites that contribute to the bioactivities of A. cinnamomea. 2,3-Oxidosqualene cyclase (OSC) is a key enzyme in triterpenoid biosynthesis, which converts 2,3-oxidosqualene (OS) into polycyclic triterpenoids. In this study, we isolated a 2,3-oxidosqualene cyclase gene from A. cinnamomea with degenerate primers and designated it as AcOSC. The full length AcOSC cDNA was subcloned into a yeast expression vector, and AcOSC activity was confirmed. RT-PCR results showed that AcOSC expression was highest in the wild-type fruiting body and correlated with a higher concentration of triterpenoids. Agrobacterium-mediated gene transformation was conducted to enhance the triterpenoid synthesis capacity of the cultured mycelium. Metabolite profiling was conducted by LC-MS/MS and principal component analysis (PCA). The compositions and contents of metabolites in the AcOSC transgenic lines were different from those in the wild-type mycelium and vector control. The levels of two important triterpenoids, dehydrosulphurenic acid (DSA) and dehydroeburicoic acid (DEA), were increased in A. cinnamomea oxidosqualene cyclase overexpression strains compared to controls. In summary an Agrobacterium-mediated gene transformation procedure was established that successfully increased the level of transgene expression and enhanced the triterpenoid content in cultured A. cinnamomea.

The role of solvent swelling in the self-assembly of squalene based nanomedicines

Squalene based nanoparticles obtained via nanoprecipitation are promising candidates as efficient anti-cancer drugs. In order to highlight their preparation process and to facilitate further clinical translation, the present study enlightens the paramount role of the solvent in the formation of these nanomedicines. Three different squalene-based nanoparticles, i.e. squalenic acid, deoxycytidine squalene and gemcitabine squalene, have been investigated before and after organic solvent evaporation. Size and structural analysis by Small Angle Neutron Scattering revealed that droplets' size was uniquely controlled by the solvent composition (ethanol-water), which evolved during their gradual formation. The particles were preferably swollen by water and the swelling increased when less ethanol was present. Either coalescence or fragmentation was observed depending on the increase or decrease of the ethanol content, supporting an equilibrium control of the size. Moreover, a high water swelling was observed for the three local organization of the nanodroplets (hexagonal for gemcitabine squalene, cubic for deoxycytidine and not structured for squalenic acid) and could be the source of the previously reported efficiency of related anti-cancer squalene based nanomedicines.

Antineoplastic Effects of siRNA against TMPRSS2-ERG Junction Oncogene in Prostate Cancer

TMPRSS2-ERG junction oncogene is present in more than 50% of patients with prostate cancer and its expression is frequently associated with poor prognosis. Our aim is to achieve gene knockdown by siRNA TMPRSS2-ERG and then to assess the biological consequences of this inhibition. First, we designed siRNAs against the two TMPRSS2-ERG fusion variants (III and IV), most frequently identified in patients’ biopsies. Two of the five siRNAs tested were found to efficiently inhibit mRNA of both TMPRSS2-ERG variants and to decrease ERG protein expression. Microarray analysis further confirmed ERG inhibition by both siRNAs TMPRSS2-ERG and revealed one common down-regulated gene, ADRA2A, involved in cell proliferation and migration. The siRNA against TMPRSS2-ERG fusion variant IV showed the highest anti-proliferative effects: Significantly decreased cell viability, increased cleaved caspase-3 and inhibited a cluster of anti-apoptotic proteins. To propose a concrete therapeutic approach, siRNA TMPRSS2-ERG IV was conjugated to squalene, which can self-organize as nanoparticles in water. The nanoparticles of siRNA TMPRSS2-ERG-squalene injected intravenously in SCID mice reduced growth of VCaP xenografted tumours, inhibited oncoprotein expression and partially restored differentiation (decrease in Ki67). In conclusion, this study offers a new prospect of treatment for prostate cancer based on siRNA-squalene nanoparticles targeting TMPRSS2-ERG junction oncogene.

[Microbial metabolites that inhibit sterol biosynthesis, their chemical diversity and characteristics of mode of action]

Inhibitors of sterol biosynthesis (ISB) are widespread in nature and characterized by appreciable diversity both in their chemical structure and mode of action. Many of these inhibitors express noticeable biological activity and approved themselves in development of various pharmaceuticals. In this review there is a detailed description of biologically active microbial metabolites with revealed chemical structure that have ability to inhibit sterol biosynthesis. Inhibitors of mevalonate pathway in fungous and mammalian cells, exhibiting hypolipidemic or antifungal activity, as well as inhibitors of alternative non-mevalonate (pyruvate gliceraldehyde phosphate) isoprenoid pathway, which are promising in the development of affective antimicrobial or antiparasitic drugs, are under consideration in this review. Chemical formulas of the main natural inhibitors and their semi-synthetic derivatives are represented. Mechanism of their action at cellular and biochemical level is discussed. Special attention is given to inhibitors of 3-hydroxy-3-methylglutaryl Coenzyme A (HMG-CoA) reductase (group of lovastatin) and inhibitors of acyl-CoA-cholesterol-acyl transferase (ACAT) that possess hypolipidemic activity and could be affective in the treatment of atherosclerosis. In case of inhibitors of late stages of sterol biosynthesis (after squalene formation) special attention is paid to compounds possessing evident antifungal and antitumoral activity. Explanation of mechanism of anticancer and antiviral action of microbial ISB, as well as the description of their ability to induce apoptosis is given.