Determination of octanol-water partition coefficient for terpenoids using reversed-phase high-performance liquid chromatography

Menthol-Based (Deep) Eutectic Solvents: A Review on Properties and Application in Extraction

In the last 10 years the interest in deep eutectic solvents (DESs) as a new class of green solvents has considerably increased. The emergence of numerous of hydrophobic DESs has stimulated intensive research into their application in extraction technologies, including sample preparation. As the properties of such systems are highly dependent on the properties of their components (hydrogen bond donors and acceptors) and can be finely tuned, DESs can be successfully used for the extraction of both metal ions and organic substances, including biomolecules. Despite the rapidly increasing number of publications on the use of DESs as an extraction medium, including review articles, information on the extraction properties of DESs in terms of their chemical composition has not yet been summarized. This review covers available literature data on the physicochemical properties of menthol-based eutectic solvents and the results of their practical application as an extraction medium. Also, the appropriateness of using the term "DES" for all mixtures with melting points lower than the melting points of their components is discussed.

A Quantitative Re-Assessment of Microencapsulation in (Pre-Treated) Yeast

Most hydrophobes easily diffuse into yeast cells, where they experience reduced evaporation and protection from oxidation, thus allowing inherently biocompatible encapsulation processes. Despite a long-standing industrial interest, the effect of parameters such as how is yeast pre-treated (extraction with ethanol, plasmolysis with hypertonic NaCl, depletion to cell walls), the polarity of the hydrophobes and the process conditions are still not fully understood. Here, we have developed thorough analytical protocols to assess how the effects of the above on S. cerevisiae's morphology, permeability, and encapsulation efficiency, using three differently polar hydrophobes (linalool, 1,6-dihydrocarvone, limonene) and three separate processes (hydrophobes as pure 'oils', water dispersions, or acetone solutions). The harsher the pre-treatment (depleted > plasmolyzed/extracted > untreated cells), the easier the diffusion into yeast became, and the lower both encapsulation efficiency and protection from evaporation, possibly due to denaturation/removal of lipid-associated (membrane) proteins. More hydrophobic terpenes performed worst in encapsulation as pure 'oils' or in water dispersion, but much less of a difference existed in acetone. This indicates the specific advantage of solvents/dispersants for 'difficult' compounds, which was confirmed by principal component analysis; furthering this concept, we have used combinations of hydrophobes (e.g., linalool and α-tocopherol), with one acting as solvent/enhancer for the other. Our results thus indicate advantages in using untreated yeast and-if necessary-processes based on solvents/secondary hydrophobes.

1,8-cineole (eucalyptol): A versatile phytochemical with therapeutic applications across multiple diseases

1,8-cineole (Eucalyptol), a naturally occurring compound derived from botanical sources such as eucalyptus, rosemary, and camphor laurel, has a long history of use in traditional medicine and exhibits an array of biological properties, including anti-inflammatory, antioxidant, antimicrobial, bronchodilatory, analgesic, and pro-apoptotic effects. Recent evidence has also indicated its potential role in managing conditions such as Alzheimer's disease, neuropathic pain, and cancer. This review spotlights the health advantages of 1,8-cineole, as demonstrated in clinical trials involving patients with respiratory disorders, including chronic obstructive pulmonary disease, asthma, bronchitis, and rhinosinusitis. In addition, we shed light on potential therapeutic applications of 1,8-cineole in various conditions, such as depression, epilepsy, peptic ulcer disease, diarrhea, cardiac-related heart diseases, and diabetes mellitus. A comprehensive understanding of 1,8-cineole's pharmacodynamics and safety aspects as well as developing effective formulations, might help to leverage its therapeutic value. This thorough review sets the stage for future research on diverse health benefits and potential uses of 1,8-cineole in tackling complex medical conditions.

Synergistic effects of 915 MHz microwave heating and essential oils on inactivation of foodborne pathogen in hot-chili sauce

Essential oil is a food additive with antimicrobial properties but with limitations due to strong organoleptic properties. However, thermal treatments can be applied to reduce essential oil content while ensuring antimicrobial activities in food matrices. In this study, the inactivation efficiency of essential oils on E. coli O157:H7, Salmonella Typhimurium and Listeria monocytogenes in buffered peptone water (BPW) and hot-chili sauce was evaluated when coupled with 915 MHz microwave heating. Essential oils used in this study did not affect the dielectric properties and further heating rate of BPW and hot-chili sauce. The dielectric constant of BPW was 76.3 and dielectric loss factor was 30.9. In addition, it took 85 s to reach 100 °C for all samples. Among essential oils, synergistic microbial inactivation with microwave heating was observed from carvacrol (CL) and citral (CI), but not from eugenol (EU) and Carvone (CN). Specifically, CL and microwave heating (M) for 45 s showed the most effective inactivation (ca. 6 log reduction) for the pathogens in BPW. Similar trends were shown in hot-chili sauce. However, M + CI inactivation did not show synergistic effects in hot-chili sauce. Microwave heating time for hot-chilis sauce was 40 s. In propidium iodide uptake study, M + CL was found to cause most severe damage to cell membrane (758.5 of PI value for E. coli O157:H7) while M + CU and M + CN had little impact. In DiBAC₄(3) test, CL resulted in the largest value (2.09 for E. coli O157:H7). These observations highlight that CL induces synergistic effects as it caused severe membrane damage along with destruction of membrane potential. The combined treatment did not show any significant difference in quality change compared to untreated hot-chili sauce (p > 0.05). The result indicates the potential application of CL and M combination for hot-chili sauce processes to ensure microbiological safety with acceptable quality.

Do Large Language Models Understand Chemistry? A Conversation with ChatGPT

Large language models (LLMs) have promised a revolution in answering complex questions using the ChatGPT model. Its application in chemistry is still in its infancy. This viewpoint addresses the question of how well ChatGPT understands chemistry by posing five simple tasks in different subareas of chemistry.

Separation of natural compounds using eutectic solvent-based biphasic systems and centrifugal partition chromatography

A study on the formation of ternary biphasic systems composed of heptane, 1-butanol or ethyl acetate and type III or type V deep eutectic solvents based on levulinic acid and choline chloride or thymol was carried. Binodal curves and densities and phase compositions of phases in equilibrium for seven systems are reported. The partition coefficients of six natural compounds, namely quercetin, apigenin, coumarin, β-ionone, retinol, and α-tocopherol, in these systems were measured. Results show that the influence of choline chloride on the partition coefficients is more significant in systems with 1-butanol or ethyl acetate than previously reported for ethanol, and that the separation of natural compounds is worst when using DES containing thymol instead of choline chloride. Based on these partition coefficients, one system composed of heptane, 1-butanol and the DES choline chloride:levulinic acid at molar ratio 1:3 was selected to be applied in centrifugal partition chromatography, and the results obtained confirmed that it allows a good separation of apigenin, coumarin, β-ionone and α-tocopherol.

Biosynthesis of geranate via isopentenol utilization pathway in Escherichia coli

Isoprenoids are a large family of natural products with diverse structures, which allow them to play diverse and important roles in the physiology of plants and animals. They also have important commercial uses as pharmaceuticals, flavoring agents, fragrances, and nutritional supplements. Recently, metabolic engineering has been intensively investigated and emerged as the technology of choice for the production of isoprenoids through microbial fermentation. Isoprenoid biosynthesis typically originates in plants from acetyl-coA in central carbon metabolism, however, a recent study reported an alternative pathway, the isopentenol utilization pathway (IUP), that can provide the building blocks of isoprenoid biosynthesis from affordable C5 substrates. In this study, we expressed the IUP in Escherichia coli to efficiently convert isopentenols into geranate, a valuable isoprenoid compound. We first established a geraniol-producing strain in E. coli that uses the IUP. Then, we extended the geraniol synthesis pathway to produce geranate through two oxidation reactions catalyzed by two alcohol/aldehyde dehydrogenases from Castellaniella defragrans. The geranate titer was further increased by optimizing the expression of the two dehydrogenases and also parameters of the fermentation process. The best strain produced 764 mg/L geranate in 24 h from 2 g/L isopentenols (a mixture of isoprenol and prenol). We also investigated if the dehydrogenases could accept other isoprenoid alcohols as substrates.

The effect of oregano essential oil on the prevention and treatment of Salmonella pullorum and Salmonella gallinarum infections in commercial Yellow-chicken breeders

In order to prevent pullorum disease and fowl typhoid in breeders, the use of oregano essential oil (OEO) was tested for the prevention and treatment of infections of multidrug-resistant Salmonella pullorum (SP) and Salmonella gallinarum (SG) in commercial Yellow-chicken breeders. In the challenge-protection experiment, commercial Hongguang-Black 1-day-old breeder chicks were randomly divided into four groups, including A (challenged, preventive dose), B (challenged, treatment dose), C (challenged, untreated), and D (unchallenged, untreated). Group A was supplemented with 200 μL/L OEO in the drinking water during the whole trial (1-35 days of age) and group B was supplemented with 400 μL/L OEO during 8-12 days of age, while groups C and D were kept as untreated controls. At 7 days of age, birds of groups A, B, and C were divided into two subgroups with equal number of birds (A₁-A₂, B₁-B₂, and C₁-C₂), and then subgroups A₁, B₁, and C₁ were challenged with SP, while subgroups A₂, B₂, and C₂ were challenged with SG. Clinical symptoms and death were observed and recorded daily. Every week during the experiment, serum antibodies against SP and SG of all the groups were detected by the plate agglutinate test (PAT). At the age of 35 days, all birds were weighed and necropsied, lesions were recorded and the challenging pathogens were isolated. The results showed that the positive rates of SP and SG isolation in groups A₁, A₂ and B₁, B₂ were significantly lower (P < 0.05) than those of groups C₁ and C₂, respectively, while groups A₁ and A₂ were slightly lower (P > 0.05) than those of groups B₁ and B₂. The average body weight (BW) of groups A₁ and A₂ were significantly higher (P < 0.05) than those of groups B₁, B₂ and C₁, C₂, respectively, but there was no significant difference (P > 0.05) with that of group D. The r-value between PAT positive and the recovery rates of Salmonella was 0.99, which means they are highly positively correlated. The results of this study demonstrated that the prevention dose (200μL/L) and the treatment dose (400 μL/L) of OEO supplemented in the drinking water could all effectively decrease infections of SP and SG and that the effect of the prevention was greater than that of the treatment and finally that the prevention could also significantly reduce the BW decline of birds challenged with SP and SG.

Medicated Lacquer For Application On Adornments To Treat Affections In Aesthetic Perforations

Aesthetic perforations are often associated with health issues, such as itching, inflammation, or microbial infection. Accordingly, this work proposed a lacquer to be applied on the adornment accessory forming a film from which a proper drug is released. For this, lacquers were formulated containing three different permeation enhancers (limonene - LIM, propylene glycol - PG, and oleic acid - AO) combined according to a mixture design with a model anti-inflammatory natural drug (naringenin) and a soluble film-former polymer (polyvinyl alcohol). Formulations were characterized by physicochemical tests and in vitro and in vivo skin permeation studies. The lacquers were stable and provided a vectorized drug release. LIM, combined with one of the other permeation enhancers, showed a synergic effect, enhancing topical skin penetration in vitro by 53% while preventing permeation to the receptor medium. The in vivo evaluation of lacquers in rodent models showed these systems could provide higher levels of drug retention in the ear (166.4 ± 14.9 µg per ear for F4 and 174.9 ± 29.3 µg per ear for F5) compared to the control (109.2 ± 16.3 µg) without allowing its permeation into the bloodstream, confirming the local drug delivery. Moreover, the anti-inflammatory activity was achieved in the animal model developed for lacquer application on the earring, obtaining inhibition of ear swelling up to 40.8% ± 2.3 compared to the untreated ear. Thus, such an innovative lacquer proved a promising vehicle for treating affections caused by adornments, enhancing skin permeation while avoiding a systemic effect.

Food Ingredients Derived from Lemongrass Byproduct Hydrodistillation: Essential Oil, Hydrolate, and Decoction

Essential oil (EO), hydrolate, and nondistilled aqueous phase (decoction) obtained from the hydrodistillation of lemongrass byproducts were studied in terms of their potential as food ingredients under a circular economy. The EO (0.21%, dry weight basis) was composed mainly of monoterpenoids (61%), the majority being citral (1.09 g/kg). The minimal inhibitory concentrations (MIC) of lemongrass EO against Escherichia coli, Salmonella enterica, and Staphylococcus aureus, were 617, 1550, and 250 μg/mL, respectively. This effect was dependent on the citral content. Particularly for Gram-negative bacteria, a synergism between citral and the remaining EO compounds enhanced the antimicrobial activity. The polymeric material obtained from the nondistilled aqueous phase was composed of phenolic compounds (25% gallic acid equivalents) and carbohydrates (22%), mainly glucose (66 mol%). This polymeric material showed high antioxidant activity due to bound phenolic compounds, allowing its application as a functional dietary fiber ingredient. Matcha green tea formulations were successfully mixed with lemongrass hydrolate containing 0.21% EO (dry weight basis) with 58% of monoterpenoids, being citral at 0.73 g/kg, minimizing matcha astringency with a citrus flavor and extending the product shelf life. This holistic approach to essential oils’ hydrodistillation of Cymbopogon citratus byproducts allows for valorizing of the essential oil, hydrolate, and decoction for use as food ingredients.

Volatile organic compound and particulate matter emissions from an ultrasonic essential oil diffuser

Ultrasonic essential oil diffusers (EODs) are a popular type of indoor scenting source. We performed a chamber study in which we measured the emissions from EODs used with lemon, lavender, eucalyptus, and grapeseed oils. Over the course of 15 min, the most abundant VOCs released from lemon, lavender, eucalyptus, and grapeseed oils were 2.6 ± 0.7 mg of d-limonene, 3.5 ± 0.4 mg of eucalyptol, 1.0 ± 0.1 mg of linalyl acetate, and 0.2 ± 0.02 mg of linalyl acetate, respectively. Each oil had a unique particulate matter (PM) emission profile in terms of size, number density, and rate. The dominant size ranges of the PM were 10-100 nm for lemon oil, 50-100 nm for lavender oil, 10-50 nm for lemon oil, and above 200 nm for grapeseed oil. PM₁ emission rates of approximately 2 mg/h, 0.1 mg/h, and 3 mg/h, were observed for lemon, lavender/eucalyptus, and grapeseed oils, respectively. A fivefold increase in PM₁ emission was measured when the EOD with eucalyptus oil was filled with tap water as opposed to deionized water. Modeling suggests that reasonable use cases of EODs can contribute substantially to primary and secondary PM in indoor environments, but this potential varies depending on the oil and water types used.

Long-term monitoring of lipophilic acaricide residues in commercial Swiss beeswax

BACKGROUND

A national survey on pesticides in recycled beeswax originating from beekeeping has been conducted in Switzerland for almost three decades. It allowed obtaining a good overview of the lipophilic products used for beekeeping within the last 30 years.

RESULTS

The use of the veterinary drugs containing bromopropylate or tau-fluvalinate two decades ago led to substantial residues in commercial beeswax. These contaminants are still detectable although in Switzerland the corresponding products have been out of use for many years. The level of coumaphos substantially increased in 2015 up to an annual value of 3.25 mg·kg-1 , suggesting that at least a few beekeepers used coumaphos-containing products. Consequently, an information campaign was launched, and the annual value decreased again. Maximal levels of thymol up to an annual value of 87.5 mg·kg-1 were measured in 2009. Since that time, a steady decrease of thymol residues suggests that beekeepers less frequently use thymol-containing products. Twenty-five years ago, 1,4-dichlorobenzene (PDCB) was widely used for the control of the wax moth, resulting in residues in beeswax up to an annual value of 10.9 mg·kg-1 whereas nowadays, PDCB residues are rarely detected in Swiss beeswax.

CONCLUSIONS

Our survey illustrates that several beekeeping-associated pesticides persist in recycled beeswax for many years. Most recent analyses show lower residue levels in Swiss beeswax as compared to previous years. Nowadays Swiss beekeepers mostly use hydrophilic substances for treatment against the Varroa destructor that do not accumulate in beeswax, thus reducing exposure of the honey bees to lipophilic contaminants.

Potential of Carvacrol and Thymol in Reducing Biofilm Formation on Technical Surfaces

Polyvinyl chloride (PVC), polypropylene (PP), polyethylene (PE), and stainless steel (SS) are commonly used in medicine and food production technologies. During contact with microorganisms on the surface of these materials, a microbial biofilm is formed. The biofilm structure is difficult to remove and promotes the development of pathogenic bacteria. For this reason, the inhibition of biofilm formation in medical and food production environments is very important. For this purpose, five naturally occurring compounds were used for antimicrobial screening tests. The two with the best antimicrobial properties were chosen to inhibit the biofilm formation of Staphylococcus aureus and Pseudomonas aeruginosa. After 3 days of exposure, thymol reduced the amount of biofilm of Pseudomonas aeruginosa within the range of 70–77% and 52–75% for Staphylococcus aureus. Carvacrol inhibited the formation of biofilms by up to 74–88% for Pseudomonas aeruginosa and up to 86–100% for Staphylococcus aureus. Those phenols decreased the enzyme activity of the biofilm by up to 40–100%. After 10 days of exposure to thymol, biofilm formation was reduced by 80–100% for Pseudomonas aeruginosa and by about 79–100% for Staphylococcus aureus. Carvacrol reduced the amount of biofilm by up to 91–100% for Pseudomonas aeruginosa and up to 95–100% for Staphylococcus aureus.

The study of the chromatographic behavior and a mass spectrometric approach to differentiating the diastereomer pair of the β-O-4 lignin dimer series

Lignin and lignans are natural products found in plant cell walls. Lignin research has historically focused on lignin degradation techniques in the hope of converting lignin into useful aromatic carbon feedstocks. In contrast, investigations of lignans existing as natural product dimers, have been focused on thier interesting biological activities. Many lignan compounds are chemically identical to dimers derived from lignin, and both lignin and lignan dimers can possess multiple chiral centers leading to observations of diastereomer pairs where one diastereomer exhibits the bulk of the activity. For example, the G-(β-O-4')-G dimer was reported to have a pro-angiogenic activity with one diastereomer of the pair showing enhanced pro-angiogenic activity. Traditional analytical techniques such as nuclear magnetic resonance (NMR) can differentiate the diastereomer pairs of β-O-4 compounds; however, isolation of a pure sample is often required for analysis. This work was aimed at exploring the potential use of tandem mass spectrometry to differentiate diastereomer pairs in the β-O-4 dimer series. Each diastereomer pair in the nine-dimer series was separated by HPLC and interrogated by tandem mass spectrometry. To understand the chromatographic behavior of the diastereomer pair in the β-O-4 dimer series, three commercially available reverse phase HPLC columns were evaluated. A temperature programming experiment using water/acetonitrile isocratic elution showed that the chromatographic retention mechanism of these diastereomers was hydrophobically driven with analytes having more methoxy groups exhibiting larger ΔH⁰ and higher octanol-water partition coefficient values. Tandem mass spectrometry performed on each of the diastereomers produced fragment ions having different ion abundances. A mechanistic study based on the ion abundance of "sequence-specific ions" and "-48 ions" was used to assign a configuration to each of the pairs of diastereomers in the nine-dimer series.

Effectiveness of recombinant Escherichia coli on the production of (R)-(+)-perillyl alcohol

Background

(R)-(+)-perillyl alcohol is a naturally oxygenated monoterpene widely used as the natural flavor additives, insecticides, jet fuels and anti-cancer therapies. It was also readily available monoterpene precursors. However, this natural product is present at low concentrations from plant sources which are not economically viable. Therefore, alternative microbial production methods are rapidly emerging as an attractive alternative to make (R)-(+)-perillyl alcohol production more sustainable and environmentally friendly.

Results

We engineered Escherichia coli to possess a heterologous mevalonate (MVA) pathway, including limonene synthase, P-cymene monoxygenase hydroxylase and P-cymene monoxygenase reductase for the production of (R)-(+)-perillyl alcohol. The concentration of (R)-(+)-limonene (the monoterpene precursor to (R)-(+)-perillyl alcohol) reached 45 mg/L from glucose. Enhanced (R)-(+)-perillyl alcohol production was therefore achieved. The strain produced (R)-(+)-perillyl alcohol at a titer of 87 mg/L and a yield of 1.5 mg/g glucose in a 5 L bioreactor fed batch system.

Conclusions

These datas highlight the efficient production of (R)-(+)-perillyl alcohol through the mevalonate pathway from glucose. This method serves as a platform for the future production of other monoterpenes.

Optimized piperine-phospholipid complex with enhanced bioavailability and hepatoprotective activity

Piper species is one of the most widely consumed spices for culinary purposes. Piperine (PIP) present in Piper species has a wide range of therapeutic activity including hepatoprotection. However, the major biological limitation of PIP is its low bioavailability after oral administration. Purpose of the study was to prepare an optimized and adequately characterized PIP-phospholipid complex (PPC) as a delivery system to overcome these limitations and to investigate the pharmacokinetics and hepato-protectivity of the formulation in the animal model. Response surface methodology was adopted to optimize the process parameters for PPC preparation. FT-IR, DTA, PXRD, SEM, molecular docking etc. were used for characterization. Solubility, log P, dissolution efficiency and in vivo pharmacokinetics were also investigated. PPC showed enhanced hepatoprotective potential as compared to pure PIP at the same dose level (25 and 50 mg/kg). PPC restored the levels of serum marker and antioxidant enzymes. PPC also increased the bioavailability of PIP in rat serum by 10.40-fold in comparison with pure PIP at the same dose level and enhanced the elimination half-life (t_{1/2 el}) from 0.477 ± 1.76 to 9.80 ± 1.98 h. Results concluded that PPC enhanced the hepatoprotection of PIP which may be due to the improved bioavailability and pharmacokinetics of PIP in rats.

Effect of formulation on properties, stability, carvacrol release and antimicrobial activity of carvacrol emulsions

The structural design of essential oil emulsions can be exploited to modulate their antimicrobial activity, through the effect that the main formulation parameters (oil phase composition and type of emulsifier) have on the release of encapsulated antimicrobial compounds. In this work, different emulsions containing carvacrol, selected as model essential oil component, were characterized in terms of emulsions size, stability, and carvacrol release and solubilization, determined in Franz cells, and tested for minimum inhibitory and microbicidal concentration against P. fluorescens, S. epidermidis, and S. cerevisiae. The results showed that carvacrol fraction in the oil phase significantly affected oil viscosity, density, and O/W interfacial tension. Carvacrol solubilization in the aqueous phase, in equilibrium with the oil mixture, increased with the concentration of carvacrol in the oil phase and with the presence of an emulsifier/stabilizer in the aqueous phase. However, when encapsulated in emulsions carvacrol solubilization exhibited a weak dependence on carvacrol fraction in oil phase because part of the emulsifier/stabilizer was adsorbed at the O/W interface. Higher carvacrol solubilization was observed for WPM Pickering emulsions, followed by WPI and T80 emulsions. The antimicrobial activity was proportional to carvacrol solubilization, suggesting that emulsion droplets act as micrometric tanks for carvacrol, which is steadily released over time in the aqueous phase. The high carvacrol solubilization in the aqueous phase at higher carvacrol fractions in the oil phase (≥75% w/w) was also responsible for lower T80 and WPI emulsion stability because of coalescence, whereas all WPM emulsions exhibited signs of flocculation.

Screening the antifungal activities of monoterpenes and their isomers against Candida species

AIM

Increasing the occurrence of non-albicans Candida species with intrinsic or acquired resistance to antifungals as well as the emergence of multidrug Candida species coupled with the limited antifungal agents challenges the treatment of candidiasis. Consequently, a class of secondary metabolites of plants exhibiting decent antifungal activity. Therefore, this study aimed to evaluate the antifungal potential of various monoterpenes including Carvone, Limonene, Pinene, Menthone, Menthol, Camphor, Thujone, Citronellol, and Piperitone against standard and clinical isolates of Candida.

METHODS AND RESULTS

Minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) of compounds were determined, using the broth Microdilution method based on M27-A3 protocol documented by clinical laboratory standard institute (CLSI). Amongst the tested monoterpenes, oxygenated terpenoids showed strong antifungal activity. Specifically, alcoholic terpenoids such as (±)-Citronellol possess more efficacy than the corresponding ketonic ones with MICs ranging from 0·03 to 2·00 μl ml^-1 (0·16-10·80 mmol l^-1 ). Among the examined yeasts, Candida tropicalis was the most susceptible species to (±)-Citronellol. Moreover, the examined monoterpenes successfully inhibited the growth of fluconazole-resistant Candida species. Moreover, statistical analysis showed no statistically significant difference between the (+) and (-) isomers, except for (±)-α-Pienene and (±) Menthone (ρ-value < 0·05).

CONCLUSION

Among the tested monoterpenes, (±)-Citronellol was the most potent compounds followed by (+)-α-Pinene and Menthol. Considering the significant antifungal activity of the examined monoterpenes, they could be used in controlling or treating candidiasis. Those potent antifungal monoterpenes with GRAS status in addition to their pleasant taste and odour make them appropriate additive or preservative compounds in food and cosmetics products. Furthermore, these data might help researchers to predict EOs antifungal activities, after determining its constituents.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study provides new information about the antifungal activities of monoterpenes and their isomers presented widely in essential oils. Screening results against pathogenic yeasts confirm the correlation between the chemical structure of tested monoterpenes and their antifungal effects. The present findings might be helpful to anticipate the antifungal activity of essential oils.

Correction: Chantasart et al. "Structure Enhancement Relationship of Chemical Penetration Enhancers in Drug Transport across the Stratum Corneum" Pharmaceutics 2012, 4, 71-92

The authors wish to make the following corrections to their paper [...].

Recovery of Natural α-Ionone from Fermentation Broth

Recently, the market value of aromas has constantly been rising. Because the supply from natural feedstock is limited, the biotechnological production has received more interest. Thus far, only a few attempts have been made to produce α-ionone, a valued essential aroma of raspberry, biotechnologically. This study reports a production process for enantiopure (R)-α-ionone from lab scale (2-150 L) with typical titer of 285 mg/L broth to industrial scale (up to 10 000 L) with a titer up to 400 mg/L broth, focusing on the development of a downstream process with a maximized yield at minimized effort. The developed recovery consists of solid-liquid extraction from the biomass at φ = 0.4 g of n-hexane/g of biomass for 90 min at ambient temperature and adsorption from the aqueous supernatant at Φ = 0.5 g of Diaion HP-20/mg of α-ionone, followed by desorption at Ψ = 30 g of n-hexane/g of Diaion HP-20. Altogether, natural α-ionone could be gained in substantial quantity and purity of >95%.

Enhanced bioavailability and hepatoprotectivity of optimized ursolic acid-phospholipid complex

OBJECTIVE

To prepare and characterize an optimized phospholipid complex of Ursolic acid (UA) to overcome the poor pharmacokinetic properties and to investigate the impact of the complex on hepatoprotective activity and bioavailability in animal model.

SIGNIFICANCE

UA is a potential phytoconstituent obtained from several plant sources, which has been explored for its diverse pharmacological activities including hepatoprotection. Its major limitation is poor absorption, rapid elimination, and hence low bioavailability after administration.

METHODS

Response surface methodology was adopted to formulate an optimized (UA) complex. The complex was characterized by differential thermal analysis (DTA), Fourier transform-Infrared Spectroscopy, Powder X ray Diffraction, molecular docking, etc. The physico-chemical profile (solubility, oil/water partition coefficient) and in vitro dissolution profile was estimated. The formulation was then used to study hepatoprotective activity and bioavailability in animal models.

RESULTS

Results showed that the phospholipid complex of UA has enhanced the hepatoprotective potential as compared to pure UA at the same dose level. The complex restored the levels of serum hepatic marker enzymes with respect to untreated group and increased the relative bioavailability of UA in rat plasma by 8.49-fold in comparison with pure compound at the same dose level. It enhanced the elimination half-life (t1/2 el) from 0.69 ± 1.76 to 8.28 ± 1.98 h.

CONCLUSION

Complexation of UA with phospholipid markedly enhanced the hepatoprotective potential of UA by improving its bioavailability and pharmacokinetic parameters. Novelty statement The present article deals with rational optimization of the formulation parameters for phospholipid complex of ursolic acid by Response Surface Methodology analysis, characterizing the formulation by in silico approach apart from conventional instrumental techniques, and evaluating the in vitro dissolution, pharmacokinetics, and hepatoprotective activity of the complex in animals. Novelty statement The present article deals with rational optimization of the formulation parameters for phospholipid complex of ursolic acid by Response Surface Methodology analysis, characterizing the formulation by in silico approach apart from conventional instrumental techniques, and evaluating the in vitro dissolution, pharmacokinetics, and hepatoprotective activity of the complex in animals.

Dietary Stress From Plant Secondary Metabolites Contributes to Grasshopper (Oedaleus asiaticus) Migration or Plague by Regulating Insect Insulin-Like Signaling Pathway

Diets essentially affect the ecological distribution of insects, and may contribute to or even accelerate pest plague outbreaks. The grasshopper, Oedaleus asiaticus B-Bienko (OA), is a persistent pest occurring in northern Asian grasslands. Migration and plague of this grasshopper is tightly related to two specific food plants, Stipa krylovii Roshev and Leymus chinensis (Trin.) Tzvel. However, how these diets regulate and contribute to plague is not clearly understood. Ecological studies have shown that L. chinensis is detrimental to OA growth due to the presence of high secondary metabolites, and that S. krylovii is beneficial because of the low levels of secondary metabolites. Moreover, in field habitats consisting mainly of these two grasses, OA density has negative correlation to high secondary metabolites and a positive correlation to nutrition content for high energy demand. These two grasses act as a 'push-pull,' thus enabling the grasshopper plague. Molecular analysis showed that gene expression and protein phosphorylation level of the IGF → FOXO cascade in the insulin-like signaling pathway (ILP) of OA negatively correlated to dietary secondary metabolites. High secondary metabolites in L. chinensis down-regulates the ILP pathway that generally is detrimental to insect survival and growth, and benefits insect detoxification with high energy cost. The changed ILP could explain the poor growth of grasshoppers and fewer distributions in the presence of L. chinensis. Plants can substantially affect grasshopper gene expression, protein function, growth, and ecological distribution. Down-regulation of grasshopper ILP due to diet stress caused by high secondary metabolites containing plants, such as L. chinensis, results in poor grasshopper growth and consequently drives grasshopper migration to preferable diet, such as S. krylovii, thus contributing to grasshopper plague outbreaks.

The influence of terpinen-4-ol and eucalyptol - The essential oil components - on fungi and plant sterol monolayers

Antifungal and herbicidal activity of terpenes, being the components of the essential oils, is directly related to the incorporation of these compounds into cellular membranes. Thus, the differences in the lipid composition of various pathogenic membranes may be the factor determining the activity of these molecules. One of the class of lipids, which form the membrane environment are sterols. The aim of this work was to compare the effect of two terpenes: terpinen-4-ol and eucalyptol on the monolayers formed by ergosterol and β - sitosterol, which are the components of fungi and plant membranes, respectively. The modifications in the sterol monolayer properties were investigated in the surface pressure-area measurements and penetration studies as well as in a micrometer scale (Brewster angle microscopy experiments) and in nanoscale (GIXD technique). It was evidenced that although at higher surface pressure the terpene molecules are in part removed from the interface, they are able to substantially modify the condensation, morphology and molecular organization of the sterol film. It was also found that the incorporation of terpenes into sterol films is comparable for both sterols, however, β - sitosterol monolayers properties are affected more strongly than ergosterol films. Finally, the analysis of the results of the studies performed on model membrane systems and the results of antimicrobial studies reported in literature, enabled us to suggest that the activity of terpenes depends on the membrane composition and that the sterol concentration may be important from the point of view of antifungal effect of terpinen-4-ol and eucalyptol.

The Biology of Essential Oils in the Pollination of Flowers

Pollination is an essential biological process in higher plant reproduction that involves the transfer of pollen to the female sexual organs of flowers or cones. It plays a critical role in the reproductive success and evolution of most plant species by allowing plants to share genetic material from other members of the same or closely-related species, thus increasing genetic diversity. In many cases, non-plant organisms are involved in carrying out this cross-pollination, including insects, bats, mammals, and birds. In order to attract such pollinators, plants have evolved the ability to produce a mind-boggling array of volatile compounds that have also found abundant use for humans when collected as essential oils. In this review, we focus on the role of essential oil compounds that are produced by flowers as chemical attractants used to draw in their often highly-specific pollinators. We examine in some detail various questions behind the biology of floral scent, including how these compounds are produced in flowers, how they are detected by potential pollinators, and how biotechnology can be used to alter their activity.

New findings on the incorporation of essential oil components into liposomes composed of lipoid S100 and cholesterol

The encapsulation of essential oil components into liposomes was demonstrated to improve their solubility and chemical stability. In this study, we investigated the effect of chemical structure, Henry's law constant (H_c), and aqueous solubility of essential oil components on their liposomal encapsulation. Estragole, eucalyptol, isoeugenol, pulegone, terpineol, and thymol were encapsulated in lipoid S100-liposomes using the ethanol injection method. The H_c values were determined. The incorporation in liposomes was more efficient (encapsulation efficiency > 90%) for the essential oil components exhibiting low aqueous solubility (estragole, isoeugenol, and pulegone). Moreover, efficient entrapment into vesicles (loading rate > 18%) was obtained for isoeugenol, terpineol, and thymol. This result suggests that the presence of a hydroxyl group in the structure and a low Hc value enhance the entrapment of essential oil components into liposomes. Furthermore, drug release rate from liposomes was controlled by the loading rate of essential oil components into liposomes, the size of particles, the location of essential oil components within the lipid bilayer, and the cholesterol incorporation rate of liposomes. Finally, considerable concentrations of isoeugenol, pulegone, terpineol, and thymol were retained in liposomes after 10 months with respect to the initial concentration.

A Kinetic Approach to Determining Drug Distribution in Complex Biphasic Systems

Pharmaceutical emulsions contain multiple components, such as micellar, aqueous, and oil phases, leading to complex drug transfer and equilibrium phenomena. These complex components present challenges for the bioequivalence assessment of the drug products. The objective of the study was to develop a method that can probe the underlying mechanism and process of drug distribution. The concept of drug partitioning into biphasic systems was used to simplify the complex transfer phenomenon. A kinetic method was developed taking into account the biphasic diffusion. Using this approach, both the rate (kinetics) and the extent (equilibrium) of distribution can be determined. For method development purpose, 3 model compounds (triamcinolone acetonide, difluprednate, and cyclosporine), with expected partition coefficient values ranging from 2 to 6, were tested using the kinetic method and the traditional shake-flask method. The values obtained by the 2 methods for all compounds correlated well (r² = 0.825). Various organic and aqueous solvents which are commonly encountered in formulations were also tested to determine the impact of phase composition on drug distribution. The kinetic method was found to offer more flexibility in terms of solvent composition and can lead to better understanding for drug distribution and potential drug release in complex biphasic systems.

An RND transporter in the monoterpene metabolism of Castellaniella defragrans

The betaproteobacterium Castellaniella defragrans 65Phen grows on monoterpenes at concentrations toxic to many bacteria. Tolerance mechanisms include modifications of the membrane fatty acid composition and the mineralization of monoterpenes. In this study, we characterized an efflux transporter associated to the monoterpene metabolism. The inner-membrane transporter AmeD (apolar monoterpene efflux) affiliated to the HAE3 (hydrophobe/amphiphile efflux) family within the Resistance-Nodulation-Division (RND) superfamily. RND pumps of the HAE3 family are known for transporting substrates into the periplasm. AmeD is co-expressed with the outer membrane protein AmeA and the periplasmic proteins AmeB and AmeC, suggesting an export channel into the environment similar to HAE1-type RND exporters. Proteins AmeABCD are encoded within a genetic island involved in the metabolism of acyclic and cyclic monoterpenes. The deletion of ameABCD translated into a decrease in tolerance to monoterpenes in liquid cultures. The addition of acetate as cosubstrate in limonene-containing cultures partially alleviated monoterpene toxicity in the deletion mutant. Accumulation of Nile Red in cells of C. defragrans required dissipation of the proton motive force with carbonyl cyanide m-chlorophenylhydrazone (CCCP). Cells lacking AmeABCD accumulated more Nile Red, suggesting an export function of the proteins. Our observations suggest that the tetrapartite RND transporter AmeABCD acts as an exporter during monoterpene detoxification in C. defragrans.

Functionalization of Lipid-Based Nutrient Supplement with β-Cyclodextrin Inclusions of Oregano Essential Oil

Intestinal parasitic infection is one of the main causes of acute undernutrition in children. Oral consumption of oregano essential oil (OEO) can reduce intestinal parasitic infections, however, its addition to therapeutic and supplementary foods is hampered by its undesirable flavor. The objective of this study was to develop a functional lipid-based nutrient supplement (LNS) containing OEO, which is stable, acceptable and provides targeted intestinal delivery of bioactive. β-cyclodextrin (β-CyD) inclusion complexes of OEO (β-CyD-OEO), and carvacrol (β-CyD-CV) (1:1 molar) were prepared using slurry complexation (-20 °C) method and characterized based on encapsulation efficiency, moisture content, morphology, and 2-phase in vitro digestion stability. Carvacrol (CV) content was measured using reverse phase HPLC-UV. LNS containing β-CyD-OEO (27.2 mg encapsulate/20 g LNS) was formulated using Indian staples and ingredients. Discriminatory sensory tests (triangle) were performed with college students (n = 58) and low-income women (n = 25), with young children at home (1 to 6 years), living in Mehsana, India to evaluate differences between LNS with and without bioactive ingredient (β-CyD-OEO only). Moisture of dried complexes ranged 9.1% to 9.7% d.b., whereas water activity 0.35 to 0.412. The complex size and encapsulation efficiency of β-CyD-OEO and β-CyD-CV were 1.5 to 7 μm and 4 to 20 μm, and 86.04 ± 4.48% and 81.39 ± 3.34%, respectively. The bioactive complexes were stable through the gastric and intestinal phases. Bioaccessibility of encapsulated CV ranged 6.0% to 7.7%. Sensory tests revealed no differences (P > 0.05) in color, aroma, and taste between LNS with and without β-CyD-OEO complexes. Functionalization of LNS with β-CyD-OEO is feasible based on in vitro stability and sensory studies.

PRACTICAL APPLICATION

Despite its antiparasitic activities, the addition of oregano essential oil into foods is limited due to its strong flavor and volatility. In this study, we evaluated the encapsulation of oregano essential oil with β-cyclodextrin and its addition into lipid-based nutrition supplements. The results revealed that complex encapsulation efficiency was above 80%. Also, the bioactive complexes were stable under in vitro gastrointestinal conditions. Sensory evaluation of LNS with and without encapsulated essential oil showed no difference in terms of color, aroma, and taste. The functional LNS can both address nutrient insufficiency as well as parasitic infection among malnourished populations in low-resource settings.

Synthesis and antioxidant evaluation of lipophilic oleuropein aglycone derivatives

Oleuropein is the most important phenolic compound present in olive cultivars, but it is scarcely present in extra virgin olive oil (EVOO) due to its high hydrophilicity and degradability. Thus, a set of oleuropein aglycone derivatives were synthesized by transacetylation under mild conditions with the aim of circumventing these drawbacks and making the active moiety in oleuropein suitable to be added to food fats. The oleuropein aglycone (closed ring form) is obtained by hydrolyzing oleuropein using Lewis acid catalysis. Then, the permeation profiles as well as the antioxidant capacity of the oleuropein aglycone derivatives were evaluated by ORAC, DPPH assays and by ROS formation using the SH-SY5Y cell line. The biological activities of the obtained compounds exhibited a dependence on their level of lipophilicity.

Parameterization of Palmitoylated Cysteine, Farnesylated Cysteine, Geranylgeranylated Cysteine, and Myristoylated Glycine for the Martini Force Field

Peripheral membrane proteins go through various post-translational modifications that covalently bind fatty acid tails to specific amino acids. These post-translational modifications significantly alter the lipophilicity of the modified proteins and allow them to anchor to biological membranes. Over 1000 different proteins have been identified to date that require such membrane-protein interactions to carry out their biological functions, including members of the Src and Ras superfamilies that play key roles in cell signaling and carcinogenesis. We have used all-atom simulations with the CHARMM36 force field to parameterize four of the most common post-translational modifications for the Martini 2.2 force field: palmitoylated cysteine, farnesylated cysteine, geranylgeranylated cysteine, and myristoylated glycine. The parameters reproduce the key features of clusters of configurations of the different anchors in lipid membranes as well as the water-octanol partitioning free energies of the anchors, which are crucial for the correct reproduction of the expected biophysical behavior of peripheral membrane proteins at the membrane-water interface. Implementation in existing Martini setup tools facilitates the use of the new parameters.

Lipophilicity assessement in drug discovery: Experimental and theoretical methods applied to xanthone derivatives

For the last several years, searching of new xanthone derivatives (XDs) with potential pharmacological activities has remained one of the main areas of interest of our group. The optimization of biological activity and drug-like properties of hits and leads is crucial at early stage of the drug discovery pipeline. Lipophilicity is one of the most important drug-like properties having a great impact in both pharmacokinetics and pharmacodynamics processes. In this work, we describe the lipophilicity of a small library of bioactive XDs, previously synthesized by our group, using different methods: computational, vortex-assisted liquid-liquid microextraction coupled with high-performance liquid chromatography (VALLME-HPLC), reversed-phase high-performance thin layer chromatography (RP-HPTLC), reversed-phase high-performance liquid chromatography (RP-HPLC), and biomembrane model by the partition between micelles and aqueous phase. The different results obtained by the used methods were compared and discussed. The methodologies and data gathered in this study will expand the investigation of lipophilicity of XDs, an important class of compounds in medicinal chemistry.

Biology, physiology and gene expression of grasshopper Oedaleus asiaticus exposed to diet stress from plant secondary compounds

We studied the role of plant primary and secondary metabolites in mediating plant-insect interactions by conducting a no-choice single-plant species field experiment to compare the suitability, enzyme activities, and gene expression of Oedaleus asiaticus grasshoppers feeding on four host and non-host plants with different chemical traits. O. asiaticus growth showed a positive relationship to food nutrition content and a negative relationship to secondary compounds content. Grasshopper amylase, chymotrypsin, and lipase activities were positively related to food starch, crude protein, and lipid content, respectively. Activity of cytochrome P450s, glutathione-S-transferase, and carboxylesterase were positively related to levels of secondary plant compounds. Gene expression of UDP-glucuronosyltransferase 2C1, cytochrome P450 6K1 were also positively related to secondary compounds content in the diet. Grasshoppers feeding on Artemisia frigida, a species with low nutrient content and a high level of secondary compounds, had reduced growth and digestive enzyme activity. They also had higher detoxification enzyme activity and gene expression compared to grasshoppers feeding on the grasses Cleistogenes squarrosa, Leymus chinensis, or Stipa krylovii. These results illustrated Oedaleus asiaticus adaptive responses to diet stress resulting from toxic chemicals, and support the hypothesis that nutritious food benefits insect growth, but plant secondary compounds are detrimental for insect growth.

Transdermal delivery of dimethyl fumarate for Alzheimer's disease: Effect of penetration enhancers

Dimethyl fumarate (DMF) is an orally administered drug with neuroprotective and immunomodulatory activities. It has potential uses in the treatment of neurodegenerative diseases such as Alzheimer's disease (AD). The objective of this study was to investigate the feasibility of transdermal delivery of DMF by studying the effect of different penetration enhancers on the skin permeation of DMF. The permeation of saturated DMF solutions was investigated in propylene glycol (PG) with varying concentrations of each of the following enhancers: Polysorbate 80 (T80), N-methyl pyrrolidone (NMP), laurocapram (Azone^®) (Az), Transcutol P (Tc), Terpineol (Terp), and cineole (Cin) using vertical Franz diffusion cells and human cadaver skin. The results showed that all penetration enhancers improved the rate of permeation of DMF. The rank order for the highest concentration of each enhancer was as follows: Cin > Az>TC > Terp>T80≥NMP. The most effective penetration enhancer was shown to be 5% cineole with a 5.3-fold increase in the enhancement ratio (ER). The amounts of drug delivered suggest that DMF is a potential candidate for transdermal drug delivery.

Studies on the Behavior of Eucalyptol and Terpinen-4-ol-Natural Food Additives and Ecological Pesticides-in Model Lipid Membranes

Effective application of the essential oils requires detailed exploration of their mechanism of action and the origin of diverse activity of their components. In this work, the influence of eucalyptol and terpinen-4-ol on artificial membranes was studied to verify whether the differences in the activity of these compounds are related to their effect on membranes. The properties of monolayers formed from structurally different lipids in the presence of terpenes were examined based on the results of the surface pressure-area measurements, penetration studies, and Brewster angle microscopy experiments. Both compounds were able to incorporate into the membrane and alter lipid/lipid interactions, making the monolayer less stable and more fluid. These effects were determined by monolayer composition (but not by its condensation per se) and the resulting rheological properties and were stronger in the presence of terpinen-4-ol. These findings confirm the hypothesis that differences in the antimicrobial potency of these terpenes are membrane-related, and membrane composition may determine their selectivity.