Monoterpene Alcohols Research Articles

Cytosolic geraniol and citronellol biosynthesis require a Nudix hydrolase in rose-scented geranium (Pelargonium graveolens).

Geraniol, citronellol and their esters are high-value acyclic monoterpenes used in food technology, perfumery and cosmetics. A major source of these compounds is the essential oil of rose-scented geraniums of the genus Pelargonium. We provide evidence that their biosynthesis mainly takes place in the cytosol of glandular trichomes via geranyl monophosphate (GP) through the action of a Nudix hydrolase. Protein preparations could convert geranyl diphosphate (GDP) to geraniol in invitro assays, a process which could be blocked by inorganic phosphatase inhibitors, suggesting a two-step conversion of GDP to geraniol. Pelargonium graveolens chemotypes enriched in either geraniol or (-)-citronellol accumulate GP or citronellyl monophosphate (CP), respectively, the presumed precursors to their monoterpenoid end products. Geranyl monophosphate was highly enriched in isolated glandular trichomes of lines producing high amounts of geraniol. In contrast, (-)-isomenthone-rich lines are depleted in these prenyl monophosphates and monoterpene alcohols and instead feature high levels of GDP, the precursor to plastidic p-menthane biosynthesis. A Nudix hydrolase cDNA from Pelargonium glandular trichomes, dubbed PgNdx1, encoded a cytosolic protein capable of hydrolyzing GDP to GP with a KM of about 750nm but is only weakly active towards farnesyl diphosphate. In citronellol-rich lines, GDP, GP and CP were detected in nearly equimolar amounts, while citronellyl diphosphate was absent, suggesting that citronellol biosynthesis may proceed by reduction of GP to CP in this species. These findings highlight the cytosol as a compartment that supports monoterpene biosynthesis and expands the roles of Nudix hydrolases in the biosynthesis of plant volatiles.

Rational Design Method Based on Techno-Economic Principles for Integration of Organic/Organic Pervaporation with Lipase Catalyzed Transesterification.

An engineering foundation is developed in this manuscript to allow the rational design of enzymatic transesterifications integrated with organic–organic pervaporation for the removal of methanol. In the first part, enzyme kinetics are elucidated for the solventless transesterification of two monoterpene alcohols with methyl acetate catalyzed by Novozym 435. Nonlinear regression revealed that three parameters (enzyme loading, forward and backward second-order reaction rate) sufficed to describe the entire conversion as a function of time. In the second part, a mathematical model for acetate ester production, integrated with organic–organic pervaporation, was developed based on a set of ordinary differential equations. To this end, empirical formulae for the pervaporation performance (of a PERVAP 2255-30 membrane and a standard HybSi® membrane) were established, relating methyl acetate and methanol flux to the methanol concentration in the reactor. The resulting digital twin, “PervApp”, allows us to study the influence of the key design parameters “enzyme loading” and “membrane surface” on, e.g., catalyst productivity. Finally, a techno-economic assessment is made for an annual production of 100 tons of geranyl acetate. The described methodology allows producers to shift from laborious, expensive and often disappointing trial-and-error approaches to the rational design of such integrated units.

Antimicrobial Activity and Chemical Composition of Essential Oil from Thymus daenensis and Thymus fedtschenkoi During Phenological Stages

Variation in chemical composition and biological activity of essential oils of medicinal plants may be observed due to the developmental stage of collected plant materials. In the present study, we compared the chemical compositions and antimicrobial activity of the essential oils from the aerial part of Thymus daenensis Celak. and Thymus fedtschenkoi Ronniger at different developmental stages. The highest essential oil content in both species was observed at the full flowering stage. The phenolic monoterpene thymol (71.9-73.9 %) and the monoterpene alcohol linalool (45.5-83.1 %) were the most abundant constituents at all phenological stages of T. daenensis and T. fedtschenkoi, respectively. All the essential oils possessed high antibacterial and antifungal activities against the microorganisms tested (Staphylococcus aureus, Bacillus cereus, Enterococcus faecium, Escherichia coli, Salmonella enteritidis, and Candida albicans), although of different degrees. The essential oils from T. fedtschenkoi appeared to be more active on almost all bacterial and fungal strains than that of T. daenensis (with MIC values of 1-16 mg/ml and 2-32 mg/ml, respectively). The effect of the plant phenological stage on the antimicrobial activity and constituents of T. fedtschenkoi essential oil was more pronounced than for T. daenensis. Interestingly, the antimicrobial effects of T. fedtschenkoi essential oil obtained at the seed set stage was noteworthy against all tested microorganisms, apart from the resistant E. faecium. Overall, this study highlighted the importance of the choice of the harvesting time to achieve the optimum of essential oil quality and quantity together with the antimicrobial activities, which are exploited in the pharmaceutical and food industries.

A “push-pull-restrain” strategy to improve citronellol production in Saccharomyces cerevisiae

Microbial production of monoterpenes has attracted increasing attention in recent years. Up to date, there are only few reports on the biosynthesis of the monoterpene alcohol citronellol that is widely used as fragrant and pharmaceutical intermediates. Here, we engineered Saccharomyces cerevisiae by employing a “push-pull-restrain” strategy to improve citronellol production based on the reduction of geraniol. Starting from a engineered geraniol-producing strain, different reductases were investigated and the best performing iridoid synthase from Catharanthus roseus (CrIS) resulted in 285.89 mg/L enantiomerically pure S-citronellol in shake flasks. Geranyl diphosphate (GPP), the most important precursor for monoterpenes, was enhanced by replacing the wild farnesyl diphosphate synthase (Erg20) with the mutant Erg20F96W, increasing the citronellol titer to 406.01 mg/L without negative influence on cell growth. Moreover, we employed synthetic protein scaffolds and protein fusion to colocalize four sequential enzymes to achieve better substrate channeling along with the deletion of an intermediate degradation pathway gene ATF1, which elevated the citronellol titer to 972.02 mg/L with the proportion of 97.8% of total monoterpenes in YPD medium. Finally, the engineered strain with complemented auxotrophic markers produced 8.30 g/L of citronellol by fed-batch fermentation, which was the highest citronellol titer reported to date. The multi-level engineering strategies developed here demonstrate the potential of monoterpenes overproduction in yeast, which can serve as a generally applicable platform for overproduction of other monoterpenes.

Classification of Botrytized Wines Based on Producing Technology Using Flow-Modulated Comprehensive Two-Dimensional Gas Chromatography.

The enantiomeric ratio of chiral compounds is known as a useful tool to estimate wine quality as well as observe an influence of wine-producing technology. The incorporation of flow-modulated comprehensive two-dimensional gas chromatography in this type of analysis provides a possibility to improve the quality of results due to the enhancement of separation capacity and resolution. In this study, flow-modulated comprehensive two-dimensional gas chromatography was incorporated in enantioselective analysis to determine the influence of winemaking technology on specific features of botrytized wines. The samples included Tokaj essences (high-sugar wines), Tokaj botrytized wines and varietal wines (Furmint, Muscat Lunel, Lipovina) and wines maturated on grape peels. The obtained data was processed with hierarchic cluster analysis to reveal variations in composition and assess classification ability for botrytized wines. A significant difference between the samples was observed for the enantiomeric distribution of ethyl lactate and presence of monoterpene alcohols. The varietal wines were successfully separated from the other types, which showed more similar results and could be divided with additional parameters. We observed a correlation between the botrytized wines and the varietal wines fermented with grape skins. As to the essences produced from juice of botrytized grapes, the results were quite similar to those of the botrytized wines, even though monoterpenes were not detected in the extracts.

Boosting the Performance of One-Step Solution-Processed Perovskite Solar Cells Using a Natural Monoterpene Alcohol as a Green Solvent Additive

The perovskite film is the core of a perovskite solar cell (PSC), and its quality is crucial for the performance of such devices. The morphology, crystallinity, and surface coverage of the perovski...

Evaluation of Variety, Maturity, and Farm on the Concentrations of Monoterpene Diglycosides and Hop Volatile/Nonvolatile Composition in Five Humulus lupulus Cultivars.

Pentose-hexose monoterpene alcohol glycosides were isolated and semiquantitatively measured in dried Humulus lupulus cones using UHPLC-qTOF-MS/MS and HPLC fractionation followed by GC-MS. The samples evaluated included hop cones from five important dual-purpose cultivars (varieties) in the United States, from two locations (farms) per variety and from three distinct harvest time points (maturities) per location, as dictated by dry-matter (% w/w) at the time of harvest. Hop variety accounted for the biggest variation among the concentrations of pentose-hexose monoterpene alcohol glycosides as well as other volatile and nonvolatile chemical factors measured in the samples. This indicates that genetics plays a major role in hop flavor production. Interestingly, "maturity", or ripeness at the time of harvest, was the next most significant factor impacting the concentrations of pentose-hexose monoterpene alcohol glycosides along with most of the other volatile and nonvolatile factors (such as total oil concentration and composition). However, maturity notably had a bigger impact on some cultivars such as Sabro, Mosaic, Simcoe, and Citra. Surprisingly, farm (i.e., location, farming practices, etc.) accounted for the least amount of variation among the concentrations of the different analytical factors. These results highlight the importance of breeding/genetics as well as considering hop maturity/ripeness at the time of harvest on the production and subsequent development of analytical chemical factors associated with driving hoppy beer flavor. It is essential for future studies assessing the impact of different farming practices and locations (i.e., regionality, terroir, etc.) on the constituents in hops important for hoppy beer flavor to consider and account for the impact of hop maturity as well as genetics.

Volatile and phenolic composition of monovarietal red wines of Valpolicella appellations

The volatile and phenolic compositions of nine monovarietal wines from the following grape varieties allowed in the Valpolicella appellation were investigated: Corvina, Corvinone, Rondinella, Molinara, Oseleta, Raboso, Croatina, Sangiovese and Cabernet-Sauvignon. Different clones were also investigated for Corvina and Corvinone, the two main varieties of the appellation. All grapes were harvested from a single experimental block and vinified following a standard protocol. Wines from different clones of Corvina were characterised by higher monoterpenols content, including linalool, α-terpineol and geraniol, as well as by a peculiar pattern of C6-alcohols. Relatively high levels of monoterpene alcohols were also found in Corvinone wines, while Oseleta showed the highest concentration of terpinen-4-ol and cis- and trans- isomers of linalool oxide. The evaluation of the wine aroma profile by means of different aromatic series indicated higher values for the “floral”, “fruity” and “ripe fruit” series for Corvina and Corvinone wines. Major differences in phenolic composition were found between the different varieties of wine. The total phenolics and total tannins values for Corvina, Corvinone, Rondinella and Molinara wines indicated relatively low phenolic content in comparison with Croatina, Oseleta, Cabernet-Sauvignon. There were also major differences in the content of individual phenolic compounds, in particular anthocyanins, between the monovarietal wines.

Biosyntheses of geranic acid and citronellic acid from monoterpene alcohols by Saccharomyces cerevisiae.

Geraniol is one of the important aromatic ingredients in alcoholic beverages. Bioconversions of geraniol to other terpenoids and genes involved in the oxidation of geraniol were investigated. Geranic acid and citronellic acid were detected in yeast culture, where geraniol or nerol was added. Addition of citral, a mixture of geranial and neral, resulted in the production of geranic acid and citronellic acid, whereas the addition of citral or citronellal resulted in the production of citronellic acid, suggesting that citronellic acid might be produced through the conversion of citral to citronellal followed by the oxidation of citronellal. Consumption of geraniol and production of geranic acid, citronellic acid, and citronellol were affected in adh1Δ, adh3Δ, adh4Δ, and sfa1Δ yeast strains, which possess single deletion of a gene encoding alcohol dehydrogenase. This is the first report of the bioconversion of monoterpene alcohols, geraniol and nerol, to geranic acid and citronellic acid in yeast culture.

Fermentative production of enantiopure (S)-linalool using a metabolically engineered Pantoea ananatis

BackgroundLinalool, an acyclic monoterpene alcohol, is extensively used in the flavor and fragrance industries and exists as two enantiomers, (S)- and (R)-linalool, which have different odors and biological properties. Linalool extraction from natural plant tissues suffers from low product yield. Although linalool can also be chemically synthesized, its enantioselective production is difficult. Microbial production of terpenes has recently emerged as a novel, environmental-friendly alternative. Stereoselective production can also be achieved using this approach via enzymatic reactions. We previously succeeded in producing enantiopure (S)-linalool using a metabolically engineered Pantoea ananatis, a member of the Enterobacteriaceae family of bacteria, via the heterologous mevalonate pathway with the highest linalool titer ever reported from engineered microbes.ResultsHere, we genetically modified a previously developed P. ananatis strain expressing the (S)-linalool synthase (AaLINS) from Actinidia arguta to further improve (S)-linalool production. AaLINS was mostly expressed as an insoluble form in P. ananatis; its soluble expression level was increased by N-terminal fusion of a halophilic β-lactamase from Chromohalobacter sp. 560 with hexahistidine. Furthermore, in combination with elevation of the precursor supply via the mevalonate pathway, the (S)-linalool titer was increased approximately 1.4-fold (4.7 ± 0.3 g/L) in comparison with the original strain (3.4 ± 0.2 g/L) in test-tube cultivation with an aqueous-organic biphasic fermentation system using isopropyl myristate as the organic solvent for in situ extraction of cytotoxic and semi-volatile (S)-linalool. The most productive strain, IP04S/pBLAAaLINS-ispA*, produced 10.9 g/L of (S)-linalool in “dual-phase” fed-batch fermentation, which was divided into a growth-phase and a subsequent production-phase. Thus far, this is the highest reported titer in the production of not only linalool but also all monoterpenes using microbes.ConclusionsThis study demonstrates the potential of our metabolically engineered P. ananatis strain as a platform for economically feasible (S)-linalool production and provides insights into the stereoselective production of terpenes with high efficiency. This system is an environmentally friendly and economically valuable (S)-linalool production alternative. Mass production of enantiopure (S)-linalool can also lead to accurate assessment of its biological properties by providing an enantiopure substrate for study.

Determination of Volatile Terpenes in Coriander Cold Pressed Oil by Vacuum Assisted Sorbent Extraction (VASE).

Cold-pressed plant oils are of high interest to consumers due to their unique and interesting flavors. As they are usually only pressed at low temperatures and filtered, without further processing stages (as refining), they preserve their character that originates from the plant the oil was extracted from. Coriander cold pressed oil is gaining popularity as a novel product, obtained from its fruits/seeds; due to the high amount of terpenes, it has very characteristic flavor. A novel, vacuum-assisted sorbent extraction (VASE) method was used to extract terpenes from coriander cold pressed oil. Optimal parameters were determined. The profile of compounds extracted using VASE was compared with that of classic hydrodistillation method. Moreover, 17 monoterpene hydrocarbons and alcohols were identified with β-linalool as the main compound, followed by α-pinene, γ-terpinene, camphor, sylvestrene, β-pinene, and o-cymene. Differences were noted between profiles of terpenes after hydrodistillation and VASE extraction. For 8 out of 17 terpenes, VASE was used for their quantitative analysis. Regarding simplicity of the method, small sample requirement (200 mg) and short extraction time (5 min), VASE combined with GC/MS is well suited for characterization of terpenes in such matrix as plant oils.

TLC/GC-FID Analysis and Antioxidant Activity of Melicope madagascariensis (Baker) T.G. Hartley (Rutaceae) Essential Oil from Madagascar East Coast Rainforest

The aim of the present study was to evaluate the chemical composition and antioxidant activity of Melicope madagascariensis essential oil from Madagascar East Coast Rainforest. Essential oil from the leaves of this plant species was extracted by hydro-distillation and analyzed by TLC and GC-FID. The extraction revealed a yield is of 0.4% for a mass of 290 g of fresh leaves. Having a bland, pungent taste, the oil has a green-black color, a slightly unpleasant odor with a clear mobile consistency. Its density is 0.8765 and refractive index 1.4956 at 20 °C and is dextrorotatory (+0.1°) at 24 °C for its rotational power. The results of GC/FID analysis revealed that the essential oil contains (Z)-β-ocimene (12.7%) and (E)-β-ocimene (25.7%) as major compounds. The preparative TLC fractionation (using DPPH radical as revelator) and GC-FID analysis of the essential oil revealed the presence of compounds of the sesquiterpene family namely trans-nerolidol (4.32%), phenylpropanoid like methyl eugenol (5.9%), terpene oxide like caryophyllene oxide (3.66%), cinnamic esters like cinnamyl acetate (4.79%) and monoterpene alcohol like linalol (2.81%). The study on M. madagascariensis essential oil is herein reported for the first time. Further studies including cytotoxicity assay in order to evaluate the selectivity/therapeutic index of this essential oil are needed before developing it as novel antioxidant drug.

Alpha-Terpineol as Antitumor Candidate in Pre-Clinical Studies.

Alpha-terpineol is monoterpene alcohol with anti-tumor activity against different tumor cell lines (lung, breast, leukemias and colorectal) through blockage of NF-kB expression, which play an important role in tumor cells growth. Evaluate the antitumor activity of alpha-terpineol in murine Sarcoma 180 cell line. For the tests, different cytotoxic and genotoxic assays were used, including Trypan blue, cytokinesis- blocked micronucleus assay, comet assay, agarose gel DNA fragmentation, flow cytometry and cell viability using fluorescence. Ascitic fluid cells from sarcoma 180 were obtained from Mus musculus peritoneal cavity and Alpha-terpineol was tested at 100, 250 and 500 μg/mL. Doxorubicin and Cisplatin were used as positive controls. Cytotoxic effects of alpha-terpineol were found in all concentrations tested, reducing cell viability in 50.9; 38.53; 30.82% at 100, 250 and 500 μg/mL, respectively. Alpha-terpineol induced genotoxic effects due to DNA fragmentation (increased frequency and index of damage), and was clastogenic by increased micronuclei formation, nucleoplasmic bridges and nuclear buds. DNA fragmentation and increased cell death indicated that alpha-terpineol can cause early, late, and necrotic apoptosis. Our data indicate that alpha-terpineol has antitumor activity revealed by cytogenetic mechanisms and / or loss of cell membrane integrity.

Chemical composition and biological properties of Pelargonium graveolens, Leptospermum petersonii and Cymbopogon martinii var. motia essential oils and of Rosa centifolia absolute

Chemical composition of the essential oils (EO) of Pelargonium graveolens, Leptospermum petersonii and Cymbopogon martinii var. motia, and the absolute of Rosa centifolia and their bioactivity were examined. Major compounds in P. graveolens EO were monoterpene alcohols citronellol, geraniol and linalool; in L. petersonii EO monoterpene aldehydes geranial, neral and citronellal; in C. martiniii var. motia EO monoterpene alcohol geraniol and ester geranyl acetate, while in absolute of R. centifolia aromatic alcohol 2-phenylethanol. The EO of L. petersonii showed the strongest antibacterial while the EO of C. martinii var. motia the strongest antifungal potential. The best biofilm inhibition capacity was observed with R. centifolia absolute. The results of scanning electron microscopy analysis indicated that the EOs of L. petersonii and P. graveolens changed the number and morphology of C. albicans cells. The L. petersonii EO was the most potent toward tumour cells and exhibited the best biological activity. This is first comparative report summarizing efficacy of studied aromatic samples against pathogenic microbes, providing deeper insight into the modes of antimicrobial action, and at the same time describing their cytotoxicity against cell lines.

Isopulegol: A Promising Phytochemical with Potential Therapeutic Benefits

Phytochemicals are naturally occurring biologically active compounds that provide promising options to existing therapeutic approaches and serve as vital resources for novel drugs. Essential oils derived from various medicinal plants contain a wide array of phytochemicals that exhibit diverse pharmacological properties. Terpenes are low molecular weight, volatile compounds that are abundant in essential oil of various plants and possess useful biological activity for treating diseases and ailments. Isopulegol is a monoterpene alcohol present in the essential oils of grape fruit, mint and rosemary. This mini review summarizes recent progress on the health benefits of isopulegol and discusses its potential mechanisms in the prevention and treatment of diseases in various experimental models.

Nutritional and flavor properties of grape juice as affected by fermentation with lactic acid bacteria

ABSTRACT Two lactic acid bacteria (LAB) strains of Lactobacillus plantarum 21802 and Lactobacillus brevis 6239 were selected and combined for fermentation of grape juice. The changes of sugars, organic acids, volatiles, phenolic compounds as well as antioxidant capacity of the grape juice were characterized. Results showed that fermentation with LAB led to a slight decrease in sugar content and increased in organic acid content. The sugars were mainly consumed at the initial stage of fermentation, while the malic acid was consumed completely during the fermentation. The contents of total phenolics and flavonoids in grape juice decreased gradually during the fermentation process. As compared with the initial contents in unfermented grape juice, the contents of proanthocyanin B2, rutin, isoquercitrin, rhamnose-3-O-glucoside in the final fermented grape juice were increased by 26.83%, 249.24%, 138.48%, 139.60%, respectively, while the contents of gallic acid, proanthocyanin B1, catechin and epicatechin were decreased by 24.49%, 14.85%, 71.68%, 42.52%, respectively. The mice fed with the fermented grape juice showed higher activity of superoxide dismutase and lower level of malondialdehyde both in serum and liver tissue than those fed with the unfermented grape juice. Fermentation with LAB also enhanced the flavor profile by increasing the total number and content of volatile compounds, especially those of monoterpene alcohols, which are the main and characteristic aroma volatile compounds in Muscat aroma grapes. This research confirmed that fermentation with LAB might be a desirable option for improving the flavor and nutritional attributes of grape juice by altering the ratio of sugar to organic acid, improving the phenolic compounds, enhancing the antioxidant capacity, intensifying of the characteristic aroma and pleasant flavor of the grape juice.

COMPONENT COMPOSITION OF ESSENTIAL OIL PRUNUS PERSICA VAR. NECTARINA GROWING IN UZBEKI-STAN

The article presents the results of determining the composition of essential oils of Prunus persica var. nectarina varieties "yellow nectarine" – "sariк luchchak (uzb.) ", growing in two regions of the Ferghana region of the Republic of Uzbekistan. The pale yellow essential oil was obtained by hydrodistillation from un-dried fresh leaves of plants. The oil composition was determined by chromatography-mass spectrometry on an Agilent 7890 AGC 6890 N gas chromotograph with a quadrupole mass spectrometer (Agilent 5975C inert MSD) as a detector on an HP-5 MS quartz capillary column. An essential oil of pale yellow color was isolated from the leaves of plants. In the composition of essential oils, 56 and 61 compounds were identified in the first and second samples, respectively, wich is 94.55 and 96.00% of the total components. The dominant components of the first saple are camphor bicyclic monoterpene ketones (24.21%), α-thujone (15.00%) and β-thujone (4.27%), aromatic aldehyde benzaldehyde (18.83%) and isobornoleol bicyclic monoterpene alcohol (6.17%). In the second sample, bicyclic monoterpenic ketones (camphor) (36.67%), α-thujone (21.81%) and β-thujone (7.06%) and bicyclic monoterpene alcohol isobornoleol (9.4%) predominate and monocyclic unsaturated monoterpene α-terpinene (2.18%). In both samples, (+)-2-bornanone (camphor) is predominant. The studied variety Prunus persica var. nectarina can serve as a raw material for the production of essential oil, the main components of which are camphor and isobornoleol.

Chemical profile and sensory evaluation of Bulgarian rose (Rosa damascena Mill.) aroma products, isolated by different techniques

ABSTRACT Comprehensive chemical profiling of threeRosa damascena Mill. essential oil samples and two extracts (supercritical and subcritical) was performed by means of GC/MS/FID. As a result 85 compounds, representing 87.9-99.2% of the detected compounds, were identified by GC/MS and simultaneously quantified by GC-FID.The main aroma constituents in the essential oil sampleswere monoterpene alcohols citronellol (20.8-30.8%), geraniol (19.3-23.3%) and nerol (8.9-10.8%), followed by the stearopten fraction with nonadecane (12.0-17.5%), nonadecene (1.0-4.0%), heneicosane (4.0-5.8%) and heptadecane (1.8-2.5%) found in highest concentration. The chemical composition of the extracts was dominated by b-phenylethyl alcohol - 56.6% found in the subcritical sample and 46.7% in the supercritical one. Fatty acids esters, waxes and triterpenoids were found in the extracts as well. In addition, sensory evaluation of the rose aroma products was performed, demonstrating intense citrus, floral and balsamic notes for the essential oils and slight herbaceous and fruity notes for the extracts.

Evaluation of Apoptosis Pathway of Geraniol on Ishikawa Cells

Endometrial cancer is the most common type of cancer in the female reproductive system. Geraniol is acyclic monoterpene alcohol derived from essential oils of aromatic plants. This study aimed to investigate the apoptosis pathway of geraniol on Ishikawa cells. The cytotoxic effects of Geraniol on Ishikawa cells were determined by an MTT test. Ishikawa cells were seeded on cover slips, the IC50 dose was applied, and the cells were incubated with antibodies against Bax, Bcl-2, and TUNEL Assay. mRNA expression analysis of apoptosis-related genes was determined by RT-qPCR with an IC50 dose of Geraniol. The IC50 dose of Geraniol decreased Bcl-2 staining significantly, but it significantly increased Bax staining and TUNEL positive cells. A significant increase in the Bax, caspase3, caspase-8, cytochrome C and Fas genes and a significant decrease in the Bcl-2 gene was observed when the IC50 dose group was compared to the cells in the control group based on their mRNA expression levels.Analysis of expression of genes whose products are involved in apoptosis suggests the involvement of the mitochondrial pathway.

Monoterpenoid Geraniol Improves Anti-mycobacterial Drug Efficiency by Interfering with Lipidome and Virulence of Mycobacteria.

Tuberculosis (TB) remains a global infectious disorder for which efficient therapeutics are elusive. Nature is a source of novel pharmacologically active compounds with many potential drugs being derived directly or indirectly from plants, microorganisms and marine organisms. The present study aimed to elucidate the antimycobacterial potential of Geraniol (Ger), monoterpene alcohol, against Mycobacterium smegmatis. Disrupted membrane integrity was studied by membrane permeability assay and PI uptake. Cell surface phenotypes were studied by colony morphology, sliding motility and cell sedimentation rate. Lipidome profile was demonstrated by thin-layer chromatography and liquid chromatography-electrospray ionization mass spectrometry. Amendment in iron homeostasis was assessed by using iron chelator ferrozine and ferroxidase assay while genotoxicity was estimated with EtBr and DAPI staining. Biofilm formation was measured by staining, dry mass and metabolic activity using crystal violet. Cell adherence was examined microscopically and spectrophotometrically. We found the antimycobacterial activity of Ger to be 500 μg/ml against M. smegmatis. Underlying mechanisms revealed impaired cell surface phenotypes. Lipidomics analysis exposed profound decrement of mycolic acids, phosphatidylinositol mannosides and triacylglycerides which are crucial for MTB pathogenicity. We further explored that Ger impairs iron homeostasis and leads to genotoxic stress. Moreover, Ger inhibited the potential virulence attributes such as biofilm formation and cell adherence to both polystyrene surface and epithelial cells. Finally, we have validated all the disrupted phenotypes by RT-PCR which showed good correlation with the biochemical assays. Taken together, the current study demonstrates the antimycobacterial mechanisms of Ger, which may be exploited as an effective candidate of pharmacological interest.