Pure Geraniol Research Articles

Geraniol and hydrophobic geraniol:thymol eutectic mixtures: Structure and thermophysical characterization

The properties of essential oils as food preservatives are well-established. These components have also been used as neoteric solvents to prepare eutectic mixtures. Their high capacity to dissolve poorly water-soluble substances makes them particularly interesting in the biotechnology industry. To implement them, it is essential to determine the structural and chemical-physical properties, as well as develop models to predict the behaviour under any operational condition. Herein, pure geraniol and geraniol/thymol mixtures are studied. Nuclear magnetic resonance experiments and molecular dynamics are used to evaluate the fluid structure. In addition, seven thermophysical properties are measured and correlated. The experimental densities, surface tensions, and viscosities were lower than 952 kg m–3, 33 mN m–1, and 36 mPa s, respectively. These values were adequate for the industrial application of these mixtures. PC-SAFT equation of state well predicted the density with an average deviation of 0.13 %, and the isobaric molar heat capacity with a deviation of 6.9 %. Greater compaction was observed at higher thymol molar ratios and dispersive interactions were predominant. Depending on the composition, geraniol was both an acceptor and donor of hydrogen bonds; conversely, thymol acted as a donor. The article provides the necessary knowledge to be able to use these mixtures and design new ones, as ecological solvents in different applications including those in the agri-food sector.

Efektifitas Reaksi Transesterifikasi Minyak Kelapa dan Sereh untuk Pembuatan Perisa Alami dengan Biokatalisator Lipase serta Penggunaan Ultrasonik

In general, flavor are synthesis through enzymatic hydrolysis and esterification reactions (up to 20 hours) using commercial ingredients based on free fatty acids and alcohol. Efficient endeavors utilizing enzymatic transesterification to expedite reactions are necessary to acquire flavored products. Substrates may originate from commercial or natural sources abundant in fatty acids and alcohol. Commercial fatty acids and alcohol (geraniol) are readily available in pure forms. Alternatively, fatty acids can be sourced from coconut oil, while geraniol can be derived from lemongrass oil, which is more cost-effective compared to commercial ingredients. Ultrasonics have emerged as a means to expedite enzymatic. The objective of this study is to investigate the impact of ultrasonic power and transesterification reaction time between coconut oil and geraniol on geraniol conversion. Utilizing lipase (415.99 U/g), coconut oil was subjected to transesterification with commercially obtained pure geraniol in a 1:3 weight ratio, conducted in an ultrasonic tank filled with water. Reaction durations spanned 30, 60, 90, 120, and 150 minutes, with ultrasonic powers set at 50, 70, and 90 watts. The study findings elucidated that the highest geraniol conversion rate of 50.59% was achieved with 70 watts of ultrasonic power over a 90-minute period. These optimal conditions were subsequently applied to transesterify coconut oil with geraniol from lemongrass oil, yielding a conversion rate of 90.29%. This finding demonsttrate the posibility of employing coconut oil and lemongrass oil in a one-stage transesterification process to produce natural flavors via enzymatic lipase catalysis expedited by ultrasonic technology, facilitating swift reaction times.

Contact allergy to citral and its constituents geranial and neral, coupled with reactions to the prehapten and prohapten geraniol

Citral is commonly used as a fragrance and flavor material and consists of the aldehydes geranial and neral. Citral is included in fragrance mix (FM) II. Geranial and neral have also been identified in autoxidation of geraniol, a fragrance compound present in FM I. To study contact allergy to citral, geranial, and neral, and concomitant reactivity to oxidized geraniol and fragrance markers of the baseline series. A total of 1476 dermatitis patients with suspected allergic contact dermatitis were patch tested using geranial, neral, and citral, all 3.5% petrolatum (pet.) as well as geraniol 6.0% and oxidized geraniol 11% pet. in addition to the Swedish baseline series. Frequencies of positive reactions to citral, geranial, and neral were 2.9%, 3.4% and 1.9%, respectively. Together, citral and geranial gave 4.2% positive patch test reactions in consecutive dermatitis patients. In patients with positive reactions to citral or its components, 25% to 34% reacted to FM II and 61% reacted to oxidized geraniol. Patch testing with citral, its components, or oxidized geraniol detects contact allergic reactions not detected using the baseline series. Patch testing with pure geraniol was shown to be of little value. Geranial and neral, although closely chemically related, are concluded to be separate haptens.

Contact allergy to oxidized geraniol among Swedish dermatitis patients-A multicentre study by the Swedish Contact Dermatitis Research Group.

Geraniol is a widely used fragrance terpene, and is included in fragrance mix I. Geraniol is prone to autoxidation, forming the skin sensitizers geranial, neral, and geraniol-7-hydroperoxide. Oxidized geraniol has previously been patch tested in 1 clinic, giving 1% to 4.6% positive reactions in consecutive patients when tested at 2% to 11%. To compare test reactions to pure and oxidized geraniol, to compare 2 different test concentrations of oxidized geraniol and to investigate the pattern of concomitant reactions to fragrance markers of the baseline series in a multicentre setting. One thousand four hundred and seventy-six consecutive patients referred for patch testing were patch tested with geraniol 6% pet. and oxidized geraniol 6% and 11% pet. Pure geraniol 6% pet., oxidized geraniol 6% pet. and oxidized geraniol 11% pet. gave 1%, 3% and 8% positive patch test reactions and 0.7%, 3% and 5% doubtful reactions, respectively. Approximately 50% of the patients with doubtful reactions to oxidized geraniol 6% pet. had positive reactions to oxidized geraniol 11% pet. Oxidized geraniol 11% pet. provides better detection than oxidized geraniol 6% pet. As most patients reacted only to oxidized geraniol, it is important to explore further whether oxidized geraniol should be included in a baseline patch test series.

English

Rhodinol is a mixture of geraniol and citronellol. It is the second fraction in fractional distillation of commercially grown Cymbopogon nardus. The physical and chemical similarities of these two compounds made them inseparable. The individual use of each compound is of great importance. A selective oxidation (hydrogen peroxide activated by platinum black) of geraniol (in rhodinol) to geranial was done while remaining citronellol intact in order to separate the two compounds into different chemical functionality. A yield of 81% geranial achieved while minimizing citronellal formation from citronellol to 17%. Chemical separation using sodium hydrogen sulfite (NaHSO3) was done to separate the aldehydes from the unreacted citronellol. Purification using fractional distillation was done to obtain pure geraniol and remove minor fraction of citronellal.

Microbiological Characterization of Pure Geraniol and Comparison with Bactericidal Activity of the Cinnamic Acid in Gram-Positive and Gram-Negative Bacteria

Geraniol is a terpene alcohol and the principal constituent compound of many essential oils of the aromatic plants. This molecule is very important for the flavors and fragrance industries due to its pleasant odor. The geraniol has the insecticidal properties and is an efficiently repellent agent and its toxicity is low. So, its antimicrobial ability can be explored to obtaining important additives for especial products applied in the food industry. The cinnamic acid is a molecule present in cinnamon oils and in coca leaves. This molecule also exhibits low toxicity and has a broad biological application spectrum for many microorganisms. This work evaluated the antimicrobial activity of the essential oil of geraniol and of the cinnamic acid against different microorganisms and compared their bactericidal activity for future applications as an additive for food packages. The bacteria studied were: Staphylococcus aureus, Listeria monocytogenes, Escherichia coli and Salmonella enterica. The Minimum Inhibitory Concentration test (MIC) and the Agar Diffusion Method were applied to available the antimicrobial susceptibility. The geraniol showed a large bactericidal activity and greater than the cinnamic acid for the bacteria studied. The geraniol showed the better bactericidal action and high application potential for use as an additive for treatment of the food or to produce active food packaging.

Cross-reactivity between citral and geraniol - can it be attributed to oxidized geraniol?

The fragrance compound geraniol is susceptible to autoxidation when in contact with air, and to cutaneous metabolism. In both processes, the isomeric aldehydes geranial and neral are formed. Citral consists of geranial and neral. Among patients with positive reactions to citral, we have previously detected concomitant reactions to geraniol in 85% of cases and to oxidized geraniol in 73% of cases. To study the pattern of concomitant reactions to geraniol and citral and its isomers geranial and neral, and to determine whether these isomers are important sensitizers in contact allergy to geraniol and oxidized geraniol. The irritancy of geranial and citral was studied. Six hundred and fifty-five patients were patch tested with geranial, neral and citral at 3.5% pet., pure geraniol at 6.0% and 11.0% pet., and oxidized geraniol at 6.0% pet. Twenty-six per cent of citral-positive patients reacted to oxidized geraniol, and 10.5% reacted to pure geraniol. Citral and/or its isomers gave positive reactions in 25% of the patients who reacted to pure geraniol. There is little cross-reactivity between pure geraniol and citral; however, concomitant reactions to citral and oxidized geraniol were common, owing to geranial. Geranial was also the main sensitizer in the mixture citral.

Finding the optimal patch test material and test concentration to detect contact allergy to geraniol

Geraniol is a commonly used fragrance terpene, and is tested in the baseline series in fragrance mix I. Geraniol is a pro-hapten and a pre-hapten, and sensitizers are formed in the autoxidation and skin metabolism of geraniol. Previous patch testing with air-exposed (oxidized) geraniol has suggested that oxidized geraniol could be a better marker for contact allergy to geraniol than pure geraniol. To find the optimal patch test substance and concentration for detecting contact allergy to geraniol. Six hundred and fifty-five patients were patch tested with pure and oxidized geraniol at 4.0%, 6.0% and 11.0% in petrolatum. Before patch testing, the irritant properties of pure and oxidized geraniol were studied in 27 patients at 2.5%, 5.0%, 10.0% and 20.0% pet. Pure geraniol detected positive reactions in 0.15-1.1% of the patients, and oxidized geraniol detected positive reactions in 0.92-4.6% of the patients. Reactions to pure geraniol in patients not reacting to oxidized geraniol indicated metabolic activation of geraniol. Neither pure nor oxidized geraniol gave significant irritant reactions. Increasing the test concentrations of pure and oxidized geraniol enables the detection of more cases of contact allergy. Oxidized geraniol detects more patients than pure geraniol, but patch testing with only oxidized geraniol does not detect all cases of contact allergy to geraniol.

Contact allergy to air‐exposed geraniol: clinical observations and report of 14 cases

The fragrance terpene geraniol forms sensitizing compounds via autoxidation and skin metabolism. Geranial and neral, the two isomers of citral, are the major haptens formed in both of these activation pathways. To investigate whether testing with oxidized geraniol detects more cases of contact allergy than testing with pure geraniol. The pattern of reactions to pure and oxidized geraniol, and metabolites/autoxidation products, was studied to investigate the importance of autoxidation or cutaneous metabolism in contact allergy to geraniol. Pure and oxidized geraniol were tested at 2.0% petrolatum in 2227 and 2179 consecutive patients, respectively. In parallel, geranial, neral and citral were tested in 2152, 1626 and 1055 consecutive patients, respectively. Pure and oxidized geraniol gave positive patch test reactions in 0.13% and 0.55% of the patients, respectively. Eight of 11 patients with positive patch test reactions to oxidized geraniol also reacted to citral or its components. Relevance for the positive patch test reactions in relation to the patients' dermatitis was found in 11 of 14 cases. Testing with oxidized geraniol could detect more cases of contact allergy to geraniol. The reaction pattern of the 14 cases presented indicates that both autoxidation and metabolism could be important in sensitization to geraniol.

Fragrance Compound Geraniol Forms Contact Allergens on Air Exposure. Identification and Quantification of Oxidation Products and Effect on Skin Sensitization

Fragrances are common causes of contact allergy. Geraniol (trans-3,7-dimethyl-2,6-octadiene-1-ol) is an important fragrance terpene. It is considered a weak contact allergen and is used for fragrance allergy screening among consecutive dermatitis patients. Analogous to other monoterpenes studied, such as limonene and linalool, geraniol has the potential to autoxidize on air exposure and form highly allergenic compounds. The aim of the present study was to investigate and propose a mechanism for the autoxidation of geraniol at room temperature. To investigate whether allergenic compounds are formed, the sensitizing potency of geraniol itself, air-exposed geraniol, and its oxidation products was determined using the local lymph node assay in mice. The results obtained show that the allylic alcohol geraniol follows an oxidation pattern different from those of linalool and limonene, which autoxidize forming hydroperoxides as the only primary oxidation products. The autoxidation of geraniol follows two paths, originating from allylic hydrogen abstraction near the two double bonds. From geraniol, hydrogen peroxide is primarily formed together with aldehydes geranial and neral from a hydroxyhydroperoxide. In addition, small amounts of a hydroperoxide are formed, analogous to the formation of the major linalool hydroperoxide. The autoxidation of geraniol greatly influenced the sensitizing effect of geraniol. The oxidized samples had moderate sensitizing capacity, quite different from that of pure geraniol. The hydroperoxide formed is believed to be the major contributor to allergenic activity, together with the aldehydes geranial and neral. On the basis of the present study and previous experience, we recommend that the possibility of autoxidation and the subsequent formation of contact allergenic oxidation products are considered in risk assessments performed on fragrance terpenes.

Japanese Beetle: A Superior Attractant, Phenethyl Propionate + Eugenol + Geraniol, 3:7:31124

Addition of geraniol and nerol, found in a commercial preparation of geraniol, to mixtures of phenethyl propionate (PEP) + eugenol significantly increased their attractancy to Popillia japonica Newman. Geraniol significantly increased attractancy more than nerol. A mixture of PEP + eugenol + geraniol, 3:7:3, was 57% more attractive to Japanese beetles than the current standard lure, PEP + eugenol, 3:7. The substitution of impure geraniol (60%) for pure geraniol in the trinary lure did not significantly decrease attractancy.

Preparation of Pure Geraniol

Preparation of Pure Geraniol