Evaluation of the Antimicrobial Activity of Geraniol and Selected Geraniol Transformation Products against Gram-Positive Bacteria.

Both geraniol and the products of its transformation, thanks to their beneficial properties, find a variety of applications in cosmetics. Due to their antioxidant and moisturizing properties, these compounds can be added to skin care products such as face creams, lotions, oils, and masks. In addition, these compounds show some antibacterial and antifungal properties, making them suitable for application in skin care products to help fight against bacteria or fungi. This study determined the antimicrobial activity of geraniol and the compounds which were formed during its transformation in relation to selected Gram-positive bacteria, and the preliminary assessment was made whether these compounds can act as ingredients of preparations with potential antimicrobial activity in the treatment of various human diseases (for example diseases of the skin, digestive system, or urinary tract). In addition, this work presents studies on the microbiological purity of cream samples obtained with different contents of geraniol and its transformation products (contents of the tested compounds: 0.5%, 1.5%, 2.5%, 4%, 8%, and 12%). Antibacterial activity tests were performed using the disc diffusion method against Gram-positive cocci, including the reference strains Staphylococcus aureus ATCC 29213 and Enterococcus faecalis ATCC 29212, and against the clinical strains Staphylococcus aureus MRSA, Staphylococcus epidermidis, Enterococcus faecalis VRE VanB, Enterococcus faecium VRE VanA, and Enterococcus faecium VRE VanB. The most active ingredient against bacteria of the Staphylococcus genus was citral, followed by linalool and then geraniol. During our tests, in the case of bacteria of the Enterococcus genus, citral also showed the highest activity, but linalool, ocimenes, and geraniol showed a slightly lower activity. Moreover, this study examined the microbiological purity of cream samples obtained with various contents of geraniol and its transformation products. In the tests of the microbiological purity of cream samples, no growth of aerobic bacteria and fungi was found, which proves the lack of microbiological contamination of the obtained cosmetic preparations. On this basis, it was assessed that these compounds have preservative properties in the prepared creams. The addition of the analyzed compounds also had influence on the durability of the creams and had no effect on the change in their consistency, did not negatively affect the separation of phases during storage, and even had a positive effect on organoleptic sensations by enriching the smell of the tested samples.

Application of RSM Method for Optimization of Geraniol Transformation Process in the Presence of Garnet.

This paper presents the results of tests obtained for the transformation of geraniol in the presence of garnet as a catalyst by the response surface method (RSM). The method analyzed the influence of the following parameters: a temperature of 50-150 °C, a catalyst concentration (garnet) of 1.0-10.0 wt% and a reaction time of 0.25-24 h. Response functions included the conversion of geraniol (GA), selectivity for conversion to neral (NE) and selectivity for conversion to citronellol (CL). In addition, the influence of all control parameters on each of the response parameters is presented in the form of second-order polynomials. The optimal parameters of the geraniol transformation process were a temperature of 55 °C, a catalyst concentration of 5 wt% and a reaction time of 2 h, for which high values of the GA conversion function and the selectivity of conversion to NE and CL were obtained. For the GA conversion, the optimum was obtained at 94 mol% at 60 °C, a catalyst concentration of 5.0 wt% and a reaction time of 2 h. For NE selectivity, the optimum value was reached at 49 mol% at 60 °C, a catalyst concentration equal to 2.5 (5.0) wt% mole and a reaction time of almost 2 h. For CL selectivity, the optimum value of 49 mol% was obtained for control factors: a temperature equal to 20 °C, a catalyst concentration equal to 5.0 wt% and a response time equal to 2 h. The optimal set of control factors for all power factors is characterized by a temperature of 55 °C, a catalyst concentration of 5 wt% and a reaction time of 2 h.

Preliminary Microbiological Tests of S-Carvone and Geraniol and Selected Derivatives of These Compounds That May Be Formed in the Processes of Isomerization and Oxidation.

This work presents a literature review on the biological activity of S-carvone, geraniol and derivatives of these compounds, which are formed in the process of isomerization (during the process of geraniol isomerization, oxidation products of this compound are also obtained). Moreover, this work presents preliminary microbiological tests of creams with the addition of these biologically active compounds: S-carvone, geraniol, carvacrol (an S-carvone isomerization product), nerol (a geraniol isomerization product), linalool (a geraniol isomerization product) and citral (a geraniol oxidation product). Because the post-reaction mixture obtained after the S-carvone isomerization has a relatively simple composition, it was also added to creams and tested without isolating pure compounds. This may be a cheaper alternative to creams prepared with the addition of pure compounds. The mixture obtained after the geraniol isomerization process has a very complex composition; therefore, only compounds with the lowest molecular weight and are easily commercially available were selected for studies. The content of the tested compounds in the creams ranged from 0.5 to 3 wet%. The following microorganisms were selected for microbiological tests: the Gram-negative bacterium Escherichia coli K12, the Gram-positive bacterium Staphylococcus epidermidis, and the fungi Candida albicans, Trichophyton rubrum, Aspergillus niger, and Penicillium chrysogenum. A content of 3% carvacrol, nerol, geraniol and citral inhibited the growth of E. coli, and attenuated the growth of C. albicans and T. rubrum. On the other hand, 3% carvacrol and citral only poorly attenuated the growth of the mould fungi P. chrysogenum and A. niger.

Conversion of Geraniol into Useful Value-Added Products in the Presence of Catalysts of Natural Origin: Diatomite and Alum.

This article presents research related to the transformation of geraniol (GA), leading to the formation of products with very valuable properties. In the planned method, heterogeneous catalysts of natural origin in the form of alum and diatomite were used as catalysts. Initially, the process which we investigated was the process of isomerization of GA, but it turned out during the studies that GA is also transformed in other reactions. Before catalytic tests, these two minerals were subjected to detailed instrumental analyses using the following methods: XRD, SEM/EDX, XRF and FTIR, which allowed to obtain their full morphological characteristics. During the catalytic tests, the influence of such relevant parameters on the GA transformations was determined: temperature from 80 to 150 °C, catalyst content from 5 to 15% by weight and the reaction time from 15 min to 24 h. The tests presented in the article were carried out under atmospheric pressure (in air) as well as without the use of a solvent. The optimal conditions for the transformations of GA were determined on the basis of its conversion and selectivities of transformation to the main products in the form of: beta-pinene (BP), 6,11-dimethyl-2,6,10-dodecatriene-1-ol (DC) and thumbergol (TH). The above products were formed with the highest selectivity, respectively: 100 mol%, 50 mol% and 52 mol%. The results of the syntheses showed that for GA the best transformation results were obtained at the temperature of 80 °C (for both tested catalysts), with the catalyst content of 1 wt % (for both tested catalysts) and for the reaction time of 1 h (for diatomite)) and 3 h (for alum).

Efficiency of Tool Steel Cutting by Water Jet with Recycled Abrasive Materials.

High-pressure water jet machining is characterized by wide possibilities of cutting diverse materials together with multi-layer materials with dissimilar properties, accurate cutting complex profiles, as well as conducting them in uncommon conditions, especially in cases of thick materials. An additional advantage of water jet technology is its environmental friendliness. This paper presents tests of the cutting performance of tool steel with the use of an abrasive water jet (AWJ). The state-of-the-art has shown insufficient scientific evidence in AWJ tool steels cutting using recycled abrasive materials. Therefore, the main motivation for this paper was to carry out research from an environment aspect. The reuse of abrasives and the use of recycled materials have immense potential to reduce processing costs while remaining environmentally friendly. The RSM method was used for modeling and optimization. A response surface design (RSM) is a package of an advanced design-of-experiment (DOE) approaches that support better understanding and optimize response, exploring the relationships between several explanatory variables and one or more response variables. Based on this research, feed rate is the key factor influencing the depth of cut, while the water nozzle diameter has a secondary effect, and the concentration of abrasive has the least influence on the depth of cut. High level of variance (the percentage of variability in the reaction that is interpreted by the formula) confirms that the models fit well to the investigational data.