The aim of this review is to present the potential application of camphor-a bicyclic monoterpene ketone-in the prevention of skin infections. Skin diseases represent a heterogeneous group of disorders characterized by prolonged symptoms that significantly diminish the quality of life. They affect the dermis, the epidermis, and even subcutaneous tissue. They very often have a bacterial or fungal background. Therapy for dermatological skin disorders is difficult and long-term. Therefore, it is important to find a compound, preferably of natural origin, that (i) prevents the initiation of this infection and (ii) supports the skin\'s repair process. Based on its documented anti-inflammatory, antibacterial, antifungal, anti-acne, anesthetic, strengthening, and warming properties, camphor can be used as a preventative measure in dermatological infectious diseases and as a component in medical and cosmetic products. This work discusses the structure and physicochemical properties of camphor, its occurrence, and methods of obtaining it from natural sources as well as through chemical synthesis. The use of camphor in industrial preparations is also presented. Additionally, after a detailed review of the literature, the metabolism of camphor, its interactions with other medicinal substances, and its antimicrobial properties against bacteria and fungi involved in skin diseases are discussed with regard to their resistance.

Monoterpenoids are an important subclass of terpenoids that play important roles in the energy, cosmetics, pharmaceuticals, and fragrances fields. With the development of biotechnology, microbial synthesis of monoterpenoids has received great attention. Yeasts such Saccharomyces cerevisiae and Yarrowia lipolytica are emerging as potential hosts for monoterpenoids production because of unique advantages including rapid growth cycles, mature gene editing tools, and clear genetic background. Recently, advancements in metabolic engineering and fermentation engineering have significantly enhanced the accumulation of monoterpenoids in cell factories. First, this review introduces the biosynthetic pathway of monoterpenoids and comprehensively summarizes the latest production strategies, which encompass enhancing precursor flux, modulating the expression of rate-limited enzymes, suppressing competitive pathway flux, mitigating cytotoxicity, optimizing substrate utilization, and refining the fermentation process. Subsequently, this review introduces four representative monoterpenoids. Finally, we outline the future prospects for efficient construction cell factories tailored for the production of monoterpenoids and other terpenoids.

Thymus daenensis Celak (Lamiaceae family), known as denaian thyme, is an Iranian endemic plant, commonly used for its carminative, expectorant, antibacterial and antifungal properties. Previous studies report the chemical profile of the essential oil of T. daenensis aerial parts, but little is known about its non volatile constituents. Herein, phytochemical and biological investigation of the polar extract of T. daenensis aerial parts to provide further insight into traditional use of this plant has been accomplished. High-performance liquid chromatography coupled to linear ion-trap and orbitrap high-resolution mass spectrometry (LC-ESI/LTQOrbitrap/MS/MS) analysis of MeOH extract was performed to guide the isolation of specialized metabolites and successive characterization by NMR analysis. MeOH extract displayed antioxidant activity evaluated by DPPH (EC50 = 48.99 ± 1.47 μg/mL) and TEAC assay (1.37 mg/mL). Successively, the biofilm inhibitory activity of extract and isolated compounds against mature biofilms of Escherichia coli, Pseudomonas aeruginosa, Acinetobacter baumannii, Listeria monocytogenes, and Staphylococcus aureus, and their influence on the metabolism of sessile bacterial cells were evaluated. Two previously unreported thymol derivatives have been identified. The biofilm inhibitory activity of isolated compounds highlighted a promising antimicrobial action for the tested compounds. In particular, vanillic acid, (3S,5R,6R,7E,9S)-megastigm-7-ene-3,5,6,9-tetrol 3-O-β-D-glucopyranoside, thymoquinol-2-O-β-D-glucopyranoside and the never reported compound daenol resulted capable of exerting inhibitory activity vs all pathogenic strains. All compounds tested at a concentration of 10 μg/mL inhibited the metabolism of the sessile cells of E. coli at a percentage ranging between 37.7% and 77.39%, and of L.monocytogenes at a percentage ranging between 21.79% and 71.17%.

Adaptation to psychosocial stress is psychologically distressing, initiating/promoting comorbidity with alcohol use disorders. Emerging evidence moreover showed that ethanol (EtOH) exacerbates social-defeat stress (SDS)-induced behavioral impairments, neurobiological sequelae, and poor therapeutic outcomes. Hence, this study investigated the effects of geraniol, an isoprenoid monoterpenoid alcohol with neuroprotective functions on EtOH escalated SDS-induced behavioral impairments, and neurobiological sequelae in mice. Male mice chronically exposed to SDS for 14 days were repeatedly fed with EtOH (2 g/kg, p. o.) from days 8-14. From days 1-14, SDS-EtOH co-exposed mice were concurrently treated with geraniol (25 and 50 mg/kg) or fluoxetine (10 mg/kg) orally. After SDS-EtOH translational interactions, arrays of behavioral tasks were examined, followed by investigations of oxido-inflammatory, neurochemicals levels, monoamine oxidase-B and acetylcholinesterase activities in the striatum, prefrontal-cortex, and hippocampus. The glial fibrillary acid protein (GFAP) expression was also quantified in the prefrontal-cortex immunohistochemically. Adrenal weights, serum glucose and corticosterone concentrations were measured. EtOH exacerbated SDS-induced low-stress resilience, social impairment characterized by anxiety, depression, and memory deficits were attenuated by geraniol (50 and 100 mg/kg) and fluoxetine. In line with this, geraniol increased the levels of dopamine, serotonin, and glutamic-acid decarboxylase enzyme, accompanied by reduced monoamine oxidase-B and acetylcholinesterase activities in the prefrontal-cortex, hippocampus, and striatum. Geraniol inhibited SDS-EtOH-induced adrenal hypertrophy, corticosterone, TNF-α, IL-6 release, malondialdehyde and nitrite levels, with increased antioxidant activities. Immunohistochemical analyses revealed that geraniol enhanced GFAP immunoreactivity in the prefrontal-cortex relative to SDS-EtOH group. We concluded that geraniol ameliorates SDS-EtOH interaction-induced behavioral changes via normalization of neuroimmune-endocrine and neurochemical dysregulations in mice brains.

Clover and lemongrass essential oils of contrasting composition, at three concentration levels (1%, 5%, 10%), were administrated via prophylactic and therapeutic inhalation to scopolamine-treated mice. Chemical analysis showed that clover oil was dominant in eugenol (47.69%) and lemongrass free of eugenol but mainly containing monoterpenoids of comparable proportions. Animal behavioural and brain biochemical tests showed that injection of scopolamine caused memory and learning deficit in mice while prophylactic and therapeutic inhalation of two oils at moderate to high concentrations all obviously reversed the cognitive impairment via inhibiting acetylcholinesterase activities, oxidation and inflammation. Lemongrass essential oil with diverse monoterpenoids can be as effective as or a little bit more potent than eugenol-rich clover essential oil possibly due to the synergistic effect of various monoterpenoids. These findings implied that sniffing of such aroma recipes could be a promising complementary approach for the mitigation of Alzheimer\'s disease-related cognitive impairment.

Monoterpene thiols are one of the classes of natural flavors that impart the smell of citrus fruits, grape must and wine, black currants, and guava and are used as flavoring agents in the food and perfume industries. Synthetic monoterpene thiols have found an application in asymmetric synthesis as chiral auxiliaries, derivatizing agents, and ligands for metal complex catalysis and organocatalysts. Since monoterpenes and monoterpenoids are a renewable source, there are emerging trends to use monoterpene thiols as monomers for producing new types of green polymers. Monoterpene thioderivatives are also known to possess antioxidant, anticoagulant, antifungal, and antibacterial activity. The current review covers methods for the synthesis of acyclic, mono-, and bicyclic monoterpene thiols, as well as some investigations related to their usage for the preparation of the compounds with antimicrobial properties.

Mango, a valued commercial fruit in India is popular mostly because of its attractive flavour. Glycosidically bound volatiles (GBV), an underrepresented warehouse of aroma, remain completely unexplored in Indian mangoes. In this study, GBV were profiled in pulps and peels of 10 Indian mango cultivars, leading to detection of 66 GBV which were dominated by monoterpenoids and phenolics. Peels were quantitatively and qualitatively richer in GBV than pulps. Hierarchical clustering and principal component analysis indicated higher contribution of peel GBV to the distinctness of cultivars. Linalool, geraniol, and eugenol were the significant contributors based on the odour units. Direct β-glucosidase treatment to the juice resulted in the release of lesser number of volatiles than those released from the purified GBV extracts. Apart from providing a comprehensive catalogue of GBV in mangoes, our data suggests the need of critical assessment of the usefulness of β-glucosidases in aroma improvement of fruit juices.

Twenty-four monoterpenoids, including three previously undescribed compounds (1-3), were isolated from the root bark of Acanthopanax gracilistylus W. W. Smith (Acanthopanacis Cortex). Their structures were unambiguously established based on spectroscopic analysis (HR-ESIMS, IR, 1D, and 2D NMR), and the absolute configurations of 1-3 were elucidated by comparing their experimental and calculated electronic circular dichroism spectra. In addition, the structure of 8 was confirmed by single-crystal X-ray diffraction. The inhibitory activities of 1-24 against neutrophil elastase, 5-lipoxygenase, and cyclooxygenase-2 (COX-2) were studied in vitro for the first time, and the results showed that compound 24 possessed a significant inhibitory effect on COX-2 with an IC50 value of 1.53 ± 0.10 μΜ. This research first reported the presence of monoterpenoids in Acanthopanacis Cortex, including one monoterpenoid 2 with an unusual 4/5 bicyclic lactone system, and compounds 4 and 5 have never been reported in nature.

The use of essential oils derived from the camphor tree to repel mosquitoes is an ancient practice that originated in Southeast Asia and gradually spread to China and across Europe via the Maritime Silk Road. The olfactory mechanisms by which these oils elicit avoidance behavior are unclear. Here we show that plant bicyclic monoterpenoids and borneol specifically activate a neural pathway that originates in the orphan olfactory receptor neuron of the capitate peg sensillum in the maxillary palp, and projects to the mediodorsal glomerulus 3 in the antennal lobe. This neuron co-locates with two olfactory receptor neurons tuned to carbon dioxide and octenol that mediate human-host detection. We also confirm that borneol elicits repellency against human-seeking female mosquitoes. Understanding the functional role of the mosquito maxillary palp is essential to investigating olfactory signal integration and host-selection behavior.

Linalool is a pleasant-smelling monoterpenoid widely found in the essential oils of most flowers. Due to its biologically active properties, linalool has considerable commercial potential, especially in the food and perfume industries. In this study, the oleaginous yeast Yarrowia lipolytica was successfully engineered to produce linalool de novo. The (S)-linalool synthase (LIS) gene from Actinidia argute was overexpressed to convert geranyl diphosphate (GPP) into linalool. Flux was diverted from farnesyl diphosphate (FPP) synthesis to GPP by introducing a mutated copy of the native ERG20F88W-N119W gene, and CrGPPS gene from Catharanthus roseus on its own and as part of a fusion with LIS. Disruption of native diacylglycerol kinase enzyme, DGK1, by oligo-mediated CRISPR-Cas9 inactivation further increased linalool production. The resulting strain accumulated 109.6 mg/L of linalool during cultivation in shake flasks with sucrose as a carbon source. CrGPPS expression in Yarrowia lipolytica increased linalool accumulation more efficiently than the ERG20F88W-N119W expression, suggesting that the increase in linalool production was predominantly influenced by the level of GPP precursor supply.