Terpenes are a widespread group of secondary metabolites that can be found in various family plants such as the Lamiaceae. In view of their numerous valuable biological activities, the industrial production of concrete terpenes and essential oils rich in the substances is intensively studied. Monoterpenes constitute a significant part of the whole group of the aforementioned secondary metabolites. This is due to their numerous biological activities and their ability to permeate the skin. Despite the fact that these substances have gain popularity, they are not comprehensively characterized. The presented review is based on studies of the biological activities of the most important monoterpenes and the essential oils rich in these compounds. The authors focused attention on antioxidant activity, inhibition towards acetyl- and butyrylcholinesterase, and α-amylase and α-glucosidase, antifungal, hepatoprotective, sedative properties, and their skin permeation enhancement.

Natural Monoterpenes: Much More than Only a Scent.

Herbs and plant metabolites/extracts are gaining wide attention owing to their multiple beneficial health effects, medicinal values, and nutraceutical properties, particularly in the present era of...

A Comprehensive Review on Chemical Profile and Pharmacological Activities of Ocimum basilicum

Lantana camara Linn. (Verbenaceae) is used traditionally for its numerous medicinal properties such as antimalarial, antibacterial, anticancer and anti-inflammatory. In the present study, we investigated the chemical composition of essential oil from the leaves of L. camara (LCEO) occurring in the Republic of Benin (West Africa) in comparison with LCEOs from other regions; evaluated its sedative effects in mice via inhalation administration; and identified the compounds responsible for activity. LCEO was extracted by hydrodistillation and chemical analyses of the oil were performed by GC and GC/MS. The oil was dominated by monoterpene hydrocarbons (60.58%) and oxygenated monoterpenes (33.39%), among which sabinene (38.81%) and 1,8-cineole (28.90%) were the most abundant. LCEO administered via inhalation to mice significantly decreased locomotor activity in a dose-dependent manner, mainly at the doses of 0.0004 and 0.04 mg per 400 μL of triethyl citrate (TEC). The oil was fractionated to give two fractions, which were further investigated, and revealed that both sabinene and 1,8-cineole were the principal active compounds. The results of the present study indicated that via inhalation administration, LCEO and its main constituents could be considered as promising candidates for the management of dementia, insomnia, attention deficit hyperactivity disorder and other central nervous system-associated diseases.

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Sedative effects of the essential oil from the leaves of Lantana camara occurring in the Republic of Benin via inhalation in mice

The anxiolytic and antidepressant-like activities of the naturally occurring monoterpene 1,8-cineole and its structural isomer 1,4-cineole were evaluated in mice via inhalation administration at doses ranging from 4 × 10-6 to 4 × 10-1 mg per 400 μL of triethyl citrate. Mice were tested for anxiety-like behaviours by using the light-dark box test (LDB) and marble-burying test (MBT) and for depression-like symptoms by using the forced swimming test (FST) and tail suspension test (TST). Diazepam and fluoxetine were used as standard drugs for anxiolytic and antidepressant tests, respectively. The results showed that 1,8-cineole at 4 × 10-4 mg, and 1,4-cineole at 4 × 10-4 and 4 × 10-3 mg significantly increased the amount of time spent in the light box and the number of entries in the light box in the LDB as well as reduced the number of marbles buried in the MBT relative to those in the control, suggesting an anxiolytic effect. Similarly, 1,8-cineole at 4 × 10-4 and 4 × 10-2 mg and 1,4-cineole at doses of 4 × 10-4 to 4 × 10-2 mg significantly reduced immobility times in the FST and TST relative to those of the control, suggesting an antidepressant activity. The role of the GABAA/benzodiazepine receptor system in the anxiolytic effects of 1,8- and 1,4-cineole was investigated through co-administration of flumazenil, a GABAergic system antagonist. Flumazenil reversed the effects of diazepam and 1,8-cineole, suggesting that 1,8-cineole affects the GABAA/benzodiazepine receptors. Collectively, the results suggest that inhaled 1,8- and 1,4-cineole prevented anxiety and depressive-like symptoms in classic mice models.

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Inhalation Administration of the Bicyclic Ethers 1,8- and 1,4-cineole Prevent Anxiety and Depressive-Like Behaviours in Mice

Putative Mode of Action of the Monoterpenoids Linalool, Methyl Eugenol, Estragole, and Citronellal on Ligand-Gated Ion Channels

The sedative effects of the essential oil released by living Ocimum basilicum (basil) plants were investigated using a mouse activity monitoring system. Ocimum basilicum plants were grown in a hydroponic chamber, and either the headspace air from the hydroponic chamber or the essential oil extracted from mature plants was administered by the inhalation route to mice in an open field test. The most effective dose of O. basilicum essential oil for reducing the locomotor activity of the mice was found to be 4.0 × 10−3 mg per cage. The headspace air was administered to mice held in a glass cage via a Teflon tube connected to a hydroponic chamber containing O. basilicum plants. A significant decrease in locomotor activity was observed when the hydroponic chamber contained nine plants. The results of this study demonstrate that the headspace air of living basil plants could effectively reduce the locomotor activity of mice.

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Sedative effects of the essential oil and headspace air of Ocimum basilicum by inhalation in mice

In this study, we extracted essential oils from four species of plants with lemony scents (Melissa officinalis L., Aloysia citriodora Palau (= Lippia citriodora (Palau) Kunth), Thymus × citriodorus, Perilla citriodora (Makino) Nakai). We then examined the components of extracts using gas chromatography (GC) and GC–mass spectrometry (GC–MS). A comparison of components indicated that the largest proportions of essential oils were caryophyllene (25%) in M. officinalis, geraniol (50%) in T. citriodorus, and citral (61 and 82%) in A. citriodora and P. citriodora. Moreover, we used a sensory evaluation method using dilute aqueous solutions of extract components, citral, linalool, d-limonene, and geraniol, to select the mixture with a flavor that mostly resembled lemon. The participants in the study felt that an aqueous citral solution flavored more like lemon than aqueous d-limonene. Furthermore, an open field study of sedative effects of citral and d-limonene, when inhaled, on mice demonstrated that citral exhibited a sedative effect at a lower concentration than that of d-limonene.

Miho Hirai

Papers

Sedative effects of the essential oil and headspace air of Ocimum basilicum by inhalation in mice

Diversity in principal constituents of plants with a lemony scent and the predominance of citral