Locomotor-reducing effects and structural characteristics of inhaled zerumbone and tetrahydrozerumbone derivatives

Zingiber zerumbet: A Scoping Review of its Medicinal Properties

Zingiber zerumbet, a plant native to tropical and subtropical Asia, has a vast range of traditional uses and has been continuously studied for its medicinal properties. However, a systematic methodological approach in evidence synthesis on the plant's efficacy is lacking, and there is a need to elicit the current research status of this plant. This scoping review was conducted to systematically explore and collate the available scientific evidence on the efficacy of Z. zerumbet and its main phytoconstituents in various formulations, their biological mechanisms, and their safety. Results included 54 articles consisting of animal studies, while there were no published human studies. Only half of the included studies provided adequate reporting on the quality-related details of Z. zerumbet formulations. Identified pharmacological activities were analgesic, anti-inflammatory, anti-diabetic, anti-hyperlipidemic, anti-neoplastic, immunomodulatory, antioxidant, antipyretic, hepatoprotective, nephroprotective, gastroprotective, and locomotor-reducing activities. Notably, the ethanolic extract of Z. zerumbet was found to be well tolerated for up to 28 days. In conclusion, Z. zerumbet and zerumbone have various pharmacological effects, especially in analgesic and anti-inflammatory models. However, there is still a pressing need for comprehensive safety data to conduct clinical trials.

Molecular Descriptors and QSAR Models for Sedative Activity of Sesquiterpenes Administered to Mice via Inhalation

Essential oils are often utilized for therapeutic purposes and are composed of complex structural molecules, including sesquiterpenes, with high molecular weight and potential for stereochemistry. A detailed study on the properties of selected sesquiterpenes was conducted as part of a broader investigation on the effects of sesquiterpenes on the central nervous system. A set of 18 sesquiterpenes, rigorously selected from an original list of 114, was divided into 2 groups i.e., the training and test sets, with each containing 9 compounds. The training set was evaluated for the sedative activity in mice through inhalation, and all compounds were sedatives at any dose in the range of 4 × 10-4-4 × 10-2 mg/cage, except for curzerene. Molecular determinants of the sedative activities of sesquiterpenes were evaluated using quantitative structure-activity relationship (QSAR) and structure-activity relationship (SAR) analyses. An additional test set of six compounds obtained from the literature was utilized for validating the QSAR model. The parental carbonyl cation and an oxygen-containing groups are possible determinants of sedative activity. The QSAR study using multiple regression models could reasonably predict the sedative activity of sesquiterpenes with statistical parameters such as the correlation coefficient r2 = 0.82 > 0.6 and q2 LOO = 0.71 > 0.5 obtained using the leave-one-out cross-validation technique. Molar refractivity and the number of hydrogen bond acceptors were statistically important in predicting the activities. The present study could help predict the sedative activity of additional sesquiterpenes, thus accelerating the process of drug development.

Zerumbone, a major sesquiterpene from Syringa pinnatifolia Hemsl., exerts the sedative effect by regulating GABAergic nervous system

ETHNOPHARMACOLOGICAL RELEVANCE

Zerumbone (ZER) is a humulane sesquiterpenoid isolated from Syringa pinnatifolia Hemsl. (SP), its content accounts for 64.7% of volatile oil and 0.86% of total ethanol extract (TEE), representing one of characteristic ingredient of SP. As a representative Mongolian medicine with anti-"Khii", anti-asthma, and clearing-heat effects, SP has been used for the treatment of cardiovascular diseases, upset, insomnia, and other symptoms.

AIM OF STUDY

Previous results showed that TEE has sedative effect, but the pharmacological substances and its sedative mechanism remains unclear. This study aims to determine whether ZER, as one of major and characteristic sesquiterpenoids of SP, contributes to the sedative effect of SP and its underlying mechanism.

MATERIALS AND METHODS

Locomotor activity and threshold dose of pentobarbital sodium sleep experiments were used to evaluate the sedative effects in mice. ELISA assay was used to examine the level of GABA/Glu ratio in rats hippocampus, cortex and hypothalamus tissue. The binding ability of ZER with glutamic acid decarboxylase 67 (GAD67) and Gephyrin protein were predicted by molecular docking. Western blot and Immunohistochemistry assay were used to determine the expression of GABAergic nerve system related proteins (GAD67, Gephyrin) in rat's hypothalamus. ZER was co-administrated with flumazenil and bicuculline (GABA_A antagonist) to determine whether it acts on GABA_A receptor. Furthermore, MQAE assay was used to test the effect of ZER on the chloride ion concentration in cerebellar granule cells.

RESULTS

Current data demonstrated that ZER dose-dependently (5-20 mg/kg) reduces the locomotor activity and sleep latency of mice, and extend sleeping time of mice. The results of ELISA showed that ZER increases the level of GABA/Glu in rats brain tissue, in particular in hypothalamus. Molecular docking results revealed that ZER has a strong affinity to GAD67 and Gephyrin protein. The Western blot and Immunohistochemistry data indicated that ZER up-regulates the expression of GAD67 and Gephyrin protein in rat's hypothalamus. Antagonism test results demonstrated that flumazenil and bicuculline reverse the effect of ZER on threshold dose of pentobarbital sodium sleep experiments. In addition, ZER also could dose-dependently (5-20 μM) increase the chloride ion concentration in cerebellar granule cell, suggesting that ZER induces the opening of chloride channel, exerts central inhibitory effect.

CONCLUSION

ZER has a significant sedative effect in mice and rat, and the effect is associated with GABAergic nervous system. The present results suggest that ZER, as one of the major bioactive ingredients of SP, contributes to the sedative effect and provide substantial evidence for its traditional use of anti-"Khii" in clinic of Syringa pinnatifolia.

Anxiolytic Activity of Ethanolic Extract of Three Species of Indonesian Lempuyang (Zingiber zerumbet, Zingiber aromaticum, and Zingiber americans)

BACKGROUND: Lempuyang, or widely known as wild ginger, has been used in Indonesia as traditional medicine for a long time. However, scientific research supporting its medicinal use is still very limited. AIM: This research was conducted to investigate the anxiolytic activity of three species of Indonesian Lempuyang (Zingiber zerumbet, Zingiber aromaticum, and Zingiber americans). METHODS: Sixty-six male Swiss Webster mice were divided into 11 groups (negative control, positive control, and experiment groups consisting of low, moderate, and high dose of Z. zerumbet, Z. aromaticum, and Z. americans extract, respectively). Anxiolytic activity was evaluated by three methods: elevated plus maze test, open field test, and hole board test. RESULTS: The results showed that these three species of Indonesian Lempuyang lowered the anxiety response in elevated plus maze test, open field test, and hole board test compared to negative control (p < 0.05). The best anxiolytic activity was achieved by moderate dose of Z. americans (8.5 mg/20 gbb), consistently through three methods applied. CONCLUSION: This research supports the potential use of the ethanolic extract of Lempuyang (Z. zerumbet, Z. aromaticum, and Z. americans) as a complementary therapy for anxiety.

Appetite-enhancing effects of inhaling cinnamon, clove, and fennel essential oils containing phenylpropanoid analogues

Cinnamon, clove, and fennel are commonly used as spices and herbal medicines, and one of their medicinal uses is as aromatic stomachics. We investigated the effect on appetite in mice of inhaling volatile compounds contained in essential oils extracted from herbal medicines used as aromatic stomachics. The appetite-enhancing effects of cinnamon and fennel essential oils were similar to those of their main components trans-cinnamaldehyde and trans-anethole, respectively. The appetite-enhancing effects of clove essential oil were observed over a wide range of doses (4.5 × 10^-4 to 4.5 × 10^-3 mg/cage), even though the active compounds showed effects within a narrow range of doses (eugenol: 4.5 × 10^-4 to 2.5 × 10^-3 mg/cage; eugenol acetate: 1.1 × 10^-3 to 4.5 × 10^-3 mg/cage). The increase in appetite at doses that differed by tenfold in mice administered clove oil was due to synergistic effects between eugenol and eugenol acetate in clove oil. Thus, loss of appetite could be treated more effectively using essential oil containing both eugenol and eugenol acetate compared with the active compounds administered separately. Administering essential oils, such as cinnamon and clove, could improve loss of appetite without strict dosage adjustment.

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

Comparison of Chemical Composition and Bioactivities of Essential Oils from Fresh and Dry Rhizomes of Zingiber zerumbet (L.) Smith

The chemical constituents and the antioxidant, antimicrobial, and cytotoxic activities of fresh rhizome essential oil (FR-EO) and dry rhizome essential oil (DR-EO) of Zingiber zerumbet (L.) Smith obtained from Southwest China were compared. Zerumbone was the predominant component in both FR-EO and DR-EO (75.0% and 41.9%, respectively). FR-EO, DR-EO, and zerumbone were all demonstrated to have significant antimicrobial capacity against Staphylococcus aureus, Bacillus subtilis, Escherichia coli, and Proteus vulgaris, with minimum inhibitory concentration (MIC) ranging from 31.25 to 156.25 μg/mL and minimum bactericidal concentration (MBC) ranging from 62.50 to 625.00 μg/mL. Zerumbone showed the strongest antimicrobial potential against all tested microorganisms compared with the fresh and dry rhizome essential oils. FR-EO was found to be more active than DR-EO against Staphylococcus aureus, Bacillus subtilis, Escherichia coli, and Proteus vulgaris. FR-EO, DR-EO, and zerumbone all showed significant cytotoxic activity against K562, PC-3, and A549 human tumor cell lines in a time- and concentration-dependent manner. Zerumbone exhibited the strongest antiproliferative activity against all tested human tumor cell lines with an IC₅₀ of 4.21–11.09 μg/mL for 72 h incubation, as compared with the fresh and dry rhizome oils. The cytotoxic activity of FR-EO (IC₅₀: 10.48–14.51 μg/mL for 72 h) was found to be significantly higher (p < 0.05) than that of DR-EO (IC₅₀: 13.83–33.24 μg/mL for 72 h). FR-EO, DR-EO, and zerumbone exhibited selective cytotoxic activity to tumor cells, with a significantly low cytotoxicity to normal cells (MRC-5, IC₅₀: 56.98–147.29 μg/mL). However, FR-EO, DR-EO, and zerumbone all exhibited weak free-radical-scavenging activity according to DPPH and ABTS analysis. The findings highlighted in this study show that FR-EO provides appreciably higher content of the bioactive compound, zerumbone, and has higher antimicrobial and cytotoxic properties than DR-EO. Thus, fresh Z. zerumbet rhizome should be preferred in cosmetic, food, and pharmaceutical applications.

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

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.

Appetite-enhancing effects of nutmeg oil and structure-activity relationship of habituation to phenylpropanoids

Nutmeg (Myristica fragrans) is widely used to flavour sweet and savoury foods and has been used as a herbal medicine to enhance appetite in Asian countries. Nutmeg oil contains compounds such as myristicin and methyl eugenol. Previously, we found that inhalation of phenylpropanoid compounds increased appetite in mice. These volatile aroma compounds with appetite-enhancing effects have attracted the attention of healthcare professionals who care for older people with dementia because many of these older people have hypophagia, which leads to frailty and becoming bedridden. Thus, appetite-enhancing agents that are inexpensive and easy to administer are particularly desirable. In this study, we showed that the inhalation of nutmeg oil, myristicin and methyl eugenol produced appetite-enhancing effects in mice. Methyl eugenol alone has shown appetite-enhancing effects and locomotor-reducing effects at the same dose. In a previous study, benzylacetone produced those two effects at the same dose and also increased the body weight of mice significantly; methyl eugenol, however, did not because the mice experienced olfactory habituation after repeated inhalations of methyl eugenol. A structure-activity study showed that a carbonyl group on the aliphatic chain prevented habituation to aroma compounds, which is important information for identifying suitable phenylpropanoid compounds for long-term treatment of loss of appetite.