Medicinal properties of alpha-santalol, a naturally occurring constituent of sandalwood oil: review

Antitumor and chemopreventive role of major phytochemicals against breast cancer development

Breast cancer continues to be one of the most commonly diagnosed cancers around the world. Despite the decrease in mortality, there has been a steady increase in its incidence. There is much evidence that naturally occurring phytochemicals could prove to be safer alternatives aimed at prevention and development of breast cancer. In the present review, we discuss important phytochemicals, namely capsaicin, alpha-santalol and diallyl trisulphide that are shown to have chemopreventive and anti-tumour properties against breast cancer development. We examined current knowledge of their bioavailability, safety and modulation of molecular mechanisms including their ability to induce apoptotic cell death, promote cell cycle arrest, and inhibit cellular proliferation in different breast cancer cell lines and in vivo models. This review emphasises the importance of these naturally occurring phytochemicals and their potential of becoming therapeutic options in the arsenal against breast cancer development provided further scientific and clinical validation.

Biological Properties of Sandalwood Oil and Microbial Synthesis of Its Major Sesquiterpenoids

Sandalwood essential oil is extracted from the heartwood part of mature sandalwood and is known for its pleasant fragrance and exceptional medicinal activities, including antimicrobial, antitumor, and anti-inflammatory properties. The (Z)-α-santalol and (Z)-β-santalol are the most vital ingredients contributing to sandalwood oil's bioactivities and unique woody odor characteristics. Metabolic engineering strategies have shown promise in transforming microorganisms such as yeast and bacteria into effective cell factories for enhancing the production of vital sesquiterpenes (santalene and santalol) found in sandalwood oil. This review aims to summarize sources of sandalwood oil, its components/ingredients, and its applications. It also highlights the biosynthesis of santalene and santalol and the various metabolic engineering strategies employed to reconstruct and enhance santalene and santalol biosynthesis pathways in heterologous hosts.

Blocking the E2F transcription factor 1/high-mobility group box 2 pathway enhances the intervention effects of α-santalol on the malignant behaviors of liver cancer cells

In view of the tumor-inhibiting effect of α-santalol in various cancers and the role of E2F transcription factor 1 (E2F1) as an important target for anticancer research, this study investigates the relation between α-santalol and E2F1, as well as the effect of α-santalol on liver cancer progression and the corresponding mechanism. Concretely, liver cancer cells were treated with different concentrations of α-santalol. The IC50 value of α-santalol was determined using Probit regression analysis. Then, transcription factors that are targeted by α-santalol and differentially expressed in liver cancer were screened out. The clinicopathological impact of E2F1 and its targets were evaluated and predicted. The expressions of E2F1 and high-mobility group box 2 (HMGB2) and their correlation in the liver cancer tissues were analyzed by bioinformatics. The effects of E2F1 and HMGB2 on the biological characteristics of liver cancer cells were examined through loss/gain-of-function and molecular assays. With the extension of treatment time, the inhibitory effects of 10 μmol/L and 20 μmol/L α-santalol on cancer cell survival rate were enhanced (P < 0.001). E2F1 and HMGB2 were highly expressed and positively correlated in liver cancer tissues (P < 0.05). High E2F1 expression was correlated with large tumors and high TNM stages (P < 0.05). E2F1 knockdown promoted the effects of α-santalol on dose-dependently inhibiting viability, colony formation, invasion and migration (P < 0.05). Moreover, E2F1 knockdown reduced the IC50 value and HMGB2 level, while HMGB2 overexpression produced opposite effects. HMGB2 overexpression and E2F1 knockdown mutually counteracted their effects on the IC50 value and on the viability and apoptosis of α-santalol-treated liver cancer cells (P < 0.01). Collectively, blocking the E2F1/HMGB2 pathway enhances the intervention effects of α-santalol on the proliferation, migration and invasion of liver cancer cells.

Network Pharmacology to Reveal the Mechanism of Fufang Banmao Capsule for Treating Unresectable Primary Liver Cancer and Clinical Data Validation

INTRODUCTION

Fufang Banmao capsule (FFBM), a traditional Chinese medicine, has been used to treat primary liver cancer (PLC) for several years. However, the bioactive ingredients, and mechanism of FFBM for treating PLC remains unclear. Our objective is to utilize network pharmacology to investigate these aspects and subsequently validate their effectiveness through clinical data.

MATERIALS AND METHODS

The FFBM ingredients were obtained from the HERB database and screened for bioactive ingredients using the SwissTargetPrediction database. The PharmMapper and GEO database were used to acquire targets and differentially expressed genes (DEGs) for FFBM and PLC, respectively. Common targets were identified using Venn diagrams, followed by enrichment and protein-protein interaction (PPI) analysis. Furthermore, the Cytoscape software was utilized to identify Hub genes and construct the ingredienttarget- pathway network. Subsequently, patients diagnosed with unresectable PLC who underwent transcatheter arterial chemoembolization (TACE) at our hospital between January 2008 and December 2019 were retrospectively collected. Finally, Cox analysis was conducted to reveal the role of FFBM in the treatment of unresectable PLC.

RESULTS

FFBM had 232 targets, and PLC had 1582 DEGs. HSP90AA1 and SRC were identified as crucial targets. Alpha-santalol, glycyrrhizin, and morroniside were identified as the top three bioactive ingredients. Enrichment analysis revealed a significant connection between FFBM utilization for treating PLC and multiple pathways, such as chemical carcinogenesis, PI3K-AKT, Rap1, FoxO, MAPK, and VEGF pathway. Clinical data revealed that consuming FFBM significantly improved the prognosis of unresectable PLC with a hazard ratio of 0.69.

CONCLUSION

Our study identified the bioactive ingredients of FFBM and its potential mechanisms for treating PLC. Additionally, we validated the effectiveness through clinical data.

Improved chromosome-level genome assembly of Indian sandalwood (Santalum album)

Santalum album is a well-known aromatic and medicinal plant that is highly valued for the essential oil (EO) extracted from its heartwood. In this study, we present a high-quality chromosome-level genome assembly of S. album after integrating PacBio Sequel, Illumina HiSeq paired-end and high-throughput chromosome conformation capture sequencing technologies. The assembled genome size is 207.39 M with a contig N50 of 7.33 M and scaffold N50 size of 18.31 M. Compared with three previously published sandalwood genomes, the N50 length of the genome assembly was longer. In total, 94.26% of the assembly was assigned to 10 pseudo-chromosomes, and the anchor rate far exceeded that of a recently released value. BUSCO analysis yielded a completeness score of 94.91%. In addition, we predicted 23,283 protein-coding genes, 89.68% of which were functionally annotated. This high-quality genome will provide a foundation for sandalwood functional genomics studies, and also for elucidating the genetic basis of EO biosynthesis in S. album.

Cannabinoid Receptor Type II Ligands from Sandalwood Oil and Synthetic α-Santalol Derivatives

Bioassay-guided fractionation of the essential oil of Santalum album led to the identification of α-santalol (1) and β-santalol (2) as new chemotypes of cannabinoid receptor type II (CB2) ligands with Ki values of 10.49 and 8.19 μM, respectively. Nine structurally new α-santalol derivatives (4a-4h and 5) were synthesized to identify more selective and potent CB2 ligands. Compound 4e with a piperazine structural moiety demonstrated a Ki value of 0.99 μM against CB2 receptor and did not show binding activity against cannabinoid receptor type I (CB1) at 10 μM. Compounds 1, 2, and 4e increased intracellular calcium influx in SH-SY5Y human neuroblastoma cells that were attenuated by CB2 antagonism or inverse agonism, supporting the results that these compounds are CB2 agonists. Molecular docking showed that 1 and 4e had similar binding poses, exhibiting a unique interaction with Thr114 within the CB2 receptor, and that the piperazine structural moiety is required for the binding affinity of 4e. A 200 ns molecular dynamics simulation of CB2 complexed with 4e confirmed the stability of the complex. This structural insight lays a foundation to further design and synthesize more potent and selective α-santalol-based CB2 ligands for drug discovery.

Santalum Genus: phytochemical constituents, biological activities and health promoting-effects

Santalum genus belongs to the family of Santalaceae, widespread in India, Australia, Hawaii, Sri Lanka, and Indonesia, and valued as traditional medicine, rituals and modern bioactivities. Sandalwood is reported to possess a plethora of bioactive compounds such as essential oil and its components (α-santalol and β-santalol), phenolic compounds and fatty acids. These bioactives play important role in contributing towards biological activities and health-promoting effects in humans. Pre-clinical and clinical studies have shown the role of sandalwood extract as antioxidant, anti-inflammatory, antibacterial, antifungal, antiviral, neuroleptic, antihyperglycemic, antihyperlipidemic, and anticancer activities. Safety studies on sandalwood essential oil (EO) and its extracts have proven them as a safe ingredient to be utilized in health promotion. Phytoconstituents, bioactivities and traditional uses established sandalwood as one of the innovative materials for application in the pharma, food, and biomedical industry.

Elucidating the Role of Santalol as a Potent Inhibitor of Tyrosinase: In Vitro and In Silico Approaches

This research work focuses on the potential application of an organic compound, santalol, obtained from santalum album, in the inhibition of the enzyme tyrosinase, which is actively involved in the biosynthesis of melanin pigment. Over-production of melanin causes undesirable pigmentation in humans as well as other organisms and significantly downgrades their aesthetic value. The study is designed to explain the purification of tyrosinase from the mushroom Agaricus bisporus, followed by activity assays and enzyme kinetics to give insight into the santalol-modulated tyrosinase inhibition in a dose-dependent manner. The multi-spectroscopic techniques such as UV-vis, fluorescence, and isothermal calorimetry are employed to deduce the efficiency of santalol as a potential candidate against tyrosinase enzyme activity. Experimental results are further verified by molecular docking. Santalol, derived from the essential oils of santalum album, has been widely used as a remedy for skin disorders and a potion for a fair complexion since ancient times. Based on enzyme kinetics and biophysical characterization, this is the first scientific evidence where santalol inhibits tyrosinase, and santalol may be employed in the agriculture, food, and cosmetic industries to prevent excess melanin formation or browning.

Establishing Komagataella phaffii as a Cell Factory for Efficient Production of Sesquiterpenoid α-Santalene

Santalene, a major component of the sandalwood essential oil, is a typical representative of sesquiterpenes and has important applications in medicine, food, flavors, and other fields. Due to the limited supply of natural sandalwood resources, there is a growing interest in engineering microbial cell factories for the mass production of santalene. In the present study, Komagataella phaffii (also known as Pichia pastoris) was established as a cell factory for high-level production of α-santalene for the first time. The metabolic fluxes were rewired toward α-santalene biosynthesis through the optimization of promoters to drive the expression of the α-santalene synthase (SAS) gene, overexpression of the key mevalonate pathway genes (i.e., tHMG1, IDI1, and ERG20), and multi-copy integration of the SAS expression cassette. In combination with medium optimization and bioprocess engineering, the optimal strain (STE-9) was able to produce α-santalene with a titer as high as 829.8 ± 70.6 mg/L, 4.4 ± 0.3 g/L, and 21.5 ± 1.6 g/L in a shake flask, batch fermenter, and fed-batch fermenter, respectively. These represented the highest production of α-santalene ever reported, highlighting the advantages of K. phaffii cell factories for the production of terpenoids and other natural products.

Metabolic Engineering of Escherichia coli for Production of α-Santalene, a Precursor of Sandalwood Oil

α-Santalene belongs to a class of natural compounds with many physiological functions and medical applications. Advances in metabolic engineering enable non-native hosts (e.g., Escherichia coli) to produce α-santalene, the precursor of sandalwood oil. However, imbalances in enzymatic activity often result in a metabolic burden on hosts and repress the synthetic capacity of the desired product. In this work, we manipulated ribosome binding sites (RBSs) to optimize an α-santalene synthetic operon in E. coli, and the best engineered E. coli NA-IS_3D strain could produce α-santalene at a titer of 412 mg·L^-1. Concerning the observation of the inverse correlation between indole synthesis and α-santalene production, this study speculated that indole-associated amino acid metabolism would be competitive to the synthesis of α-santalene rather than indole toxicity itself. The deletion of tnaA could lead to a 1.5-fold increase in α-santalene production to a titer of 599 mg·L^-1 in E. coli tnaA^- NA-IS_3D. Our results suggested that the optimization of RBS sets of the synthetic module and attenuation of the competitive pathway are promising approaches for improving the production of terpenoids including α-santalene.

Prevention of post-surgical adhesion bands by local administration of frankincense n-hexane extract

Background

and purpose: The formation of postoperative intra-abdominal adhesion band formation may lead to severe complications. This study aimed to evaluate the preventive effect of local administration of frankincense n-hexane extract (FHE) on the formation of postsurgical adhesion bands.

Materials and methods

FHE was extracted from the resin of a Boswellia sacra tree and its components were identified by gas chromatography-mass spectrometry (GC-MS). In an animal model, the expression levels of TNF-α and TGF-β1 cytokines after application of FHE were assessed to check the inflammatory and fibrotic cues, respectively.

Results

Following FHE compound analysis, in vivo experiments demonstrated that intraoperative local administration of FHE resulted in the prevention of adhesion band formation. The adhesion grades in the FHE-treated group were significantly lower than those in the negative control (NC) and the positive control (Interceed). The infiltration of inflammatory cells observed by histopathology revealed a significant anti-inflammatory potential of FHE. Furthermore, the gene expression results proved that significant suppression of TNF-α and TGF-β1 was responsible for its antiadhesion properties.

Conclusions

The study reported the potential of FHE as an ointment for the prevention of adhesion bands.

•

Recognition of compounds with anti-inflammatory, antifibrotic activities in FHE using gas chromatography-mass spectrometry.

•

The avoidance of adhesion bands formation, in vivo following intraoperative local administration of FHE.

•

A notable anti-inflammatory potential of FHE detected by histopathology results.

•

Approving the regulation of TNF-α and TGF-β1 involved in the intra-abdomen adhesion preventive properties of FHE.

Potential use of wood metabolites for cancer treatment

The study of medicinal plants for cancer treatment has gained attention due to an increasing incidence of cancer worldwide and antineoplastics-related undesirable secondary effects. Most of the natural products of medicinal plants that have been evaluated for cytotoxic activity, are derived from leaves, bark, roots and flowers. However, natural products derived from wood have demonstrated a cytotoxic effect with promising results. Moreover, some fractions and compounds have been isolated of wood in order to increase the effect. This review presents in vitro experimental evidence of cytotoxic effect of natural products from wood against cancer cell lines. It also provides considerations and recommendations to obtain herbal medicines over time.

Cloning and expression analysis of mevalonate kinase and phosphomevalonate kinase genes associated with the MVA pathway in Santalum album

Sandalwood (Santalum album L.) is highly valued for its fragrant heartwood and extracted oil. Santalols, which are the main components of that oil, are terpenoids, and these are biosynthesized via the mevalonic acid (MVA) pathway. Mevalonate kinase (MK) and phosphomevalonate kinase (PMK) are key enzymes in the MVA pathway. Little is known about the genes that encode MK and PMK in S. album or the mechanism that regulates their expression. To isolate and identify the functional genes involved in santalol biosynthesis in S. album, an MK gene designated as SaMK, and a PMK gene designated as SaPMK, were cloned from S. album. The sequences of these genes were analyzed. A bioinformatics analysis was conducted to assess the homology of SaMK and SaPMK with MK and PMK genes from other plants. The subcellular localization of SaMK and SaPMK proteins was also investigated, as was the functional complementation of SaMK and SaPMK in yeast. Our results show that the full-length cDNA sequences of SaMK and SaPMK were 1409 bp and 1679 bp long, respectively. SaMK contained a 1381 bp open reading frame (ORF) encoding a polypeptide of 460 amino acids and SaPMK contained a 1527 bp ORF encoding a polypeptide of 508 amino acids. SaMK and SaPMK showed high homology with MK and PMK genes of other plant species. Functional complementation of SaMK in a MK-deficient mutant yeast strain YMR208W and SaPMK in a PMK-deficient mutant yeast strain YMR220W confirmed that cloned SaMK and SaPMK cDNA encode a functional MK and PMK, respectively, mediating MVA biosynthesis in yeast. An analysis of tissue expression patterns revealed that SaMK and SaPMK were constitutively expressed in all the tested tissues. SaMK was highly expressed in young leaves but weakly expressed in sapwood. SaPMK was highly expressed in roots and mature leaves, but weakly expressed in young leaves. Induction experiments with several elicitors showed that SaMK and SaPMK expression was upregulated by methyl jasmonate. These results will help to further study the role of MK and PMK genes during santalol biosynthesis in S. album.

A Comparison of the Composition of Selected Commercial Sandalwood Oils with the International Standard

Sandalwood oils are highly desired but expensive, and hence many counterfeit oils are sold in high street shops. The study aimed to determine the content of oils sold under the name sandalwood oil and then compare their chromatographic profile and α- and β santalol content with the requirements of ISO 3518:2002. Gas chromatography with mass spectrometry analysis found that none of the six tested “sandalwood” oils met the ISO standard, especially in terms of α-santalol content. Only one sample was found to contain both α- and β-santalol, characteristic of Santalum album. In three samples, valerianol, elemol, eudesmol isomers, and caryophyllene dominated, indicating the presence of Amyris balsamifera oil. Another two oil samples were found to be synthetic mixtures: benzyl benzoate predominating in one, and synthetic alcohols, such as javanol, polysantol and ebanol, in the other. The product label only gave correct information in three cases: one sample containing Santalum album oil and two samples containing Amyris balsamifera oil. The synthetic samples described as 100% natural essential oil from sandalwood are particularly dangerous and misleading to the consumer. Moreover, the toxicological properties of javanol, polysantol and ebanol, for example, are unknown.

Medicine in motion: Opportunities, challenges and data analytics-based solutions for traditional medicine integration into western medical practice

ETHNOPHARMACOLOGICAL RELEVANCE

Traditional pharmacopeias have been developed by multiple cultures and evaluated for efficacy and safety through both historical/empirical iteration and more recently through controlled studies using Western scientific paradigms and an increasing emphasis on data science methodologies for network pharmacology. Traditional medicines represent likely sources of relatively inexpensive drugs for symptomatic management as well as potential libraries of new therapeutic approaches. Leveraging this potential requires hard evidence for efficacy that separates science from pseudoscience.

MATERIALS AND METHODS

We performed a review of non-Western medical systems and developed case studies that illustrate the epistemological and practical translative barriers that hamper their transition to integration with Western approaches. We developed a new data analytics approach, in silico convergence analysis, to deconvolve modes of action, and potentially predict desirable components of TM-derived formulations based on computational consensus analysis across cultures and medical systems.

RESULTS

Abstraction, simplification and altered dose and delivery modalities were identified as factors that influence actual and perceived efficacy once a medicine is moved from a non-Western to Western setting. Case studies on these factors highlighted issues with translation between non-Western and Western epistemologies, including those where epistemological and medicinal systems drive markets that can be epicenters for zoonoses such as the novel Coronavirus. The proposed novel data science approach demonstrated the ability to identify and predict desirable medicinal components for a test indication, pain.

CONCLUSIONS

Relegation of traditional therapies to the relatively unregulated nutraceutical industry may lead healthcare providers and patients to underestimate the therapeutic potential of these medicines. We suggest three areas of emphasis for this field: First, vertical integration and embedding of traditional medicines into healthcare systems would subject them to appropriate regulation and evidence-based practice, as viable integrative implementation mode. Second, we offer a new Bradford-Hill-like framework for setting research priorities and evaluating efficacy, with the goal of rescuing potentially valuable therapies from the nutraceutical market and discrediting those that are pseudoscience. Third, data analytics pipelines offer new capacity to generate new types of TMS-inspired medicines that are rationally-designed based on integrated knowledge across cultures, and also provide an evaluative framework against which to test claims of fidelity and efficacy to TMS made for nutraceuticals.

A systems pharmacology approach to identify the autophagy-inducing effects of Traditional Persian medicinal plants

Aging is correlated with several complex diseases, including type 2 diabetes, neurodegeneration diseases, and cancer. Identifying the nature of this correlation and treatment of age-related diseases has been a major subject of both modern and traditional medicine. Traditional Persian Medicine (TPM) embodies many prescriptions for the treatment of ARDs. Given that autophagy plays a critical role in antiaging processes, the present study aimed to examine whether the documented effect of plants used in TPM might be relevant to the induction of autophagy? To this end, the TPM-based medicinal herbs used in the treatment of the ARDs were identified from modern and traditional references. The known phytochemicals of these plants were then examined against literature for evidence of having autophagy inducing effects. As a result, several plants were identified to have multiple active ingredients, which indeed regulate the autophagy or its upstream pathways. In addition, gene set enrichment analysis of the identified targets confirmed the collective contribution of the identified targets in autophagy regulating processes. Also, the protein-protein interaction (PPI) network of the targets was reconstructed. Network centrality analysis of the PPI network identified mTOR as the key network hub. Given the well-documented role of mTOR in inhibiting autophagy, our results hence support the hypothesis that the antiaging mechanism of TPM-based medicines might involve autophagy induction. Chemoinformatics study of the phytochemicals using docking and molecular dynamics simulation identified, among other compounds, the cyclo-trijuglone of Juglans regia L. as a potential ATP-competitive inhibitor of mTOR. Our results hence, provide a basis for the study of TPM-based prescriptions using modern tools in the quest for developing synergistic therapies for ARDs.

Network pharmacology-based therapeutic mechanism of Kuanxiong aerosol for angina pectoris

ETHNOPHARMACOLOGICAL RELEVANCE

Kuanxiong aerosol has been reported to be an effective and safe clinical treatment for angina pectoris (AP).

AIM OF THE STUDY

To explore the potential pharmacological mechanism of Kuanxiong aerosol by combined methods of network pharmacology prediction and experimental verification.

MATERIALS AND METHODS

Networks of Kuanxiong aerosol-associated targets and AP-related genes were constructed through STRING database. Potential targets and pathway enrichment analysis related to the therapeutic efficacy of Kuanxiong aerosol were identified using Cytoscape and Database for Annotation, Visualization and Integrated Discovery (DAVID). To explore the mechanism of action of Kuanxiong aerosol, its in vitro effects on myocardial hypoxia, inflammatory cytokines, and oxidative injury, and its in vivo pharmacological effects on myocardial ischemia and cardiac fibrosis were studied in rat models.

RESULTS

Network pharmacology analysis revealed that the potential targets mainly include the Fas ligand (FASLG), interleukin 4 (IL4), and catalase (CAT), which mediated the processes of apoptosis, and cellular responses to hypoxia, lipopolysaccharide (LPS), reactive oxygen species (ROS), and mechanical stimulus. Multiple pathways, such as the hypoxia-inducible factor 1 (HIF1) and tumor necrosis factor (TNF) pathways were found to be closely related to the pharmacological protective mechanism of Kuanxiong aerosol against AP. In addition, Kuanxiong aerosol suppressed the hypoxia, LPS, and hydrogen peroxide (H₂O₂)-induced injuries of H9c2 cardiomyocytes through the regulation of HIF1A, suppressed expression of IL6 and TNF, and antioxidant property. In the rat model of myocardial ischemia, Kuanxiong aerosol was found to lower the creatine kinase (CK), creatine kinase-myocardial band (CK-MB), and lactate dehydrogenase (LDH) levels, without altering the hemodynamic function. Kuanxiong aerosol was capable of attenuating cardiac fibrosis and improving cardiac function in a cardiac fibrosis rat model.

CONCLUSIONS

This study revealed that the pharmacological mechanisms of Kuanxiong aerosol for AP therapy were related to anti-myocardial ischemia, anti-inflammation, and anti-oxidation via a non-hemodynamic manner, indicating that Kuanxiong aerosol is a preferable drug clinically for AP treatment due to its both preventive and protective effects.

Investigation of the Adulteration of Essential Oils by GC-MS

Background:

A lack of regulation about the chemical composition of essential oils and the growing popularity of these oils among consumers presents an urgent need for the accurate characterization of various oil types from a variety of manufacturers. The aim of this paper was to characterize the composition of essential oils bought from a popular retail location, with the goal of understanding the chemical composition and presence of adulterants with potential toxicity.

Methods:

Reported herein is an investigation into the components of a variety of essential oils using gas chromatography-mass spectrometry (GC-MS). The investigation initially focused on two popular oils, tea tree and lavender oil, and then moved to investigate four additional essential oils from the same brand (sandalwood, rose, eucalyptus, and lemongrass).

Results:

Results of this analysis indicated that all six store brand essential oils contained Carbitol (in concentrations from 23% to 35%), and four of the six oils had diethyl phthalate (in concentrations ranging from 0.33% to 16%). These toxicants are particularly concerning because they are known inhalation hazards, and the intended usage of these oils is for aromatherapy (i.e. inhalation).

Conclusion:

These results highlight a potentially significant and under-reported health concern from inhalation of toxic contaminants in the store brand oils, and showcase the need for more regulation and transparency about the composition of these commercial products.

Essential Oils and Their Main Chemical Components: The Past 20 Years of Preclinical Studies in Melanoma

Simple Summary

In the last years, targeted therapy and immunotherapy modified the landscape for metastatic melanoma treatment. These therapeutic approaches led to an impressive improvement in patients overall survival. Unfortunately, the emergence of drug resistance and side effects occurring during therapy strongly limit the long-term efficacy of such treatments. Several preclinical studies demonstrate the efficacy of essential oils as antitumoral agents, and clinical trials support their use to reduce side effects emerging during therapy. In this review we have summarized studies describing the molecular mechanism through which essential oils induce in vitro and in vivo cell death in melanoma models. We also pointed to clinical trials investigating the use of essential oils in reducing the side effects experienced by cancer patients or those undergoing anticancer therapy. From this review emerged that further studies are necessary to validate the effectiveness of essential oils for the management of melanoma.

Abstract

The last two decades have seen the development of effective therapies, which have saved the lives of a large number of melanoma patients. However, therapeutic options are still limited for patients without BRAF mutations or in relapse from current treatments, and severe side effects often occur during therapy. Thus, additional insights to improve treatment efficacy with the aim to decrease the likelihood of chemoresistance, as well as reducing side effects of current therapies, are required. Natural products offer great opportunities for the discovery of antineoplastic drugs, and still represent a useful source of novel molecules. Among them, essential oils, representing the volatile fraction of aromatic plants, are always being actively investigated by several research groups and show promising biological activities for their use as complementary or alternative medicine for several diseases, including cancer. In this review, we focused on studies reporting the mechanism through which essential oils exert antitumor action in preclinical wild type or mutant BRAF melanoma models. We also discussed the latest use of essential oils in improving cancer patients’ quality of life. As evidenced by the many studies listed in this review, through their effect on apoptosis and tumor progression-associated properties, essential oils can therefore be considered as potential natural pharmaceutical resources for cancer management.

Characterization of Guaiene Synthases from Stellera chamaejasme L. Flowers and Their Application in De novo Production of (-)-Rotundone in Yeast

Four terpene synthases for the biosynthesis of volatile terpenoids were identified from the transcriptome of Stellera chamaejasme L. flowers, including SchTPS1, SchTPS2, SchTPS3, and SchTPS4. Their functions were characterized by synthetic biology approaches in Escherichia coli and in vitro enzymatic assays. SchTPS1, SchTPS2, and SchTPS3 are guaiene synthases, while SchTPS4 is an (E,E)-geranyl linalool synthase. Next, SchTPS1 and α-guaiene 2-oxidase VvSTO2 were co-expressed in Saccharomyces cerevisiae to reconstruct the biosynthetic pathway of (-)-rotundone, which is a unique aroma compound in fruits, vegetables, and wines. This is the first report for the construction of a (-)-rotundone-producing microbial platform.

Sesquiterpenes in grapes and wines: Occurrence, biosynthesis, functionality, and influence of winemaking processes

Grapes are an important global horticultural product, and are mainly used for winemaking. Typically, grapes and wines are rich in various phytochemicals, including phenolics, terpenes, pyrazines, and benzenoids, with different compounds responsible for different nutritional and sensory properties. Among these compounds, sesquiterpenes, a subcategory of the terpenes, are attracting increasing interest as they affect aroma and have potential health benefits. The characteristics of sesquiterpenes in grapes and wines in terms of classification, biosynthesis pathway, and active functions have not been extensively reviewed. This paper summarizes 97 different sesquiterpenes reported in grapes and wines and reviews their biosynthesis pathways and relevant bio-regulation mechanisms. This review further discusses the functionalities of these sesquiterpenes including their aroma contribution to grapes and wines and potential health benefits, as well as how winemaking processes affect sesquiterpene concentrations.

Sedative and hypnotic effects of compound Anshen essential oil inhalation for insomnia

BACKGROUNDS

The chemical composition of many essential oils indicates that they have sedative and hypnotic effects, but there is still a lack of systematic studies on the sedative and hypnotic effects of essential oils. In addition, aromatherapy does not seem to have the side effects of many traditional psychotropic substances, which is clearly worthwhile for further clinical and scientific research. The clinical application of essential oils in aromatherapy has received increasing attention, and detailed studies on the pharmacological activities of inhaled essential oils are increasingly needed.

HYPOTHESIS/PURPOSE

As insomniacs are usually accompanied by symptoms of depression and anxiety of varying degrees, based on the theory of aromatherapy of Traditional Chinese Medicine, this experiment is to study a Compound Anshen essential oil that is compatible with Lavender essential oil, Sweet Orange essential oil, Sandalwood essential oil and other aromatic medicine essential oils with sedative and hypnotic effects, anti-anxiety and anti-depression effects. To study the sedative and hypnotic effects of Compound Anshen essential oil inhaled and the main chemical components of Compound Anshen essential oil, and to compare and analyze the pharmacodynamics of diazepam, a commonly used drug for insomnia.

METHODS

The Open field test and Pentobarbital-induced sleep latency and sleep time experiments were used to analyze and compare the sedative and hypnotic effects of inhaling Compound Anshen essential oil and the administration of diazepam on mice. The changes of 5-HT and GABA in mouse brain were analyzed by Elisa. The main volatile constituents of Compound Anshen essential oil were analyzed by gas chromatography-mass spectrometry (GC-MS).

RESULTS

Inhalation of Compound Anshen essential oil can significantly reduce the spontaneous activity of mice, reduce latency of sleeping time and prolong duration of sleeping time. The results of enzyme-linked immunosorbent assay showed that Compound Anshen essential oil can increase the content of 5-HT and GABA in mouse brain. The main volatile chemical constituents of the Compound Anshen essential oil are D-limonene (24.07%), Linalool (21.98%), Linalyl acetate (15.37%), α-Pinene (5.39%), and α-Santalol (4.8%).

CONCLUSION

The study found that the inhalation of Compound Anshen essential oil has sedative and hypnotic effect. This study provides a theoretical basis for further research and development of the sedative and hypnotic effects of Compound Anshen essential oil based on the theory of aromatherapy.

East Indian sandalwood (Santalum album L.) oil confers neuroprotection and geroprotection in Caenorhabditis elegans via activating SKN-1/Nrf2 signaling pathway

East Indian Sandalwood Oil (EISO) has diverse beneficial effects and has been used for thousands of years in traditional folk-medicine for treatment of different human ailments. However, there has been no in-depth scientific investigation to decipher the neuroprotective and geroprotective mechanism of EISO and its principle components, α- and β-santalol. Hence the current study was undertaken to assess the protective effects of EISO, and α- and β-santalol against neurotoxic (6-OHDA/6-hydroxydopamine) and proteotoxic (α-synuclein) stresses in a Caenorhabditis elegans model. Initially, we found that EISO and its principle components exerted an excellent antioxidant and antiapoptotic activity as it was able to extend the lifespan, and inhibit the ROS generation, and germline cell apoptosis in 6-OHDA-intoxicated C. elegans. Further, we showed that supplementation of EISO, and α- and β-santalol reduced the 6-OHDA and α-synuclein-induced Parkinson's disease associated pathologies and improved the physiological functions. The genetic and reporter gene expression analysis revealed that an EISO, or α- and β-santalol-mediated protective effect does not appear to rely on DAF-2/DAF-16, but selectively regulates SKN-1 and its downstream targets involved in antioxidant defense and geroprotective processes. Together, our findings indicated that EISO and its principle components are worth exploring further as a candidate redox-based neuroprotectant for the prevention and management of age-related neurological disorders.

East Indian Sandalwood Oil Is a Phosphodiesterase Inhibitor: A New Therapeutic Option in the Treatment of Inflammatory Skin Disease

Cyclic adenosine monophosphate phosphodiesterases (PDEs) regulate pro-inflammatory cytokine production. One isoform, PDE4, is overactive in chronic relapsing inflammatory skin diseases: psoriasis and eczema/atopic dermatitis, and in several cancers. East Indian sandalwood oil (EISO) has significant anti-inflammatory properties. Here, we report that 75% of pediatric eczema/atopic dermatitis patients treated with topical EISO formulations achieved a >50% reduction in their Eczema Area and Severity Index score. EISO treatment of a psoriasis model reduced PDE4 expression and reversed histopathology. EISO directly inhibited PDE enzymatic activity in vitro. In lipopolysaccharide-stimulated human dermal fibroblast, BEAS-2B, A549, and THP-1 cells, EISO suppressed total cellular PDE activity, PDE4, and 7 transcript levels, nuclear factor kappa B (NF-κB) activation, and pro-inflammatory cytokines/chemokine production. These results suggest that EISO anti-inflammatory activity is mediated through suppressing PDE activity, thus facilitating cAMP-regulated inhibition of NF-κB and indicate EISO as an attractive natural therapeutic for chronic and acute inflammatory disorders.