Chemical Constituents and Pharmacological Activity of Agarwood and Aquilaria Plants

Sesquiterpenoids in Agarwood: Biosynthesis, Microbial Induction, and Pharmacological Activities

Agarwood, derived from the Aquilaria genus, is widely utilized in perfumery, traditional medicine, and cultural practices throughout Asia. Agarwood is rich in terpenes, especially sesquiterpenes, which are considered to be the source of its rare and exquisite fragrance. This Review consolidates recent research on sesquiterpene biosynthesis in agarwood and the influence of fungi on these processes, alongside a discussion of the potential medicinal value of agarwood sesquiterpenes. This Review commences by elucidating the general biosynthesis of sesquiterpenes and identifying the main enzymes and transcription factors involved in the production of agarwood sesquiterpenes. This Review also summarizes the fungi associated with agarwood and highlights how commensal fungi stimulate agarwood and sesquiterpene production. We then scrutinize the pharmacological properties of sesquiterpenes, underscoring their anti-inflammatory and antimicrobial effects, which are closely linked to cellular signaling pathways, such as the NF-κB and MAPK pathways. Additionally, we review the potential therapeutic benefits of agarwood essential oil for its antidepressant properties, which are linked to the regulation of stress-related neurochemical and hormonal pathways. This Review also addresses the challenges of sustainable agarwood production, highlighting issues such as overharvesting and habitat loss while discussing the potential strategy of harnessing microbes in agarwood production to support the ecological preservation of wild resources. By advancing our knowledge of agarwood and sesquiterpene characteristics, we propose potential directions for the future application and sustainable development of agarwood research.

Aromatic components and endophytic fungi during the formation of agarwood in Aquilaria sinensis were induced by exogenous substances

The process of formation of aromatic components for agarwood in Aquilaria sinensis is closely related to endophytic fungi and the result of complex multiple long-term joint interactions with them. However, the interactions between the aromatic components and endophytic fungi remain unclear during the formation of agarwood. In this study, precise mixed solution of hormones, inorganic salts, and fungi was used to induce its formation in A. sinensis, and sample blocks of wood were collected at different times after inoculation. This study showed that the aromatic compounds found in the three treatments of A. sinensis were primarily chromones (31.70-33.65%), terpenes (16.68-27.10%), alkanes (15.99-23.83%), and aromatics (3.13-5.07%). Chromones and terpenes were the primary components that characterized the aroma. The different sampling times had a more pronounced impact on the richness and diversity of endophytic fungal communities in the A. sinensis xylem than the induction treatments. The species annotation of the operational taxonomic units (OTUs) demonstrated that the endophytic fungi were primarily composed of 18 dominant families and 20 dominant genera. A linear regression analysis of the network topology properties with induction time showed that the interactions among the fungal species continued to strengthen, and the network structure tended to become more complex. The terpenes significantly negatively correlated with the Pielou evenness index (p < 0.05), while the chromones significantly positively correlated with the OTUs and Shannon indices.

Bioeconomy and ethnopharmacology - Translational perspective and sustainability of the bioresources of northeast region of India

ETHNOPHARMACOLOGICAL RELEVANCE

The ecological environment of Northeast region of India (NER), with its high humidity, has resulted in greater speciation and genetic diversity of plant, animal, and microbial species. This region is not only rich in ethnic and cultural diversity, but it is also a major biodiversity hotspot. The sustainable use of these bioresources can contribute to the region's bioeconomic development.

AIM OF THE STUDY

The review aimed to deliver various perspectives on the development of bioeconomy from NER bioresources under the tenets of sustainable utilization and socioeconomic expansion.

MATERIALS AND METHODS

Relevant information related to prospects of the approaches and techniques pertaining to the sustainable use of ethnomedicine resources for the growth of the bioeconomy were retrieved from PubMed, ScienceDirect, Google Scholar, Scopus, and Springer from 1984 to 2023. All the appropriate abstracts, full-text articles and various book chapters on bioeconomy and ethnopharmacology were conferred.

RESULT

As the population grows, so does the demand for basic necessities such as food, health, and energy resources, where insufficient resource utilization and unsustainable pattern of material consumption cause impediments to economic development. On the other hand, the bioeconomy concept leads to "the production of renewable biological resources and the conversion of these resources and waste streams into value-added products.

CONCLUSIONS

In this context, major emphasis should be placed on strengthening the economy's backbone in order to ensure sustainable use of these resources and livelihood security; in other words, it can boost the bio-economy by empowering the local people in general.

Dynamics of Physiological Properties and Endophytic Fungal Communities in the Xylem of Aquilaria sinensis (Lour.) with Different Induction Times

Xylem-associated fungus can secrete many secondary metabolites to help Aquilaria trees resist various stresses and play a crucial role in facilitating agarwood formation. However, the dynamics of endophytic fungi in Aquilaria sinensis xylem after artificial induction have not been fully elaborated. Endophytic fungi communities and xylem physio-biochemical properties were examined before and after induction with an inorganic salt solution, including four different times (pre-induction (0M), the third (3M), sixth (6M) and ninth (9M) month after induction treatment). The relationships between fungal diversity and physio-biochemical indices were evaluated. The results showed that superoxide dismutase (SOD) and peroxidase (POD) activities, malondialdehyde (MDA) and soluble sugar content first increased and then decreased with induction time, while starch was heavily consumed after induction treatment. Endophytic fungal diversity was significantly lower after induction treatment than before, but the species richness was promoted. Fungal β-diversity was also clustered into four groups according to different times. Core species shifted from rare to dominant taxa with induction time, and growing species interactions in the network indicate a gradual complication of fungal community structure. Endophytic fungi diversity and potential functions were closely related to physicochemical indices that had less effect on the relative abundance of the dominant species. These findings help assess the regulatory mechanisms of microorganisms that expedite agarwood formation after artificial induction.

Salty treatment increased bioactive compounds accumulation during agarwood development in Aquilaria sinensis trees

To compare the bioactive compounds in agarwood induced by different methods in Aquilaria sinensis(Lour.) Gilg trees, a two dimensional thin layer chromatograph(2D-TLC) combined with effect directive analysis(EDA) was developed. Three antioxidants were found by 2D-TLC-DPPH and further identified as 2-(2-phenylethyl) chromones(PECs) with LC-MS/MS. The 3 antioxidants decreased along agarwood formation and their compositions in drilling induced agarwood differed with those in microbe culture induced agarwood. Further study showed NaCl treatment promoted antioxidants accumulation in agarwood induced by drilling or hot drilling. Hot drilling combined with salty stimulation was most efficient in some chemicals accumulation, which were identified as PECs with antioxidant, tyrosinase or β-glucosidase inhibiting activities by 2D-TLC-EDA-LC-MS/MS. This study provided a 2D-TLC-EDA-LC-MS/MS method for bioactive compounds screen and qualification of agarwood. Based on this method, non-conventional methods were found to accelerate the accumulation of some bioactive PECs in A. sinensis trees.

Biological and Medicinal Properties of Natural Chromones and Chromanones

Emerging threats to human health require a concerted effort to search for new treatment therapies. One of the biggest challenges is finding medicines with few or no side effects. Natural products have historically contributed to major advances in the field of pharmacotherapy, as they offer special characteristics compared to conventional synthetic molecules. Interest in natural products is being revitalized, in a continuous search for lead structures that can be used as models for the development of new medicines by the pharmaceutical industry. Chromone and chromanones are recognized as privileged structures and useful templates for the design of diversified therapeutic molecules with potential pharmacological interest. Chromones and chromanones are widely distributed in plants and fungi, and significant biological activities, namely antioxidant, anti-inflammatory, antimicrobial, antiviral, etc., have been reported for these compounds, suggesting their potential as lead drug candidates. This review aims to update the literature published over the last 6 years (2018-2023) regarding the natural occurrence and biological activity of chromones and chromanones, highlighting the recent findings and the perspectives that they hold for future research and applications namely in health, cosmetic, and food industries.

Chemical Investigation on the Volatile Part of the CO2 Supercritical Fluid Extract of Infected Aquilaria sinensis (Chinese Agarwood)

This work is focused on the characterization of the composition of a CO2 supercritical fluid extract of Aquilaria sinensis (Chinese agarwood) collected in the Dongguan area (China) and infected by mechanical methods. The constituents of this extract were analyzed by gas chromatography-mass spectrometry (GC-MS) and quantified accurately by gas chromatography with a flame ionization detector (GC-FID), using an internal reference and predicted response factors. Since a significant number of components of this extract remained non-identified after the initial GC-MS analysis of the whole extract, its fractionation by chromatography on silica gel helped to characterize several additional constituents by isolation and structural analysis by NMR spectroscopy. The main components are the classical agarwood chromones (Flindersia chromone and its mono-, di-, and trimethoxylated analogues (respectively, 11.01% and 0.11-4.02%) along with sesquiterpenic constituents typically found in agarwood essential oils, like baimuxinal (1.90%) and kusunol (1.24%), as well as less common selinane dialdehydes (1.58-2.27%) recently described in the literature. Moreover, the structure and stereochemistry of a new sesquiterpenic alcohol, 14β,15β-dimethyl-7αH-eremophila-9,11-dien-8β-ol (0.67%), was determined unambiguously by the combination of structural analysis (NMR, MS), hemisynthesis, and total synthesis, leading to dihydrokaranone and a neopetasane epimer.

Applications and advancements of nanoparticle-based drug delivery in alleviating lung cancer and chronic obstructive pulmonary disease

Lung cancer (LC) and chronic obstructive pulmonary disease (COPD) are among the leading causes of mortality worldwide. Cigarette smoking is among the main aetiologic factors for both ailments. These diseases share common pathogenetic mechanisms including inflammation, oxidative stress, and tissue remodelling. Current therapeutic approaches are limited by low efficacy and adverse effects. Consequentially, LC has a 5-year survival of < 20%, while COPD is incurable, underlining the necessity for innovative treatment strategies. Two promising emerging classes of therapy against these diseases include plant-derived molecules (phytoceuticals) and nucleic acid-based therapies. The clinical application of both is limited by issues including poor solubility, poor permeability, and, in the case of nucleic acids, susceptibility to enzymatic degradation, large size, and electrostatic charge density. Nanoparticle-based advanced drug delivery systems are currently being explored as flexible systems allowing to overcome these limitations. In this review, an updated summary of the most recent studies using nanoparticle-based advanced drug delivery systems to improve the delivery of nucleic acids and phytoceuticals for the treatment of LC and COPD is provided. This review highlights the enormous relevance of these delivery systems as tools that are set to facilitate the clinical application of novel categories of therapeutics with poor pharmacokinetic properties.

Network pharmacology-based strategy combined with molecular docking to explore the potential mechanism of agarwood against recurrent aphthous stomatitis

To explore the antiinflammatory mechanism of agarwood on recurrent aphthous stomatitis (RAS). RAS is the most common mucosal disease in the oral cavity. The clinical application of traditional Chinese medicine found that agarwood has significant curative effect on peptic ulcer, but the effect and mechanism of agarwood on RAS remain unclear. This study is intended to predict the potential antiinflammatory mechanisms by which agarwood acts on RAS through network pharmacology and molecular docking. TCMSP database was used to screen the active components of agarwood. RAS targets were screened in Genecards, DisGeNET, and OMIM database. Venny, an online tool, screens for interacting genes between the two. Cytoscape software was used to construct the gene regulation map of active compounds target of agarwood. String Database building protein-protein interaction network. Gene ontology and Kyoto Encyclopedia of Genes and Genomes pathways were enriched in DAVID database. The key active ingredients and core targets were further verified by molecular docking. There were 9 effective compounds and 186 target genes in agarwood; RAS has 793 target genes. There were 41 interacting genes between agarwood and RAS. Interleukin 6, tumor necrosis factor, interleukin 1 beta, and cellular component motif ligand 2 may be key targets. Gene ontology and Kyoto Encyclopedia of Genes and Genomes enrichment analyses predicted multiple pathways associated with RAS. Molecular docking results showed that the active compounds of agarwood combined well and stably with the target. The Chinese herbal medicine agarwood can relieve the inflammation of RAS through multiple targets and various ways. Its active compounds may be nominated as candidates for antiinflammatory drugs of RAS.

Ethnopharmacologically important highly subsidized Indian medicinal plants: Systematic review on their traditional uses, phytochemistry, pharmacology, quality control, conservation status and future prospective

ETHNOPHARMACOLOGICAL RELEVANCE

India has an extensive reservoir of traditional wisdom and a diverse range of medicinal plants that enrich its heritage. Plants have actively been used for healthcare practices globally since the time immemorial. Medicinal uses of plants have been well recognized in India, evident from plant species documented in different traditional medicinal systems such as Ayurveda (1400-1800 species), Siddha (500-900 species), Unani (400-700 species), Homeopathy (about 372 species), and Sowa-Rigpa (about 250 species), etc. AIM OF THE STUDY: The primary purpose of this review is to provide systematic updated information on thirteen medicinal plants prioritized by the Indian government (providing75 % subsidy on cultivation cost) based on the availability and market demand of these plants. Updated information regarding the traditional uses, phytochemistry, pharmacology, quality control, and conservation status of these plants will help in understanding their pharmacological and commercial importance. This will also help in developing new strategies for their conservation.

MATERIAL AND METHODS

Online databases such as SciFinder, Web of Science, Pubmed, and Google Scholar were used to collect the electronically available literature on targeted thirteen plants. Also, different Indian government official websites such as AYUSH (https://www.ayush.gov.in); NMPB (National Medicinal Plants Board) (https://nmpb.nic.in); e.charak (https://echarak.in) were used for collecting information related to the amount of subsidy, trade and price related information of these plants.

RESULTS

To promote medicinal plant cultivation, the Indian government provides subsidies for cultivating some traditionally important medicinal plants. These plants are divided into three categories according to the subsidy provided to farmers, i.e., 30%, 50%, and 75% of the cost of cultivation. Thirteen medicinal plants which are provided 75% subsidy are Aconitum ferox Wall., Aconitum heterophyllum Wall., Aquilaria agallocha Roxb., Berberis aristata DC., Commiphora wightii (Arn.) Bhandari, Nardostachys jatamansi (D.Don) DC., Oroxylum indicum (L.) Benth. ex Kurz, Picrorhiza kurroa Royle ex Benth., Podophyllum hexandrum Royle, Pterocarpus santalinus L.f., Santalum Album L., Saussurea costus (Falc.) Lipsch., and Swertia chirayita (Roxb.) H.Karst. The literature survey reveals the enormous traditional medicinal importance, wide geographical distribution, diverse range of natural products, and broad spectrum of pharmacological activities of these plants.

CONCLUSION

A comprehensive literature survey revealed that although remarkable progress has been made in isolation, bioactivity evaluation, quality assessment, and conservation, there is still a lot of scope for further scientific interventions. Scientific validation of traditionally claimed medicinal potential is lacking for various bioactivities. Some of the bioactivities are performed just on extracts/fractions, so there is a need for proper phytochemical studies to identify active constituents responsible for the specific bioactivity. Further, quality assessment methods using both targeted and non-targeted tools are required to evaluate the quality of these highly-priced medicinal plants and their adulterants. Ultimately, to encourage the cultivation of these endangered medicinal plant species, it is imperative to implement proper legislation and employ in-situ and ex-situ conservation tools.

2-(2-Phenylethyl)chromone-enriched extract of Chinese agarwood (Aquilaria sinensis) inhibits atherosclerosis progression through endoplasmic reticulum stress-mediated CD36 expression in macrophages

ETHNOPHARMACOLOGICAL RELEVANCE

Chinese agarwood, derived from the Aquilaria sinensis (Lour.) Gilg (Thymelaeaceae), has a long history of use in Traditional Chinese Medicine for the management of cardiovascular disease. However, the specific active ingredients responsible for its impact on atherosclerosis are yet to be fully understood.

AIM OF THE STUDY

The aim of this study is to investigate the anti-atherosclerotic effectiveness of the 2-(2-phenylethyl)chromone-enriched extract derived from Chinese agarwood (CPE) through the ER stress-mediated CD36 pathway.

MATERIALS AND METHODS

To assess the effectiveness of CPE, an atherosclerotic mouse model was established using ApoE-/- mice with a high-fat diet. Then we assessed the impact of CPE on lipid accumulation in THP-1 macrophages that were exposed to oxLDL. Subsequently, the effect of CPE on the expression of CD36 and markers related to ER stress was characterized.

RESULTS

Our in vivo research confirmed that CPE effectively reduces the formation of aortic plaques in atherosclerotic ApoE-/- mice. Additionally, our in vitro study observed that CPE inhibits the uptake of oxLDL and hinders the generation of foam cells. This effect is achieved by downregulating the level of CD36 in macrophages. Furthermore, our study revealed that the increase in CD36 expression, resulting from oxLDL exposure, is governed by the activation of JNK1/2/3 signaling pathways and the initiation of ER stress.

CONCLUSION

CPE demonstrated significant efficacy to inhibit the atherosclerosis. The ER stress/P-JNK/PPARγ/CD36 signaling pathway plays critical involvement in modulating the foam cell formation in vitro and in vivo. These findings underscore the efficacy of CPE as a viable therapeutic intervention for the treatment of atherosclerosis.

Solid-Phase Microextraction/Gas Chromatography-Time-of-Flight Mass Spectrometry Approach Combined with Network Pharmacology Analysis to Evaluate the Quality of Agarwood from Different Regions against Anxiety Disorder

Agarwood (Aquilaria malaccensis Lam.) is a resinous material from different geographical locations. The current evaluation of agarwood quality is usually based on its physical properties and chemical compounds, yet only a few studies have linked agarwood quality with its anxiolytic effect, as indicated by characteristic compounds. In this study, using solid-phase microextraction/gas chromatography-time-of-flight mass spectrometry (SPME/GC-TOFMS) and multivariate analysis, we found 116 significantly different compounds in agarwood samples from four locations in Southeast Asia with regard to their quality. Brunei and Nha Trang agarwood had abundant sesquiterpenoids, exhibiting notable pharmacological efficacy in relieving anxiety. Malaysian and Irian agarwood had abundant alcohols and aldehydes, qualifying them as high-quality spices. Compound-target-disease network and pathway enrichment analysis were further employed to predict 79 gene targets and 20 pathways associated with the anxiolytic effects based on the 62 sesquiterpenoids. The correlated relationships among the sesquiterpenoids and targets suggest that agarwood treats anxiety via multiple compounds acting on multiple targets. Varying levels of sesquiterpenes across agarwood groups might lead to differences in the anxiolytic effects via signaling pathways, such as neurotransmitter- and hormone-regulated pathways. Our study originally evaluates agarwood quality and its anxiolytic effect by linking the characteristic compounds to potential gene targets and pathways.

Agarwood oil nanoemulsion counteracts LPS-induced inflammation and oxidative stress in RAW264.7 mouse macrophages

PURPOSE

Oxidative stress and inflammation are key pathophysiological features of chronic respiratory diseases, including asthma and chronic obstructive pulmonary disease (COPD). Agarwood oil obtained from Aquilaria trees has promising antioxidant and anti-inflammatory activities. However, its clinical application is hampered by poor solubility. A viable approach to overcome this involves formulation of oily constituents into emulsions. Here, we have investigated the antioxidant and anti-inflammatory potential of an agarwood oil-based nanoemulsion (DE'RAAQSIN) against lipopolysaccharide (LPS)-induced RAW264.7 mouse macrophages in vitro.

METHODS

The antioxidant and anti-inflammatory activity of DE'RAAQSIN was assessed by measuring the levels of ROS and nitric oxide (NO) produced, using the DCF-DA assay and the Griess reagent assay, respectively. The molecular pathways activated by DE'RAAQSIN were investigated via qPCR.

RESULTS

LPS stimulation of RAW264.7 cells increased the production of nitric oxide (NO) and ROS and resulted in the overexpression of the inducible nitric oxide synthase (iNOS) gene. Furthermore, LPS induced the upregulation of the expression of key proinflammatory genes (IL-6, TNF-α, IL-1β, and CXCL1) and of the antioxidant gene heme oxygenase-1 (HO-1). DE'RAAQSIN demonstrated potent antioxidant and anti-inflammatory activity by significantly reducing the levels of ROS and of secreted NO, simultaneously counteracting the LPS-induced overexpression of iNOS, IL-6, TNF-α, IL-1β, and HO-1. These findings were corroborated by in silico activity prediction and physicochemical analysis of the main agarwood oil components.

CONCLUSIONS

We propose DE'RAAQSIN as a promising alternative managing inflammatory disorders, opening the platform for further studies aimed at understanding the effectiveness of DE'RAAQSIN.

Investigating the potential anti-inflammatory mechanism of benzophenone compounds from the leaves of Aquilaria sinensis (Lour.) Gilg based on network pharmacology and molecular docking strategies

BACKGROUND

Aquilaria sinensis (Lour.) Gilg (ASG) has been used as traditional medicine for centuries. However, the active ingredients from leaves and their anti-inflammatory mechanism are rarely reported. The network pharmacology and molecular docking strategies were applied to explore the potential mechanisms of Benzophenone compounds from the leaves of ASG (BLASG) against inflammation.

METHODS

BLASG-related targets were obtained from the SwissTargetPrediction and PharmMapper databases. Inflammation-associated targets were retrieved from GeneGards, DisGeNET, and CTD databases. Cytoscape software was used to draw a network diagram of BLASG and its corresponding targets. DAVID database was applied for enrichment analyses. A protein-protein interaction (PPI) network was constructed to identify the hub targets of BLASG. Molecular docking analyses were performed by AutoDockTools 1.5.6. Moreover, we used ELISA and qRT-PCR assays to validate the anti-inflammatory effects of BLASG by cell experiments.

RESULTS

Four BLASG were extracted from ASG, and corresponding 225 potential targets were identified. PPI network analysis indicated that SRC, PIK3R1, AKT1, and other targets were the core therapeutic targets. Enrichment analyses revealed that the effects of BLASG are regulated by targets associated with apoptosis and inflammation-related pathways. In addition, molecular docking revealed that BLASG combined well with PI3K and AKT1. Furthermore, BLASG significantly decreased the inflammatory cytokines levels and down-regulated PIK3R1 and AKT1 gene expression in RAW264.7 cells.

CONCLUSION

Our study predicted the potential targets and pathways of BLASG against inflammation, which offered a promising strategy to reveal the therapeutic mechanism of natural active components in the treatment of diseases.

Metabolite profiling of Borneo's Gonystylus bancanus through comprehensive extraction from various polarity of solvents

Gonystylus bancanus wood or ramin wood has been generally known as a source of agarwood (gaharu) bouya, a kind of agarwood inferior type, or under the exported trading name of aetoxylon oil. The massive exploitation of ramin wood is causing this plant's extinction and putting it on Appendix II CITES and IUCN Red List of Threatened Species. To date, no scientific publication concerns the chemical exploration of G. bancanus wood and preserving this germplasm through its metabolite profiling. Therefore, research focused on chemical components profiling of G. bancanus is promised. This research is aimed to explore metabolomics and analyze the influence of solvent polarities on the partitioning of metabolites in G. bancanus wood. A range of solvents in different polarities was applied to provide comprehensive extraction of metabolites in G. bancanus wood. Moreover, a hydrodistillation was also carried out to extract the volatile compounds despite the non-volatile ones. LCMS and GCMS analyses were performed to identify volatile and non-volatile components in the extracts and essential oil. Multivariate data analysis was processed using Principal Component Analysis (PCA) and agglomerative hierarchical clustering. 142 metabolites were identified by LCMS analysis, while 89 metabolites were identified by GCMS analysis. Terpenoids, flavonoids, phenyl propanoids, and saccharides are some major compound classes available from LCMS data. Oxygenated sesquiterpenes, especially 10-epi-γ-eudesmol, and β-eudesmol, are the major volatile components identified from GCMS analysis. PCA of LCMS analysis demonstrated that PC1 discriminated two clusters: essential oil, dichloromethane, and n-hexane extracts were in the positive quadrant, while methanol and ethyl acetate extracts were in the negative quadrant. Three-dimensional analysis of GCMS data revealed that n-hexane extract was in the superior quadrant, and its composition can be significantly distinguished from other extracts and essential oil. G. bancanus wood comprises valuable metabolites, i.e., terpenoids, which benefit the essential oil industry. Comprehensive extraction by performing solvents in different polarities on G. bancanus wood could allow exploration of fully extracted metabolites, supported by the exhibition of identified metabolites from LCMS and GCMS analysis.

Identification of a diarylpentanoid-producing polyketide synthase in the biosynthesis of 2-(2-phenylethyl)chromones in agarwood

Agarwood has been valued as an exquisite, high-grade fragrant wood since ancient times. Due to the scarcity of high-quality agarwood, it is quite expensive, and the number of original plants has been drastically reduced due to overharvesting, including illegal logging. Despite this, a reliable method of agarwood cultivation has yet to be developed. Thus, identifying the biosynthetic pathways of the fragrant components in agarwood might help developers to optimize the culture conditions and create artificial agarwood, by monitoring the expression of the biosynthetic enzymes or their genes. This review presents the characteristics of our recently identified key enzyme, 2-(2-phenylethyl)chromone precursor synthase (PECPS), which generates the common precursor of 2-(2-phenylethyl)chromones (PECs), the main fragrances in agarwood, as well as our reasoning to reach these conclusions. We also discuss the biosynthetic pathway of PECs, unveiled following the identification of PECPS.

Wound-Induced Temporal Reprogramming of Gene Expression during Agarwood Formation in Aquilaria sinensis

Agarwood is a resinous heartwood of Aquilaria sinensis that is formed in response to mechanical wounding. However, the transcriptional response of A. sinensis to mechanical wounding during the agarwood formation process is still unclear. Here, three five-year-old A. sinensis trees were mechanically damaged by a chisel, and time-series transcriptomic analysis of xylem tissues in the treated area (TA) was performed at 15 (TA1), 70 (TA2) and 180 days after treatment (TA3). Samples from untreated areas at the corresponding time points (UA1, UA2, UA3, respectively) were collected as controls. A total of 1862 (TA1 vs. UA1), 961 (TA2 vs. UA2), 1370 (TA3 vs. UA3), 3305 (TA2 vs. TA1), 2625 (TA3 vs. TA1), 2899 (TA3 vs. TA2), 782 (UA2 vs. UA1), 4443 (UA3 vs. UA1) and 4031 (UA3 vs. UA2) genes were differentially expressed (DEGs). Functional enrichment analysis showed that DEGs were significantly enriched for secondary metabolic processes, signal transduction and transcriptional regulation processes. Most of the genes involved in lignin biosynthesis were more abundant in the TA groups, which included phenylalanine ammonia-lyase, 4-coumarate CoA ligase, cinnamate 4-hydroxylase, caffeoyl-CoA O-methyltransferase and cinnamoyl-CoA reductase. DEGs involved in sesquiterpene biosynthesis were also identified. Hydroxymethylglutaryl-CoA synthase, 3-hydroxy-3-methylglutaryl-coenzyme A reductase, phosphomevalonate kinase and terpene synthase genes were significantly increased in the TA groups, promoting sesquiterpene biosynthesis in the wounded xylem tissues. The TF-gene transcriptomic networks suggested that MYB DNA-binding, NAM, WRKY, HLH and AP2 TFs co-expressed with genes related to lignin and sesquiterpene synthesis, indicating their critical regulatory roles in the biosynthesis of these compounds. Overall, our study reveals a dynamic transcriptional response of A. sinensis to mechanical wounding, provides a resource for identifying candidate genes for molecular breeding of agarwood quality, and sheds light on the molecular mechanisms of agarwood formation in A. sinensis.

Five new sesquiterpenoids from agarwood of Aquilaria sinensis

Five new eudesmane-type sesquiterpenoids (aquisinenoids F-J (1-5)) and five known compounds (6-10) were isolated from the agarwood of Aquilaria sinensis. Their structures, including absolute configurations, were identified by comprehensive spectroscopic analyses and computational methods. Inspired by our previous study on the same kinds of skeletons, we speculated that the new compounds have anticancer and anti-inflammatory activities. The results did not show any activity, but they revealed the structure-activity relationships (SAR).

Genome-wide investigation of Cytochrome P450 superfamily of Aquilaria agallocha: Association with terpenoids and phenylpropanoids biosynthesis

Agarwood is a dark resinous wood, produced when Aquilaria tree responds to wounding and microbial infection resulting in the accumulation of fragrant metabolites. Sesquiterpenoids and 2-(2-phenylethyl) chromones are the major phytochemicals in agarwood and Cytochrome P450s (CYPs) are one of the important enzymes in the biosynthesis of these fragrant chemicals. Thus, understanding the repertoire of CYP superfamily in Aquilaria can not only give insights into the fundamentals of agarwood formation, but can also provide a tool for the overproduction of the aroma chemicals. Therefore, current study was designed to investigate CYPs of an agarwood producing plant, Aquilaria agallocha. We identified 136 CYP genes from A. agallocha genome (AaCYPs) and classified them into 8 clans and 38 families. The promoter regions had stress and hormone-related cis-regulatory elements which indicate their participation in the stress response. Duplication and synteny analysis revealed segmental and tandem duplicated and evolutionary related CYP members in other plants. Potential members involved in the biosynthesis of sesquiterpenoids and phenylpropanoids were identified and found to be upregulated in methyl jasmonate-induced callus and infected Aquilaria trees by real-time quantitative PCR analyses. This study highlights the possible involvement of AaCYPs in agarwood resin development and their complex regulation during stress exposure.

Agarwood Oil Nanoemulsion Attenuates Cigarette Smoke-Induced Inflammation and Oxidative Stress Markers in BCi-NS1.1 Airway Epithelial Cells

Chronic obstructive pulmonary disease (COPD) is an irreversible inflammatory respiratory disease characterized by frequent exacerbations and symptoms such as cough and wheezing that lead to irreversible airway damage and hyperresponsiveness. The primary risk factor for COPD is chronic cigarette smoke exposure, which promotes oxidative stress and a general pro-inflammatory condition by stimulating pro-oxidant and pro-inflammatory pathways and, simultaneously, inactivating anti-inflammatory and antioxidant detoxification pathways. These events cause progressive damage resulting in impaired cell function and disease progression. Treatments available for COPD are generally aimed at reducing the symptoms of exacerbation. Failure to regulate oxidative stress and inflammation results in lung damage. In the quest for innovative treatment strategies, phytochemicals, and complex plant extracts such as agarwood essential oil are promising sources of molecules with antioxidant and anti-inflammatory activity. However, their clinical use is limited by issues such as low solubility and poor pharmacokinetic properties. These can be overcome by encapsulating the therapeutic molecules using advanced drug delivery systems such as polymeric nanosystems and nanoemulsions. In this study, agarwood oil nanoemulsion (agarwood-NE) was formulated and tested for its antioxidant and anti-inflammatory potential in cigarette smoke extract (CSE)-treated BCi-NS1.1 airway basal epithelial cells. The findings suggest successful counteractivity of agarwood-NE against CSE-mediated pro-inflammatory effects by reducing the expression of the pro-inflammatory cytokines IL-1α, IL-1β, IL-8, and GDF-15. In addition, agarwood-NE induced the expression of the anti-inflammatory mediators IL-10, IL-18BP, TFF3, GH, VDBP, relaxin-2, IFN-γ, and PDGF. Furthermore, agarwood-NE also induced the expression of antioxidant genes such as GCLC and GSTP1, simultaneously activating the PI3K pro-survival signalling pathway. This study provides proof of the dual anti-inflammatory and antioxidant activity of agarwood-NE, highlighting its enormous potential for COPD treatment.

RNA-Sequencing Reveals the Involvement of Sesquiterpene Biosynthesis Genes and Transcription Factors during an Early Response to Mechanical Wounding of Aquilaria sinensis

Plants respond to wounding by reprogramming the expression of genes involved in secondary metabolism. Aquilaria trees produce many bioactive secondary metabolites in response to wounding, but the regulatory mechanism of agarwood formation in the early response to mechanical wounding has remained unclear. To gain insights into the process of transcriptome changes and to determine the regulatory networks of Aquilaria sinensis to an early response (15 days) to mechanical wounding, we collected A. sinensis samples from the untreated (Asc1) and treated (Asf1) xylem tissues and performed RNA sequencing (RNA-seq). This generated 49,102,523 (Asc1) and 45,180,981 (Asf1) clean reads, which corresponded to 18,927 (Asc1) and 19,258 (Asf1) genes, respectively. A total of 1596 differentially expressed genes (DEGs) were detected in Asf1 vs. Asc1 (|log2 (fold change)| ≥ 1, Padj ≤ 0.05), of which 1088 were up-regulated and 508 genes were down-regulated. GO and KEGG enrichment analysis of DEGs showed that flavonoid biosynthesis, phenylpropanoid biosynthesis, and sesquiterpenoid and triterpenoid biosynthesis pathways might play important roles in wound-induced agarwood formation. Based on the transcription factor (TF)-gene regulatory network analysis, we inferred that the bHLH TF family could regulate all DEGs encoding for farnesyl diphosphate synthase, sesquiterpene synthase, and 1-deoxy-D-xylulose-5-phosphate synthase (DXS), which contribute to the biosynthesis and accumulation of agarwood sesquiterpenes. This study provides insight into the molecular mechanism regulating agarwood formation in A. sinensis, and will be helpful in selecting candidate genes for improving the yield and quality of agarwood.

Endophytic Fungi Associated with Aquilaria sinensis (Agarwood) from China Show Antagonism against Bacterial and Fungal Pathogens

Agarwood is the most expensive non-construction wood product in the world. As a therapeutic agent, agarwood can cure some diseases, but few studies have been carried out on the antagonistic abilities of endophytic fungi associated with agarwood. Agarwood is mainly found in the genus Aquiaria. The objectives of this study are to understand the antimicrobial activities and their potential as biocontrol agents of the endophytic fungi of Aquilaria sinensis. First, fresh samples of A. sinensis were collected from Yunnan and Guangdong Provinces in 2020-2021, and the endophytic fungi were isolated and identified to genus level based on the phylogenetic analyses of the Internal Transcribed Spacer (ITS) region. In this bioassay, 47 endophytic strains were selected to check their bioactivities against three bacterial pathogens viz. Erwinia amylovora, Pseudomonas syringae, and Salmonella enterica; and three fungal pathogens viz. Alternaria alternata, Botrytis cinerea, and Penicillium digitatum. The antibiosis test was carried out by the dual culture assay (10 days), and among the 47 strains selected, 40 strains belong to 18 genera viz. Alternaria, Annulohypoxylon, Aspergillus, Botryosphaeria, Colletotrichum, Corynespora, Curvularia, Daldinia, Diaporthe, Fusarium, Lasiodiplodia, Neofusicoccum, Neopestalotiopsis, Nigrospora, Paracamarosporium, Pseudopithomyces, Trichoderma, Trichosporon and one strain belongs to Xylariaceae had antimicrobial activities. In particular, Lasiodiplodia sp. (YNA-D3) showed the inhibition of all the bacterial and fungal pathogens with a significant inhibition rate. In addition, the strains viz; Curvularia sp. (GDA-3A9), Diaporthe sp. (GDA-2A1), Lasiodiplodia sp. (YNA-D3), Neofusicoccum sp. (YNA-1C3), Nigrospora sp. (GDA-4C1), and Trichoderma sp. (YNA-1C1) showed significant antimicrobial activities and are considered worthy of further studies to identify individual fungal species and their bioactive compounds. This study enriches the diversity of endophytic fungi associated with agarwood, and their potential antagonistic effects against bacterial and fungal pathogens.

New 2-(2-Phenylethyl)chromone derivatives from agarwood originating from Aquilaria sinensis

Two new dimeric 2-(2-phenylethyl)chromones, aquilasinenones L and M (1 and 2), and one new monomer analogue, 5S, 6 R, 7S, 8 R-tetrahydroxy-[2-(3-methoxy-4-hydroxyphenyl)ethyl]- 5,6,7,8-tetrahydrochromone (3), together with two known compounds, were isolated from the artificial agarwood originating from Aquilaria sinensis. Compound 1 was the first structure found with C8-O-C4"' linkage among 2-(2-phenylethyl)chromone dimers. Their structures were unambiguously elucidated based on 1 D and 2 D NMR spectroscopy, as well as by comparison with the literature. The absolute configuration was determined by ECD calculation. None of the compounds exhibited acetylcholinesterase inhibitory activity.

Next-generation sequencing in the biodiversity conservation of endangered medicinal plants

Medicinal plants have been used as traditional herbal medicines in the treatment of various types of diseases. However, the increased demand for these plants highlights the importance of conservation specifically for endangered species. Significant advancements in next-generation sequencing (NGS) technologies have accelerated medicinal plant research while reducing costs and time demands. NGS systems enable high-throughput whole genome sequencing as well as direct RNA sequencing and transcriptome analysis. The sequence data sets created can be used in a variety of areas of study, including biodiversity conservation, comparative genomics, transcriptomic analysis, single cell mining, metagenomics, epigenetics, molecular marker discovery, multi genome sequencing, and so on. Commercial sequencing service providers are constantly working to improve technologies to address bioinformatics problems in NGS data analysis. Several genome sequencing projects on medicinal plants have been completed recently and a few more are in the works. In some medicinal plants, massive NGS-based data has been developed. In the present review, we have attempted to briefly discuss advancements in NGS technology on medicinally essential plants in India. The review will also provide ideas for applying NGS technologies for exploring genomes of various endangered medicinal plants whose genome sequences are not normally available and thus provides valuable insights for the conservation of these vulnerable species.

The Role of Myrrh Metabolites in Cancer, Inflammation, and Wound Healing: Prospects for a Multi-Targeted Drug Therapy

Background: Myrrh extract is a well-known medicinal plant with significant therapeutic benefits attributed to the activity of its diverse metabolites. It has promising activity against cancer and inflammatory diseases, and could serve as a potential therapeutic alternative since most therapeutic agents have severe side effects that impair quality of life. Method: The current study identified the active metabolites from the myrrh resin methanolic extract. Then, the extracts were tested for in vitro anti-inflammatory and anti-cancer activity using cancer cell lines and Tamm-Horsfall Protein 1 (Thp-1)-like macrophage cell lines. Furthermore, using an in vivo rat model, the extracts’ anti-inflammatory and wound-healing activity was investigated. In addition, in silico predictions of the myrrh constituents highlighted the pharmacokinetic properties, molecular targets, and safety profile, including cytochrome P 450 (CYP) inhibition and organ toxicity. Results: Nine secondary metabolites were identified, and computational predictions suggested a good absorption profile, anticancer, anti-inflammatory, and wound-healing effects. The myrrh extract had moderate cytotoxic activity against both HL60 and K562 leukemia cell lines and the KAIMRC1 breast cancer cell line. Myrrh caused a dose-dependent effect on macrophages to increase the reactive oxygen species (ROS) levels, promote their polarization to classically activated macrophages (M1) and alternatively activated macrophages (M2) phenotypes, and consequently induce apoptosis, highlighting its ability to modulate macrophage function, which could potentially aid in several desired therapeutic processes, including the resolution of inflammation, and autophagy which is an important aspect to consider in cancer treatment. The topical application of myrrh improved wound healing, with no delayed inflammatory response, and promoted complete re-epithelization of the skin, similar to the positive control. In conclusion, we provide evidence for the methanolic extract of myrrh having cytotoxic activity against cancer cells and anti-inflammatory wound-healing properties, which may be attributed to its role in modulating macrophage function. Furthermore, we suggest the active constituents responsible for these properties, which warrants further studies focusing on the precise roles of the active metabolites.

Agarwood-The Fragrant Molecules of a Wounded Tree

Agarwood, popularly known as oudh or gaharu, is a fragrant resinous wood of high commercial value, traded worldwide and primarily used for its distinctive fragrance in incense, perfumes, and medicine. This fragrant wood is created when Aquilaria trees are wounded and infected by fungi, producing resin as a defense mechanism. The depletion of natural agarwood caused by overharvesting amidst increasing demand has caused this fragrant defensive resin of endangered Aquilaria to become a rare and valuable commodity. Given that instances of natural infection are quite low, artificial induction, including biological inoculation, is being conducted to induce agarwood formation. A long-term investigation could unravel insights contributing toward Aquilaria being sustainably cultivated. This review will look at the different methods of induction, including physical, chemical, and biological, and compare the production, yield, and quality of such treatments with naturally formed agarwood. Pharmaceutical properties and medicinal benefits of fragrance-associated compounds such as chromones and terpenoids are also discussed.

Rediscovering the Therapeutic Potential of Agarwood in the Management of Chronic Inflammatory Diseases

The inflammatory response is a central aspect of the human immune system that acts as a defense mechanism to protect the body against infections and injuries. A dysregulated inflammatory response is a major health concern, as it can disrupt homeostasis and lead to a plethora of chronic inflammatory conditions. These chronic inflammatory diseases are one of the major causes of morbidity and mortality worldwide and the need for them to be managed in the long term has become a crucial task to alleviate symptoms and improve patients’ overall quality of life. Although various synthetic anti-inflammatory agents have been developed to date, these medications are associated with several adverse effects that have led to poor therapeutic outcomes. The hunt for novel alternatives to modulate underlying chronic inflammatory processes has unveiled nature to be a plentiful source. One such example is agarwood, which is a valuable resinous wood from the trees of Aquilaria spp. Agarwood has been widely utilized for medicinal purposes since ancient times due to its ability to relieve pain, asthmatic symptoms, and arrest vomiting. In terms of inflammation, the major constituent of agarwood, agarwood oil, has been shown to possess multiple bioactive compounds that can regulate molecular mechanisms of chronic inflammation, thereby producing a multitude of pharmacological functions for treating various inflammatory disorders. As such, agarwood oil presents great potential to be developed as a novel anti-inflammatory therapeutic to overcome the drawbacks of existing therapies and improve treatment outcomes. In this review, we have summarized the current literature on agarwood and its bioactive components and have highlighted the potential roles of agarwood oil in treating various chronic inflammatory diseases.

Identification of a diarylpentanoid-producing polyketide synthase revealing an unusual biosynthetic pathway of 2-(2-phenylethyl)chromones in agarwood

2-(2-Phenylethyl)chromones (PECs) are the principal constituents contributing to the distinctive fragrance of agarwood. How PECs are biosynthesized is currently unknown. In this work, we describe a diarylpentanoid-producing polyketide synthase (PECPS) identified from Aquilaria sinensis. Through biotransformation experiments using fluorine-labeled substrate, transient expression of PECPS in Nicotiana benthamiana, and knockdown of PECPS expression in A. sinensis calli, we demonstrate that the C6-C5-C6 scaffold of diarylpentanoid is the common precursor of PECs, and PECPS plays a crucial role in PECs biosynthesis. Crystal structure (1.98 Å) analyses and site-directed mutagenesis reveal that, due to its small active site cavity (247 Å3), PECPS employs a one-pot formation mechanism including a "diketide-CoA intermediate-released" step for the formation of the C6-C5-C6 scaffold. The identification of PECPS, the pivotal enzyme of PECs biosynthesis, provides insight into not only the feasibility of overproduction of pharmaceutically important PECs using metabolic engineering approaches, but also further exploration of how agarwood is formed.

Inhalation Administration of Agarwood Incense Rescues Scopolamine-Induced Learning and Memory Impairment in Mice

Background: Agarwood, a type of herbal medicine widely used in Asian countries, is noted in traditional medicine for its intelligence-enhancing effects. Agarwood incense is traditionally administered by oral and nasal inhalation. To verify whether agarwood incense can exert its intelligence-enhancing effects in this way to rescue learning and memory impairment, typical clinical manifestations of dementia, we conducted a set of behavioral tests related to learning and memory.

Methods: C57BL/6 mice were divided into six groups. In addition to the control and model groups, we added a donepezil treatment group to evaluate the effect of three different agarwood administration doses. After a week of administration, scopolamine was injected 30 min before each behavioral test to create a learning and memory impairment model. A series of behavioral tests [the Morris water maze test (MWM), the novel object recognition test (NOR), and the step-down test (SDT)] were used to assess their learning ability, as well as their spatial and recognition memory.

Results: After scopolamine injection, the model group showed significant learning and memory impairment (i.e., longer latencies, lower crossing times, and lesser distance travelled in the target quadrant in MWM; a lower recognition index in NOR; and longer latencies and higher error times in SDT). The other four treatment groups all showed improvements in these indicators, and the overall therapeutic effect of agarwood was superior.

Conclusion: The inhalation administration of agarwood can significantly improve the learning and memory impairment caused by scopolamine in mice, and the therapeutic effect varied between doses.

In Vitro Inhibitory Effects of Agarwood Tea (Aquilaria malaccensis Lamk) Aqueous Extract on Human Cytochrome P450 (CYP) Enzyme Activities

BACKGROUND

Agarwood tea derived from Aquilaria malaccensis Lamk is becoming an increasingly popular herbal drink that is said to have multiple health benefits. Co-administration of this tea and clinical used drugs is possible, but it increases the risk of drug-herb interactions.

OBJECTIVE

This in vitro study investigated the inhibitory effects of agarwood tea aqueous extract on the eight major human drug-metabolising cytochrome P450 (CYP) enzyme activities.

METHODS

High-throughput fluorescence-based Vivid® CYP450 screening kits were employed to obtain the enzyme activities before and after incubation with agarwood tea aqueous extract.

RESULTS

Agarwood aqueous extract potently inhibited CYP2C9, CYP2D6, and CYP3A4 activities with Ki values of 5.1, 34.5, and 20.3μg/ml, respectively. The most likely inhibition mode responsible for these inhibitions was non-competitive inhibition. On the other hand, at 1000μg/ml, agarwood tea aqueous extract negligibly inhibited CYP1A2, CYP2B6, CYP2C19, CYP2E1, and CYP3A5 activities.

CONCLUSION

These findings can be used to design additional in vitro investigations using clinical relevant drug substrates for CYP2C9, CYP2D6, and CYP3A4. Subsequently, future studies can be conducted to determine potential interactions between agarwood tea aqueous extract and CYP using in vivo models.

The Chemistry of Agarwood Odorants

The phytochemistry of the fragrant infected heartwood of Aquilaria and Gyrinops species, agarwood (oud), is critically reviewed, highlighting the use of this remarkable natural raw material in perfumery. The chemistry of the two main groups of constituents of agarwood (sesquiterpenoids and chromones) is discussed, focusing particularly on the former structural type. The identities of the main key odorants of agarwood essential oil and of the smoke produced by heating the wood of agarwood are also discussed.

Aquilaria Species (Thymelaeaceae) Distribution, Volatile and Non-Volatile Phytochemicals, Pharmacological Uses, Agarwood Grading System, and Induction Methods

Agarwood is a highly valuable fragrant wood of Aquilaria spp. (Thymelaeaceae) which has been widely utilized in traditional medicine, religious rites, and cultural activities. This study summarizes a review on the identification of Aquilaria cultivars, volatile and non-volatile phytochemicals, pharmacological uses, and agarwood grading system to determine its quality, and different agarwood induction methods. Due to the highly demanding and depleted natural resources, the research on agarwood is still insufficient, and it has broad research and development prospects in many industries. However, due to the significant scientific nature of agarwood application, developing high-quality products and drugs from agarwood have become highly important, while no one has discussed in detail the phytochemicals uses and provided a summary until now. The main phytochemicals of agarwood include terpenoids, dominated by sesquiterpenes. For centuries, terpenoids have been used in traditional Chinese medicine and have been shown to possess various pharmacological properties, including bacteriostatic, antibacterial, sedation, analgesia, anti-inflammation, anti-asthmatic, hypoglycemic, antidepressant, and many others. Alongside biological activity screening, phytochemical advances and pharmacological research have also made certain progress. Therefore, this review discusses the research progress of agarwood in recent years and provides a reference basis for further study of Aquilaria plants and agarwood.

Eudesmane-type and agarospirane-type sesquiterpenes from agarwood of Aquilaria agallocha

Eleven previously unreported sesquiterpenes, including nine eudesmane-type (agalleudesmanol A-I) and two agarospirane-type sesquiterpenes (agarospiranic aldehyde A-B), together with eight known sesquiterpenes, were isolated from the agarwood of Aquilaria agallocha Roxb. The structures were established based on extensive spectroscopic analyses, including infrared (IR), high-resolution electrospray ionisation mass spectrometry (HRESIMS), nuclear magnetic resonance (NMR), X-ray diffraction, quantum chemical calculations based on empirical electronic circular dichroism (ECD) data, and DP4+ probability analysis. The bioactivity of these undescribed compounds against lipopolysaccharide (LPS)-induced NO production in RAW 264.7 cells was evaluated. Compounds 1 and 2 exhibited significant anti-inflammatory activities, with IC₅₀ values of 5.46-14.07 μM (aminoguanidine as positive control, IC₅₀ 20.33 ± 1.08 μM).

An integrated chemical characterization based on FT-NIR, GC-MS and LC-MS for the comparative metabolite profiling of wild and cultivated agarwood

Agarwood is a well-known and precious traditional Chinese medicine, has been widely applied as drugs and spices for century. The large demand for this material has deeply stimulated the emergence of numerous cultivated products. However, it is difficult to distinguish wild agarwood from cultivated agarwood, and the chemical composition difference between them is not clear. In this study, an integrated method of Fourier transform near-infrared (FT-NIR), gas chromatography-mass spectrometry (GC-MS) and ultraperformance liquid chromatography Quadrupole-Exactive Orbitrap tandem mass spectrometry (UHPLC-Q-Exactive Orbitrap/MS) was developed to explore chemical variation between wild and cultivated agarwood in combination with multivariate statistical analysis. Twenty-four wild and cultivated agarwood samples were collected from different regions. FT-NIR profiles were used to obtain the holistic metabolic characterization in combination with principal component analysis (PCA). A total of seventy-six and seventy-nine metabolites, including volatile components and 2-(2-phenethyl) chromones derivatives, were successfully identified by GC-MS and UHPLC-Q-Exactive Orbitrap/MS, respectively. Thereafter, the orthogonal-partial least square method-discriminant analysis (OPLS-DA) and variable importance in the projection (VIP) were used to screen potential characteristic chemical components (VIP > 1) in wild and cultivated agarwood, respectively. Finally, eight key chemical markers were putatively identified by two techniques to distinguish agarwood from different origins, which can be found that sesquiterpenes, aromatics, terpenoids, 2-(2-phenylethyl) chromones of the flidersia type (FTPECs) and tetrahydro-2-(2-phenylethyl) chromones (THPECs) are the most important metabolites. Summary, this research presented a comprehensive metabolomic variation between wild and cultivated agarwood on the basis of a multi-technology platform, which laid a foundation for distinguishing the two ecotypes of agarwood and was conducive to the quality control of this resource.

Sesquiterpenoids and 2-(2-Phenylethyl)chromone Derivatives from the Resinous Heartwood of Aquilaria sinensis

One novel spirolactone, aquilarisinolide (1), three new sesquiterpenoids, (2R,4S,5R,7R)-2-hydroxyeremophila-9,11-dien-8-one (2), (1R,4S,5S,7R,11R)-13-hydroxyepidaphnauran-9-en-8-one (3), and (4R,5S,7R,8S,10S,13R)-8,13-dihydroxyrotunda-1,11-dien-3-one (4), together with 13 known compounds (5-17) were isolated from the resinous heartwood of Aquilaria sinensis (Thymelaeaceae). The structures of the new compounds were elucidated based on the analysis of NMR and MS data and theoretical calculations their ECD spectra. The isolated compounds were evaluated for their protective activities against PC12 cell injury induced by corticosterone (CORT) and 1-methyl-4-phenylpyridine ion (MPP+), as well as inhibitory activities against BACE1. Compound 4, 5,6-dihydroxy-2-(2-phenylethyl)chromone (5), daphnauranol B (7), 6-methoxy-2-[2-(3-methyoxyphenyl)ethyl]chromone (10), isoagarotetrol (14), and 1-hydroxy-1,5-diphenylpentan-3-one (16) showed significant protective effects on CORT-induced injury in PC12 cells at a concentration of 20 μM (P < 0.001). Isoagarotetrol (14) showed a significant protective effect on MPP+-induced injury in PC12 cells at a concentration of 20 μM (P < 0.001), while compound 4 showed a moderate activity (P < 0.01). The BACE1-inhibitory activities of all tested compounds were very weak with less than 30% inhibition at a concentration of 20 μM.

A tetraploidization event shaped the Aquilaria sinensis genome and contributed to the ability of sesquiterpenes synthesis

BACKGROUND

Agarwood, generated from the Aquilaria sinensis, has high economic and medicinal value. Although its genome has been sequenced, the ploidy of A. sinensis paleopolyploid remains unclear. Moreover, the expression changes of genes associated with agarwood formation were not analyzed either.

RESULTS

In the present work, we reanalyzed the genome of A. sinensis and found that it experienced a recent tetraploidization event ~ 63-71 million years ago (Mya). The results also demonstrated that the A. sinensis genome had suffered extensive gene deletion or relocation after the tetraploidization event, and exhibited accelerated evolutionary rates. At the same time, an alignment of homologous genes related to different events of polyploidization and speciation were generated as well, which provides an important comparative genomics resource for Thymelaeaceae and related families. Interestingly, the expression changes of genes related to sesquiterpene synthesis in wounded stems of A. sinensis were also observed. Further analysis demonstrated that polyploidization promotes the functional differentiation of the key genes in the sesquiterpene synthesis pathway.

CONCLUSIONS

By reanalyzing its genome, we found that the tetraploidization event shaped the A. sinensis genome and contributed to the ability of sesquiterpenes synthesis. We hope that these results will facilitate our understanding of the evolution of A. sinensis and the function of genes involved in agarwood formation.

Genome-wide detection and classification of terpene synthase genes in Aquilaria agallochum

Agarwood, one of the precious woods in the globe, is produced by Aquilaria plant species during an upshot of wounding and infection. Produced as a defence response, the dark, fragrant resin gets secreted in the plant's duramen, which is impregnated with fragrant molecules with the due course. Agarwood has gained worldwide popularity due to its high aromatic oil, fragrance, and pharmaceutical value, which makes it highly solicited by numerous industries. Predominant chemical constituents of agarwood, sesquiterpenoids, and 2-(2-phenylethyl) chromones have been scrutinized to comprehend the scientific nature of the fragrant wood and develop novel products. However, the genes involved in the biosynthesis of these aromatic compounds are still not comprehensively studied in Aquilaria. In this study, publicly available genomic and transcriptomics data of Aquilaria agallochum were integrated to identify putative functional terpene synthase genes (TPSs). The in silico study enabled us to identify ninety-six TPSs, of which thirty-nine full-length genes were systematically classified into TPS-a, TPS-b, TPS-c, TPS-e, TPS-f, and TPS-g subfamilies based on their gene structure, conserve motif, and phylogenetic comparison with TPSs from other plant species. Analysis of the cis-regulatory elements present upstream of AaTPSs revealed their association with hormone, stress and light responses. In silico expression studies detected their up-regulation in stress induced tissue. This study provides a basic understanding of terpene synthase gene repertoire in Aquilaria agallochum and unlatches opportunities for the biochemical characterization and biotechnological exploration of these genes.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s12298-021-01040-z.

LC-PDA-MS/MS-Based Characterization of Key Phytochemicals in Eurycoma Longifolia Roots

The objective of the study was to fractionate the crude extract of Eurycoma longifolia (E. longifolia) roots and identify the intense peaks using HPLC-PDA-MS/MS, UPLC-MS/MS and H-NMR. Column chromatography was used to fractionate the crude extract into individual fractions using six solvent systems ranged from ethyl acetate, methanol and water in increasing polarity. Two fractions with nearly pure and intense peaks were selected for compound identification. Chromenone (coumarin) and chromone derivatives were putatively identified, besides several previously reported quassinoid glycosides (eurycomanone derived glycoside, 2,3-dehydro-4α-hydroxylongilactone glucoside, eurycomanol glycoside and eurycomanol trimer) in the fraction 11 of 100% methanol. A newly reported compound, namely hydroxyl glyyunanprosapogenin D (838 g/mol) was proposed to be the compound detected in the fraction 11 of 50% ethyl acetate and 50% methanol. This is also the first study to report the identification of chromenones and chromones in E. longifolia extract.

Novel serotonin-boosting effect of incense smoke from Kynam agarwood in mice: The involvement of multiple neuroactive pathways

ETHNOPHARMACOLOGICAL RELEVANCE

Stress is a state of feeling that inhibits one from responding properly in the face of a threat. Agarwood smoke has been used in traditional medicine as a sedative anti-anxious, and anti-restless therapy. Its scent emitted from heat induces people to enter a stable state; however, the underlying molecular effect is still unclear.

AIM OF THE STUDY

This study analyzed novel biological events and gene expression signatures induced by agarwood incense smoke in mice.

MATERIALS AND METHODS

Incense smoke was produced by heating at 150 °C for 30 min in a headspace autosampler oven. We treated mice with exposure to incense smoke from Kynam agarwood for 45 min/day for 7 consecutive days. After a 7-day inhalation period, the potent agarwood smoke affected-indicators in serum were measured, and the RNA profiles of the mouse brains were analyzed by microarray to elucidate the biological events induced by agarwood incense smoke.

RESULTS

Chemical profile analysis showed that the major component in the incense smoke of Kynam was 2-(2-phenylethyl) chromone (26.82%). Incense smoke from Kynam induced mice to enter a stable state and increased the levels of serotonin in sera. The emotion-related pathways, including dopaminergic synapse, serotonergic synapse, GABAergic synapse, long-term depression and neuroactive ligand-receptor interaction, were significantly affected by incense smoke. Moreover, the expression of Crhr2 and Chrnd genes, involved with neuroactive ligand-receptor interaction pathway, was upregulated by incense smoke.

CONCLUSIONS

By a newly-established incense smoke exposure system, we first identified that anti-anxious and anti-depressant effects of agarwood incense smoke were likely associated with the increase of serotonin levels and multiple neuroactive pathways in mice.

Volatile Constituents of Endophytic Fungi Isolated from Aquilaria sinensis with Descriptions of Two New Species of Nemania

Algae, bacteria, and fungi, as well as higher plants, produce a wide variety of secondary metabolites known as natural products. Natural products are well known as remarkable sources of many therapeutic agents. The genus Nemania is a wood-decaying fungus that belongs to family Xylariaceae. Nemania is often found as an endophyte in diverse hosts and some species are known to produce useful secondary metabolites. In this study, two Nemania species were isolated as an endophytic fungus from Aquilaria sinensis. Multi-gene phylogenetic studies showed that the newly described strains of Nemania are new to science, and this is the first report of Nemania from the host Aquilaria. One of the fermented species, Nemania aquilariae (KUMCC 20-0268), resulted in five sesquiterpenoids, which were previously reported from agarwood, and their structures were identified by gas chromatography-mass spectrometry (GC-MS). In addition, five different media were investigated in vitro to optimize conditions for growing the fungal biomass of Nemania aquilariae and N. yunnanensis.

The Combination of Aquilaria sinensis (Lour.) Gilg and Aucklandia costus Falc. Volatile Oils Exerts Antidepressant Effects in a CUMS-Induced Rat Model by Regulating the HPA Axis and Levels of Neurotransmitters

The Aquilaria sinensis (Lour.) Gilg (CX)-Aucklandia costus Falc. (MX) herbal pair is frequently used in traditional Chinese medicine prescriptions for treating depression. The volatile oil from CX and MX has been shown to have good pharmacological activities on the central nervous system, but its curative effect and mechanism in the treatment of depression are unclear. Therefore, the antidepressant effect of the volatile oil from CX-MX (CMVO) was studied in chronic unpredictable mild stress (CUMS) rats. The suppressive effects of CMVO (25, 50, 100 μL/kg) against CUMS-induced depression-like behavior were evaluated using the forced swimming test (FST), open field test (OFT) and sucrose preference test (SPT). The results showed that CMVO exhibited an antidepressant effect, reversed the decreased sugar preference in the SPT and prolongation of immobility time in the FST induced by CUMS, increased the average speed, time to enter the central area, total moving distance, and enhanced the willingness of rats to explore the environment in the OFT. Inhalational administration of CMVO decreased levels of adrenocorticotropic hormone and corticosterone in serum and the expression of corticotropin-releasing hormone mRNA in the hypothalamus, which indicated regulation of over-activation of the hypothalamic-pituitary-adrenal (HPA) axis. In addition, CMVO restored levels of 5-hydroxytryptamine (5-HT), dopamine, norepinephrine and acetylcholine in the hippocampus. The RT-PCR and immunohistochemistry results showed that CMVO up-regulated the expression of 5-HT_1A mRNA. This study demonstrated the antidepressant effect of CMVO in CUMS rats, which was possibly mediated via modulation of monoamine and cholinergic neurotransmitters and regulation of the HPA axis.

Neuroprotective compounds from the resinous heartwood of Aquilaria sinensis

Six undescribed compounds, including three sesquiterpenoids [(4S,5S,7S,8S,11R)-7-hydroxyguai-1(10)-en-8,12-olide, aquilarisinone, and 2Z,7(13),9E-humulatrien-12-ol-5-one], one diphenylpentanone [1-(2-hydroxyphenyl)-5-phenylpentan-3-one], and two 2-(2-phenylethyl)chromones (6-epiagarotetrol and triepoxyhexahydrochromone A), along with 15 known compounds, were isolated from the resinous heartwood of Aquilaria sinensis (Thymelaeaceae). Their structures were determined by mass (MS) and nuclear magnetic resonance (NMR) spectroscopic data. The absolute configuration of (4S,5S,7S,8S,11R)-7-hydroxyguai-1(10)-en-8,12-olide was confirmed by X-ray diffraction analysis, and the configurations of (4S,7S,8S,10R,11R)-7,10-epoxyguai-1(5)-en-8,12-olide, aquilarisinone, 6-epiagarotetrol, and triepoxyhexahydrochromone A were confirmed by electronic circular dichroism (ECD) calculations. The neuroprotective activities of the compounds were evaluated using models of BACE1 inhibition and PC12 cells with corticosterone- and 1-methyl-4-phenylpyridine ion (MPP⁺)-induced damage. At concentrations of 1, 2, and 5 μM, triepoxyhexahydrochromone A, (+)-(7R,10R)-selina-4,11(13)-diene-12,15-dial, (-)-(5R,7R,10R)-12,15-dioxo-α-selinene, and (+)-(1R,4S,5R)-1β-hydroxyeremophila-7(11),9-dien-8-one exerted significant protective effects (p < 0.01) on PC12 cell injury induced by corticosterone, while triepoxyhexahydrochromone A and (-)-(5R,7R,10R)-12,15-dioxo-α-selinene exerted significant protective effects (p < 0.01) on MPP⁺-induced PC12 cell injury at concentrations of 1, 2, and 5 μM. No compounds produced significant inhibitory effects on BACE1, with inhibition rates of less than 20% observed at a concentration of 20 μM.

UHPLC-QTOF-MS based metabolite profiling analysis and the correlation with biological properties of wild and artificial agarwood

To date, the agarwood has been over exploited worldwide in the wild due to high demand. As an alternative, the agarwood obtained through artificial methods has greatly resolved the shortage of agarwood supply in the global market. However, little information about the difference in chemical constituents and bioactivities of the wild agarwood and the artificial agarwood is available. This study aims to systematically compare the chemical composition and the bioactivities between wild and artificial agarwood on the basis of the integrated method of ultra-high-performance liquid chromatography coupled with time-of-flight mass spectrometry (UHPLC-TOF-MS) and multivariate statistical analysis. The invitro antioxidant activity was determined using the 2,2'-azino-bis (3-ethylbenzthiazoline-6-sulphonic acid) (ABTS) and 2,2-diphenyl-1-picrylhydrazyl hydrate (DPPH) radical scavenging activity assays. The cytotoxic activity of agarwood from different origin against three human cancer cell lines (i.e., A375, U251, and Skov3) were compared using the MTT assay. Fifty metabolites from UPLC-QTOF-MS spectra were identified and included in the multivariate analysis. Among these metabolites, 2-(2-phenylethyl) chromone derivatives (PECs), bi-2-(2-phenylethyl) chromone derivatives (BPECs) and sesquiterpene-2-(2-phenylethyl) chromone conjugates (SPECs) were found to be the major metabolites and acted as discriminant compounds in agarwood from different origin. The antioxidant activity study showed that the wild agarwood displayed significant antioxidant capacity compared with the artificial agarwood. Particularly, the content of secondary metabolites of SPEC analogs shown a positive effect on the radical scavenging activities, whereas the PECs were negatively correlated. Interestingly, no significant difference was observed between wild and artificial agarwood in terms of cytotoxic activity against three human cancer cell lines (i.e., A375, U251, and Skov3). To the best of our knowledge, this research is the first to study the metabolite profiles and bioactivities of the wild and the artificial agarwood in a holistic approach, and is expected to provide a rational basis for the quality assessment of artificial agarwood as a substitute for wild agarwood.

Natural products in agarwood and Aquilaria plants: chemistry, biological activities and biosynthesis

Covering: Up to the end of 2019.Agarwood is a resinous portion of Aquilaria trees, which is formed in response to environmental stress factors such as physical injury or microbial attack. It is very sought-after among the natural incenses, as well as for its medicinal properties in traditional Chinese and Ayurvedic medicine. Interestingly, the chemical constituents of agarwood and healthy Aquilaria trees are quite different. Sesquiterpenes and 2-(2-phenethyl)chromones with diverse scaffolds commonly accumulate in agarwood. Similar structures have rarely been reported from the original trees that mainly contain flavonoids, benzophenones, xanthones, lignans, simple phenolic compounds, megastigmanes, diterpenoids, triterpenoids, steroids, alkaloids, etc. This review summarizes the chemical constituents and biological activities both in agarwood and Aquilaria trees, and their biosynthesis is discussed in order to give a comprehensive overview of the research progress on agarwood.

Chemical Constituents and Anti-Inflammatory Effect of Incense Smoke from Agarwood Determined by GC-MS

Agarwood is generally used to make incense sticks in China and Southeast Asia. It emits smoke with a pleasant odor when burned. There are few reports on the chemical components of smoke generated by burning or heating agarwood. The agarwoods were produced by the whole-tree agarwood-inducing technique (AWIT), agarwood induced by axe wounds (AAW), burning-chisel-drilling agarwood (BCDA), wood of Aquilaria sinensis trees (AS), respectively. Herein, we used GC-MS to analyze the chemical constituents of incense smoke generated from AWIT, AAW, BCDA, AS, and the extracts of sticks from agarwood produced by the whole-tree agarwood-inducing technique (EAWIT), and 484 compounds were identified. A total of 61 chemical constituents were shared among AWIT, AAW, and BCDA. The experimental data showed that aromatic compounds were the main chemical constituents in agarwood smoke and that some chromone derivatives could be cracked into low-molecular-weight aromatic compounds (LACs) at high temperature. Furthermore, agarwood incense smoke showed anti-inflammatory activities by inhibiting lipopolysaccharide- (LPS-) induced TNF-α and IL-1α release in RAW264.7 cells.

Fusarium solani induces the formation of agarwood in Gyrinops versteegii (Gilg.) Domke branches

Agarwood is a resinous wood produced by some members of plant family Thymelaeaceae under certain conditions. Agarwood is highly prized, but its formation requires a long-time process in nature. Therefore, various induction techniques have been explored to hasten the process. In this study, we induced agarwood in Gyrinops versteegii, one of the most abundant agarwood-producing trees in Indonesia. We used 12 trees and wounded four branches on each tree through an injection process. We used two strains of the endophytic fungi Fusarium solani isolated from Gorontalo and Jambi Provinces. After 3 months, the inoculated wood had an extensive resinous zone, when compared to wounded control wood. Gas chromatographic-mass spectrometric analysis of the inoculated samples revealed the presence of several sesquiterpenes characteristic of agarwood. These included alloaromadendrene, β-eudesmol and β-selinene as well as the chromone derivatives 2-(2-phenylethyl) chromen-4-one, 6-methoxy-2-(2-phenylethyl) chromen-4-one, and 6,7-dimethoxy-2-(2-phenylethyl) chromen-4-one. We conclude that this method successfully induced agarwood to form in a matter of months and could be used to enhance the success of agarwood cultivation.