New sesquiterpene from Vietnamese agarwood and its induction effect on brain-derived neurotrophic factor mRNA expression in vitro

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.

Chemical Composition and Potential Properties in Mental Illness (Anxiety, Depression and Insomnia) of Agarwood Essential Oil: A Review

As a valuable medicinal herb and spice, agarwood is widely used in the fields of daily chemistry, traditional medicine, religion and literary collection. It mainly contains sesquiterpenes and 2-(2-phenylethyl)chromones, which are often used to soothe the body and mind, relieve anxiety, act as an antidepressant and treat insomnia and other mental disorders, presenting a good calming effect. This paper reviews the chemical composition of the essential oils of different sources of agarwood, as well as the progress of research on the sedative and tranquilizing pharmacological activity and mechanism of action of agarwood essential oil (AEO), and then analyzes the current problems of AEO research and its application prospects in the treatment of mental diseases.

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.

Spirovetivane- and Eudesmane-Type Sesquiterpenoids Isolated from the Culture Media of Two Cyanobacterial Strains

As part of a study examining polar metabolites produced by cyanobacterial strains, we examined media extracts of a Calothrix sp. (strain R-3-1) and a Scytonema sp. (strain U-3-3). The cell mass of each was separated from the media, and HP20 resin was added for adsorption of secreted metabolites, a relatively unexplored area of cyanobacterial chemistry. HPLC-UV-LCMS-guided isolation led to the discovery of seven sesquiterpenoid compounds with five new, one known, and one previously isolated as the methyl ester. Through a complement of 1D and 2D NMR spectroscopic techniques, the planar structures and relative configurations of the seven compounds were elucidated. Spironostoic acid (1), 11,12-didehydrospironostoic acid (2), and 12-hydroxy-2-oxo-11-epi-hinesol (4) are spirovetivane-type compounds from R-3-1, while stigolone (5), 11R,12-dihydroxystigolone (6), and 11S,12-dihydroxystigolone (7) are three eudesmane-type compounds from U-3-3. Circular dichroism was utilized to decipher the absolute configurations of new compounds 1, 2, 4, 5, 6, and 7. Due to the structural variety observed among the spirovetivane- and eudesmane-type compounds in the literature and often a lack of clarity in how determinations were made, computational spectra and model compounds were used to support the interpretation of ECD and NMR spectra. A straightforward process to determine the configuration of these systems is presented.

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.

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.

Isolation Process and Compound Identification of Agarwood Essential Oils from Aquilaria crassna Cultivated at Three Different Locations in Vietnam

Agarwood and agarwood essential oils are commodities with great commercial value. In Vietnam, the agarwood industry has been growing, with more than 10,000 ha of forest land reserved for the cultivation of Aquilaria crassna, an agarwood-producing tree. The aim of this study was to present a hydrodistillation process to recover agarwood essential oil and to compare chemical compositions of agarwood samples harvested from various locations in Vietnam. Three agarwood samples representing products from A. crassna trees cultivated in the provinces of Bac Giang and Khanh Hoa, and on the Phu Quoc island (Kien Giang province) of Vietnam were subjected to hydrodistillation, resulting in essential oil yields of 0.32%, 0.27%, and 0.25% (w/w), respectively. Using GC–MS analysis, a total of 44 volatile compounds were identified in the obtained oils. Most of the constituents were oxygenated sesquiterpenes and had been previously found in other agarwood oil samples. Notable compounds of other chemical classes were aromatics and fatty acids. The three oil samples showed a common volatile profile, which is characterized by the dominance of eremophilane, agarofurans, and eudesmane sesquiterpenes, while vetispirane and guaiane sesquiterpenes were found in smaller quantities. Desired compounds, such as neopetasane (7.47–8.29%), dihydrokaranone (2.63–3.59%), β-agarofuran (3.04–6.18%), and agarospirol (2.98–3.42%), were present in substantial quantities, suggesting that the essential oils could be commercialized as fragrant materials of high value.

Overview of sesquiterpenes and chromones of agarwood originating from four main species of the genus Aquilaria

The main chemical constituents of agarwood are sesquiterpenes and chromones, which can be divided into different categories depending on their molecular skeletons. Agarwoods are obtained from different plant species: Aquilaria sinensis, A. malaccensis, A. crassna, and A. subintegra. In this review, we systematically summarized the structures of 367 compounds isolated from agarwoods originating from four main species. We structurally classified all the components into 11 different types and summarized the number of compounds in each type. Different and identical components were obtained by enumerating the chemical compositions of the different species. Knowledge regarding the chemical constituents of agarwoods of different species will aid understanding of the chemical compositions of agarwoods and will subsequently identify similar compounds that can serve as standards for quality control to provide a reference for future studies on agarwoods from different species and to increase their usefulness.

Agarwood Essential Oil Ameliorates Restrain Stress-Induced Anxiety and Depression by Inhibiting HPA Axis Hyperactivity

In our previous investigation, we found that agarwood essential oil (AEO) has a sedative-hypnotic effect. Sedative-hypnotic drugs usually have an anxiolytic effect, where concomitant anxiety and depression are a common comorbidity. Therefore, this study further investigated the anxiolytic and antidepressant effects of AEO using a series of animal behavior tests on a restraint stress-induced mice model. The elevated plus maze (EPM) test, the light dark exploration (LDE) test, and the open field (OF) test demonstrated that AEO has a significant anxiolytic effect. Simultaneously, the tail suspension (TS) test and the forced swimming (FS) test illuminated that AEO has an antidepressant effect with the immobility time decreased. Stress can cause cytokine and nitric oxide (NO) elevation, and further lead to hypothalamic-pituitary-adrenal (HPA) axis hyperactivity. AEO was shown to dose-dependently inhibit the levels of cytokines, including interleukin 1α (IL-1α), IL-1β, and IL-6 in serum, significantly decrease the mRNA level of neural nitric oxide synthase (nNOS) in the cerebral cortex and hippocampus, and inhibit the nNOS protein level in the hippocampus. Concomitant measurements of the HPA axis upstream regulator corticotropin releasing factor (CRF) and its receptor CRFR found that AEO significantly decreases the gene expression of CRF, and significantly inhibits the gene transcription and protein expression of CRFR in the cerebral cortex and hippocampus. Additionally, AEO dose-dependently reduces the concentrations of adrenocorticotropic hormone (ACTH) and corticosterone (CORT) downstream of the HPA axis, as measured by ELISA kits. These results together demonstrate that AEO exerts anxiolytic and antidepressant effects which are related to the inhibition of CRF and hyperactivity of the HPA axis.

Review: Secondary Metabolites of Aquilaria, a Thymelaeaceae Genus

Background:

Aquilaria, a genus belonging to the Thymelaeaceae, produces fragrant resinous agarwood, also known as eaglewood, which has been used as incense since old times. The intense fra-grance is the result of the presence of a wide variety of secondary metabolites.

Objective:

This genus was reported contained sesquiterpenes, chromones, flavonoids, benzophenones, diterpenoids, triterpenoids, and lignans.

Conclusion:

Here, we review the different secondary metabolites that have been identified in Aquilaria to show their diversity and to allow comparison with other Thymelaeaceae genera.

Qinanmer, a new compound from Chinese agarwood 'Qi-Nan' originating from Aquilaria sinensis

Qinanmer (1), a new compound comprising 2-(2-phenylethyl)chromone and sesquiterpene moieties, together with two known 2-(2-phenylethyl)chromone derivatives (2-3), was isolated from the high-quality Chinese agarwood "Qi-Nan" originating from Aquilaria sinensis (Lour.) Glig. The structure of 1 was elucidated by spectroscopic techniques (UV, IR, 1D and 2D NMR), MS analyses, ECD spectra analyses, and quantum ¹³C NMR calculations.

A new 2-(2-phenylethyl)chromone glycoside in Chinese agarwood "Qi-Nan" from Aquilaria sinensis

A new 2-(2-phenylethyl)chromone glycoside, 2-[2-(4-glucosyloxy-3-methoxyphenyl)ethyl]chromone (1), was isolated from the high-quality Chinese agarwood "Qi-Nan" originating from Aquilaria sinensis (Lour.) Glig. The structure including the absolute configuration of the sugar moiety was elucidated by spectroscopic techniques (UV, IR, 1D and 2D NMR), MS analysis, PMP-labeling HPLC analysis methods, as well as comparison with literature data. To the best of our knowledge, it is the first time that chromone glycoside was discovered in agarwood, or even in the whole Aquilaria plants.

Aquilaria spp. (agarwood) as source of health beneficial compounds: A review of traditional use, phytochemistry and pharmacology

ETHNOPHARMACOLOGICAL RELEVANCE

Aquilaria spp. (agarwood) has been a part of Ayurvedic and Traditional Chinese Medicine for centuries. Agarwood has also been used as a traditional medicine in Southeast Asian countries, Bangladesh and Tibet. Its common uses include the treatment of joint pain, inflammatory-related ailments, and diarrhoea, as well as a stimulant, sedative and cardioprotective agent. In this paper, we aim to provide an overview of the phytochemistry, ethnomedicinal use, pharmacological activities and safety of plant materials from Aquilaria spp. as an evidence base to further appraise its potential use as a source of health beneficial compounds.

MATERIALS AND METHODS

Literature abstracts and full text articles from journals, books, reports and electronic searches (Google Scholar, Elsevier, PubMed, Read Cube, Scopus, Springer, and Web of Science), as well as from other relevant websites, are surveyed, analysed and included in this review.

RESULTS

A literature survey of agarwood plant materials showed that they contain sesquiterpenes, 2(-2-phenylethyl)-4H-chromen-4-one derivatives, genkwanins, mangiferins, iriflophenones, cucurbitacins, terpenoids and phenolic acids. The crude extracts and some of the isolated compounds exhibit anti-allergic, anti-inflammatory, anti-diabetic, anti-cancer, anti-oxidant, anti-ischemic, anti-microbial, hepatoprotective, laxative, and mosquitocidal properties and effects on the central nervous system. Agarwood plant materials are considered to be safe based on the doses tested. However, the toxicity and safety of the materials, including the smoke from agarwood incense burning, should be further investigated. Future research should be directed towards the bio-guided isolation of bioactive compounds with proper chemical characterisation and investigations of the underlying mechanisms towards drug discovery.

CONCLUSIONS

The traditional medicinal use of agarwood plant materials has provided clues to their pharmacological properties. Indeed, agarwood contains a plethora of bioactive compounds that now elegantly support their use in traditional medicine. As wild agarwood trees are critically endangered and vulnerable, sustainable agricultural and forestry practices are necessary for the further development and utilization of agarwood as a source of health beneficial compounds.

Hepatoprotective potential of ethanolic extract of Aquilaria agallocha leaves against paracetamol induced hepatotoxicity in SD rats

Many traditional systems of medicines employ herbal drugs for the hepatoprotection. Aim of the study was designed to evaluate the hepatoprotective potential of 'ethanolic extract of Aquilaria agallocha ( Chen Xiang) leaves' (AAE) against paracetamol (PCM) induced hepatotoxicity in SD rats. Group I animals were treated with 1% CMC for 8 days. Group II, III, IV and V animals were first treated with '1% CMC' 1 ml/kg/day, AAE 200 mg/kg/day, AAE 400 mg/kg/day and silymarin 100 mg/kg/day respectively for 7 days and then, orally administered with PCM 3 g/kg b. wt. on 8th day in a single dose. 24 h after the last dosing by PCM, the blood was obtained through the retro-orbital plexus under light anesthesia and the animals were sacrificed. Hepatoprotective potential was assessed by various biochemical parameters such as ALT, AST, ALP, LDH, bilirubin, cholesterol, TP and ALB. Group IV rats showed significant (p < 0.01) decrease in ALT, AST, ALP, LDH, cholesterol, bilirubin, liver wt. and relative liver wt. levels while significant (p < 0.01) increase in final b. wt., TP and ALB levels as compared to group II rats. Hepatoprotective potential of AAE 400 mg/kg/day was comparable to that of standard drug silymarin 100 mg/kg/day. Results of the study were well supported by the histopathological observations. This study confirms that AAE possesses hepatoprotective potential comparable to that of standard drug silymarin as it exhibited comparable protective potential against PCM induced hepatotoxicity in SD rats.

Anti-neuroinflammatory sesquiterpenes from Chinese eaglewood

Nine new sesquiterpenes (1-9), together with seventeen known ones (10-26), were isolated from Chinese eaglewood. Their structures were established by extensive spectroscopic analysis, and the absolute configuration of 6 was determined by the modified Mosher's method. Compounds 7, 10, 14, 15, and 21 exhibited significant inhibition of nitric oxide production in lipopolysaccharide-stimulated BV-2 microglial cells with IC50 values in the range 7.1-53.8 μM.

Measuring Agarwood Formation Ratio Quantitatively by Fluorescence Spectral Imaging Technique

Agarwood is a kind of important and precious traditional Chinese medicine. With the decreasing of natural agarwood, artificial cultivation has become more and more important in recent years. Quantifying the formation of agarwood is an essential work which could provide information for guiding cultivation and controlling quality. But people only can judge the amount of agarwood qualitatively by experience before. Fluorescence multispectral imaging method is presented to measure the agarwood quantitatively in this paper. A spectral cube from 450 nm to 800 nm was captured under the 365 nm excitation sources. The nonagarwood, agarwood, and rotten wood in the same sample were distinguished based on analyzing the spectral cube. Then the area ratio of agarwood to the whole sample was worked out, which is the quantitative information of agarwood area percentage. To our knowledge, this is the first time that the formation of agarwood was quantified accurately and nondestructively.

The effect of red light and far-red light conditions on secondary metabolism in agarwood

BACKGROUND

Agarwood, a heartwood derived from Aquilaria trees, is a valuable commodity that has seen prevalent use among many cultures. In particular, it is widely used in herbal medicine and many compounds in agarwood are known to exhibit medicinal properties. Although there exists much research into medicinal herbs and extraction of high value compounds, few have focused on increasing the quantity of target compounds through stimulation of its related pathways in this species.

RESULTS

In this study, we observed that cucurbitacin yield can be increased through the use of different light conditions to stimulate related pathways and conducted three types of high-throughput sequencing experiments in order to study the effect of light conditions on secondary metabolism in agarwood. We constructed genome-wide profiles of RNA expression, small RNA, and DNA methylation under red light and far-red light conditions. With these profiles, we identified a set of small RNA which potentially regulates gene expression via the RNA-directed DNA methylation pathway.

CONCLUSIONS

We demonstrate that light conditions can be used to stimulate pathways related to secondary metabolism, increasing the yield of cucurbitacins. The genome-wide expression and methylation profiles from our study provide insight into the effect of light on gene expression for secondary metabolism in agarwood and provide compelling new candidates towards the study of functional secondary metabolic components.

Identification of cucurbitacins and assembly of a draft genome for Aquilaria agallocha

BACKGROUND

Agarwood is derived from Aquilaria trees, the trade of which has come under strict control with a listing in Appendix II of the Convention on International Trade in Endangered Species of Wild Fauna and Flora. Many secondary metabolites of agarwood are known to have medicinal value to humans, including compounds that have been shown to elicit sedative effects and exhibit anti-cancer properties. However, little is known about the genome, transcriptome, and the biosynthetic pathways responsible for producing such secondary metabolites in agarwood.

RESULTS

In this study, we present a draft genome and a putative pathway for cucurbitacin E and I, compounds with known medicinal value, from in vitro Aquilaria agallocha agarwood. DNA and RNA data are utilized to annotate many genes and protein functions in the draft genome. The expression changes for cucurbitacin E and I are shown to be consistent with known responses of A. agallocha to biotic stress and a set of homologous genes in Arabidopsis thaliana related to cucurbitacin bio-synthesis is presented and validated through qRT-PCR.

CONCLUSIONS

This study is the first attempt to identify cucurbitacin E and I from in vitro agarwood and the first draft genome for any species of Aquilaria. The results of this study will aid in future investigations of secondary metabolite pathways in Aquilaria and other non-model medicinal plants.

A new 2-(2-phenylethyl)chromone derivative in Chinese agarwood 'Qi-Nan' from Aquilaria sinensis

Phytochemical analysis of the high quality Chinese agarwood 'Qi-Nan' originating from Aquilaria sinensis (Lour.) Glig led to the isolation of a new 2-(2-phenylethyl)chromone derivative, qinanones G (1), and four known 2-(2-phenylethyl)chromones (2-5). Their structures were elucidated by spectroscopic techniques (UV, IR, 1D and 2D NMR) and MS analyses. The NMR data of chromones 1-3 were first reported, and chromones 2 and 3 showed weak inhibitory activity against acetylcholinesterase.

Anti-inflammatory components from the root of Solanum erianthum

Two new norsesquiterpenoids, solanerianones A and B (1-2), together with nine known compounds, including four sesquiterpenoids, (-)-solavetivone (3), (+)-anhydro-β-rotunol (4), solafuranone (5), lycifuranone A (6); one alkaloid, N-trans-feruloyltyramine (7); one fatty acid, palmitic acid (8); one phenylalkanoid, acetovanillone (9), and two steroids, β-sitosterol (10) and stigmasterol (11) were isolated from the n-hexane-soluble part of the roots of Solanum erianthum. Their structures were elucidated on the basis of physical and spectroscopic data analyses. The anti-inflammatory activity of these isolates was monitored by nitric oxide (NO) production in lipopolysaccharide (LPS)-activated murine macrophage RAW264.7 cells. The cytotoxicity towards human lung squamous carcinoma (CH27), human hepatocellular carcinoma (Hep 3B), human oral squamous carcinoma (HSC-3) and human melanoma (M21) cell lines was also screened by using an MTT assay. Of the compounds tested, 3 exhibited the strongest NO inhibition with the average maximum inhibition (Emax) at 100 μM and median inhibitory concentration (IC50) values of 98.23% ± 0.08% and 65.54 ± 0.18 μM, respectively. None of compounds (1-9) was found to possess cytotoxic activity against human cancer cell lines at concentrations up to 30 μM.

Spirodionic Acid, a Novel Metabolite fromStreptomyces sp., Part 1: Structure Elucidation and Diels–Alder-Type Biosynthesis

Spirodionic acid (1), a novel microbial metabolite with a spiro[4.5]decene skeleton, the 6-ethyl-2H-pyrone 5, dihydrosarkomycin (6), and other metabolites were isolated from the strain Streptomyces sp. Tü 6077. Structural elucidation was accomplished by NMR spectroscopic and mass-spectrometric studies, and the biosyntheses of compounds 1, 5, and 6 were investigated by feeding experiments with (13)C-labeled precursors. All results indicate a biogenetic sequence with metabolite 5 and sarkomycin (7) as precursors in the formation of spirocyclus 1 through an intermolecular Diels-Alder-type reaction.