Effects of plant growth regulators, carbon sources and pH values on callus induction in Aquilaria malaccensis leaf explants and characteristics of the resultant calli

The endangered tropical tree, Aquilaria malaccensis, produces agarwood for use in fragrance and medicines. Efforts are currently un-derway to produce valuable agarwood compoundsn tissue culture. The purpose of this study was to develop an optimal growth medium, specif-ically, the best hormone combination for callus suspension culture. Using nursery-grown A. malaccensis, sterilized leaf explants were first incu-bated on basic Murashige and Skoog （MS） gel medium containing 15g/L sucrose and at pH 5.7. Different auxin types including 1-naphthaleneacetic acid （NAA）, 2,4-dichlorophenoxyacetic acid （2,4-D）, and indole-3-butyric acid （IBA）, were tested at various concentrations （0.55, 1.1 and 1.65 μM） using the basic medium. Leaf explants were incubated for 30 days in the dark. Callus induced by 1.1 μM NAA had the highest biomass dry weight （DW） of 17.3 mg;however the callus was of a compact type. This auxin concentration was then combined with either 6-benzylaminopurine （BAP） or kinetin at 0.55, 1.1, 2.2 or 3.3 μM to induce growth of friable callus. The 1.1μM NAA＋2.2μM BAP com-bination produced friable callus with the highest biomass （93.3mg DW）. When testing the different carbon sources and pHs, sucrose at 15g/L and pH at 5.7 yielded highest biomasses at 87.7mg and 83mg DW, respec-tively. Microscopic observations revealed the arrangement of the friable cells as loosely packed with relatively large cells, while for the compact callus, the cells were small and densely packed. We concluded that MS medium containing 15 g/L sucrose, 1.1 μM NAA ＋ 2.2 μM BAP hor-mone combination, and a pH of 5.7 was highly effective for inducing friable callus from leaf explants of A. malaccensis for the purpose of establishing cell suspension culture.

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 20μM(P<0.001).Isoagarotetrol(14)showed a significant protective effect on MPP+-induced injury in PC12 cells at a concentration of 20μM(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 20μM.

Advance in Studies on Chemical Constituents, Pharmacology and Quality Control of Aquilaria sinensis

Aquilaria sinensis(Thymelaeaceae)is widely cultivated in southern China for its significant medicinal usage.The resinous wood,the most used part of the plant as traditional Chinese medicine(TCM),locally called“Chen Xiang(沉香)”or Chinese agarwood,has been traditionally used for the treatment of circulatory disorders,abdominal pain,vomiting,and dyspnea.Till date,over 249 compounds have been isolated and identified from this plant.A range of bioactivities,including α-glucosidase inhibitory effects,anti-inflammatory,cytotoxicity,neuroprotective,anti-neuroinflammatory,antimicrobial and acetylcholinesterase inhibitory effects,along with some of the pharmacological mechanisms have been reported for the pure compounds or extracts of Aquilaria sinensis.For the purpose of quality control and clinical safety of drug usage,modern analytical instruments and chemical analysis methods have been applied for analyses of Aquilaria sinensis.In order to comprehensively understand the medicinal application and to fully utilize the plant,a literature search on the herb based on databases including SciFinder,Web of Science,Pubmed,Google Scholar and others was performed and the information regarding to the phytochemistry investigations,pharmacological studies and quality control was summarized in this paper.

Natural products against HIV latency

Antiretroviral therapy has achieved great success in suppressing human immunodeficiency virus(HIV)replication and transforming HIV infection from a fatal disease to a manageable chronic disease.However,the latent HIV reservoir persists in the body of HIVinfected individuals and is prone to reactivation.Therefore,the development of new treatment methods aimed at a complete cure for HIV is needed.The leading strategy for HIV eradication is based on eliminating and preventing the reactivation of latent reservoirs through an approach known as“shock and kill.”This strategy involves the use of latency-reversing agents(LRAs)to activate the HIV provirus in latent viral reservoir cells.Many LRAs can be obtained from natural resources,including plants and marine organisms.In this review,we provide an overview of natural products used to eliminate HIV latency.

A new coumarin glycoside from Daphne giraldii

A new coumarin glycoside was isolated from the ethanol extract of the barks of stem of Daphne giraldii Nitsche. Its structure was defined as daphnetin 8-O-β-D-glucopyranosyl-（1 → 6）-β-D-glucopyranoside on the basis of spectral evidences.

Five new 2-(2-phenylethyl)chromone derivatives and three new sesquiterpenoids from the heartwood of Aquilaria sinensis, an aromatic medicine in China

Five new 2-(2-phenylethyl)chromone derivatives,(5S,6R,7R,8S,7ʹR)-7ʹ-hydroxyagarotetrol(1),(5S,6R,7R,8S,7ʹS)-7ʹ-hydroxyagarotetrol(2),(6S,7S,8R)-2-[2-(4-methoxyphenyl)ethyl]-6,7,8-trihydroxy-5,6,7,8-tetrahydrochromone(3),(6S,7S,8R)-2-(2-phenylethyl)-6,7,8-trihydroxy-5,6,7,8-tetrahydrochromone(4),(5S,6R,7S,8R)-2-(2-phenylethyl)-5,6,7-trihydroxy-5,6,7,8-tetrahydro-8-[2-(2-phenylethyl)-7-methoxychromonyl-6-oxy]chromone(5),three new sesquiterpenoids,(4S,5S,7S,8S,10S,13R)-7,8,13-trihydroxyrotunda-1,11-dien-3-one(6),(4S,5S,7S,8S,10S,13S)-7,8,13-trihydroxyrotunda-1,11-dien-3-one(7),and(4R,5S,7S,8S,10S,13S)-7,8,13-trihydroxyrotunda-1,11-dien-3-one(8),along with 14 known compounds were isolated from the resinous heartwood of Aquilaria sinensis(Thymelaeaceae).The chemical structures of these new compounds were elucidated by 1D and 2D NMR and MS data,single-crystal X-ray diffraction analysis,and electronic circular dichroism(ECD)calculations.The neuroprotective activities of these isolates were evaluated using an in vitro model of rat adrenal pheochromocytoma(PC12)cell injury induced by corticosterone.At concentrations from 5 to 40μM,compounds 4 and 6,agarotetrol(9),and 6-hydroxy-2-(2-phenylethyl)chromone(17)showed significant protective activities against corticosterone-induced PC12 cell injury(P<0.001).

Bioassay-guided isolation of cytotoxic constituents from the flowers of Aquilaria sinensis

Bioassay-guided fractionation of the EtOH extract from the flowers of Aquilaria sinensis(Lour.)Spreng.(Thyme-laeaceae)led to the isolation of a new cucurbitane-type triterpenoid,aquilarolide A(1),along with five known compounds(2-6).The structure of 1 was elucidated by extensive 1D and 2D nuclear magnetic resonance(NMR)experiments and mass spectrometry(MS)data and theoretical calculations of its electronic circular dichroism(ECD)spectra.Aquilarolide A,cucurbitacin E(3),cucurbitacin B(4),and 7-hydroxy-6-methoxy-2-[2-(4-methoxyphenyl)ethyl]-4H-1-benzopyran-4-one(6)showed significant cytotoxicity against human lung adenocarcinoma SPC-A-1,human lung squamous cell carcinoma NCI-H520,human lung adenocarcinoma A549,and paclitaxel-resistant A549(A549/Taxol)cell lines.All four active compounds,with IC_(50) values ranging from 0.002 to 0.91μM,had better inhibitory activities against A549/Taxol cells than paclitaxel(IC_(50)=1.80μM).Among them,cucurbitacin E(IC_(50)=0.002μM)is the most active.Further studies are needed to evaluate their in vivo antitumor activities and to clarify their mechanisms.

Chemical constituents from Aquilaria sinensis(Lour.) Gilg

To investigate the chemical constituents of the stems ofAquilaria sinensis （Lour.） Gilg, the separation and purification were performed by solvent extraction, repeated chromatography on silica gel, Sephadex LH-20 and prep-HPLC. The structures were determined by spectrum analysis. Thirteen known compounds were isolated and their structures were identified as justicidin A （1）, justidin F （2）, ciwujiatone （3）, （＋） syringaresinol （4）, syringaresinol-4,4＇-di-O-13-D-glucopyranoside （5）, syringaresinol-4＂O-β-D- glucopyranoside （6）, curuilignan D （7）, syringin （8）, koaburaside （9）, 3,4,5-trimethoxyphenyl-l-O-β-D-glucopyranoside （10）, 3,4,5-trimethoxyphenyl-l-O-13-D-apiofuranosyl-（1 ＂→6＇） glucopyranoside （11）, 7-ketositosterol （12）, 7-oxo-5,6-dihydrostigmasterol （13）. All the compounds described above were isolated from genus Aquilaria for the first time.

A new biflavone glucoside from the roots of Stellera chamaejasme

The present study investigated the chemical constituents of the roots of Stellera chamaejasme(Thymelaeaceae).One new biflavone glucoside(1),along with other thirteen known compounds(2–14),was isolated by repeated column chromatographic methods and their structures were elucidated on the basis of spectral analyses.The cytotoxic activities of selected compounds were evaluated against four human cancer cell lines(A549,BEL-7402,HCT-116,and MDA-MB-231) by the SRB assay method.Compound 9 showed remarkable cytotoxicity against BEL-7402 with IC50 value being 0.65 μg·mL-1; compounds 7,8,and 12 exhibited significant cytotoxic activity against A549 with IC50 values being 2.38,1.57,and 2.35 μg·m L-1,respectively.

Five new benzophenone glycosides from the leaves of Aquilaria sinensis(Lour.) Gilg

Phytochemical investigation on the ethanol extract from the leaves of Aquitaria sinensis led to the isolation of five new benzophenone glycosides,aquilarinensides A-E（1-5）.Their structures were elucidated by a combination of 1D and 2D NMR,HRMS,and chemical analysis.