Three new 1-(p-hydroxybenzyl)phenanthrenes from Bletilla striata

Biological evaluation, molecular modeling and dynamics simulation of phenanthrenes isolated from Bletilla striata as butyrylcholinesterase inhibitors

As part of our continuous studies on natural cholinesterase inhibitors from plant kingdom, the 95% ethanol extract from tubers of Bletillastriata showed promising butyrylcholinesterase (BChE) inhibition (IC₅₀ = 8.6 μg/mL). The extracts with different polarities (petroleum ether, ethyl acetate, n-butanol, and water) were prepared and evaluated for their inhibition of cholinesterases. The most active ethyl acetate extract was subjected to a bioassay-guided isolation and afforded twenty-two bibenzyls and phenanthrenes (1–22). All isolates were further evaluated for their BChE inhibition activity, and five phenanthrenes presented promising capacity (IC₅₀ < 10 μM). Further kinetic studies indicated their modes of inhibition. Compounds 6, 8, and 14 were found to be mixed-type inhibitors, while compounds 10 and 12 could be classified as non-competitive inhibitors. The potential interaction mechanism of them with BChE was demonstrated by molecular docking and molecular dynamics simulation, showing that they could interact with catalytic active site and peripheral anionic site of BChE. These natural phenanthrenes provide new scaffold for the further design and optimization, with the aim to discover new selective BChE inhibitors for the treatment of AD.

Glucosyloxybenzyl 2-isobutylmalates and phenolic glycosides from the flowers of Bletilla striata

Four previously undescribed compounds, including three glucosyloxybenzyl 2-isobutylmalates (1-3), one phenolic glycoside (4), along with ten known compounds were isolated from the flowers of Bletilla striata. The structures and absolute configurations of the undescribed compounds were elucidated on the basis of HR-ESIMS, NMR spectroscopy, optical rotation value, and acid hydrolysis experiment. Cytotoxicity of the isolated compounds against A549, HCT-116, and SW1990 cells and protective effects of t-BHP-induced L02 cytotoxic were assayed. The antioxidant activities of the isolated compounds were also evaluated.

The medicinal uses of the genus Bletilla in traditional Chinese medicine: A phytochemical and pharmacological review

ETHNOPHARMACOLOGICAL RELEVANCE

Different orchids are important in traditional medicine, and species belonging to the genus Bletilla are important. Bletilla species have been used for thousands of years in Traditional Chinese Medicine (TCM) for the treatment of several health disorders, such as gastrointestinal disorders, peptic ulcer, lung disorders, and traumatic bleeding etc. AIM OF THIS REVIEW: This review aims to provide a systematic overview and objective analysis of Bletilla species and to find the probable relationship between their traditional use, chemical constituents, and pharmacological activities, while assessing their therapeutic potential in treatment of different human diseases.

MATERIALS AND METHODS

Relevant literatures on Bletilla species have been collected using the keywords "Bletilla", "phytochemistry", and "pharmacology" in scientific databases, such as "PubMed", "Scifinder", "The Plant List", "Elsevier", "China Knowledge Resource Integrated databases (CNKI)", "Google Scholar", "Baidu Scholar", and other literature sources, etc. RESULTS: This review indicates the isolation and identification of over 261 compounds from this genus, till December 2020. These chemical isolates belong to the stilbenes (bibenzyls and phenanthrenes), flavonoids, triterpenoids, steroids, simple phenolics, and glucosyloxybenzyl 2-isobutylmalates classes of compounds. These compounds have been reported to be characteristically distributed in Bletilla striata (Thunb.) Rchb. f. (BS), Bletilla ochracea Schltr. (BO), and Bletilla formosana (Hayata) Schltr. (BF). The crude extracts and pure compounds derived from the three Bletilla species have reportedly exhibited a wide spectrum of in vitro and in vivo pharmacological effects, such as hemostatic, anti-inflammatory, anti-tumor, and anti-microbial activities. As a Traditional Chinese Medicine (TCM), Bletilla species or preparations containing Bletilla species have been used for the treatment of epistaxis, gastrointestinal bleeding, cough and hemoptysis, gastric and duodenal ulcer, and traumatic injuries. Thus, Bletilla species have proven potential both in traditional uses and scientific studies.

CONCLUSIONS

Pharmacological studies have validated the use of Bletilla species in the traditional medicine, especially hemorrhagic diseases. Polysaccharides and stilbenes are the major bioactive chemical constituents of Bletilla genus according to the literatures. However, the mechanism of action of these molecules is yet to be studied. In addition, a detailed comparative analysis of the phytochemistry and biological activities of the three Bletilla species (BS, BO and BF) is highly recommended for understanding their ethnopharmacological uses and applications in clinics. Clinical toxicity tests on BS have been found to be negative, but it can't be used with Aconitum carmichaeli in traditional uses. Furthermore, not many reports are present in the literature regarding the conservation of Bletilla species.

Phytochemistry and pharmacological activities of Arundina graminifolia (D.Don) Hochr. And other common Orchidaceae medicinal plants

ETHNOPHARMACOLOGICAL RELEVANCE

Arundina graminifolia (Orchidaceae) has been widely used for heat clearance and detoxification, anti-inflammatory diuretic, and anti-microbes for two thousand years in national minorities, especially among the Dai people. It was known as "Zhuyelan" (Chinese: ), "Wenshanghai" (Chinese: ) and "Baiyangjie" (Chinese: ) in the Dai nationality, and mainly used as antidote, which is characterized by "relieving the poison before getting sick and treating illness". Therefore, it has been typically applied in the treatment of food poisoning, snake bites, rheumatism, stomachache and traumatic injuries. It is also used to treat bronchitis, tuberculosis and pneumonia in the Bulang and the Wa ethnic people.

AIM OF THIS REVIEW

This review aims to provide up-to-date information about the botanical characterization, traditional uses, phytochemistry, and pharmacology of A. graminifolia, and the related importantly medicinal plants (e.g. Bletilla striata, Cremastra appendiculata, and Dendrobium officinale) of the same Orchidaceae family. Our work aims to further promote scientific cognition, basic research and in-depth discovery of potential drug candidates for Minority Medicine of our nation.

MATERIALS AND METHODS

Relevant information was obtained via piles of resources including classic books about Chinese herbal medicine, and worldwide accepted scientific databases including Web of Science, Pubmed, Google Scholar, SciFinder, Elsevier, Springer, NCBI, ACS Publications, CNKI and Wanfang data.

RESULTS

Phytochemical investigations have been intensively performed for these two decades, over 134 compounds, mainly include stilbenoids, phenanthrenes, quinones, ketones, phenolic acids, and glycosides, have been isolated and identified from A. graminifolia. The literature surveys exhibited that the ethnomedicinal uses of A. graminifolia, such as detoxification, anti-inflammation and the ability to cure trauma and pain associated with infections, are correlated with its modern pharmacological activities, including antibacterial, anti-oxidation, anti-lipid peroxidation. Stilbenoids and phenanthrenes have been regarded as the main active substances, among which stilbenoids with open ring style have superior antitumor activity. Furthermore, phytochemical investigations, biological activities, as well as the main molecular mechanism involved the coexisted stilbenoids and phenanthrenes from other most common used medicinal plants of the same Orchidaceae family were presented, compared and discussed together.

CONCLUSIONS

This review presents the current research findings of A. graminifolia and three other related medicinal plants of the same family. Some of the traditional uses of A. graminifolia have been assessed by pharmacological studies. Despite A. graminifolia is used as an antidote and anti-aging dote, a few unsolved problems including the molecular mechanism underlying biological activities, pharmacokinetics, and in vivo detoxification tests still need to be settled extensively. Therefore, it is necessary to conduct a comprehensive survey and collect investigation information on A. graminifolia.

Dimeric 9,10-dihydrophenanthrene derivatives from Bletilla striata and their atropisomeric nature

Four pairs of undescribed racemic bi(9,10-dihydro) phenanthrene and phenanthrene/bibenzyl atropisomers, bletistriatins A-D (1-4), along with 22 known compounds were isolated from the rhizomes of Bletilla striata. These dimeric derivatives were constructed through direct C-C connection or an oxygen bridge. The structures of new compounds were fully established by extensive analysis of MS, and 1D and 2D NMR spectroscopic data. Owing to sterically hindered rotation around the biaryl axis, these dimeric 9,10-dihydrophenanthrene derivatives can exist as a pair of enantiomers, but were isolated as racemates. Their racemates were separated to yield enantiomerically pure compounds by HPLC on an optically active stationary phase, and were stereochemically characterized on-line by circular dichroism (CD) spectroscopy (LC-CD coupling). Some isolates were evaluated for cytotoxicity against human cancer cell lines HL-60 and A549. Compounds 13, 17, and 20 showed cytotoxicity against HL-60 and A-549 cell lines with IC₅₀ values ranging from 2.56 to 8.67 μM.

Callus growth kinetics and accumulation of secondary metabolites of Bletilla striata Rchb.f. using a callus suspension culture

Bletilla striata is an endangered traditional Chinese medicinal plant with multiple uses and a slow regeneration rate of its germplasm resources. To evaluate the callus growth kinetics and accumulation of secondary metabolites (SMs), a callus suspension culture was proven to be a valuable approach for acquiring high yields of medicinal compounds. An effective callus suspension culture for obtaining B. striata callus growth and its SMs was achieved with the in vitro induction of calluses from B. striata seeds. The callus growth kinetics and accumulation of SMs were analyzed using a mathematical model. The resulting callus growth kinetic model revealed that the growth curves of B. striata suspension-cultured calluses were sigmoidal, indicating changes in the growth of the suspension-cultured calluses. Improved Murashige and Skoog callus growth medium was the most favorable medium for B. striata callus formation, with the highest callus growth occurring during the stationary phase of the cultivation period. Callus growth acceleration started after 7 days and thereafter gradually decreased until day 24 of the cultivation period and reached its highest at day 36 period in both the dry weight and fresh weight analyses. The coelonin concentration peaked during the exponential growth stage and decreased afterward during the stationary stage of the callus suspension culture. The maximum content of coelonin (approximately 0.3323 mg/g callus dry weight) was observed on the 18th day of the cultivation cycle, while dactylorhin A and militarine reached the highest concentrations at day 24, and p-hydroxybenzyl alcohol at day 39. This investigation also laid a foundation for a multimathematical model to better describe the accumulation variation of SMs. The production of SMs showed great specificity during callus growth and development. This research provided a well-organized way to increase the accumulation and production of SMs during the scaled-up biosynthesis of calluses in B. striata callus suspension cultures.

Chemical constituents of Bletilla striata

A new triphenanthrene compound named 2,2',2'',7,7',7''-hexahydroxy-4,4',4''-trimethoxy-[9,9',9'',10,10',10'']-hexahydro-1,8,1',6''-triphenanthrene (1), together with eleven known compounds (2－12), were isolated from tubers of Bletilla striata. Their structures were determined by analysis of spectroscopic data.

Chemical Constituents, Pharmacologic Properties, and Clinical Applications of Bletilla striata

Bletilla striata is a plant from the Orchidaceae family that has been employed as a traditional Chinese medicine (TCM) for thousands of years in China. Here, we briefly review the published studies of the last 30 years that were related to chemical constituents, pharmacologic activities, and clinical applications of B. striata. Approximately 158 compounds have been extracted from B. striata tubers with clarified molecular structures that were classified as glucosides, bibenzyls, phenanthrenes, quinones, biphenanthrenes, dihydrophenanthrenes, anthocyanins, steroids, triterpenoids, and phenolic acids. These chemicals support the pharmacological properties of hemostasis and wound healing, and also exhibit anti-oxidation, anti-cancer, anti-viral, and anti-bacterial activities. Additionally, various clinical trials conducted on B. striata have demonstrated its marked activities as an embolizing and mucosa-protective agent, and its application for use in novel biomaterials, quality control, and toxicology. It also has been widely used as a constituent of many preparations in TCM formulations, but because there are insufficient studies on its clinical properties, its efficacy and safety cannot be established from a scientific point of view. We hope that this review will provide reference for further research and development of this unique plant.

Isolation, Structural Elucidation, Optical Resolution, and Antineuroinflammatory Activity of Phenanthrene and 9,10-Dihydrophenanthrene Derivatives from Bletilla striata

A phytochemical investigation of the aqueous EtOH extract of Bletilla striata tubers afforded 34 phenanthrene and 9,10-dihydrophenanthrene derivatives, including four new compounds, 1-4. These compounds were identified using physicochemical analyses and various spectroscopic methods. Twelve of these compounds were resolved into their enantiomers, and the absolute configurations were determined by comparison of experimental and calculated ECD spectra. The antineuroinflammatory activities were evaluated by measuring the inhibition of nitric oxide production in lipopolysaccharide-stimulated BV-2 microglial cells. Compounds 7, 32, and 33 displayed inhibitory activities, with IC₅₀ values of 1.9, 5.0, and 1.0 μM, respectively, suggesting that they should be subjected to development as potential inhibitors of neuroinflammation.