Recent Advances in the Phytochemistry of Bryophytes: Distribution, Structures and Biological Activity of Bibenzyl and Bisbibenzyl Compounds

Research on bryophyte phytochemistry has revealed the presence of different phytochemicals like fatty acids, terpenoids, small phenolic molecules, etc. Small phenolic molecules, i.e., bibenzyls (of two aromatic rings) and bisbibenzyls (four aromatic rings), are unique signature molecules of liverworts. The first bisbibenzyls marchantin A and riccardin A were discovered in two consecutive years, i.e., 1982 and 1983, respectively, by Asakawa and coworkers. Since then, about 70 bisbibenzyls have been reported. These molecules are characterized and identified using different spectroscopic techniques and surveyed for different bioactivity and structure-activity relations. Biochemistry is determined by the season, geography, and environment. In this review, quantitative and qualitative information on bibenzyls and bisbibenzyl compounds and their distribution in different liverworts across, geographies along withtraditional to advanced extraction methods, and characterization techniques are summarized. Also, a comprehensive account of characteristic spectra of different bisbibenzyl compounds, their subtypes, and their basic skeleton patterns are compared. A comprehensive table is provided here for the first time presenting the quantity of bibenzyls, bisbenzyls, and their derivatives found in bryophytes, mentioning the spectroscopic data and mass profiles of the compounds. The significance of these compounds in different bioactivities like antibiotic, antioxidative, antitumor, antivenomous, anti-influenza, insect antifeedant, cytotoxic, and anticancerous activities are surveyed and critically enumerated.

Phytochemical Analysis of Pinus cembra Heartwood-UHPLC-DAD-ESI-MSn with Focus on Flavonoids, Stilbenes, Bibenzyls and Improved HPLC Separation

The heartwood of the Swiss Stone Pine, Pinus cembra L., has been scarcely investigated for secondary metabolites for a long period of time. Considering age and relative simplicity of heartwood investigations dating back to the 1940s to 1960s, we conducted the first investigation of P. cembra heartwood by HPLC, using UHPLC-DAD-ESI-MSn and HPLC-DAD techniques in combination with isolation and NMR spectroscopy, with focus on stilbenes, bibenzyls and flavonoids. Analytical problems in the HPLC analysis of Pinus stilbenes and flavonoids on reversed stationary phases were also challenged, by comparing HPLC on pentafluorophenyl (PFP) and C18 stationary phases. Seven flavonoids (1, 2, 3, 7, 8, 11, 12), four stilbenes (4, 6, 10, 13), two bibenzyls (5, 9), three fatty acids (14, 16, 17) and one diterpenic acid (15) were detected in an ethanolic extract of Pinus cembra heartwood. HPLC comparison of reversed stationary phases in HPLC showed that the antifungal, antibacterial and chemosensitizing dihydropinosylvin monomethyl ether (9) and pinosylvin monomethyl ether (10) can be separated on PFP, but not on C18 material, when eluting with a screening gradient of 20-100% acetonitrile. Flavonoid separation showed additional benefits of combining analyses on different stationary phases, as flavonoids 7 and 8 could only be separated on one of two C18 stationary phases. Earlier phytochemical results for heartwood investigations were shown to be mostly correct, yet expandable. Substances 5 to 12 were found in alignment with these references, proving remarkable phytochemical analyses at the time. Evidence for the described presence of pinobanksin could not be found. Substances 1 to 4 and 13 have to our knowledge not yet been described for P. cembra.

[Effects of mycorrhizal planting on small molecular chemical components of Dendrobium officinale]

This study aimed to provide a scientific basis for the application of the mycorrhizal planting technology of Dendrobium officinale by investigating the effects of mycorrhizal planting on the fingerprints of D. officinale and the content of six chemical components. Seventeen samples of D. officinale under mycorrhizal and conventional planting were collected from four regions, such as Jinhua of Zhejiang. The HPLC fingerprints were established to evaluate the similarity of the samples. The content of six chemical components of the samples was determined by HPLC. There were 15 common peaks in the fingerprints, and five of them were identified by marker compounds, which were naringenin, 4,4'-dihydroxy-3,5-dimethoxybibenzyl, 3,4'-dihydroxy-5-methoxybibenzyl, 3',4-dihydroxy-3,5'-dimethoxybibenzyl(gigantol), and 3,4-dihydroxy-4',5-dimethoxybibenzyl(DDB-2). The similarities of the fingerprints of mycorrhizal and conventional planting samples and the control fingerprint were in the ranges of 0.733-0.936 and 0.834-0.942, respectively. The influences of mycorrhizal planting on fingerprints were related to planting regions, the germplasm of D. officianle, and the amount of fungal agent. The content of six chemical components in the samples varied greatly, and the content of DDB-2 was the highest, ranging from 69.83 to 488.47 μg·g~(-1). The mycorrhizal planting samples from Chongming of Shanghai and Taizhou of Jiangsu showed an increase in the content of 5-6 components, while samples from Zhangzhou of Fujian and Jinhua of Zhejiang showed an increase in the content of 1-2 components. The results showed that mycorrhizal planting technology did not change the chemical profile of small molecular chemical components of D. officinale, but affected the content of chemical components such as bibenzyls, which has a good application prospect.

Methoxylated bibenzyls and isoflavones from Baphia massaiensis Taub

Chemical investigation of the stem bark of Baphia massaiensis Taub. led to the isolation of two new natural compounds named 3-hydroxy-2,5,2'-trimethoxybibenzyl (1) and 2'-hydroxy-2,3,5,6-tetramethoxybibenzyl (2), the latter has been previously reported as a synthetic compound, together with twelve known compounds 3-14. The chemical structures of the isolated compounds were elucidated by using NMR analysis and mass spectrometry, as well as comparisons with the reported data in the literature. Known bibenzyls 3-5, bauhinoxepin J (6), and isoflavones 7-10 and 12-14, were reported from genus Baphia for the first time. The isolated compounds were evaluated for their antibacterial activities in-vitro against Staphylococcus aureus and Escherichia coli. The bioactivity evaluation revealed that bibenzyls 1 and 2 showed weak inhibitory activity with MIC values of 1000 µg/mL against S. aureus and bauhinoxepin J (6) showed moderate inhibitory activity with MIC value of 63 µg/mL against S. aureus.

Identification of bibenzyls and evaluation of imitative wild planting techniques in Dendrobium officinale by HPLC-ESI-MSn

Dendrobium officinale is a traditional Chinese herb with beneficial properties. Modern pharmacological studies show that bibenzyl is one of the antitumor active ingredients, but there is no effective quality control method for identifying ingredients. In this study, the composition of bibenzyls in Dendrobium officinale was studied by high-performance liquid chromatography coupled with electrospray ionization multistage mass spectrometry (HPLC-ESI-MSⁿ ). A total of nine isolated bibenzyls and their glycosides, 22 bis (bibenzyls), and two phenylpropanol bibenzyl derivatives were identified. The results of HPLC characteristic chromatogram analysis and statistical analysis showed that the relative content of bibenzyls in wild imitation cultivation of samples had been significantly higher than that in greenhouse cultivation. In addition, the relative content of bibenzyls increased with the growth of the original plant. This study provided a scientific reference for controlling the quality of bibenzyls in Dendrobium officinale, developing the cultivation technology and improving the quality of Dendrobium officinale. HIGHLIGHTS: HPLC-ESI-MS/MS method for the analysis of bibenzyls and bis (bibenzyls) in Dendrobium officinale. Easy-to-use method facilitating rapid measurement of large sample quantities. The method requires only small volumes of samples for the analysis. Applicable for the establishment of Chinese medicine studies and the quality control standard of Chinese herbs.

Spatial Distribution, Antioxidant Capacity, and Spore Germination-Promoting Effect of Bibenzyls from Marchantia polymorpha

Liverworts, considered to be the first plant type to successfully make the transition from water to land, can resist different oxidative stress. As characteristic constituents of liverworts, the bibenzyls are efficient antioxidants. In this study, spatial distributions of the bibenzyls within Marchantia polymorpha L., the model species of liverworts, were mapped using airflow-assisted desorption electrospray ionization imaging mass spectrometry. Bibenzyls were found to largely exist in the female receptacle of M. polymorpha, where lunularic acid was found to focus in the central region and bisbibenzyls were enriched in the periphery. The region-specific gene expression and antioxidant activities were characterized. In line with the spatial feature of bibenzyls, higher MpSTCS1A and Mp4CL expression levels and antioxidant ability were exhibited in the archegoniophore. The expression level of MpSTCS1A, and the content of total phenolic acid was increased after UV-B irradiation, suggesting bibenzyls play an important role in UV-B tolerance. Moreover, lunularic acid and extract of archegoniophore at a certain concentration can stimulate the spore germination under normal conditions and UV-B stress. These works broaden our understanding of the significance of bibenzyls in spore propagation and environmental adaptation.

Mechanisms and Active Compounds Polysaccharides and Bibenzyls of Medicinal Dendrobiums for Diabetes Management

BACKGROUND

Medicinal dendrobiums are used popularly in traditional Chinese medicine for the treatment of diabetes, while their active compounds and mechanism remain unclear. This review aimed to evaluate the mechanism and active compounds of medicinal dendrobiums in diabetes management through a systematic approach.

METHODS

A systematic approach was conducted to search for the mechanism and active phytochemicals in Dendrobium responsible for anti-diabetic actions using databases PubMed, Embase, and SciFinder.

RESULTS

Current literature indicates polysaccharides, bibenzyls, phenanthrene, and alkaloids are commonly isolated in Dendrobium genusin which polysaccharides and bibenzyls are most aboundant. Many animal studies have shown that polysaccharides from the species of Dendrobium provide with antidiabetic effects by lowering glucose level and reversing chronic inflammation of T2DM taken orally at 200 mg/kg. Dendrobium polysaccharides protect pancreatic β-cell dysfunction and insulin resistance in liver. Dendrobium polysaccharides up-regulate the abundance of short-chain fatty acid to stimulate GLP-1 secretion through gut microbiota. Bibenzyls also have great potency to inhibit the progression of the chronic inflammation in cellular studies.

CONCLUSION

Polysaccharides and bibenzyls are the major active compounds in medicinal dendrobiums for diabetic management through the mechanisms of lowering glucose level and reversing chronic inflammation of T2DM by modulating pancreatic β-cell dysfunction and insulin resistance in liver as a result from gut microbita regulation.

[Bibenzyls from Dendrobium officinale]

Fifteen bibenzyls were isolated and purified from the ethyl acetate extract of the stems of Dendrobium officinale by macroporous resin, MCI, silica gel, Sephadex LH-20, and ODS column chromatographies, as well as preparative thin-layer chromatography and preparative HPLC. The structures of compounds were identified according to the spectra data of ~1H-NMR, ~(13)C-NMR, and MS, and the physical and physiochemical properties: dendrocandin X(1), 3,4'-dihydroxy-4,5-dimethoxybibenzyl(2), 6″-de-O-methyldendrofindlaphenol A(3), 3,4-dihydroxy-4',5-dimethoxybibenzyl(4), dendrosinen B(5), 3,4,4'-trihydroxy-5-methoxybibenzyl(6), 3,3'-dihydroxy-4,5-dimethoxybibenzyl(7), 3,4'-dihydroxy-5-methoxybibenzyl(8), moscatilin(9), gigantol(10), 4,4'-dihydroxy-3,5-dimethoxybibenzyl(11), 3,4',5-trihydroxy-3'-methoxybibenzyl(12), 3-O-methylgigantol(13), dendrocandin U(14), and dendrocandin N(15). Compound 1 was a novel compound. Compound 2 was isolated from Dendrobium species for the first time. Compounds 3-7 were isolated from D. officinale for the first time.

[Study on chemical bibenzyls in Dendrobium gratiosissimum]

Nineteen compounds were isolated and structurally characterized from an ethanol extract of Dendrobium gratiossimum, including dendrogratiol A(1), DDB-1(2), 3,4-dihydroxyl-5,3',4'-trimethoxybibenzyl(3), amoenylin(4), chrysotoxine(5), DTB(6), 3,4,4'-trihydroxyl-5,3'-dimethoxybenzyl(7), 3-methylgiga(8), aloifol(9), gigantol tetramethyl ether(10), batatasin Ⅲ(11), moscatilin(12), moniliformine(13), gigantol(14), DMB(15), flavanthrinin(16), cannithrene-2(17), 3,4-dihydroxyl-5,4'-dimethoxystilbene(18) and 4-hydroxy-3,5,4'-trimethoxystilbene(19). 1 was a new compound, and 2-10, 16, 18 and 19 were obtained from this plant species for the first time. In vitro cytotoxic and antiviral activities of these isolates were evaluated, which displayed that 4 showed moderate cytotoxicity against human hepatoma cell line HepG2 with the IC_(50) of 10.15 μmol·L~(-1); 7 and 12 exhibited moderate inhibitory activity towards HIV virus with the IC_(50) of 9.35 and 9.15 μmol·L~(-1), respectively; and 10 displayed inhibitory activity against IAV virus with the IC_(50) of 8.90 μmol·L~(-1).

Bibenzyls and bisbybenzyls of bryophytic origin as promising source of novel therapeutics: pharmacology, synthesis and structure-activity

BACKGROUND

The amphibian, non-vascular, gametophyte-dominant, bio-indicator class, bryophytes; with their wide ranges of habitat have attained importance due to their promising medicinal attributions and therapeutic role; mostly aided by presence of aromatic bibenzyl and bisbybenzyl class of compounds. Bibenzyls are steroidal ethane derivatives, resembling the structural moiety of bioactive dihydro-stilbenoids or iso-quinoline alkaloids. These stress triggered secondary metabolites are the by-products of the flavonoid biosynthetic pathway. Different classes of bryophytes (Bryophyta, Marchantiophyta and Anthocerotophyta) possess different subtypes of bibenzyls and dimeric bisbibenzyls. Among the liverwort, hornwort and mosses, former one is mostly enriched with bibenzyl type constituents as per the extensive study conducted for phytochemical deposit. Considering macrocyclic and acyclic group of bibenzyls and bisbybenzyls, generally marchantin type compounds are reported vividly for significant biological activity that includes neuro-nephro-cardio-protection besides anti-allergic, anti-microbial, anti-apoptotic and cytotoxic activities studied on in-vitro and in-vivo models or on cell lines.

RESULT

The critical analysis of reported chemical and pharmaceutical attributions of bibenzyls and bis-bibenzyls yielded detailed report on this compound class along with their application, mode of action, natural source, techniques of synthesis, extraction procedure, isolation and characterization. Further, the structure activity relationship studies and bioactivity of bibenzyls derived from non-bryophytic origin were also summarized.

CONCLUSION

This review encompasses prospective biological application of botanical reservoir of this primarily ignored, primeval land plant group where recent technical advances has paved the way for qualitative and quantitative isolation and estimation of novel compounds as well as marker components to study their impact on environment, as bio-control agents and as key leads in future drug designing. Graphical abstract.

Chemical Constituents and Biological Activity Profiles on Pleione (Orchidaceae)

Pleione (Orchidaceae) is not only famous for the ornamental value in Europe because of its special color, but also endemic in Southern Asia for its use in traditional medicine. A great deal of research about its secondary metabolites and biological activities has been done on only three of 30 species of Pleione. Up to now, 183 chemical compounds, such as phenanthrenes, bibenzyls, glucosyloxybenzyl succinate derivatives, flavonoids, lignans, terpenoids, etc., have been obtained from Pleione. These compounds have been demonstrated to play a significant role in anti-tumor, anti-neurodegenerative and anti-inflammatory biological activities and improve immunity. In order to further develop the drugs and utilize the plants, the chemical structural analysis and biological activities of Pleione are summarized in this review.

[Chemical constituents from tuber of Bletilla striata]

Eighteen compounds were isolated from the EtOAc soluble fraction of Bletilla striata by various chromatographic techniques, such as silica gel, ODS, Sephadex LH-20, RP-HPLC. Their structures were identified by spectroscopic methods and physicochemical properties, as 5-hydroxy-2-(p-hydroxybenzyl)- 3- methoxybibenzyl(1), shancigusins B(2), shanciguol(3),arundinan(4), 3',5-dihydroxy-2,4-di(p-hydroxybenzyl)-3-methoxybibenzyl(5), arundin(6), 3,3'-dihydroxy-2-(p-hydroxybenzyl)-5-methoxybibenzyl(7), 3, 3'-dihydroxy-2', 6'-bis(p-hydroxybenzyl)-5-methoxybibenzyl(8), 7-hydroxy-2,4-dimethoxyphenanthrene(9), bleformin B(10),nudol(11), 3,7-dihydroxy-2, 4-dimethoxyphenanthrene(12), 2, 7-dihydroxy-4-methoxy-9,10-dihydrophenathrene(13), bleformin D(14), 4,4'-dimethoxy-9,10-dyhydro-[6,1'-biphenanthrene]-2,2',7,7'-tetraol(15),gymconopin C(16),(2,3-trans)-2-(4-hydroxy-3-methoxyphenyl)-3-hydroxymethyl-10-methoxy-2,3,4,5-tetrahydro-phenanthro[2,1-b]furan-7-ol(17),shanciol(18). Among them, compound 1 was a new compound, Compounds 2-6,9,15-18 were isolated from this genus for the first time.

A new antifungal and antiprotozoal bibenzyl derivative from Gavilea lutea

A new bibenzyl derivative (4), together with two glycosylated flavonoids (1 and 2), batatasin III (3) and the phenanthrene isohircinol (5) were isolated from the aerial parts of Gavilea lutea. Their structures were elucidated on the basis of spectroscopic studies including 1D and 2D NMR, UV, IR and HRESIMS. All isolated compounds were evaluated for their antifungal activity towards Candida albicans. The new compound 4 showed inhibitory activity with a MIQ of 50 μg. In addition, compound 4 exhibited a selective activity (IC₅₀ = 2.3 μg/mL) against Leishmania donovani.

Cytotoxic and anti-metastatic activities of phenolic compounds from Dendrobium ellipsophyllum

BACKGROUND/AIM

Phenolic compounds isolated from Dendrobium ellipsophyllum Tang & Wang (Orchidaceae) have been shown to possess potential pharmacological activity; however, their anticancer as well as anti-metastasis activities are largely unknown. The aim of the present study was to isolate active compounds from D. ellipsophyllum and to explore the possible effects of phenolic compounds isolated from the plant for cytotoxic as well as anti-metastatic properties.

MATERIALS AND METHODS

The compounds were isolated by using chromatographic techniques including silica gel and Sephadex LH20. Each of the isolates was evaluated for their cytotoxicity on H292 human lung cancer cell lines by 2,3-Bis(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide assay. The cytotoxic compounds were further evaluated for apoptosis-inducing and anoikis-sensitizing effects.

RESULTS

Ten phenolic compounds were isolated, 5,7-dihydroxy-chromen-4-one (1:); 4,5-dihydroxy-2,3-dimethoxy-9,10-dihydrophenanthrene (2:); moscatilin (3:), 4,4'-dihydroxy-3,5-dimethoxybibenzyl (4:); 4,5,4'-trihydroxy-3,3'-dimethoxybibenzyl (5:); (2S)-homoeriodictyol (6:); (2S)-eriodictyol (7:); chrysoeriol (8:); phloretic acid (9:); and luteolin (10:). Compounds 4:, 5:, 8: and 10: exhibited appreciable cytotoxic activity with 50% inhibitory concentration values less than 250 μM. These compounds also showed potential apoptosis induction and anoikis-sensitizing effect at non-toxic concentrations.

CONCLUSION

Compounds 4:, 5:, 8: and 10: are responsible for cytotoxic and anti-metastatic activities of D. ellipsophyllum.