Antimitotic activity of two macrocyclic bis(bibenzyls), isoplagiochins A and B from the Liverwort Plagiochila fruticosa

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.

Discovery and Anticancer Activity of the Plagiochilins from the Liverwort Genus Plagiochila

The present analysis retraces the discovery of plagiochilins A-to-W, a series of seco-aromadendrane-type sesquiterpenes isolated from diverse leafy liverworts of the genus Plagiochila. Between 1978, with the first isolation of the leader product plagiochilin A from P. yokogurensis, and 2005, with the characterization of plagiochilin X from P. asplenioides, a set of 24 plagiochilins and several derivatives (plagiochilide, plagiochilal A-B) has been isolated and characterized. Analogue compounds recently described are also evoked, such as the plagiochianins and plagicosins. All these compounds have been little studied from a pharmacological viewpoint. However, plagiochilins A and C have revealed marked antiproliferative activities against cultured cancer cells. Plagiochilin A functions as an inhibitor of the termination phase of cytokinesis: the membrane abscission stage. This unique, innovative mechanism of action, coupled with its marked anticancer action, notably against prostate cancer cells, make plagiochilin A an interesting lead molecule for the development of novel anticancer agents. There are known options to increase its potency, as deduced from structure–activity relationships. The analysis shed light on this family of bryophyte species and the little-known group of bioactive terpenoid plagiochilins. Plagiochilin A and derivatives shall be further exploited for the design of novel anticancer targeting the cytokinesis pathway.

Tissue Culture of Plagiochasma appendiculatum and the Effect of Callus Differentiation on Types and Content of Bisbibenzyls

Plagiochasma appendiculatum, a thalloid liverwort, contains high levels of bisbibenzyls, aromatic compounds with potent antitumor as well as antifungal activities. In the present study, rapid growth callus was induced from the thallus of P. appendiculatum, and optimal culture conditions, including medium, temperature, pH, and plant growth regulators for callus production were evaluated. Under optimal culture conditions, the biomass of the callus doubled with a sigmoidal growth curve after 15 days. Differentiation and plant regeneration were studied on a medium supplemented with different plant hormones (α-naphthaleneacetic acid [NAA], 6-benzyladenine [6-BA], and 2,4-dichlorophenoxyacetic acid [2,4-D]). NAA and 6-BA stimulated rhizoid and thallus differentiation, respectively, whereas 2,4-D inhibited the differentiation of thallus and rhizoid. Different metabolic profiles of callus, differentiated thallus, and thallus in the soil were studied by high-performance liquid chromatography. The results showed that both the callus and thallus could synthesize bisbibenzyls. In addition, the kinds and content of bisbibenzyl differed significantly between the callus and thallus. In conclusion, P. appendiculatum thallus cultured in vitro possesses the ability to biosynthesize bisbibenzyl, and it may be utilized for the mass production of specific bisbibenzyls in an appropriate growth environment.

Assessment of the Biological Effects of Pellia endiviifolia and its Constituents in Vitro

Liverworts are characterized by a high content of bioactive compounds reported to show antimicrobial, anticancer, and antioxidant properties. In this study, the biological effects of the methanol extract of the liverwort Pellia endiviifolia and its constituents, bis-bibenzyls perrottetin E, 10′-hydroxyperrottetin E, and 10,10′-dihydroxyperrottetin E, were investigated using human peripheral blood cells as a model system. The assessment of the investigated compounds comprised testing their genotoxicity, apoptotic potential, and redox modulating activities. The genotoxicity testing indicated that medium (25 µM) and high concentrations (100 µM) of the investigated compounds displayed genotoxic and antiproliferative effects in human lymphocytes as revealed by significant, concentration-dependent enhancement of the micronuclei incidence and decrease in the cytokinesis-block proliferation index compared to the control ( P < .001). Analysis of leukocyte apoptosis showed a substantial potential of all investigated compounds to induce apoptosis, which was not concentration-dependent. The P endiviifolia extract and perrottetin E demonstrated considerable pro-apoptotic potential, even at the lowest concentration (1 µM) applied. Evaluation of the redox modulating effects, which comprised measuring erythrocyte catalase activity and the lymphocyte malondialdehyde level, showed that the investigated compounds did not induce oxidative stress in human peripheral blood cells ( P > .05). The observed genotoxic, antiproliferative, and proapoptotic effects of the investigated compounds make them suitable for further comprehensive studies related to their possible applications as anticancer agents.

Separation Three Phenanthrenes and Two Bibenzyls from Chloroform fractions of Pholidota articulata Lindl. by Using HPLC

BACKGROUND

Pholidota articulata Lindl has been used as a traditional medicine and Yi-nationality herbal medicine for the treatment of various diseases. Phenanthrenes and bibenzyls commonly found in genus Pholidota are one of the most important natural ingredients owing to their various biological activities.

OBJECTIVE

This study aimed to establish a HPLC method for determination of the levels of three phenenthrenes (flavidin, lusianthridin, coelonin) and two bibenzyls (batatasin III, cirrhopetalidin) in rhizomes of P. articulata Lindl.

METHODS

The separated and elucidated compounds from chloroform fractions of P. articulata Lindl was used as standards and analyzed by gradient elution HPLC with variable wavelength detector (VWD) at 274 nm.

RESULTS

The calibration curves exhibited good linearity (R2 = 0.9999) that was ranged from 20 to 960 ng/mL, the average recoveries were between 91.5 and 102.9%, and the relative standard deviation (RSD) values of precision, stability and repeatability were less than 2.34%. There were significant differences in the content of phenenthrenes and bibenzyls from the plants of genus Pholidota, Dendrobium and Bulbophyllum. Furthermore, this is the first report on the validation of a method for the quantitative analysis of flavidin (a) and cirrhopetalidin (e).

CONCLUSIONS

The present study will provide an alternative method for the rapid separation of phenanthrenes and bibenzyls from natural products and lay a foundation for the study of biological activity.

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.

Chemotypes and Biomarkers of Seven Species of New Caledonian Liverworts from the Bazzanioideae Subfamily

Volatile components of seven species of the Bazzanioideae sub-family (Lepidoziaceae) native to New Caledonia, including three endemic species (Bazzania marginata, Acromastigum caledonicum and A. tenax), were analyzed by GC-FID-MS in order to index these plants to known or new chemotypes. Detected volatile constituents in studied species were constituted mainly by sesquiterpene, as well as diterpene compounds. All so-established compositions cannot successfully index some of them to known chemotypes but afforded the discovery of new chemotypes such as cuparane/fusicoccane. The major component of B. francana was isolated and characterized as a new zierane-type sesquiterpene called ziera-12(13),10(14)-dien-5-ol (23). In addition, qualitative intraspecies variations of chemical composition were very important particularly for B. francana which possessed three clearly defined different compositions. We report here also the first phytochemical investigation of Acromastigum species. Moreover, crude diethyl ether extract of B. vitatta afforded a new bis(bibenzyl) called vittatin (51), for which a putative biosynthesis was suggested.

Chemical Constituents of Bryophytes: Structures and Biological Activity

Comparatively little attention has been paid to the bryophytes for use in the human diet or medicine in spite of the presence of 23 000 species globally. Several hundred new compounds have been isolated from the liverworts (Marchantiophyta), and more than 40 new carbon skeletons of terpenoids and aromatic compounds were found. Most of the liverworts studied elaborate characteristic odiferous, pungent, and bitter-tasting compounds, of which many show antimicrobial, antifungal, antiviral, allergic contact dermatitis, cytotoxic, insecticidal, anti-HIV, plant growth regulatory, neurotrophic, NO production and superoxide anion radical release inhibitory, muscle relaxing, antiobesity, piscicidal, and nematocidal activities. The biological effects ascribed to the liverworts are mainly due to lipophilic sesqui- and diterpenoids, phenolic compounds, and polyketides, which are the principal constituents of their oil bodies. Some mosses and liverworts produce significant levels of vitamin B₂ and tocopherols, as well as prostaglandin-like highly unsaturated fatty acids. The most characteristic chemical phenomenon of the liverworts is that most of the sesqui- and diterpenoids are enantiomers of those found in higher plants. In this review, the chemical constituents and potential medicinal uses of bryophytes are discussed.

Phytochemical and biological studies of bryophytes

The bryophytes contain the Marchantiophyta (liverworts), Bryophyta (mosses) and Anthocerotophyta (hornworts). Of these, the Marchantiophyta have a cellular oil body which produce a number of mono-, sesqui- and di-terpenoids, aromatic compounds like bibenzyl, bis-bibenzyls and acetogenins. Most sesqui- and di-terpenoids obtained from liverworts are enantiomers of those found in higher plants. Many of these compounds display a characteristic odor, and can have interesting biological activities. These include: allergenic contact dermatitis, antimicrobial, antifungal and antiviral, cytotoxic, insecticidal, insect antifeedant, superoxide anion radical release, 5-lipoxygenase, calmodulin, hyaluronidase, cyclooxygenase, DNA polymerase β, and α-glucosidase and NO production inhibitory, antioxidant, piscicidal, neurotrophic and muscle relaxing activities among others. Each liverwort biosynthesizes unique components, which are valuable for their chemotaxonomic classification. Typical chemical structures and biological activity of the selected liverwort constituents as well as the hemi- and total synthesis of some biologically active compounds are summarized.

Terpenoids from the Chinese liverwort Plagiochila pulcherrima and their cytotoxic effects

Three new pimarane-type diterpenoids, 7β,11α-dihydroxypimara-8(14),15-diene (1), 1β,11α-dihydroxypimara-8(14),15-diene (2), and 11α-hydroxypimara-8(14),15-diene (3), five 2,3-secoaromadendrane-type sesquiterpenoids, including a new one, ethyoxyplagiochiline A2 (4), and three known fusicoccane-type diterpenoids were isolated from the Chinese liverwort Plagiochila pulcherrima. Their structures were established on the basis of extensive spectroscopic analysis. Compounds 6 and 7 exhibited moderate inhibitory activity on the proliferation of human cancer cell lines Hela, A172, and H460. Moreover, the cytotoxicity of compound 6 to Hela cells was related to apoptotis as confirmed by DAPI nuclear staining and flow cytometry.

Synthesis of macrocyclic bisbibenzyl derivatives and their anticancer effects as anti-tubulin agents

Based on the core skeleton of the total synthesized bisbibenzyl marchantin C, riccardin D and plagiochin E, a series of brominated and aminomethylated derivatives of above three bisbibenzyls have been synthesized and their cytotoxic activity against KB, MCF-7 and PC3 cell lines has been preliminary evaluated. The bio-test results revealed that the brominated derivatives 21, 22, 24, 25 and 28 exhibited excellent antiproliferative activity, with IC(50) value lower than their parent compounds. As a most potent microtubule depolymerization agent, compound 28 was found to arrest cells at the G(2)/M phase of the cell cycle as determined by the flow cytometry assay in PC3 cell line. The remarkable biological profile and novel structure of these bisbibenzyl derivatives make them possible as promising candidates for clinical development as chemotherapeutic agents.

Anti-influenza activity of marchantins, macrocyclic bisbibenzyls contained in liverworts

The H1N1 influenza A virus of swine-origin caused pandemics throughout the world in 2009 and the highly pathogenic H5N1 avian influenza virus has also caused epidemics in Southeast Asia in recent years. The threat of influenza A thus remains a serious global health issue and novel drugs that target these viruses are highly desirable. Influenza A possesses an endonuclease within its RNA polymerase which comprises PA, PB1 and PB2 subunits. To identify potential new anti-influenza compounds in our current study, we screened 33 different types of phytochemicals using a PA endonuclease inhibition assay in vitro and an anti-influenza A virus assay. The marchantins are macrocyclic bisbibenzyls found in liverworts, and plagiochin A and perrottetin F are marchantin-related phytochemicals. We found from our screen that marchantin A, B, E, plagiochin A and perrottetin F inhibit influenza PA endonuclease activity in vitro. These compounds have a 3,4-dihydroxyphenethyl group in common, indicating the importance of this moiety for the inhibition of PA endonuclease. Docking simulations of marchantin E with PA endonuclease suggest a putative “fitting and chelating model” as the mechanism underlying PA endonuclease inhibition. The docking amino acids are well conserved between influenza A and B. In a cultured cell system, marchantin E was further found to inhibit the growth of both H3N2 and H1N1 influenza A viruses, and marchantin A, E and perrotein F showed inhibitory properties towards the growth of influenza B. These marchantins also decreased the viral infectivity titer, with marchantin E showing the strongest activity in this assay. We additionally identified a chemical group that is conserved among different anti-influenza chemicals including marchantins, green tea catechins and dihydroxy phenethylphenylphthalimides. Our present results indicate that marchantins are candidate anti-influenza drugs and demonstrate the utility of the PA endonuclease assay in the screening of phytochemicals for anti-influenza characteristics.

Determination of atropisomeric configurations of macrocyclic bisbibenzyls by HPLC-CD/UV and quantum chemical calculations

Isoriccardin C (1) and riccardin D (2), isolated from the liverwort Reboulia hemisphaerica, were first characterized to be a mixture of two enantiomeric atropisomers by online chiral high-performance liquid chromatography-circular dichroism (HPLC-CD) analysis. Exemplarily for bisbibenzyls of the diarylether-biphenyl type, the absolute atropisomeric configurations of compunds 1 and 2 were determined by the analysis of their CD data coupled with quantum chemical CD calculations.

Antimitotic activity of lobaric acid and a new benzofuran, sakisacaulon A from Stereocaulon sasakii

Lobaric acid (1) has been isolated from lichen, Stereocaulon sasakii together with a new benzofuran, sakisacaulon A (2). Lobaric acid (1) inhibited the polymerization of tubulin. Structure-activity relationship of lobaric acid and its derivatives on inhibitory activity of tubulin polymerization was discussed.