Antifungal Abietane-Type Diterpenes from the Cones of Taxodium distichum Rich

Inducing breast cancer cell death: The impact of taxodone on proliferation through apoptosis

Breast cancer is the most prevalent form of cancer in women and a major contributor to cancer-related fatalities worldwide. Several factors play a role in the development of breast cancer, encompassing age, hormone levels, etc. Taxodone has shown significant anti-tumor properties in both laboratory experiments and living organisms. However, its impact on the human MCF-7 breast cancer cell line has not been researched. This investigation explores the chemo-preventive potential of taxodone in the MCF-7 breast cancer cells. The anticancer potential of taxodone against MCF-7 cells was determined by MTT assay. Further, the induction of apoptosis in MCF-7 breast cancer cells was confirmed via ELISA, which indicated the increased incidences of chromatin condensation and ssDNA breakage in the MCF-7 apoptotic cells upon 24 h of taxodone treatment. The intracellular reactive oxygen species (ROS) level was evaluated using H2DCFDA fluorescent dye to elucidate the mechanism of action triggered upon taxodone treatment. The increasing intercellular ROS level sequentially activated the caspase-mediated apoptosis pathway. Consequently, the outcomes revealed that taxodone decreased the cell viability of MCF-7 dose-dependently. Taxodone triggers apoptosis in MCF-7 cells by increasing intracellular ROS levels and activating the caspase cascade through the mitochondrial apoptosis-induced channel, an early marker of apoptosis onset. Our results indicate that taxodone exhibits anti-proliferative and apoptotic properties against human MCF-7 breast cancer cells, suggesting it to be a natural anticancer agent.

Taxodin A, a Cytotoxic C30 Terpenoid from Taxodium mucronatum with a Unique Skeleton

Taxodin A (1), a unique C30 terpenoid featuring an unprecedented skeleton composed of an abietane-type diterpene and a menthane-type monoterpene, was obtained from the leaves and branches of Taxodium mucronatum. The structure and absolute configuration of compound 1 was unequivocally established by the combination of extensive spectroscopic analyses and X-ray single-crystal diffraction analysis. Compound 1 exhibited potent cytotoxic activities against A549, SMMC-7721, MDA-MB-231, and SW480 cell lines with IC50 values of 15.35±0.73, 8.49±0.35, 17.53±0.79, 18.93±0.60 μM, respectively.

Unified short syntheses of oxygenated tricyclic aromatic diterpenes by radical cyclization with a photoredox catalyst

The biomimetic two-phase strategy employing polyene cyclization and subsequent oxidation/substitution is an effective approach for divergent syntheses of [6-6-6]-tricyclic diterpenes. However, this strategy requires lengthy sequences for syntheses of oxygenated tricyclic aromatic abietane/podocarpane diterpenes owing to the many linear oxidation/substitution steps after cyclization. Here, we present a new synthetic route based on a convergent reverse two-phase strategy employing a reverse radical cyclization approach, which enabled the unified short syntheses of four aromatic abietane/podocarpane diterpenes and the divergent short syntheses of other related diterpenes. Oxygenated and substituted precursors for cyclization were convergently prepared through Friedel-Crafts acylation and rhodium-catalyzed site-selective iodination. Radical redox cyclization using an iridium photoredox catalyst involving neophyl rearrangement furnished the thermodynamically favored 6-membered ring preferentially. (±)-5,6-Dehydrosugiol, salvinolone, crossogumerin A, and Δ5-nimbidiol were synthesized in only 8 steps. An oxygenated cyclized intermediate was also useful for divergent derivatization to sugiol, ferruginol, saprorthoquinone, cryptomeriololide, and salvinolone.

Arylcyanomethylenequinone Oximes: An Overview of Synthesis, Chemical Transformations, and Biological Activity

Quinone methides are a class of biologically active compounds that can be used in medicine as antibacterial, antifungal, antiviral, antioxidant, and anti-inflammatory agents. In addition, quinone methides have the potential to be used as pesticides, dyes, and additives for rubber and plastics. In this paper, we discuss a subclass of quinone methides: methylenequinone oximes. Although the first representatives of the subgroup were synthesized in the distant past, they still need to be additionally studied, while their chemistry, biological properties, and perspective of practical applications require to be comprehensively summarised. Based on the analysis of the literature, it can be concluded that methylenequinone oximes exhibit a diversified profile of properties and outstanding potential as new drug candidates and reagents in organic synthesis, both of electrophilic and nucleophilic nature, worthy of wide-ranging further research.

Synthesis of Cyclohexanones by a Tandem Photocatalyzed Annulation

The rapid synthesis of cyclic scaffolds is of high importance to the chemistry community. Strategies for the convergent synthesis of substituted carbocycles and heterocycles remain underexplored despite the plethora of applications that these cyclic motifs have in the pharmaceutical and materials industries. Reported herein is a tandem carbene and photoredox-catalyzed process for the convergent synthesis of substituted cycloalkanones via a formal [5 + 1] cycloaddition. Featuring two distinct photoredox cycles and a novel α-oxidation of benzylic ketones, this reaction offers a mild approach to construct two contiguous C-C bonds and eliminates the need for strong bases or expensive metal catalysts. The utility of this method is highlighted through various product diversification reactions that allow access to a range of important cyclic scaffolds.

Euphorbia Diterpenes: An Update of Isolation, Structure, Pharmacological Activities and Structure-Activity Relationship

Euphorbia species have a rich history of ethnomedicinal use and ethnopharmacological applications in drug discovery. This is due to the presence of a wide range of diterpenes exhibiting great structural diversity and pharmacological activities. As a result, Euphorbia diterpenes have remained the focus of drug discovery investigations from natural products. The current review documents over 350 diterpenes, isolated from Euphorbia species, their structures, classification, biosynthetic pathways, and their structure-activity relationships for the period covering 2013-2020. Among the isolated diterpenes, over 20 skeletal structures were identified. Lathyrane, jatrophane, ingenane, ingenol, and ingol were identified as the major diterpenes in most Euphorbia species. Most of the isolated diterpenes were evaluated for their cytotoxicity activities, multidrug resistance abilities, and inhibitory activities in vitro, and reported good activities with significant half-inhibitory concentration (IC50) values ranging from 10-50 µM. The lathyranes, isopimaranes, and jatrophanes diterpenes were further found to show potent inhibition of P-glycoprotein, which is known to confer drug resistance abilities in cells leading to decreased cytotoxic effects. Structure-activity relationship (SAR) studies revealed the significance of a free hydroxyl group at position C-3 in enhancing the anticancer and anti-inflammatory activities and the negative effect it has in position C-2. Esterification of this functionality, in selected diterpenes, was found to enhance these activities. Thus, Euphorbia diterpenes offer a valuable source of lead compounds that could be investigated further as potential candidates for drug discovery.

Discovery and characterization of diterpene synthases in Chamaecyparis formosensis Matsum. which participated in an unprecedented diterpenoid biosynthesis route in conifer

Chamaecyparis formosensis Matsum. is an endemic and precious coniferous species of Taiwan, and is known for a high abundance of specialized metabolites, which contributes to the excellent timber durability. Several terpenoids were identified and isolated from C. formosensis wood and needles, and exhibit anti-fungal and anti-bacterial bioactivities, which may participate in plant defense against pathogens. In various identified compounds, not only cadinene and ferruginol, were identified in C. formosensis extracts but also unique diterpenoids, which include pisferal, totarol, and derivates of isoabienol. To understand the biosynthesis of these specific diterpenoids, we conducted a series of functional characterization of the C. formosensis diterpene synthases (CfdiTPSs), which participate in skeleton formation and differentiation of diterpenes. In this study, we identified eight diTPSs from C. formosensis transcriptome, and they all contain either class I or class II motif, which indicates they are all monofunctional enzymes. These candidates consist of three class II diTPSs and five class I diTPSs, and after conducting in vivo and in vitro assays, class II diTPS CfCPS1 was characterized as a (+)-copalyl diphosphate synthase ((+)-CPS), and class I diTPSs CfKSL1 could further convert (+)-copalyl diphosphate ((+)-CPP) to levopimaradiene. Meanwhile, CfKSL1 also accepted labda-13-en-8-ol diphosphate (LPP) as substrate and formed monoyl oxide. Another class I diTPS, CfKSL4, exhibits a strong enzymatic ability of isoabienol synthase, which is firstly reported in conifer. This finding provides potential participants in the biosynthesis of unique diterpenoids, and with this knowledge, we can further expand our understanding of diterpenoid metabolism in Cupressaceae and their potential role in plant defense.

In Vivo Biological Evaluation of a Synthetic Royleanone Derivative as a Promising Fast-Acting Trypanocidal Agent by Inducing Mitochondrial-Dependent Necrosis

The life-long and life-threatening Chagas disease is one of the most neglected tropical diseases caused by the protozoan parasite Trypanosoma cruzi. It is a major public health problem in Latin America, as six to seven million people are infected, being the principal cause of mortality in many endemic regions. Moreover, Chagas disease has become widespread due to migrant populations. Additionally, there are no vaccines nor effective treatments to fight the disease because of its long-term nature and complex pathology. Therefore, these facts emphasize how crucial the international effort for the development of new treatments against Chagas disease is. Here, we present the in vitro and in vivo trypanocidal activity of some oxygenated abietane diterpenoids and related compounds. The 1,4-benzoquinone 15, not yet reported, was identified as a fast-acting trypanocidal drug with efficacy against different strains in vitro and higher activity and lower toxicity than benznidazole in both phases of murine Chagas disease. The mode of action was also evaluated, suggesting that quinone 15 kills T. cruzi by inducing mitochondrion-dependent necrosis through a bioenergetics collapse caused by a mitochondrial membrane depolarization and iron-containing superoxide dismutase inhibition. Therefore, the abietane 1,4-benzoquinone 15 can be considered as a new candidate molecule for the development of an appropriate and commercially accessible anti-Chagas drug.

Cytotoxic Activity of Abietane-Type Diterpenes Isolated From Taxodium distichum Against Cancer Cells Adapted to Nutrient-Starved Conditions

The mechanisms of cancer cell adaptation to tumor microenvironmental conditions, such as hypoxia and nutrient starvation, are currently receiving much attention as possible therapeutic targets. In an attempt to identify selectively cytotoxic substances against cancer cells adapted to nutrient starvation, 4 abietane-type diterpenes, sugiol (1), 6-α-hydroxysugiol (2), cryptojaponol (3), and 6-hydroxy-5,6-dehydrosugiol (4), were isolated from the bark of Taxodium distichum L. Rich var. distichum (bald cypress). Compounds 1, 2, and 4 showed potent cytotoxic activity against PANC-1 cells adapted to nutrient-starved conditions with half-maximal effective concentration (EC50) values of 6.4-9.2 µM, whereas the EC50 values of these compounds against PANC-1 cells under general culture conditions were more than 100 µM. Alternatively, compound 3, which we report for the first time in the genus Taxodium, showed moderate cytotoxicity against PANC-1 cells under nutrient-starved conditions with an EC50 of 37.9 µM. The selective index (S.I.), which compared the activity under nutrient-starved conditions with that under general culture conditions, was low (7.9). Further investigation revealed that the selective cytotoxic activity of compound 2 might be affecting the mitochondria.

Terpenoids of the Swamp Cypress Subfamily (Taxodioideae), Cupressaceae, an Overview by GC-MS

The resins bled from stems and in seed cones and leaves of Cryptomeria japonica, Glyptostrobus pensilis, Taxodium distichum, and T. mucronatum were characterized to provide an overview of their major natural product compositions. The total solvent extract solutions were analyzed as the free and derivatized products by gas chromatography-mass spectrometry to identify the compounds, which comprised minor mono- and sesquiterpenoids, and dominant di- and triterpenoids, plus aliphatic lipids (e.g., n-nonacosan-10-ol). Ferruginol, 7α-p-cymenylferruginol, and chamaecydin were the major characteristic markers for the Taxodioideae conifer subfamily. The mass spectrometric data can aid polar compound elucidation in environmental, geological, archeological, forensic and pharmaceutical studies.

Comparative evaluation of cytotoxic, antimicrobial and antioxidant activities of the crude extracts of three Plectranthus species grown in Saudi Arabia

Natural products from medicinal plants represent major resource of novel therapeutic substances for combating serious diseases including cancers and microbial infections. The genus Plectranthus (Family: Labiatae) represents a large and widespread group of species with a diversity of traditional uses in treatment of various ailments. Therefore, this research study aimed to evaluate the cytotoxic, antimicrobial and antioxidant activities of three Plectranthus species growing in Saudi Arabia namely P. cylindraceus Hocst. ex Benth., P. asirensis JRI Wood and P. barbatus Andrews. Moreover, this work focused on the isolation of the active constituents responsible for the activities from the most active Plectranthus species.

The extracts were tested for their cytotoxic activity against three cancer cell lines (Hela, HepG2 and HT-29), using MTT-test, antimicrobial activity against Gram positive, Gram negative bacterial and fungal strains using broth micro-dilution assay for minimum inhibitory and bactericidal concentrations (MIC and MBC) and antioxidant activity using scavenging activity of DPPH radical and β-carotene-linoleic acid methods. The ethanolic extracts of the Plectranthus species showed remarkable cytotoxic activity against all cancer cell lines with IC₅₀ values ranging between 10.1 ± 0.33 to 102.6 ± 8.66 μg/mL and a great and antimicrobial activity with MIC values between 62.5 and 250 µg/mL. In addition, the three Plectranthus species showed almost moderate antioxidant activity. The most interesting cytotoxic and antimicrobial results were observed with the extract of P. barbatus. Consequently, this extract was partitioned between water and n-hexane, chloroform and n-butanol and tested. The cytotoxic activity resided predominantly in the n-hexane and chloroform fractions. The analysis of the chloroform fraction led to the isolation of four diterpenoid compounds, two of labdane- and two of abietane-type, which were identified as coleonol B, forskolin, sugiol and 5,6-dehydrosugiol. Purification of the n-hexane fraction led to isolation of a major abietane-type diterpene, which was identified as ferruginol. Sugiol, 5,6-dehydrosugiol and ferruginol were isolated for the first time from P. barbatus in this study. The isolated diterpenoids showed variable cytotoxic effects with IC₅₀ values between 15.1 ± 2.03 and 242 ± 13.3 µg/mL, a great antimicrobial activity with MIC values between 15.6 and 129 µg/mL and a total antioxidant activity ranging from 23.1 ± 2.9 to 69.2 ± 3.8%.

Crystal structure of 6,7-de-hydro-royleanone isolated from Taxodium distichum (L.) Rich

The title compound, 6,7-de-hydro-royleanone, C20H26O3 [systematic name: (4bS)-3-hy-droxy-2-isopropyl-4b,8,8-trimethyl-4b,5,6,7,8,8a-hexa-hydro-phenanthrene-1,4-dione] was isolated from Taxodium distichum (L.) Rich. The compound crystallizes in the space group P21. The crystal structure features two O-H⋯O hydrogen bonds, forming chains along the [010] direction.

An extract from Taxodium distichum targets hemagglutinin- and neuraminidase-related activities of influenza virus in vitro

Influenza virus remains an emerging virus and causes pandemics with high levels of fatality. After screening different plant extracts with potential anti-influenza activity, a water extract of Taxodium distichum stems (TDSWex) showed excellent activity against influenza viruses. The EC₅₀ of TDSWex was 0.051 ± 0.024 mg/mL against influenza virus A/WSN/33. TDSWex had excellent antiviral efficacy against various strains of human influenza A and B viruses, particularly oseltamivir-resistant clinical isolates and a swine-origin influenza strain. We observed that the synthesis of viral RNA and protein were inhibited in the presence of TDSWex. The results of the time-of-addition assay suggested that TDSWex inhibited viral entry and budding. In the hemagglutination inhibition assay, TDSWex inhibited the hemagglutination of red blood cells, implying that the extract targeted hemagglutin-related functions such as viral entry. In the attachment and penetration assay, TDSWex showed antiviral activity with EC₅₀s of 0.045 ± 0.026 and 0.012 ± 0.003 mg/mL, respectively. In addition, TDSWex blocked neuraminidase activity. We conclude that TDSWex has bimodal activities against both hemagglutinin and neuraminidase during viral replication.

Antifilarial activity of diterpenoids from Taxodium distichum

BACKGROUND

Lymphatic filariasis caused by Wuchereria bancrofti, Brugia malayi and B. timori, is a debilitating disease with an adverse social and economic impact. The infection remains unabated in spite of treatment with existing antifilarial drugs diethylcarbamazine (DEC) and ivermectin which are chiefly microfilaricides. There is therefore, need for macrofilaricides, embryostatic agents and better microfilaricides. In the present study we explored the antifilarial potential of crude extract and its molecular fractions of the plant Taxodium distichum using in vitro assay systems and rodent models of B. malayi infection.

METHODS

Ethanolic extract (A001) of aerial parts of T. distichum was solvent fractionated and sub-fractionated. Four molecules, 3-Acetoxylabda-8(20), 13-diene-15-oic acid (K001), Beta-sitosterol (K002), labda-8(20),13-diene-15-oic acid (K003) and Metasequoic acid A (K004) were isolated from the fractions and their structure determined by spectroscopic analysis. The extract, subfractions and molecules were evaluated for antifilarial activity against B. malayi by 3-(4,5-dimethylthiazol-2-yl)-2,5 diphenyltetrazolium bromide (MTT) reduction and motility assays in vitro and in two animal models, Meriones unguiculatus and Mastomys coucha, harbouring B. malayi infection.

RESULTS

A001 was effective in killing microfilariae (mf) and adult worms in vitro. The diterpenoid K003 produced 100 % reduction in motility of both mf and adult worms and > 80 % inhibition in MTT reduction potential of adult female worms. In B. malayi-M. unguiculatus model, A001 killed all the adult worms in > 80 % of infected animals. K003 was embryostatic (> 95 %) in this model. In the B. malayi-M. coucha model, K003 killed ~54 % of adult worms (macrofilaricidal activity) and rendered > 36 % female worms sterile; it also stopped any further rise in microfilaraemia after day 42 post-initiation of treatment.

CONCLUSION

Ethanolic extract of aerial parts of the plant T. distichum possesses potent antifilarial activity and the active principle was localised to K003 which showed significant macrofilaricidal activity and late suppression of peripheral microfilaraemia and some embryostatic activity. These findings indicate that labdane diterpenoid molecule(s) may provide valuable leads for design and development of new macrofilaricidal agent(s). To the best of our knowledge, this is the first report on antifilarial efficacy of products from the plant T. distichum.

Phytophthora austrocedri Elicitates Changes in Diterpene Profile of Austrocedrus chilensis

The populations of the Andean Cupressaceae Austrocedrus chilensis have been severely affected by a disease caused by the phytopathogenic fungus Phytophthora austrocedri. A study was undertaken to disclose changes in the resin composition of P. austrocedri-infected individuals, including naturally infected and artificially inoculated trees, compared with healthy A. chilensis trees. GC-MS and ¹H-NMR studies showed a clear differentiation among healthy and infected resins, with the diterpene isopimara-8(9),15-dien-19-ol as a relevant constituent in resins from infected trees. The effect of resin fractions from P. austrocedri infected trees on the pathogen was assessed by measuring the mycelial growth in agar plates. The most active fractions from resin obtained from infected trees inhibited fungal growth by nearly 50% at 1 mg/dish (35.37 µg/cm²). The main constituent in the active fractions were 18-hydroxymanool and the aldehyde torulosal. Both compounds are oxidation products of manool and can be a chemical response of the tree to the pathogen or be formed from the pathogen as a biotransformation product of manool by microbial oxidation. While the diterpene profiles from A. chilensis tree resins can easily differentiate healthy and P. austrocedri infected individuals, the possible conversion of manool to the antifungal derivatives 4 and 6 by the microorganism remains to be established.

Contrasting Patterns of Diterpene Acid Induction by Red Pine and White Spruce to Simulated Bark Beetle Attack, and Interspecific Differences in Sensitivity Among Fungal Associates

Conifers possess a suite of physiochemical defenses that protect their subcortical tissues from bark beetle - fungal complexes. These defenses include rapid induction of terpenoids and phenolics at the site of attack. Studies of the distribution, induction, and bioactivity of conifer terpenoids have focused heavily on monoterpenes. We assessed induction of diterpene acids in white spruce (Picea glauca) and red pine (Pinus resinosa) to fungal associates of two bark beetles, and the responses of four spruce beetle (Dendroctonus rufipennis)-associated fungi to three diterpene acids. Constitutive phloem contents differed between species, in that red pine had extremely low concentrations of diterpene acids, whereas white spruce had substantial constitutive levels. Induction differed quantitatively. Both red pine and white spruce exhibited marked increases, but red pine underwent greater increases and achieved higher concentrations than white spruce. Induction also differed qualitatively in that red pine showed lower diversity and fewer compositional changes during induction than white spruce. In red pine,fungal inoculation accompanying wounding elicited greater increases than wounding alone, but in white spruce total concentrations were higher following wounding alone. Spruce beetle fungal symbiont growth varied among species and compounds. Some diterpenes elicited both stimulatory and inhibitory effects on fungi, depending on concentration. All four fungi exhibited higher tolerances compared to those associated with pine bark beetles in previous studies. Variation in tolerances to, and potentially metabolism of, diterpene acids by symbionts may reflect differences in constitutive levels between spruce and pine, and partially explain differences in concentrations achieved during induction.

Proteomics investigation reveals cell death-associated proteins of basidiomycete fungus Trametes versicolor treated with Ferruginol

Ferruginol has antifungal activity against wood-rot fungi (basidiomycetes). However, specific research on the antifungal mechanisms of ferruginol is scarce. Two-dimensional gel electrophoresis and fluorescent image analysis were employed to evaluate the differential protein expression of wood-rot fungus Trametes versicolor treated with or without ferruginol. Results from protein identification of tryptic peptides via liquid chromatography–electrospray ionization tandem mass spectrometry (LC–ESI-MS/MS) analyses revealed 17 protein assignments with differential expression. Downregulation of cytoskeleton β-tubulin 3 indicates that ferruginol has potential to be used as a microtubule-disrupting agent. Downregulation of major facilitator superfamily (MFS)–multiple drug resistance (MDR) transporter and peroxiredoxin TSA1 were observed, suggesting reduction in self-defensive capabilities of T. versicolor. In addition, the proteins involved in polypeptide sorting and DNA repair were also downregulated, while heat shock proteins and autophagy-related protein 7 were upregulated. These observations reveal that such cellular dysfunction and damage caused by ferruginol lead to growth inhibition and autophagic cell death of fungi.

Aromatic abietane diterpenoids: their biological activity and synthesis

In this study, the biological properties of abietane-type diterpenoids with an aromatic C ring are reviewed. The review contains about 160 references.

In vitro antiprotozoal activity of abietane diterpenoids isolated from Plectranthus barbatus Andr

Chromatographic separation of the n-hexane extract of the aerial part of Plectranthus barbatus led to the isolation of five abietane-type diterpenes: dehydroabietane (1); 5,6-didehydro-7-hydroxy-taxodone (2); taxodione (3); 20-deoxocarnosol (4) and 6α,11,12,-trihydroxy-7β,20-epoxy-8,11,13-abietatriene (5). The structures were determined using spectroscopic methods including one- and two-dimensional NMR methods. Compounds (1)–(3) and (5) are isolated here for the first time from the genus Plectranthus. The isolated abietane-type diterpenes tested in vitro for their antiprotozoal activity against erythrocytic schizonts of Plasmodium falciparum, intracellular amastigotes of Leishmania infantum and Trypanosoma cruzi and free trypomastigotes of T. brucei. Cytotoxicity was determined against fibroblast cell line MRC-5. Compound (2) 5,6-didehydro-7-hydroxy-taxodone showed remarkable activity with acceptable selectivity against P. falciparum (IC₅₀ 9.2 μM, SI 10.4) and T. brucei (IC₅₀ 1.9 μM, SI 50.5). Compounds (3)–(5) exhibited non-specific antiprotozoal activity due to high cytotoxicity. Compound (1) dehydroabietane showed no antiprotozoal potential.