Understanding the Enzyme (S)-Norcoclaurine Synthase Promiscuity to Aldehydes and Ketones.

The (S)-norcoclaurine synthase from Thalictrum flavum (TfNCS) stereoselectively catalyzes the Pictet-Spengler reaction between dopamine and 4-hydroxyphenylacetaldehyde to give (S)-norcoclaurine. TfNCS can catalyze the Pictet-Spengler reaction with various aldehydes and ketones, leading to diverse tetrahydroisoquinolines. This substrate promiscuity positions TfNCS as a highly promising enzyme for synthesizing fine chemicals. Understanding carbonyl-containing substrates' structural and electronic signatures that influence TfNCS activity can help expand its applications in the synthesis of different compounds and aid in protein optimization strategies. In this study, we investigated the influence of the molecular properties of aldehydes and ketones on their reactivity in the TfNCS-catalyzed Pictet-Spengler reaction. Initially, we compiled a library of reactive and unreactive compounds from previous publications. We also performed enzymatic assays using nuclear magnetic resonance to identify some reactive and unreactive carbonyl compounds, which were then included in the library. Subsequently, we employed QSAR and DFT calculations to establish correlations between substrate-candidate structures and reactivity. Our findings highlight correlations of structural and stereoelectronic features, including the electrophilicity of the carbonyl group, to the reactivity of aldehydes and ketones toward the TfNCS-catalyzed Pictet-Spengler reaction. Interestingly, experimental data of seven compounds out of fifty-three did not correlate with the electrophilicity of the carbonyl group. For these seven compounds, we identified unfavorable interactions between them and the TfNCS. Our results demonstrate the applications of in silico techniques in understanding enzyme promiscuity and specificity, with a particular emphasis on machine learning methodologies, DFT electronic structure calculations, and molecular dynamic (MD) simulations.

Dimeric benzylisoquinoline alkaloids from Thalictrum delavayi and their biological activities.

A phytochemical investigation of the whole plants of T. delavayi led to the isolation of five new dimeric benzylisoquinoline alkaloids, thalidelavines A-E (1-5), together with six known congeners (6-11). The structures and absolute configurations of new compounds were established based on analyses of spectroscopic data, ECD calculations, and single crystal X-ray crystallography. Thalidelavines A-E (1-5) were structurally complex bisbenzylisoquinoline alkaloids with various configurations. These isolated alkaloids were evaluated for their cytotoxic and immunosuppressive effects. Among them, both 9 and 10 displayed significant cytotoxicities against T98G cell lines with an IC50 value of 2.1 µM, compared with the positive CPT-11 (IC50 = 3.0 µM). In addition, 5-7 showed remarkable immunosuppressive effects. These findings not only enrich the structural diversity of bisbenzylisoquinoline alkaloids, but also provide potential candidates for the further development of the antitumor and immunosuppressive agents.

[Isoquinoline alkaloids from two species of Thalictrum genus plants].

The chemical constituents from the roots of Thalictrum cultratum and T. baicalense were investigated. By various isolation methods, such as silica gel, aluminium oxide, ODS, and Sephadex LH-20 column chromatographies, and semi-preparative HPLC, 11 simple isoquinoline alkaloids were isolated from the ethanol extract of the roots of these two plants, including a new compound, named dehydrothalflavine(1), and ten known ones(2-11): N-methylcorydaline(2), N-methylthalidaldine(3), thaliflavine(4), oxyhydrastinine(5), noroxyhydrastinine(6), dimethoxyisoquinolone(7), thalactamine(8), dehydronoroxyhydrastinine(9), 6,7-dimethoxy-2-methyl-1,2,3,4-tetrahydroisoquinoline(10), and isopicnarrhine(11). Their structures were elucidated on the basis of HR-ESI-MS and 1 D and 2 D NMR techniques. Compound 1 was a new isoquinoline alkaloid. Compound 11 was obtained from Tha-lictrum plant for the first time. All compounds did not show cytotoxic activities against HL-60, U937, HCT116, Caco-2, and HepG2 cancer cell lines.

Baicalensines A and B, Two Isoquinoline Alkaloids from the Roots of Thalictrum baicalense.

Baicalensines A (1) and B (2) were isolated from the roots of Thalictrum baicalense and structurally characterized using spectroscopic data, 13C NMR calculations, and the CASE algorithm. Compound 1, representing a new class of alkaloid dimers, contains berberine conjugated to a ring-opened isoquinoline. Compound 2 is the first reported natural benzylisoquinoline bearing a formyl group at C-3. Plausible biosynthetic pathways are proposed. Compound 1 exerted moderate cytotoxicity against the Caco-2 and HL-60 cell lines.

Thalictrum foliolosum: A lesser unexplored medicinal herb from the Himalayan region as a source of valuable benzyl isoquinoline alkaloids.

ETHNOPHARMACOLOGICAL RELEVANCE: Thalictrum foliolosum DC (Ranunculaceae) is a perennial flowering herb traditionally used as a tonic, antiperiodic, diuretic, febrifuge, purgative and stomachic and for the treatment of snakebite, jaundice, and rheumatism. AIM OF THE STUDY: To provide a critical assessment of the state-of-the-art related to the traditional uses, phytochemistry, and pharmacology of T. foliolosum with the ultimate objective of providing further research strategies to facilitate the exploitation of the therapeutic potential of T. foliolosum for the treatment of human disorders. MATERIALS AND METHODS: Exhaustive bibliographic research related to T. foliolosum plant was carried out using scientific research engines and databases such as Google Scholar, PubMed, Web of Science covering all retrieved relevant manuscripts written in English. RESULTS: Several alkaloids such as berberine, jatrorrhizine, palmatine, thalrugosidine, thalrugosaminine, thalisopine (thaligosine), thalirugidine, thalirugine, 8-oxyberberine (berlambine), noroxyhydrastinine, N,O,O-trimethylsparsiflorine, thalicarpine, thalidasine, thalfoliolosumines A and thalfoliolosumines B were reported from T. foliolosum. Ethnomedicinal studies revealed much wider scope of T. foliolosum in developing various drugs to solve multiple challenges in the health sector. Therapeutic effects were attributed to the bioactivities of the secondary metabolites present in T. foliolosum. CONCLUSIONS: T. foliolosum is rich in berberine and other benzylisoquinoline alkaloids. T. foliolosum can be used as an excellent and effective herbal remedy for various human ailments since there are no reports on the toxicity of this herb.

Racemic immunosuppressive seco-aporphine derivatives from Thalictrum wangii.

Thallactones A (1) and B (2), enantiomeric aporphine alkaloids with rare cleaved rings A and B, as well as thaliglucine N-oxide (3) and their biosynthetically related precursor, northalphenine (4), were isolated from the whole plant of Thalictrum wangii. Their structures with absolute configurations were elucidated by spectral techniques and electronic circular dichroism (ECD). Moreover, compounds 1, 3, and northalphenine inhibited concanavalin A (Con A)-stimulated proliferation of mice splenocyte significantly in a dose-dependent manner.

The protective effects of Thalictrum minus L. on lipopolysaccharide-induced acute lung injury.

ETHNOPHARMACOLOGICAL RELEVANCE: Thalictrum minus L., a Mongolian folk medicinal plant, was applied for the treatment of bacterial and fungal infection, tuberculosis and lung inflammation. AIM OF THE STUDY: The present work aims to elucidate the protective effects of Thalictrum minus L.(TML) against lipopolysaccharide (LPS)-induced acute lung injury and the underlying mechanisms. METHODS: The mice model of acute lung injury was induced by LPS via endotracheal drip, and TML (10, 20, 40 mg/kg) were administered orally 1 h prior to LPS. The efficacy and molecular mechanisms in the presence or absence of TML were investigated. RESULTS: We demonstrated that treatment with TML aqueous extract protected the mice from acute lung injury induced by LPS administration. TML significantly inhibited weight loss in mice, decreased the lung wet to dry weight (W/D) ratios and attenuated lung histopathological changes, such as infiltration of inflammatory cells and coagulation, pulmonary edema. Furthermore, we found that TML markedly reduced the LPS-induced inflammatory cytokines including tumor necrosis factor-α (TNF-α) and interleukin-1ß (IL-1ß), decreased nitric oxide (NO), and increased superoxide dismutase (SOD) in bronchoalveolar lavage fluid (BALF), and effectively ameliorated LPS-induced increased total protein, leukocyte and macrophages in BALF. In addition, TML pronouncedly suppressed the activation of the MAPKs p38-NLRP3/caspase-1 and COX2, increased the expression of p-AMPK-Nrf2, and suppressed the expression of KEAP, apoptotic-related protein as well as autophagy. CONCLUSIONS: These results suggested that TML ameliorated LPS-induced acute lung injury by inhibiting the release of inflammatory cytokines and reducing oxidative damage associated with the MAPKs p38-NLRP3/caspase-1 and COX2 signaling pathways, AMPK-Nrf2/KEAP signaling pathways, as well as apoptosis and autophagy.

New aporphine alkaloids with selective cytotoxicity against glioma stem cells from Thalictrum foetidum.

Seven new isoquinoline alkaloids, 9-(2'-formyl-5', 6'-dimethoxyphenoxy)-1, 2, 3, 10-tetramethoxy dehydroaporphine (1), 9-(2'-formyl-5', 6'-dimethoxyphenoxy)-1, 2, 3, 10-tetramethoxy oxoaporphine (2), 3-methoxy-2'-formyl oxohernandalin (3), (-)-9-(2'-methoxycarbonyl-5', 6'-dimethoxyphenoxy)-1, 2, 3, 10-tetramethoxy aporphine (4), (-)-2'-methoxycarbonyl thaliadin (5), (-)-9-(2'-methoxyethyl-5', 6'-dimethoxyphenoxy)-1, 2, 3, 10-tetramethoxy aporphine (6), (-)-3-methoxy hydroxyhernandalinol (7), together with six known isoquinoline alkaloids (8-13) were isolated from the roots of Thalictrum foetidum. Their structures were elucidated by extensive spectroscopic measurements. Compounds 1 and 2 showed significant selective cytotoxicity against glioma stem cells (GSC-3# and GSC-18#) with IC50 values ranging from 2.36 to 5.37 µg·mL-1.

Comparison of Anticancer Activity and HPLC-DAD Determination of Selected Isoquinoline Alkaloids from Thalictrum foetidum, Berberis sp. and Chelidonium majus Extracts.

Background: Plants are an important origin of natural substances that the raw material for various pharmaceutical and therapeutic applications due to the presence of phytochemicals, such as alkaloids. Alkaloids, which are found in different plant species, possess numerous biological activities. Some alkaloids have strong cytotoxic effects on various cancer cells. The search for new drugs to treat various cancers is one of the most important challenges of modern scientific research. Objective: This study aimed to investigate of cytotoxic activity of extracts that were obtained from Chelidonium Majus; Berberis sp.; Thalictrum foetidum containing various alkaloids on selected cancer cell lines. The aim was also the quantification of selected alkaloids in the investigated extracts by HPLC. Methods: The analysis of alkaloids contents were performed while using HPLC in reversed phase (RP) mode using Polar RP column and mobile phase containing acetonitrile, water, and ionic liquid. The cytotoxic effect of the tested plant extracts and respective alkaloids' standards were examined while using human pharyngeal squamous carcinoma cells (FaDu), human tongue squamous carcinoma cells (SCC-25), human breast adenocarcinoma cell line (MCF-7), and human triple-negative breast adenocarcinoma cell line (MDA-MB-231). Conclusion: All of the investigated plant extracts possess cytotoxic activity against cancer cell lines: FaDu, SCC-25, MCF-7, and MDA-MB-231. The highest cytotoxic activity against FaDu and MDA-MB-231 cells was observed for Chelidonium majus root extract, while the highest cytotoxic activity against SCC-25 and MCF-7 cells was estimated for the Thalictrum foetidum root extract. There obtained significant differences in the cytotoxic activity of extracts that were obtained from the roots and herbs of Chelidonium majus and Thalictrum foetidum. Based on these results, investigated plant extracts can be recommended for further investigations of anticancer activity.

Benzophenanthridine alkaloids from the roots of Thalictrum microgynum Lecoy.ex Oliv.

A new benzophenanthridine alkaloid, 2,3,9-trimethoxy-7,8-methylenedioxy-5-methylbenzo[c]-6(5H) phenanthridone (2) and a benzophenanthridine alkaloid first found from natural sources, 2,3-dimethoxy-7,8- methylenedioxy-5-methylbenzo[c]-6(5H)- phenanthridone (1) together with two known benzophenanthridine alkaloids, Dihydrosanguinarine (3) and Dihydrochelilutine (4) were isolated from the roots of Thalictrum microgynum Lecoy.ex Oliv. The structures of 1 and 2 were elucidated using various spectroscopic techniques including HRESIMS and 1 D and 2 D NMR. Antibacterial activity of these compounds were tested. Compound 1, 3 and 4 showed antibacterial activity against Staphylococcus aureus with MIC values of 50, 100, 25 µg/mL, respectively.

New benzyl-aporphine alkaloids from Thalictrum cultratum.

Two new rare benzyl-aporphine alkaloids, thaliculine (1) and 6a,7-dehydrothaliculine (2), were isolated from the roots of Thalictrum cultratum Wall. Their structures were determined based on spectroscopic analysis including 1D, 2D NMR, and HR-ESI-MS. The stereochemistry of 1 was assigned by ECD spectroscopy. Compound 1 exhibited weak cytotoxicity against HL-60 cell line with IC50 value of 31.40 µM.

Immune-inhibitive phenyl-C1 substituent aporphine alkaloids from Thalictrum cirrhosum.

Five new phenyl-C1 substituent aporphine alkaloids, 6aR-2'-methoxycarbonyl-thaliadin (1), 6aR-2'-carboxyl-thaliadin (2), 6aR-3-methoxy-hernandalinol (3), 6aS-1,3,10-trimethoxy-natalamine (4), and 3-methoxy-2'-methoxycarbonyl-oxohernandalincin (5), together with sixteen known isoquinoline alkaloids (6-21) were isolated from the whole herb of Thalictrum cirrhosum (Levl.). Their structures were elucidated by extensive spectroscopic measurements, and six isoquinoline alkaloids showed significant inhibitory activity on concanavalin A-stimulated splenocytes proliferation with IC50 values 36-44 µM by the immunosuppressive bioassay.

Antitumor aporphine alkaloids from Thalictrum wangii.

Nine new isoquinoline alkaloids, including two proaporphine (1-2), three aporphine (3-5), two oxoaporphine (6-7), and two seco-bisbenzylisoquinoline (8-9), together with three known alkaloids (10-12) were isolated from the whole plant of Thalictrum wangii. Their structures were established on the basis of spectroscopic data. The antitumor activities of the isolated compounds were evaluated in vitro against glioma stem cells. Compounds 3-8 showed the cytotoxicity with IC50 values 15-20 µg/mL.

Antiproliferative Dimeric Aporphinoid Alkaloids from the Roots of Thalictrum cultratum.

Inspired by the intriguing structures and bioactivities of dimeric alkaloids, 11 new thalifaberine-type aporphine-benzylisoquinoline alkaloids, thalicultratines A-K, a tetrahydroprotoberberine-aporphine alkaloid, thalicultratine L, and five known ones were isolated from the roots of Thalictrum cultratum. Their structures were defined on the basis of NMR and HRESIMS data. The antiproliferative activities of compounds 1-17 were evaluated against human leukemia HL-60 and prostate cancer PC-3 cells. Most alkaloids showed potent cytotoxicity against selected cancer cells. Preliminary SARs are discussed. The most active new compound (3), with an IC50 value of 1.06 µM against HL-60 cells, was selected for mechanism of action studies. The results revealed that compound 3 induced apoptosis and arrested the HL-60 cell cycle at the S phase with the loss of mitochondria membrane potential. The nuclear morphological Hoechst 33258 staining assay was also carried out, and the results confirmed apoptosis.

Cycloartane triterpenoid saponins from the herbs of Thalictrum fortunei.

Six new cycloartane triterpenoid saponins, thalisides A-F (1-6), along with four known ones (7-10), were isolated from Thalictrum fortunei. The new structures were elucidated by using spectroscopic data (NMR, IR, UV, and MS). Compounds 1-10 were examined for their in vitro cytotoxicity against two human cancer cell lines (HepG2, A549) and antiviral activity against influenza A virus (H1N1) and found to be inactive.

Structural and Functional Studies of Pavine N-Methyltransferase from Thalictrum flavum Reveal Novel Insights into Substrate Recognition and Catalytic Mechanism.

Benzylisoquinoline alkaloids (BIAs) are produced in a wide variety of plants and include many common analgesic, antitussive, and anticancer compounds. Several members of a distinct family of S-adenosylmethionine (SAM)-dependent N-methyltransferases (NMTs) play critical roles in BIA biosynthesis, but the molecular basis of substrate recognition and catalysis is not known for NMTs involved in BIA metabolism. To address this issue, the crystal structure of pavine NMT from Thalictrum flavum was solved using selenomethionine-substituted protein (dmin = 2.8 Å). Additional structures were determined for the native protein (dmin = 2.0 Å) as well as binary complexes with SAM (dmin = 2.3 Å) or the reaction product S-adenosylhomocysteine (dmin = 1.6 Å). The structure of a complex with S-adenosylhomocysteine and two molecules of tetrahydropapaverine (THP; one as the S conformer and a second in the R configuration) (dmin = 1.8 Å) revealed key features of substrate recognition. Pavine NMT converted racemic THP to laudanosine, but the enzyme showed a preference for (±)-pavine and (S)-reticuline as substrates. These structures suggest the involvement of highly conserved residues at the active site. Mutagenesis of three residues near the methyl group of SAM and the nitrogen atom of the alkaloid acceptor decreased enzyme activity without disrupting the structure of the protein. The binding site for THP provides a framework for understanding substrate specificity among numerous NMTs involved in the biosynthesis of BIAs and other specialized metabolites. This information will facilitate metabolic engineering efforts aimed at producing medicinally important compounds in heterologous systems, such as yeast.

Preliminary in vitro antiplasmodial activity of Aristolochia griffithii and Thalictrum foliolosum DC extracts against malaria parasite Plasmodium falciparum.

BACKGROUND: Resistance development in human malaria parasites against commonly used antimalarial drugs has necessitated the scientific exploration of traditionally used antimalarial plants. Plant derivatives have been used for curing malaria historically. The present study involves in vitro evaluation of two medicinally important plants Aristolochia griffithii and Thalictrum foliolosum DC used in antimalarial chemotherapy by the tribes of northeast India. METHOD: Chloroform, ethyl acetate and n-butanol extracts of Aristolochia griffithii and Thalictrum foliolosum DC were evaluated in vitro against chloroquine sensitive (SS) and chloroquine resistance strains (RS) of P. falciparum. The tests were conducted following WHO standard method and the inhibition of parasite (IC50) was calculated. RESULTS: In A. griffithii, the IC50 value for ethyl acetate extracts against SS was 6.2 ± 0.02 µg/ml and found to be lower than chloroform extracts, which exhibited an IC50 value of 14.1 ± 0.1 µg/ml (t = 191.1; p < 0.0001). The IC50 values of both chloroform and ethyl acetate extracts for RS were higher as compared to the SS (p < 0.0001). In T. foliolosum DC the IC50 concentration of chloroform extracts for SS and RS were 0.5 ± 0.0 and 1.1 ± 0.0 µg/ml respectively (t = 54.2; p < 0.0001). CONCLUSION: The present findings, although preliminary, but scientifically demonstrate that identification and isolation of active compounds of these two plant materials and testing against different Plasmodium species could lead to the development of potential antimalarial drugs for future.

A new bisbenzylisoquinoline alkaloid isolated from Thalictrum foliolosum, as a potent inhibitor of DNA topoisomerase IB of Leishmania donovani.

Chemical investigation of the stem of Thalictrum foliolosum resulted in the isolation of two new bisbenzylisoquinoline alkaloids (1 and 2) along with known protoberberine group of isoquinoline alkaloids thalifendine (3) and berberine (4). The structures of the new compounds were established by detailed 2D NMR spectral analysis with their configurations determined from their optical rotation values and confirmed using circular dichroism. Inhibitory activities of these four compounds against DNA topoisomerase IB of Leishmania donovani were evaluated. Compound 2 exhibited almost complete inhibition of the enzyme activity at 50 µM concentration and it was found to be effective in killing both wild type as well as SAG resistant promastigotes of the parasite.

Northalrugosidine is a bisbenzyltetrahydroisoquinoline alkaloid from Thalictrum alpinum with in vivo antileishmanial activity.

Screening of a plant-derived natural product library led to the observation of in vitro antileishmanial activity by three bisbenzyltetrahydroisoquinoline alkaloids (1-3) that were purified previously from Thalictrum alpinum. A spectroscopic study of the active compounds was conducted to confirm their identities. Of the compounds tested, northalrugosidine (1) showed the most potent in vitro activity against Leishmania donovani promastigotes (0.28 µM) and the highest selectivity (29.3-fold) versus its general cytotoxicity against HT-29 human colon adenocarcinoma cells. Northalrugosidine was tested in vivo using a murine model of visceral leishmaniasis, resulting in the observation of a dose-dependent reduction of the parasitic burden in the liver and spleen without overt toxicity effects at 2.8, 5.6, and 11.1 mg/kg per animal when administered intravenously. This represents the first report of a bisbenzyltetrahydroisoquinoline alkaloid with in vivo efficacy against visceral leishmaniasis.

Anti-bacterial activities and phytochemical screening of extracts of different parts of Thalictrum rhynchocarpum.

Parts of the plant Thalictrum rhyncocarpum are used in herbal medicine in Kenya to treat various infections. The aim of this study was to evaluate in-vitro anti-bacteria activities and phytochemical profiles of solvent extracts of the leaves, stem bark and root of Thalictrum rhyncocarpum against Bacillus subtilis-6633, Staphylococcus aures-SG 511, Escherichia coli SG 458, Pseudomonus aeruginosa-K799/61 and Mycobacterium vaccae-10670. Anti-bacterial activity tests were carried out using disc diffusion assay and tube dilution technique, and phytochemical screening was carried out through Thin Layer Chromatography. The crude extracts showed antibacterial effects on M. vaccae, P. aeruginosa and B. subtilis. M. vaccae was most sensitive, particularly to the methanol root extract. Phytochemical screening of the extracts suggested the presence of glycosides and alkaloids in the stem bark and root extracts, and flavonoids and triterpenes in the leaf extracts. The study showed interesting levels of activities of solvent extracts of different parts of T. rhyncocarpum against some of the bacteria tested (M. vaccae, P. aeruginosa and B. subtilis). The results provide some scientific rationale for the traditional use of the plant in Kenya to treat different microbial infections.