Candenatenins A-F, phenolic compounds from the heartwood of Dalbergia candenatensis

The Emerging Role of Natural Products in Cancer Treatment

The exploration of natural products as potential agents for cancer treatment has garnered significant attention in recent years. In this comprehensive review, we delve into the diverse array of natural compounds, including alkaloids, carbohydrates, flavonoids, lignans, polyketides, saponins, tannins, and terpenoids, highlighting their emerging roles in cancer therapy. These compounds, derived from various botanical sources, exhibit a wide range of mechanisms of action, targeting critical pathways involved in cancer progression such as cell proliferation, apoptosis, angiogenesis, and metastasis. Through a meticulous examination of preclinical and clinical studies, we provide insights into the therapeutic potential of these natural products across different cancer types. Furthermore, we discuss the advantages and challenges associated with their use in cancer treatment, emphasizing the need for further research to optimize their efficacy, pharmacokinetics, and delivery methods. Overall, this review underscores the importance of natural products in advancing cancer therapeutics and paves the way for future investigations into their clinical applications.

Asymmetric synthesis of spiro[4H-chromene-3,3'-oxindoles] via a squaramide-organocatalytic three-component cascade Knoevenagel/Michael/cyclization sequence

Asymmetric synthesis of spiro[4H-chromene-3,3'-oxindole] derivatives was realized through an organocatalytic cascade Knoevenagel/Michael/cyclization reaction using a quinidine-derived squaramide. Under the optimized conditions, the reactions of isatins, malononitrile, and sesamol yield the desired spirooxindoles in good yields (75-87%) and moderate to high ee values (up to 90% ee).

Silver-Catalyzed Chlorocyclization for the Synthesis of 3-Chloro-2H-chromenes

A silver-catalyzed chlorocyclization reaction of aryl 3-aryl-2-propyn-1-yl ethers in the presence of NCS under darkness was accomplished, which provides a straightforward and efficient access to 3-chloro-2H-chromenes.

Iron(III)-Catalyzed Carboannulations of Homopropargylic Alcohols: A One-Pot General Synthesis of 4-(2,2-Diarylvinyl)quinolines and 4-(2,2-Diarylvinyl)-2H-chromenes

A simple and efficient approach for the general synthesis of 4-(2,2-diarylvinyl)quinolines 5 and 4-(2,2-diarylvinyl)-2H-chromenes 6 has been developed using Fe(III)-catalyzed intramolecular annulations of homopropargyl substrates 1 and 2, respectively. The high yields (up to 98%) achieved using simple substrates, an environmentally benign low-cost catalyst, and less hazardous reaction conditions make the methodology inherently attractive.

4-Dimethylaminopyridine (DMAP), A Superior Mediator for Morita-Balylis-Hillman Reaction-Triggered Annulative Condensation of Salicylaldehydes and Acrylonitrile to Form 3-Cyano-2H-chromenes

We unveiled superior base mediators for the annulative condensation of salicylaldehydes and acrylonitrile to give 3-cyano-2H-chromenes, which has been mediated only by 1,4-diazabicyclo[2.2.2]octane (DABCO) over the past two decades. The reactions were most efficiently mediated by 4-dimethylaminopyridine (DMAP), which yielded 3-cyano-2H-chromenes in higher yields than DABCO in most cases. We also confirmed that the reaction remained high yielding in a decagram-scale experiment with a catalytic amount of DMAP. The utility of this reaction was also exemplified by derivatization of an obtained 3-cyano-2H-chromene into a known 2H-chromene-3-carboxylic acid, which was previously synthesized with a non-readily available reagent.

Metal-Free One-Pot Annulative Coupling of 2-Hydroxybenzaldehydes with β-Ketothioamides: Access to Diverse 2-Arylimino-2H-Chromenes

A concise and practical one-pot sustainable approach for expedient synthesis of 2-arylimino-2H-chromenes by two-component cascade [4 + 2] annulative coupling of easily available 2-hydroxybenzaldehydes with β-ketothioamides has been developed in good yields for the first time. Remarkably, metal- and additive-free conditions, use of simple K₂CO₃ as a mild base, open atmosphere, exclusive regioselectivity, step/atom economy, nonhazardous reagents, and easy purification are added characteristics to the strategy. This annulative protocol will not only provide an efficient method to access diverse chromene scaffolds, but also enrich the research domain of β-ketothioamides.

A rare isoflavone-quinone and a new flavanone from the roots of Dalbergia stipulacea Roxb

Two previously undescribed compounds, namely dalpulapans F and G (1 and 2), along with 11 known compounds were isolated from the MeOH crude extract of the roots of Dalbergia stipulacea. Dalpulapan F was found as a rare isoflavone-quinone derivative. Their structures and absolute configurations were supported by extensive spectroscopic data analysis, including 1 D and 2 D NMR, HRESIMS data, specific rotation data, and comparison of the experimental and calculated ECD data. Cytotoxicity evaluation of the isolated compounds against HepG2 and KKU-M156 cell lines revealed that isoflavonoid 9 and rotenoid 13 exhibited the most activity against the two cell lines.

Ethnobotanical study of plants used by the Munda ethnic group living around the Sundarbans, the world's largest mangrove forest in southwestern Bangladesh

ETHNOPHARMACOLOGICAL RELEVANCE

Indigenous knowledge of medicinal plants is an integral part of the primary health care (PHC) system in almost every society. For more than two centuries, Munda, a small ethnic group in Bangladesh, has lived around the Sundarbans, the world's largest mangrove forest. This mangrove is rich in biodiversity but is threatened by global climate change. Information on the therapeutic use of plants by Munda ethnic minorities remains completely unknown. Therefore, it needs urgent documentation.

AIM OF THE STUDY

The purpose of the study is (1) to search and compile data on the diversity of medicinal plants used by the Munda people for PHC needs, and (2) Quantitative analysis of these data to identify important medicinal plants and diseases related to treatment by this species.

MATERIAL AND METHODS

We conducted repeated field surveys and interviews among 79 Munda informants to collect ethnobotanical data. Informants were selected through random sampling techniques and interviewed using an open and semi-structured questionnaire. We reported the primary (absolute) data as use reports (URs) with frequency citation (FC). The International Classification of Primary Care-2 (ICPC-2) was followed to categorize the therapeutic use of medicinal plants, and quantitative analysis was performed using the FC and informant consensus factor (ICF).

RESULTS

The present study explored and compiled a total of 3199 medicinal URs for 98 medicinal plant species to treat 132 ailment conditions under sixteen (16) ICPC-2 pathological groups. The highest URs (948) were noted for the digestive (D) group treated by 69 plant species, where the highest ICF value was measured for the social problem (Z) disease category (ICF: 1.00). Of the recorded medicinal plants, 17 were identified as true Mangrove (MNG), 24 as Mangrove Associates (MNA), and 57 as Non-Mangrove (NMG) species. Fabaceae (13 species) represented the leading family, followed by Lamiaceae and Compositae (5 species). Herbs (43%) have shown dominant life forms, and the leaves (41%) were frequently used plant parts. The most commonly cited preparation method was juice (24%), and the prevalent mode of administration was oral (62%). Azadirachta indica A. Juss. was the most widely used therapeutic plant species based on FC (39) values. The comparative literature review study reveals that the practices of 15 plants and their ethnomedicinal use by the Munda people are still entirely unexplored and newly reported in Bangladesh. Additionally, therapeutic use of 2 species, Brownlowia tersa (L.) Kosterm., and Dalbergia candenatensis (Dennst.) Prain has not been previously reported worldwide. In addition, 51 plant species (52%) of the total plants studied enlisted on the IUCN Red List of Threatened Species.

CONCLUSION

To our knowledge, this is the first ethnobotanical study on the Munda ethnic group in Bangladesh. This study indicates that Munda people still rely on medicinal plants for PHC and have a rich and varied traditional knowledge about the therapeutic use of plants. This study also warns of the high risk of the current availability status of plants in the study area. Therefore, this study calls for urgent steps to protect and conserve high-risk plants that can be done by taking both in-situ and ex-situ measures. In addition, further phytochemical and pharmacological investigations of the important medicinal plants cited in the study have been suggested.

Synthesis of 2H-chromenes: recent advances and perspectives

As one type of chromene, 2H-chromenes represent important oxygen heterocycles, which not only widely exist in natural products, pharmaceutical agents and biologically relevant molecules, but have also been used broadly in materials science and organic synthesis. Two major synthetic strategies have been developed towards such compounds. This review mainly focuses on the recent advances in this field, including benzopyran ring formation involving cyclization reactions and the late-stage functionalization of the parent 2H-chromenes.

Dalpulapans A-E from the roots of Dalbergia stipulacea

Five new compounds, dalpulapans A–E (1–5), were isolated from the hexane extract of the roots of Dalbergia stipulacea Roxb. Five new compounds, dalpulapans A–E (1–5), were isolated from the hexane extract of the roots of Dalbergia stipulacea Roxb. An evaluation of cytotoxic activity against HeLa, A549 and normal cell lines using MTT assay was performed. The results showed that R,R-velucarpin A (6) was the most active against HeLa cells with an IC₅₀ value of 10.9 ± 0.42 μM, while fortunately this compound exhibited weak cytotoxicity against normal cells (29.20 ± 1.16 μM). Structures of all isolates were identified from their 1D and 2D NMR spectroscopic data and MS analysis. Experimental and calculated ECD spectra were studied to define the absolute configurations.

Five new compounds, dalpulapans A–E (1–5), were isolated from the hexane extract of the roots of Dalbergia stipulacea Roxb.

Chromene- and Quinoline-3-Carbaldehydes: Useful Intermediates in the Synthesis of Heterocyclic Scaffolds

Chromenes and quinolines are recognized as important scaffolds in medicinal chemistry. Herein, the efficient use of chromene- and quinoline-3-carbaldehydes to synthesize other valuable heterocycles is described. These carbaldehydes are obtained in excellent yields through the Vilsmeyer-Haack reaction of flavanones and azaflavanones. Protocols towards the synthesis of new heterocycles, such as 3H-chromeno[3–c]quinolines, (Z/E)-2-aryl-4-chloro-3-styryl-2H-chromenes, and (E)-2-aryl-4-chloro-3-styrylquinoline-1(2H)-carbaldehydes were established. Altogether, we demonstrate the value of chromene- and quinoline-3-carbaldehydes as building blocks.

Velucarpin D, a new pterocarpan from the stems of Dalbergia velutina and its cytotoxicity

A new pterocarpan, named velucarpin D (1), along with nine known pterocarpans (2-10) were isolated from the stems of Dalbergia velutina. Their structures were determined by spectroscopic analysis. All isolated compounds were evaluated for their cytotoxicity against five human cancer cell lines (KB, HeLa S-3, MCF-7, Hep G2, and HT-29). Compound 2 showed potent cytotoxicity against all the five human cancer cell lines with IC₅₀ values in the range of 4.74-8.46 µM. In addition, compounds 1, 3, 4, 5 and 9 showed moderate cytotoxicity against both KB and HeLa S-3 cells with IC₅₀ values in the range of 14.23-29.35 µM.

In Vivo and In Vitro Evaluation of Pharmacological Potentials of Secondary Bioactive Metabolites of Dalbergia candenatensis Leaves

Background. Dalbergia species has wide range of secondary metabolites and is traditionally used in treatment of painful micturition, swelling, and leprosy and as blood tonic. The study evaluates membrane stabilizing, anticoagulant, analgesic, cytotoxic, subacute anti-inflammatory, and depression potentials of D. candenatensis leaves metabolites. Methods. Membrane stabilizing activity was evaluated by hypotonic induced hemolysis assay, whereas anticoagulant activity is done through extrinsic pathway by measuring prothrombin time. Analgesic action, cytotoxic effect, and subacute anti-inflammatory activity were determined by acetic acid induced writhing model, brine shrimp lethality bioassay, and formaldehyde induced model, respectively. Depression activity was measured by the Open Field, Hole Cross, Hole Board, and thiopentone induced sleeping time measuring methods. Results. D. candenatensis contains phenolic, flavonoid, and tannin, quantified as 416.25 mg, 330.00 mg, and 432.22 mg Gallic Acid Equivalent/100 g of dry extract, respectively. Extract showed maximum inhibition of writhe, hemolysis, and edema, approximate to 57.14%, 36.62%, and 34.1%, respectively. LC₅₀ value for nauplii was 151.499 μg/ml. Mean prothrombin time was approximate to 31.0 ± 2.31 seconds at 1.0 mg/ml. Extract showed depression activity, and maximum sleeping time was noted to be about 141 minutes. Conclusion. D. candenatensis leaves show dose dependent membrane stabilizing, anticoagulant, depression, analgesic, moderate cytotoxic, and subacute anti-inflammatory activities.

Enantioselective Synthesis of Chromenes via a Palladium-Catalyzed Asymmetric Redox-Relay Heck Reaction

A palladium-catalyzed asymmetric redox-relay Heck reaction of 4H-chromenes and arylboronic acids has been successfully developed. The reaction proceeded in moderate to good yields with good to high enantioselectivities. The resulting product is an advanced intermediate of bio-active compound BW683C.

Zinc-mediated α-regioselective Barbier-type cinnamylation reactions of aldehydes, ketones and esters

We report a simple, efficient, and general method for the zinc-mediated regioselective cinnamylation of aldehydes and ketones under Barbier-type conditions in a one-pot synthesis affording the corresponding α-cinnamylated alcohols in moderate to excellent yields. Compared to the literature procedures, this approach is operationally simple, uses simple reactants, and provides direct access to linear α-cinnamylated alcohols with excellent regioselectivity. Experimental results suggest that the reactions proceed through the radical pathway. In addition, the reaction was found to be scalable to the gram-scale and the one-pot protocol is also applicable to less reactive esters leading to bishomoallylic alcohols which were valuable intermediates for desymmetrizing intramolecular Heck cyclization, allowing for the elaboration to functionalized building blocks.

Syntheses and Anti-inflammatory Activity of Natural 1,3-Diarylpropenes

First syntheses of five natural 1,3-diarylpropenes (cinnamylphenols) 2-4, 7, and 8 along with synthesis of two other natural 1,3-diarylpropenes 1 and 5 and E-isomer of mucronulastyrene (6) were achieved by Friedel-Crafts alkylation as a key step. Subsequently, their anti-inflammatory effects were also investigated in lipopolysaccharide (LPS)-induced RAW264.7 macrophages. The compounds exhibited significant inhibition of inflammatory mediated nitric oxide (NO) production with no cytotoxicity except compound 8 (dalberatin B) at 10 µM concentration and IC50 values were found in the range from 4.05 to 16.76 µM.

Aniline-Promoted Cyclization-Replacement Cascade Reactions of 2-Hydroxycinnamaldehydes with Various Carbonic Nucleophiles through In Situ Formed N,O-Acetals

In this study, we report the harnessing of new reactivity of N,O-acetals in an aminocatalytic fashion for organic synthesis. Unlike widely used strategies requiring the use of acids and/or elevated temperatures, direct replacement of the amine component of the N,O-acetals by carbon-centered nucleophiles for C-C bond formation is realized under mild reaction conditions. Furthermore, without necessary preformation of the N,O-acetals, an amine-catalyzed in situ formation of N,O-acetals is developed. Coupling both reactions into a one-pot operation enables the achievement of a catalytic process. We demonstrate the employment of simple anilines as promoters for the cyclization-substitution cascade reactions of trans-2-hydroxycinnamaldehydes with various carbonic nucleophiles including indoles, pyrroles, naphthols, phenols, and silyl enol ethers. The process offers an alternative approach to structurally diverse, "privileged" 2-substituted 2H-chromenes. The synthetic power of the new process is furthermore shown by its application in a 2-step synthesis of the natural product candenatenin E and for the facile installation of 2-substituted 2H-chromene moieties into biologically active indoles.

Direct olefination of benzaldehydes into 1,3-diarylpropenes via a copper-catalyzed heterodomino Knoevenagel-decarboxylation-Csp3-H activation sequence

Copper-catalyzed direct olefination of benzaldehydes into unsymmetrical 1,3-diarylpropenes by a novel domino Knoevenagel-decarboxylation-Csp³-H activation sequence using simpler substrates like benzaldehydes.

Catalytic enantioselective synthesis of 2-aryl-chromenes

An enantioselective Pd-catalyzed 6-endo-trig reaction for the synthesis of 2-aryl-chromenes has been developed. A systematic optimization of a TADDOL-derived ligand set resulted in the identification of a novel monodentate phosphoramidite-palladium catalyst that accesses 2-aryl-2H-chromenes with high yield and enantioselectivity under mild conditions. The products obtained from this method can be transformed into biologically active compounds through functionalization of the chromene alkene.

Cytotoxic oxepinochromenone and flavonoids from the flower buds of Rosa rugosa

A new oxepinochromenone, rugosachromenone A (1), seven new flavonoids, rugosaflavonoids A-G (2-8), and 11 known compounds (9-19) were isolated from the flower buds of Rosa rugosa. Compound 1 is found from Nature for the first time. Compound 2 displayed cytotoxicity against NB4, SHSY5Y, and MCF7 cells with IC50 values of 2.2, 2.5, and 2.3 μM, respectively, and 3 was toxic to A549 and MCF7 cells with IC50 values of 1.2 and 2.8 μM, respectively.

Alstoniaphyllines A-C, unusual nitrogenous derivatives from the bark of Alstonia macrophylla

Chemical investigation of an alkaloidal extract of Alstonia macrophylla bark led to the isolation and identification of two new nitrogenous derivatives, alstoniaphyllines A (1) and B (2), a new indole alkaloid, alstoniaphylline C (4), and eight known alkaloids (3, 5-11). Alstonisine (9) exhibited antiplasmodial activity against Plasmodium falciparum, with an IC50 of 7.6 μM.

Antiviral phenolic compounds from Arundina gramnifolia

Five new phenolic compounds, gramniphenols C-G (1-5), and eight known compounds (6-13) were isolated from the whole plant of Arundina gramnifolia. Compounds 1, 4, and 5 showed anti-tobacco mosaic virus activity, with IC(50) values of 20.8, 40.8, and 57.7 μM, respectively. Compounds 1-10 were also tested for their anti-HIV-1 activity; compounds 2, 3, and 6 displayed anti-HIV-1 activity with therapeutic index values above 100:1.

Chemical constituents of red Mexican propolis

Chemical investigation of a red-type Mexican propolis sample has led to the isolation of three new compounds, 1-(3',4'-dihydroxy-2'-methoxyphenyl)-3-(phenyl)propane (1), (Z)-1-(2'-methoxy-4',5'-dihydroxyphenyl)-2-(3-phenyl)propene (2) and 3-hydroxy-5,6-dimethoxyflavan (3), together with seven known flavanones, isoflavans, and pterocarpans. Structural determination, was accomplished by spectroscopic analysis, particularly 2D NMR and ESI-MS/MS techniques. The present study appears to be the first report on the occurrence of isoflavonoids in Mexican propolis. In addition, the presence of compounds with a 1,3-diarylpropane and 1,3-diarylpropene carbon skeleton were found for the first time in propolis. Isolated compounds 1-10 indicated the possible relation between red Mexican propolis and the genus Dalbergia.

Enantioselective syntheses of candenatenins B and C using a chiral anthracene auxiliary

An asymmetric synthesis of two anticancer natural products, candenatenins B and C, is described, leading to a revision of the originally assigned stereochemistry. The synthesis follows a Diels-Alder/retro-Diels Alder strategy using a chiral anthracene auxiliary to access both targets with 90% ee. The inherent structural qualities of the auxiliary allow for both regio- and diastereoselective transformations.