Synthesis and biological evaluation of amino analogs of Ludartin: Potent and selective cytotoxic agents

Synthesis and Antiproliferative Effects of Grossheimin-Derived Aminoanalogues

Grossheimin, a guaiane-type sesquiterpene lactone, displayed a diverse range of biological activities, including anticancer, anti-inflammatory and antimicrobial effects. Various amino analogues of grossheimin were prepared through a Michael addition at its highly active α-methylene-γ-lactone motif. On the other hand, grossheimin was reduced to diol, which was then subjected to nucleophilic addition or acetylation to introduce heteroatoms associated with oxygen, sulfur or nitrogen functionalities. All of the synthesised Michael and acetylated adducts were evaluated for their in vitro cytotoxic action on human colon adenocarcinoma lines, including Colo205 and Colo320. The bioassay results indicated that the acetylated adducts displayed a potent cytotoxic effect compared to grossheimin, the parent molecule. A docking study was also performed to exploit the observed results.

Design and synthesis of ludartin derivatives as potential anticancer agents against hepatocellular carcinoma

Our previous study demonstrated that guaiane-type sesquiterpenoid ludartin showed potent antihepatoma activity against two human hepatocellular carcinoma cell lines, HepG2 and Huh7, with IC₅₀ values of 32.7 and 34.3 μM, respectively. In this study, 34 ludartin derivatives were designed, synthesized and evaluated for their cytotoxic activities against HepG2 and Huh7 cell lines using an MTT assay in vitro. As a result, 17 compounds increased the activity against HepG2 cells, and 20 compounds enhanced the activity against Huh7 cells; 14 derivatives 2, 4-7, 9, 11, 17, 24, 28-30 and 32-33 were superior to ludartin on both HepG2 and Huh7 cells. In particular, dimeric derivative 33 as the most active compound showed 20-fold and 17-fold enhancement of cytotoxicity against HepG2 and Huh7 cells compared to that of ludartin. These results suggested that compound 33 could serve as a promising lead compound against liver cancer.

Syntheses Based on 3,4α-Epoxy-1,5,7α,6β(H)-guai-10(14),11(13)-dien-6,12-olide

The sesquiterpene γ-lactone estafiatin 1, the molecule of which has a structure of 3,4α-epoxy-1,5,7α,6β(H)-guai-10(14),11(13)-dien-6,12-olide, is characteristic of plants of the genera Achillea L. and Artemisia L. of the Asteraceae family. This article presents the results of chemical modification for three reaction centers of the estafiatin molecule 1: epoxy cycle, exomethylene group conjugated with γ-lactone carbonyl, and exomethylene group in position C10=C14; and at the same time 33 new derivatives were synthesized, the structures of which were established based on physicochemical constants, spectral data (IR-, PMR-, ¹³C-NMR), and X-ray diffraction analysis. The stereo- and regiospecificity, as well as the chemoselectivity of the reaction based on estafiatin molecule 1, are discussed. The reactivity of the substrate is significantly influenced by the stereochemistry of its molecule, the nature of the reagent, and the reaction medium. Based on the results of in silico screening, derivatives of estafiatin with high binding energies for both DNA-topoisomerase I and DNA-topoisomerase II were identified. The values of the inhibitory dose of IC₅₀ for estafiatin 1 and its derivatives were determined on cell lines of eight types of tumors. in vivo experiments of the samples made it possible to establish that estafiatin 1 and its derivatives have pronounced antitumor activity against Pliss lymphosarcoma, Walker’s carcinosarcoma, sarcoma 45, sarcoma-180, alveolar liver cancer PC-1, leukemia P-388 and L-1210, and sarcoma-45 resistant to 5-fluorouracil.

Natural Products Containing Olefinic Bond: Important Substrates for Semi-synthetic Modification Towards Value Addition

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Semi-synthesis, the way of preparing novel bioactive molecules via modification of compounds isolated from natural sources is very much useful nowadays in the drug discovery process. The modification is based on the reaction of functional group(s) present in a natural compound. Among the examples of functional group transformation, double bond modification is also common in the literature. Several reactions like hydrogenation, cyclopropanation, epoxidation, addition reaction (halogenations, hydroxylation), Michael addition, Heck reaction, cycloaddition, dipolar cycloaddition, etc. are employed for this purpose. In this review, we have tried to gather the reactions performed with several double bond containing classes of natural products like diterpenes, xanthones, sesquiterpene exomethylene lactones, diaryl heptanoids, steroidal lactones, triterpenoids, limonoids, and alkamides. Where available, the effects of transformations on the biological activities of the molecules are also mentioned.

Hemisynthesis, computational and molecular docking studies of novel nitrogen containing steroidal aromatase inhibitors: testolactam and testololactam

Combined DFT and molecular docking studies of synthesized steroidal lactams reveal their potential as aromatase inhibitors.

Synthesis of an unusual quinazoline alkaloid: theoretical and experimental investigations of its structural, electronic, molecular and biological properties

An unusual quinazoline alkaloid (1) was obtained when 2-aminobenzaldehyde was refluxed with pyrrolidine in ethanol for 12 h. The synthesized compound was characterized using spectral data analysis augmented with X-ray and literature precedent. Single crystal analysis depicted four conformations differing slightly in bond angles and bond lengths. Compound 1 crystallizes in a triclinic crystal system with a P1̄ space group having two molecules within the unit cell. The experimentally obtained parameters were compared to those obtained theoretically, which depicted a good agreement. Using the DFT/B3LYP/6-31G (d,p) level of theory, HOMO–LUMO energy gap, molecular electrostatic potential (MEP), vibrational (IR) and NMR analyses were carried out. The HOMO–LUMO energy gap allowed the calculation of chemical hardness, chemical inertness, electronegativity and the electrophilicity index of the molecule, which depicted its potential kinetic stability and reactivity. Prediction of activity spectra of the target compound revealed that compound 1 possesses notable antineoplastic activity with P_a = 0.884. The molecule was therefore evaluated against various cancerous cell lines in an in vitro SRB assay which depicted that compound 1 possesses the highest growth inhibition activity against THP-1 cell lines with an IC₅₀ of 7 μM.

A comparative overview of theoretical and experimental studies concerning the electronic, structural and biological domains of the synthesized unusual quinazoline alkaloid is presented.

Design and Synthesis of Antitumor Heck-Coupled Sclareol Analogues: Modulation of BH3 Family Members by SS-12 in Autophagy and Apoptotic Cell Death

Sclareol, a promising anticancer labdane diterpene, was isolated from Salvia sclarea. Keeping the basic stereochemistry-rich framework of the molecule intact, a method for the synthesis of novel sclareol analogues was designed using palladium(II)-catalyzed oxidative Heck coupling reaction in order to study their structure-activity relationship. Both sclareol and its derivatives showed an interesting cytotoxicity profile, with 15-(4-fluorophenyl)sclareol (SS-12) as the most potent analogue, having IC50 = 0.082 μM against PC-3 cells. It was found that SS-12 commonly interacts with Bcl-2 and Beclin 1 BH3 domain proteins and enhances autophagic flux by modulating autophagy-related proteins. Moreover, inhibition of autophagy by autophagy inhibitors protected against SS-12-induced apoptosis. Finally, SS-12 effectively suppressed tumor growth in vivo in Ehrlich's ascitic and solid Sarcoma-180 mouse models.

Phytosterols as precursors for the synthesis of aromatase inhibitors: Hemisynthesis of testololactone and testolactone

Using β-sitosterol and stigmasterol as precursor materials, a concise and efficient hemisynthesis of aromatase inhibitors: testololactone and testolactone was accomplished in a well-established reaction scheme. It involves highly effective Oppaneur oxidation of both β-sitosterol as well as stigmasterol to generate the required enone moiety in ring 'A' of the desired steroid system. The Oppaneur oxidation products of both β-sitosterol and stigmasterol were then subjected to oxidative cleavage of the side chain to produce 4-androstene-3,17-dione. Baeyer-Villiger oxidation of 4-androstene-3,17-dione using m-CPBA yielded testololactone. Dehydrogenation of 4-androstene-3,17-dione using phenylselenyl chloride in ethyl acetate followed by selenoxide elimination with H2O2 in dichloromethane furnished androstenedienone. Baeyer-Villiger oxidation of the resulting androstenedienone yielded the desired testolactone (overall yield 33%). This expeditious reaction scheme may be exploited for the bulk production of aromatase inhibitors (especially testolactone marketed under the brand name Teslac) from the most abundant and naturally occurring phytosterols like β-sitosterol.

Synthesis of 1-O-acetylbritannilactone analogues from Inula britannica and in vitro evaluation of their anticancer potential

A series of novel ABL analogues was synthesized by N/O-atom installing and aromatic ring esterifying, and 4a showed in vitro markedly anticancer activities against HeLa cells associated with induction of apoptosis, activation of caspase-3 and G2/M cell arrest.

Isolation, cytotoxicity evaluation and HPLC-quantification of the chemical constituents from Artemisia amygdalina Decne

The hexane extracts of both shoot and root parts of Artemisia amygdalina Decne displayed potent cytotoxic effects. Phytochemical analysis of these active extracts led to the isolation of six cytotoxic constituents, viz., Ergostadien-3β-ol (1), ludartin (2), 5-hydroxy-6,7,3',4'-tetramethoxyflavone (3) (from shoot) and trans-matricaria ester (4), diacetylenic spiroenol ether (5) and cis-matricaria ester (6) (from root) for the first time from this plant. The constituents were identified using spectral techniques in the light of literature. Sulphorhodamine B cytotoxicity screening of the isolated constituents was carried out against four human cancer cell lines including Lung (A-549), Leukaemia (THP-1), Prostate (PC-3) and Colon (HCT-116) cell lines. Ludartin (2) exhibited the highest cytotoxicity with IC50 values of 7.4μM, 3.1μM, 7.5μM and 6.9μM against Lung (A-549), Leukaemia (THP-1), Prostate (PC-3), Colon (HCT-116) cancer cell lines respectively. To test against in vitro skin cancer models [human dermal fibroblasts (CRL-1635)] all the isolates were further subjected to 3-(4,5-Dimethylthiazol-yl)-diphenyl tetrazolium bromide (MTT) cytotoxicity screening. Ludartin (2) being highly cytotoxic was again evaluated against mouse melanoma (B16F10) and human epidermoid carcinoma (A-431) cells by MTT assay displaying IC50 values of 6.6μM and 19.0μM respectively. Finally a simple and reliable HPLC method was developed (RP-HPLC-DAD) and validated for the simultaneous quantification of these cytotoxic constituents in A. amygdalina Decne. Excellent specificity and high linearity for all the standard calibration curves having regression coefficients of the respective linear equations in the range of 0.9962-0.9999 was observed. Relative recovery rates varied between 98.37±0.90 and 105.15±1.74 with relative standard deviation less than 4%. Based on our results, the developed method features good quantification parameters, accuracy, precision and can serve as effective quality control method for standardisation of A. amygdalina Decne.