Antitumor agents 32. Synthesis and antitumor activity of cyclopentenone derivatives related to helenalin

Phytochemical Investigation, Antioxidant Properties and In Vivo Evaluation of the Toxic Effects of Parthenium hysterophorus

Parthenium hysterophorus L. is a poisonous Asteraceae weed. The phytochemical profile, antioxidant activity, total phenolic contents (TPC), total flavonoid contents (TFC), and cytotoxicity of Parthenium hysterophorus L. flower extract were evaluated in this study, and the toxic effects were assessed in rabbits. The HPLC-DAD system was used for phytochemical analysis. The hemolytic and DPPH assays were performed. The effects of orally administering the flower crude extract to rabbits (n = 5) at four different doses (10, 20, 40, and 80 mg/kg) for ten days on hematological and biochemical parameters were investigated. The crude extract of the flower contained phenolic compounds such as Gallic acid, Chlorogenic acid, Ellagic acid, and P Coumaric acid, which were detected at different retention times, according to the HPLC results. With a sample peak of 4667.475 %, chlorogenic acid was abundant. At concentrations of 80 µg, the methanolic extract of flowers had total phenolic contents (89.364 ± 4.715 g GAE/g) and total flavonoid contents (65.022 ± 2.694 g QE/g). In the DPPH free radical scavenging assay, 80 µg of extract had the highest cell inhibition of 76.90% with an IC50 value of 54.278 µg/µL, while in the hemolytic assay 200 µg of extract had the highest cell inhibition of 76.90% with an IC50 > 500. The biochemical and hematological parameters were altered in the flower extract-fed groups as compared to the control (p < 0.05). The toxic effects on the blood, liver, and kidneys were confirmed. The findings also confirmed the presence of phenolic and flavonoid content in the flower extract, both of which contribute to the plant’s antioxidant potential.

Targeting NF-κB p65 with a Helenalin Inspired Bis-electrophile

The canonical NF-κB signaling pathway is a mediator of the cellular inflammatory response and a target for developing therapeutics for multiple human diseases. The furthest downstream proteins in the pathway, the p50/p65 transcription factor heterodimer, have been recalcitrant toward small molecule inhibition despite the substantial number of compounds known to inhibit upstream proteins in the activation pathway. Given the roles of many of these upstream proteins in multiple biochemical pathways, targeting the p50/p65 heterodimer offers an opportunity for enhanced on-target specificity. Toward this end, the p65 protein presents two nondisulfide cysteines, Cys38 and Cys120, at its DNA-binding interface that are amenable to targeting by covalent molecules. The natural product helenalin, a sesquiterpene lactone, has been previously shown to target Cys38 on p65 and ablate its DNA-binding ability. Using helenalin as inspiration, simplified helenalin analogues were designed, synthesized, and shown to inhibit induced canonical NF-κB signaling in cell culture. Moreover, two simplified helenalin probes were proficient at forming covalent protein adducts, binding to Cys38 on recombinant p65, and targeting p65 in HeLa cells without engaging canonical NF-κB signaling proteins IκBα, p50, and IKKα/β. These studies further support that targeting the p65 transcription factor-DNA interface with covalent small molecule inhibitors is a viable approach toward regulating canonical NF-κB signaling.

Identification and structure-activity relationship studies of 3-methylene-2-norbornanone as potent anti-proliferative agents presumably working through p53 mediated apoptosis

We have identified a novel series of alpha-methylene carbonyl compounds through structure-activity relationship (SAR) studies with high levels of anti-proliferative activities. The lead molecule, 3-methylene-2-norbornanone (3) showed potent activity (LC(50)=3-8 microM) against mutant p53 cell types and many fold selectivity (>13-29) over wild-type p53 cells. Further, compound 3 and its analogs showed refolding of mutant p53 protein comparable to their anti-proliferative activities suggesting possible interaction with mutant p53 protein.

Computer-assisted structure-activity correlations

Several types of Michael acceptors, including alpha,beta-unsaturated ketones, lactones, and lactams, have been extensively studied as potential anticancer agents. A concerted effort was made to explore the relationship between the structures of these compounds and their antitumor activity against P388 and L1210 leukemias. This article describes the computer-assisted structure-activity evaluation of more than 14,000 compounds, representing different classes of Michael acceptors, in the NCI file. In this study, advantage has been taken of the computer's ability to search substructures according to precise definitions and to manipulate these substructures utilizing Boolean logic. Olefinic conjugated Michael-type acceptors, e.g., styrenes with different activating groups, cinnamic acid derivatives, and alpha,beta-unsaturated nitro, cyano, sulfone, sulfoxide, and acetylenic compounds, have shown appreciable activity against P388 lymphocytic leukemia. The analysis of lactones and lactams includes substructures representing a wide variety of exocyclic and endocyclic alpha,beta-unsaturated compounds. The analysis describes the effect of certain groups, such as an --OH, --OR, alpha,beta-unsaturated ester, or epoxide, adjacent to the alpha,beta-unsaturated center, on the antitumor activity of these compounds. A combination of one or more of these activating groups with an alpha-methylene-gamma-lactone moiety significantly enhanced the activity against P388. In general, many of the classes of compounds studied have shown poor activity against the more stringent L1210 lymphoid leukemia.