Honorina Cidade

Prenylated derivatives of baicalein and 3,7-dihydroxyflavone: Synthesis and study of their effects on tumor cell lines growth, cell cycle and apoptosis

Fourteen baicalein and 3,7-dihydroxyflavone derivatives were synthesized and evaluated for their inhibitory activity against the in vitro growth of three human tumor cell lines. The synthetic approaches were based on the reaction with prenyl or geranyl bromide in alkaline medium, followed by cyclization of the respective monoprenylated derivative. Dihydropyranoflavonoids were also obtained by one-pot synthesis, using Montmorillonite K10 clay as catalyst combined with microwave irradiation. In vitro screening of the compounds for cell growth inhibitory activity revealed that the presence of one geranyl group was associated with a remarkable increase in the inhibitory activity. Moreover, for the 3,7-dihydroxyflavone derivatives a marked increase in growth inhibitory effect was also observed for compounds with furan and pyran fused rings. The most active compounds were also studied regarding their effect on cell cycle profile and induction of apoptosis. Overall the results point to the relevant role of the prenylation of flavone scaffold in the growth inhibitory activity of cancer cells.

Inhibition of lymphocyte proliferation by prenylated flavones: artelastin as a potent inhibitor.

Eight natural prenylated flavones, previously isolated from Artocarpus elasticus, were evaluated for their effect on the mitogenic response of human lymphocytes to PHA. They all exhibited a dose-dependent suppression effect. An interesting relationship was observed between their antiproliferative activity and their chemical structure. Indeed, the most potent flavones possessed a 3,3-dymethylallyl group (prenyl) at C-8, such as artelastin, which exhibited the highest antiproliferative activity. Studies of the mechanism underlying its effect revealed that artelastin had an irreversible inhibitory effect on the PHA-induced lymphocyte proliferation and could affect the course of the ongoing mitogenic response either at the initial induction phase or at the late phase of proliferation. This prenylated flavone was also shown to be a potent inhibitor of both T- and B-lymphocyte mitogen induced proliferation although B-mitogenic response was the more sensitive one. Artelastin did not affect either the basal levels of the early marker of activation CD69 on non-stimulated splenocytes or its expression on ConA- or LPS-stimulated splenocytes. However, it decreased the production of IFN-gamma, IL-2, IL-4 and IL-10 in ConA-stimulated splenocytes. Furthermore, artelastin had no effect on apoptosis of splenocytes.

Prenylflavonoids from Artocarpus elasticus

Three new prenylated flavones, artelastin, artelastochromene and artelasticin, along with the known artocarpesin, were isolated from the wood of Artocarpus elasticus. Structures were elucidated by spectroscopic techniques.

Further prenylflavonoids from Artocarpus elasticus

Abstract Further study of one of the fractions from the wood of Artocarpus elasticus gave two prenylated flavones artelastinin and artelastofuran in addition to artelasticin and cyclocommunin. Structures were elucidated by spectroscopic techniques.

Synthesis of a Natural Chalcone and Its Prenyl Analogs - Evaluation of Tumor Cell Growth-Inhibitory Activities, and Effects on Cell Cycle and Apoptosis

Six prenyl (=3‐methylbut‐2‐en‐1‐yl) chalcones (=1,3‐diphenylprop‐2‐en‐1‐ones), 2–7, and one natural non‐prenylated chalcone, 1, have been synthesized and evaluated for their in vitro growth‐inhibitory activity against three human tumor cell lines. A pronounced dose‐dependent growth‐inhibitory effect was observed for all prenylated derivatives, except for 7. The chalcone possessing one prenyloxy group at C(2′), i.e., 2, was the most active derivative against the three human tumor cell lines (5.9

The natural prenylated flavone artelastin is an inhibitor of ROS and NO production

Artelastin, a prenylated flavone previously isolated from Artocarpus elasticus, was evaluated for its effect on the production of reactive oxygen species (ROS) by human polymorphonuclear neutrophils (PMNs) and nitric oxide (NO) by J774 murine macrophage cell line. Artelastin showed to be an inhibitor of ROS production due to a strong O2- scavenging activity. No effect was observed on the activity of myeloperoxidase (MPO). Artelastin showed also to be an inhibitor of NO production without NO scavenging activity. This flavone seems to interfere with the expression of the inducible nitric oxide synthase (iNOS) immediately after LPS-IFNgamma-macrophage stimulation.

Potential small-molecule activators of caspase-7 identified using yeast-based caspase-3 and -7 screening assays

Caspases-3 and -7 are at the core of the execution phase of apoptosis. The search for activators of these proteases has therefore deserved particular attention in the field of anticancer drug discovery. Here, a simplified yeast-based screening approach was developed and used to search for activators of caspases-3 and -7, followed by evaluation of the activity of the selected compounds in the human tumor cell lines HL-60 (acute promyelocytic leukemia) and MCF-7 (breast adenocarcinoma). By using the yeast approach, two potential activators of caspase-7, 5,6-dihydroxy-7-prenyloxyflavone (1a) and 3-hydroxy-7-geranyloxyflavone (2a), were identified. Unlike the known caspases-3 and -7 activator, the procaspase activating compound-1 (PAC-1), these flavonoids did not interfere with the caspase-3 activity in yeast. Moreover, flavonoids 1a and 2a processed procaspase-7 to the active caspase-7 both in yeast and in vitro processing assays, and inhibited the growth of HL-60 and MCF-7 human tumor cells with higher potencies than PAC-1, particularly in the absence of caspase-3 (MCF-7 cells). In MCF-7 cells, the flavonoids processed procaspase-7, increased its activity and sensitized these cells to the effects of the cytotoxic drug, etoposide. In conclusion, the developed yeast target-based screening assays led to the identification of potential caspase-7 activators. A proof of concept is therefore provided for the effectiveness of the yeast assays in the discovery of caspase activators. Additionally, the identified compounds may pave the way for a new class of caspase activators with improved anticancer properties.

Chiral Derivatives of Xanthones: Investigation of the Effect of Enantioselectivity on Inhibition of Cyclooxygenases (COX-1 and COX-2) and Binding Interaction with Human Serum Albumin

Searching of new enantiomerically pure chiral derivatives of xanthones (CDXs) with potential pharmacological properties, particularly those with anti-inflammatory activity, has remained an area of interest of our group. Herein, we describe in silico studies and in vitro inhibitory assays of cyclooxygenases (COX-1 and COX-2) for different enantiomeric pairs of CDXs. The evaluation of the inhibitory activities was performed by using the COX Inhibitor Screening Assay Kit. Docking simulations between the small molecules (CDXs; known ligands and decoys) and the enzyme targets were undertaken with AutoDock Vina embedded in PyRx—Virtual Screening Tool software. All the CDXs evaluated exhibited COX-1 and COX-2 inhibition potential as predicted. Considering that the (S)-(−)-enantiomer of the nonsteroidal anti-inflammatory drug ketoprofen preferentially binds to albumin, resulting in lower free plasma concentration than (R)-(+)-enantiomer, protein binding affinity for CDXs was also evaluated by spectrofluorimetry as well as in in silico. For some CDXs enantioselectivity was observed.

Xanthone and Flavone Derivatives as Dual Agents with Acetylcholinesterase Inhibition and Antioxidant Activity as Potential Anti-Alzheimer Agents

Alzheimer’s disease (AD) is a multifactorial neurodegenerative disorder that is associated with the elderly. The current therapy that is used to treat AD is based mainly on the administration of acetylcholinesterase (AChE) inhibitors. Due to their low efficacy there is a considerable need for other therapeutic strategies. Considering that the malfunctions of different, but interconnected, biochemical complex pathways play an important role in the pathogenesis of this disease, a promising therapy may consist in administration of drugs that act on more than a target on biochemical scenery of AD. In this work, the synthesis and evaluation of xanthone and flavone derivatives as antioxidants with AChE inhibitory activity were accomplished. Among the obtained compounds, Mannich bases 3 and 14 showed capacity to inhibit AChE and antioxidant property, exerting dual activity. Moreover, for the most promising AChE inhibitors, docking studies on the target have been performed aiming to predict the binding mechanism. The results presented here may help to identify new xanthone and flavone derivatives as dual anti-Alzheimer agents with AChE inhibitory and antioxidant activities.

Prenylated Chalcone 2 Acts as an Antimitotic Agent and Enhances the Chemosensitivity of Tumor Cells to Paclitaxel

We previously reported that prenylated chalcone 2 (PC2), the O-prenyl derivative (2) of 2′-hydroxy-3,4,4′,5,6′-pentamethoxychalcone (1), induced cytotoxicity of tumor cells via disruption of p53-MDM2 interaction. However, the cellular changes through which PC2 exerts its cytotoxic activity and its antitumor potential, remain to be addressed. In the present work, we aimed to (i) characterize the effect of PC2 on mitotic progression and the underlying mechanism; and to (ii) explore this information to evaluate its ability to sensitize tumor cells to paclitaxel in a combination regimen. PC2 was able to arrest breast adenocarcinoma MCF-7 and non-small cell lung cancer NCI-H460 cells in mitosis. All mitosis-arrested cells showed collapsed mitotic spindles with randomly distributed chromosomes, and activated spindle assembly checkpoint. Live-cell imaging revealed that the compound induced a prolonged delay (up to 14 h) in mitosis, culminating in massive cell death by blebbing. Importantly, PC2 in combination with paclitaxel enhanced the effect on cell growth inhibition as determined by cell viability and proliferation assays. Our findings demonstrate that the cytotoxicity induced by PC2 is mediated through antimitotic activity as a result of mitotic spindle damage. The enhancement effects of PC2 on chemosensitivity of cancer cells to paclitaxel encourage further validation of the clinical potential of this combination.