Inhibitory activity of prostaglandin E2 production by the synthetic 2′-hydroxychalcone analogues: Synthesis and SAR study

Chalcone Derivatives as Potential Inhibitors of P-Glycoprotein and NorA: An In Silico and In Vitro Study

The human P-glycoprotein (P-gp) and the NorA transporter are the major culprits of multidrug resistance observed in various bacterial strains and cancer cell lines, by extruding drug molecules out of the targeted cells, leading to treatment failures in clinical settings. Inhibiting the activity of these efflux pumps has been a well-known strategy of drug design studies in this regard. In this manuscript, our earlier published machine learning models and homology structures of P-gp and NorA were utilized to screen a chemolibrary of 95 in-house chalcone derivatives, identifying two hit compounds, namely, F88 and F90, as potential modulators of both transporters, whose activity on Staphylococcus aureus strains overexpressing NorA and resistant to ciprofloxacin was subsequently confirmed. The findings of this study are expected to guide future research towards developing novel potent chalconic inhibitors of P-gp and/or NorA.

Characterization, molecular modeling and pharmacology of some 2́-hydroxychalcone derivatives as SARS-CoV-2 inhibitor

This work presented the microwave assisted synthesis of six new 2́-hydroxychalcones and their characterization based on FTIR, UV-Vis, ¹H NMR, and mass spectral analysis. Quantum chemical studies confirmed the structures of prepared chalcones. Antioxidant, in vitro antimicrobial and in silico antiviral studies have been performed to evaluate their biological performance. Results of molecular docking of prepared 2́-hydroxychalcones against SARS-CoV-2 (7BQY) main protease disclosed their inhibition which is comparable to standard, remdesivir and better than hydroxychloroquine (HCQ). ADMET prediction revealed them to be non-carcinogenic and relatively safe.

Impact of new cyclooxygenase 2 inhibitors on human cytomegalovirus replication in vitro

Background

Human cytomegalovirus (HCMV) is involved in complications on immunocompromised patients. Current therapeutics are associated with several drawbacks, such as nephrotoxicity.

Purpose:

As HCMV infection affects inflammation pathways, especially prostaglandin E2 (PGE2) production via cyclooxygenase 2 enzyme (COX-2), we designed 2'-hydroxychalcone compounds to inhibit human cytomegalovirus.

Study design

We first selected the most efficient new synthetic chalcones for their effect against COX-2-catalyzed PGE2.

Study sample

Among the selected compounds, we assessed the antiviral efficacy against different HCMV strains, such as the laboratory strain AD169 and clinical strains (naïve or multi-resistant to conventional drugs) and toxicity on human cells.

Results

The most efficient and less toxic compound (chalcone 7) was tested against HCMV in combination with other antiviral molecules: artesunate (ART), baicalein (BAI), maribavir (MBV), ganciclovir (GCV), and quercetin (QUER) using Compusyn software. Association of chalcone 7 with MBV and BAI is synergistic, antagonistic with QUER, and additive with GCV and ART.

Conclusion

These results provide a promising search path for potential bitherapies against HCMV.

Non-ulcerogenic pyrazolyl 2-hydroxychalcones and pyrazolylpyrazolines derived from naturally existing furochromone (khellin): semi-synthesis, docking study and anti-inflammatory activity

Novel pyrazolyl 2-hydroxychalcone derivatives 3a-e and pyrazolylpyrazoline derivatives 4a-e and 5a-j derived from the naturally existing furochromone (Khellin) were synthesized and evaluated for their in vivo anti-inflammatory activity. Most of the synthesized compounds showed better or comparable activity to that of Diclofenac as reference drug. Twelve compounds were evaluated for their ulcerogenic potential and exhibited no ulcerogenic effect. In addition compounds 3c, 5c and 5h as examples showed PGE₂ inhibition % 88.86, 65.87 and 44.06, respectively and TNFα inhibition % 48.62, 31.11 and 16.02, respectively in rat serum samples. Compounds 3c, 5c, 5h and Celecoxib were subjected to in vitro COX-1 and COX-2 inhibition assay, showed selectivity index 45.04, 102.04, 131.58 and 185.18, respectively. The computational finding supported those of in vitro, where the pyrazolylpyrazolines interacted with the COX-2 enzyme in a similar orientation to that of Celecoxib, while chlacones were found to exhibit similar orientation to that of Diclofenac.

Photoisomerization-mechanism-associated excited-state hydrogen transfer in 2'-hydroxychalcone revealed by on-the-fly trajectory surface-hopping molecular dynamics simulation

By performing global-switching on-the-fly trajectory surface-hopping molecular dynamics simulation at the OM2/MRCI (14,15) quantum level, we probed the S3(ππ*) photoisomerization mechanisms associated with excited-state intramolecular hydrogen transfer for 2'-hydroxychalcone (2HC) within the interwoven conical intersection networks from four singlet electronic states (S3, S2, S1, and S0). The simulated quantum yields of 0.03 for cis-to-trans and zero for trans-to-cis photoisomerization were due to almost all the conical intersections being localized either in the cis-2HC or in trans-2HC region, and there was little chance for sampling trajectories to reach the rotation conical intersection (S1/S0) in between cis-2HC and trans-2HC that is key for reactive isomerization. The potential energy well on the S1 state in the trans-2HC region prevents trajectories from trans-to-cis photoisomerization, while the fact there is no well on S1 state in cis-2HC region opens a few chances for trajectories to reach the rotation conical intersections. The present simulation found that excited-state intramolecular hydrogen transfers in 2HC have a negative impact for reactive isomerization, and that hydrogen transfers take place on the S1 state, while back-transfer on the S0 state prevents sampling trajectories reaching rotational conical intersections. It was realized that it could be possible to enhance the quantum yield of 2HC photoisomerization by suppressing the hydrogen transfer (such as by changing an electron-donating substitution or adjusting the substitution position to decrease the acidity of the phenol group). From a perspective view of the potential energy surfaces, the theoretical design of such 2HC derivatives could enhance (control) the quantum yield by shifting the conical intersections away from the cis- and trans-region.

Synthesis of Hydroxybenzofuranyl-pyrazolyl and Hydroxyphenyl-pyrazolyl Chalcones and Their Corresponding Pyrazoline Derivatives as COX Inhibitors, Anti-inflammatory and Gastroprotective Agents

Five new series of hydroxybenzofuranyl-pyrazolyl chalcones 3a,b, hydroxyphenyl-pyrazolyl chalcones 6a-c and their corresponding pyrazolylpyrazolines 4a, d, 7a-c and 8a-f have been synthesized and evaluated for their in vitro cyclooxygenase (COX)-1 and COX-2 inhibitory activity. All the synthesized compounds exhibited dual COX-1 and COX-2 inhibitory activity with obvious selectivity against COX-2. The pyrazolylpyrazolines 4a-d and 8a-f bearing two vicinal aryl moieties in the pyrazoline nucleus showed more selectivity towards COX-2. Within these two series, derivatives 4c, d and 8d-f bearing the benzenesulfonamide group were the most selective. Compounds 4a-d and 8a-f were further subjected to in vivo anti-inflammatory screening, ulcerogenic liability and showed good anti-inflammatory activity with no ulcerogenic effect. In addition compounds 4c and 8d as examples showed prostaglandin (PG)E2 inhibition % 44.23 and 51.4 respectively, tumor necrosis factor α (TNFα) inhibition % 33.48 and 41.41 respectively and gastroprotective effect in ethanol induced rodent gastric ulcer model. In addition, to explore the binding mode and selectivity of our compounds, 8d and celecoxib were docked into the active site of COX-1 and COX-2. It was found that compound 8d exhibited a binding pattern and interactions similar to that of celecoxib with COX-2 active site, while bitter manner of interaction than celecoxib to COX-1 active site.

Heterocyclization of polarized system: synthesis, antioxidant and anti-inflammatory 4-(pyridin-3-yl)-6-(thiophen-2-yl) pyrimidine-2-thiol derivatives

Background

Chalcones are intent in the daily diet as a favorable chemotherapeutic compound; on the other hand thiophene moiety is present in a large number of bioactive molecules having diverse biological efficiency.

Results

Our current goal is the synthesis of (E)-1-(pyridin-3-yl)-3-(thiophen-2-yl) prop-2-en-1-one 3 that^’s used as a starting compound to synthesize the novel pyrimidine-2-thiol, pyrazole, pyran derivatives. Chalcones 3 was prepared by condensation of 3-acetylpyridine with thiophene 2-carboxaldehyde which reacted with thiourea to obtain pyrimidinthiol derivative 4. Compound 4 was allowed to react with hydrazine hydrate to afford 2-hydrazinylpyrimidine derivative 5. Compound 5 was used as a key intermediate for a facile synthesis of the targets 6 and 7. In contrast, pyranone 8 was obtained by transformation of compound 5. Using as a precursor for the synthesis of new pyrazolo pyrimidine derivatives 9–10. The major incentive behind the preparation of these compounds was the immense biological activities associated to these heterocyclic derivatives.

Conclusions

The newly synthesized compounds (1–4) showed potent anti-inflammatory activities both in vitro and in vivo. They also exhibited promising antioxidant vitalities against α, α-diphenyl-β-picrylhydrazyl scavenging activity and lipid peroxidation. In conclusion, compound 1 showed a hopefully anti-inflammatory and antioxidant activities.

Biocatalytic hydrogenation of the C=C bond in the enone unit of hydroxylated chalcones-process arising from cyanobacterial adaptations

To verify the hypothesis that cyanobacteria naturally biosynthesising polyphenolic compounds possess an active enzymatic system that enables them to transform these substances, such an ability of the biocatalytic systems of whole cells of these biota was assessed for the first time. One halophilic strain and seven freshwater strains of cyanobacteria representing four of the five taxonomic orders of Cyanophyta were examined to determine the following: (i) whether they contain polyphenols, including flavonoids; (ii) the resistance of their cultures when suppressed by the presence of exogenous hydroxychalcones—precursors of flavonoid biosynthesis and (iii) whether these photoautotrophs can transform hydroxylated chalcones. All examined strains were found to contain polyphenols and flavonoids, and the growth of their cultures was inhibited in the presence of 2′-hydroxychalcone, 2″-hydroxychalcone and 4″-hydroxychalcone. We also confirmed that the examined cyanobacteria transformed hydroxychalcones via hydrogenative bio-reduction and formed the corresponding hydroxydihydro derivatives with yields above 90% whenever the substrates were bioavailable for such a conversion. Moreover, we observed that the routes and efficiency of biohydrogenation (and hydroxylation) of chalcones were dependent on the location of the hydroxyl substituent. The final products obtained as the results of biotransformations were extracted from the media and identified by mass spectrometry (LC-MS/MS) and nuclear magnetic resonance (¹H NMR, ¹³C NMR, COSY, HSQC). Based on those results, we believe that the very efficient biohydrogenation of hydroxychalcones, which may easy be scaled up for biotechnological purposes, reflects the natural activity of the cyanobacterial defence system, because hydroxydihydrochalcones were less active inhibitors of the growth of cyanobacterial cultures than the corresponding substrates.

Absence of genotoxic effects of the chalcone (E)-1-(2-hydroxyphenyl)-3-(4-methylphenyl)-prop-2-en-1-one) and its potential chemoprevention against DNA damage using in vitro and in vivo assays

The chalcone (E)-1-(2-hydroxyphenyl)-3-(4-methylphenyl)-prop-2-en-1-one), or 2HMC, displays antileishmanial, antimalarial, and antioxidant activities. The aim of this study was to investigate the cytotoxic, genotoxic, mutagenic, and protective effects of 2HMC using the Ames mutagenicity test, the mouse bone marrow micronucleus test, and the comet assay in mice. In the assessment using the Ames test, 2HMC did not increase the number of His⁺ revertants in Salmonella typhimurium strains, demonstrating lack of mutagenicity. 2HMC showed no significant increase in micronucleated polychromatic erythrocyte frequency (MNPCE) in the micronucleus test, or in DNA strand breaks using the comet assay, evidencing absence of genotoxicity. Regarding cytotoxicity, 2HMC exhibited moderate cytotoxicity in mouse bone marrow cells by micronucleus test. 2HMC showed antimutagenic action in co-administration with the positive controls, sodium azide (SA) and 4-nitroquinoline-1-oxide (4NQO), in the Ames test. Co-administered and mainly pre-administered with cyclophosphamide (CPA), 2HMC caused a decrease in the frequency of MNPCE using the micronucleus test and in DNA strand breaks using the comet assay. Thus, 2HMC exhibited antimutagenic and antigenotoxic effects, displaying a DNA-protective effect against CPA, SA, and 4NQO carcinogens. In conclusion, 2HMC presented antimutagenic, antigenotoxic and moderate cytotoxic effects; therefore it is a promising molecule for cancer prevention.

QSAR Studies on Bacterial Efflux Pump Inhibitors

Antimicrobial drug resistance occurs when bacteria undergo certain modifications to eliminate the effectiveness of drugs, chemicals, or other agents designed to cure infections. To date, the burden of resistance has remained one of the major clinical concerns as it renders prolonged and complicated treatments, thereby increasing the medical costs with lengthier hospital stays. Of complex causes for bacterial resistance, there has been increasing evidence that proved the significant role of efflux pumps in antibiotic resistance. Coadministration of Efflux Pump Inhibitors (EPIs) with antibiotics has been considered one of the promising ways not only to improve the efficacy but also to extend the clinical utility of existing antibiotics. This chapter begins with outlining current knowledge about bacterial efflux pumps and drug designs applied in identification of their modulating compounds. Following, the chapter addresses and provides a discussion on Quantitative Structure-Activity Relationship (QSAR) analyses in search of novel and potent efflux pump inhibitors.

Synthesis and Selective Cytotoxic Activities on Rhabdomyosarcoma and Noncancerous Cells of Some Heterocyclic Chalcones

Chemically diverse heterocyclic chalcones were prepared and evaluated for cytotoxicity, aiming to push forward potency and selectivity. They were tested against rhabdomyosarcoma (RMS) and noncancerous cell line (LLC-PK1). The influence of heteroaryl patterns on rings A and B was studied. Heterocycle functionalities on both rings, such as phenothiazine, thiophene, furan and pyridine were evaluated. Notably, the introduction of three methoxy groups at positions 3, 4, 5 on ring B appears to be critical for cytotoxicity. The best compound, with potent and selective cytotoxicity (IC₅₀ = 12.51 μM in comparison with the value 10.84 μM of paclitaxel), contains a phenothiazine moiety on ring A and a thiophene heterocycle on ring B. Most of the potential compounds only show weak cytoxicity on the noncancerous cell line LLC-PK1.

Diverse Molecular Targets for Chalcones with Varied Bioactivities

Natural or synthetic chalcones with different substituents have revealed a variety of biological activities that may benefit human health. The underlying mechanisms of action, particularly with respect to the direct cellular targets and the modes of interaction with the targets, have not been rigorously characterized, which imposes challenges to structure-guided rational development of therapeutic agents or chemical probes with acceptable target-selectivity profile. This review summarizes literature evidence on chalcones’ direct molecular targets in the context of their biological activities.

Insect Antifeedant Potential of Xanthohumol, Isoxanthohumol, and Their Derivatives

Xanthohumol (14) and isoxanthohumol (6) derived from hop (Humulus lupulus L., Cannabaceae) and selected chalcone and chromene derivatives, obtained by chemical synthesis, were studied for antifeedant activity against the peach-potato aphid (Myzus persicae [Sulz.]). The study used also commercially available 4-chromanone (1), flavanone (4), naringenin (5), chromone (7), flavone (8), 7-aminoflavone (9), trans-chalcone (10), and 4-methoxychalcone (12). For chromone derivatives it was observed that the presence of a phenyl substituent at C-2 in the chromone (7) skeleton increased the insect antifeedant activity, and this activity was observed for a longer time. Also, the introduction of an amino group at C-7 of flavone (8) considerably increased the insect antifeedant activity, which was observed for the whole test time. Among the compounds examined, the strongest deterrents were isoxanthohumol (6), 7-methoxy-2,2-dimethylchroman-4-one (3), 7-aminoflavone (9), and 4-ethyl-4'-methoxychalcone (13).

QSAR Studies on Bacterial Efflux Pump Inhibitors

Antimicrobial drug resistance occurs when bacteria undergo certain modifications to eliminate the effectiveness of drugs, chemicals, or other agents designed to cure infections. To date, the burden of resistance has remained one of the major clinical concerns as it renders prolonged and complicated treatments, thereby increasing the medical costs with lengthier hospital stays. Of complex causes for bacterial resistance, there has been increasing evidence that proved the significant role of efflux pumps in antibiotic resistance. Coadministration of Efflux Pump Inhibitors (EPIs) with antibiotics has been considered one of the promising ways not only to improve the efficacy but also to extend the clinical utility of existing antibiotics. This chapter begins with outlining current knowledge about bacterial efflux pumps and drug designs applied in identification of their modulating compounds. Following, the chapter addresses and provides a discussion on Quantitative Structure-Activity Relationship (QSAR) analyses in search of novel and potent efflux pump inhibitors.

Synthesis, characterization and biological evaluation of novel 4'-fluoro-2'-hydroxy-chalcone derivatives as antioxidant, anti-inflammatory and analgesic agents

In an effort to develop safe and potent anti-inflammatory agents, a series of novel 4'-fluoro-2'-hydroxychalcones 5a-d and their dihydropyrazole derivatives 6a-d was prepared. It was synthesized via aldol condensation of 4'-fluoro-2'-hydroxyacetophenone with appropriately substituted aldehydes followed by cyclization with hydrazine hydrate. All the synthesized compounds were evaluated for their antioxidant, anti-inflammatory, cyclooxygenase inhibition selectivity and analgesic activities. The dimethoxychalcone 5a and its dihydropyrazole derivative 6a showed the highest antioxidant activity, while the monomethoxychalcone 5d and its dihydropyrazole derivative 6d showed the highest analgesic and anti-inflammatory activities. It was also found that there is a close correlation between 4'-fluoro-2'-hydroxychalcones 5a-d and their dihydropyrazole derivatives 6a-d in the screened biological activities. To explain the correlation between the synthesized chalcones and their dihydropyrazole derivatives, especially for the anti-inflammatory activity, docking studies were performed.

SAR studies of o-hydroxychalcones and their cyclized analogs and study them as novel inhibitors of cathepsin B and cathepsin H

Cathepsins have emerged as a potential target for anti-cancer drug development. In the present study, we have synthesized three structurally related series of flavanoids i.e., 2'-hydroxychalcones, flavanones and flavones and assayed in vitro to study their inhibitory potency against cathepsin B and H, promising drug candidate for cancer therapy. Enzyme kinetics studies were carried out in presence of these compounds after preliminary proteolytic studies on endogenous protein substrates. SAR studies suggested that open chain flavanoids were better inhibitors as compared to their cyclized analogs. The most potent inhibitors among the three series were nitro substituted compounds 1g, 2g and 3g with Ki values of ∼6.18×10(-8) M, 4.8×10(-7) M and 7.85×10(-7) M for cathepsin B and Ki values of ∼2.8×10(-7) M, 31.8×10(-6) M and 33.7×10(-6) M for cathepsin H, respectively. The relationship between chalcone, flavanones and flavone structures interpreted by docking studies on cathepsin B and H also provided useful insights.

1H and 13C NMR spectral assignments of 2'-hydroxychalcones

Chalcones are of interest to medicinal chemists because their structures can be easily modified with various functional groups. The syntheses and biological activities of chalcones from natural sources are well known. In this study, 24 2'-hydroxychalcones bearing methoxy substituents were synthesized, among which five are new. The NMR data for all synthesized chalcones are described for the first time. The complete assignments of the (1)H and (13)C NMR data can be used for the identification of newly discovered and widely isolated, synthesized chalcones.

Effects of polyphenol compounds on influenza A virus replication and definition of their mechanism of action

A set of polyphenol compounds was synthesized and assayed for their ability in inhibiting influenza A virus replication. A sub-set of them showed low toxicity. The best compounds within this sub-set were 4 and 6g, which inhibited the viral replication in a dose-dependent manner. The antiviral activity of these molecules was demonstrated to be caused by their interference with intracellular pathways exploited for viral replication: (1) MAP kinases controlling nuclear-cytoplasmic traffic of viral ribonucleoprotein complex; (2) redox-sensitive pathways, involved in maturation of viral hemagglutinin protein.

Synthesis and antibacterial activity of some heterocyclic chalcone analogues alone and in combination with antibiotics

A series of simple heterocyclic chalcone analogues have been synthesized by Claisen Schmidt condensation reactions between substituted benzaldehydes and heteroaryl methyl ketones and evaluated for their antibacterial activity. The structures of the synthesized chalcones were established by IR and ¹H-NMR analysis. The biological data shows that compounds p₅, f₆ and t₅ had strong activities against both susceptible and resistant Staphylococcus aureus strains, but not activity against a vancomycin and methicillin resistant Staphylococcus aureus isolated from a human sample. The structure and activity relationships confirmed that compounds f₅, f₆ and t₅ are potential candidates for future drug discovery and development.

Synthesis and anti-inflammatory activity of some benzofuran and benzopyran-4-one derivatives

New series of furosalicylic acids 3a-c, furosalicylanilides 6a-n, furobenzoxazines 8a-f, 1-benzofuran-3-arylprop-2-en-1-ones 12a,b, 6-(aryl-3-oxoprop-1-enyl)-4H-chromen-4-ones 16a-c and 6-[6-aryl-2-thioxo-2,5-dihydropyrimidin-4-yl]-4H-chromen-4-ones 17a-c were synthesized. Anti-inflammatory activity evaluation was performed using carrageenan-induced paw edema model in rats and prostaglandin E(2) (PGE(2)) synthesis inhibition activity. Some of the tested compounds revealed comparable activity with less ulcerogenic effect than Diclofenac at a dose 100 mg/kg. All the synthesized compounds were docked on the active site of cyclooxygenase-2 (COX-2) enzyme and most of them showed good interactions with the amino acids of the active site comparable to the interactions exhibited by Diclofenac.

(E)-3-(4-Chloro-phen-yl)-1-(5-hy-droxy-2,2-dimethyl-2H-chromen-6-yl)prop-2-en-1-one

There are two independent mol-ecules in the asymmetric unit of the title compound, C(20)H(17)ClO(3), each having an E configuration about the -C=C- bond. The dihedral angles between the two benzene rings in the two mol-ecules are 7.17 (11) and 9.82 (11)°. In both mol-ecules, the hy-droxy group is involved in an intra-molecular O-H⋯O hydrogen bond.

(E)-1-(5-Hy-droxy-2,2-dimethyl-2H-chromen-6-yl)-3-(3,4,5-trimeth-oxy-phen-yl)prop-2-en-1-one

The title compound, C(23)H(24)O(6), crystallizes with two independent mol-ecules (A and B) in the asymmetric unit. The dihedral angles between the benzopyran ring and the α,β-unsaturated ketone unit and between the α,β-unsaturated ketone group and the benzene ring are 9.4 (10) and 12.96 (13)°, respectively, in mol-ecule A and 1.40 (17) and 4.44 (17)°, respectively, in mol-ecule B. The two meth-oxy groups at the meta positions of the benzene ring are close to being coplanar with the ring [C-O-C-C = 6.2 (3) and -1.4 (3)° in mol-ecule A and -4.2 (4) and 3.7 (3)° in mol-ecule B], whereas the third meth-oxy group, at the para position, is (+)-anti-clinal with respect to the benzene ring [C-O-C-C = 81.7 (3)°] in mol-ecule A and is (-)-synclinal with respect to the benzene ring [C-O-C-C = -103.2 (3)°] in mol-ecule B. In both independent mol-ecules, the hy-droxy group is involved in an intra-molecular O-H⋯O hydrogen bond.

Fluorinated 2'-hydroxychalcones as garcinol analogs with enhanced antioxidant and anticancer activities

Chalcones are involved in the synthesis of flavonoids and are themselves known to exhibit multiple pharmacological properties. However, compared to other structurally similar phytochemicals like garcinol and curcumin, the therapeutic use of chalcones is limited because of their lower bioavailability and rapid metabolic clearance from biological system. In the present work, we have attempted to overcome these limitations in case of 2'-hydroxychalcones through bioisosteric substitution of fluoro groups in place of phenolic hydroxyls. The fluorinated chalcones were found to be more potent antioxidant and anti-proliferative compounds than their hydroxyl counterparts indicating the influence of metabolically stable C-F bonds towards bioavailability. The difluoro derivatives were found to be most effective against human pancreatic BxPC-3 cancer cells which possess up-regulated COX-2 expression and also showed activity against human breast cancer BT-20 cells with triple negative phenotype, suggesting that these compounds will have broader application in the future.

Natural and synthetic 2'-hydroxy-chalcones and aurones: synthesis, characterization and evaluation of the antioxidant and soybean lipoxygenase inhibitory activity

A series of 2'-hydroxy-chalcones and their oxidative cyclization products, aurones, have been synthesized and tested for their antioxidant and lipoxygenase inhibitory activity. The natural product aureusidin (31) was synthesized in high yield by a new approach. An extensive structure-relationship study was performed and revealed that several chalcones and aurones possess an appealing pharmacological profile combining high antioxidant and lipid peroxidation activity with potent soybean LOX inhibition.

(E)-3-[4-(Pent-yloxy)phen-yl]-1-phenyl-prop-2-en-1-one

The title compound, C₂₀H₂₂O₂, crystallizes with two independent mol­ecules in the asymmetric unit. In each mol­ecule, all the non-H atoms lie in a common plane (r.m.s. deviations of 0.098 and 0.079 Å). There is a π–π stacking inter­action in the crystal structure. The central aromatic rings of the two mol­ecules, which are stacked head-to-tail one above the other, are separated by centroid-to-centroid distances of 3.872 (13) and 3.999 (10) Å.