Biological Activity and Stability of Aeruginosamides from Cyanobacteria.

Aeruginosamides (AEGs) are classified as cyanobactins, ribosomally synthesized peptides with post-translational modifications. They have been identified in cyanobacteria of genera Microcystis, Oscillatoria, and Limnoraphis. In this work, the new data on the in vitro activities of three AEG variants, AEG A, AEG625 and AEG657, and their interactions with metabolic enzymes are reported. Two aeruginosamides, AEG625 and AEG657, decreased the viability of human breast cancer cell line T47D, but neither of the peptides was active against human liver cancer cell line Huh7. AEGs also did not change the expression of MIR92b-3p, but for AEG625, the induction of oxidative stress was observed. In the presence of a liver S9 fraction containing microsomal and cytosolic enzymes, AEG625 and AEG657 showed high stability. In the same assays, quick removal of AEG A was recorded. The peptides had mild activity against three cytochrome P450 enzymes, CYP2C9, CYP2D6 and CYP3A4, but only at the highest concentration used in the study (60 µM). The properties of AEGs, i.e., cytotoxic activity and in vitro interactions with important metabolic enzymes, form a good basis for further studies on their pharmacological potential.

Diaryl triazenes inhibit cytochrome P450 1A1 and 1B1 more strongly than aryl morpholino triazenes.

Several diaryl triazene derivatives were synthesized and tested for their ability to inhibit cytochrome P450 1A1 and 1B1 as a potential means to prevent and treat cancer. These compounds are more planar than their conformational flexible aryl morpholino triazene counterparts that were previously shown to inhibit the above enzymes. As a result, the diaryl triazenes are more likely to exhibit increased binding to the enzyme active sites and inhibit these enzymes more strongly than the aryl morpholino triazenes. The data indicates that the diaryl triazenes inhibit cytochrome P450 1A1 and 1B1 one to two orders of magnitude more strongly than the aryl morpholino triazenes. Furthermore, compounds 8-10 strongly inhibited cytochrome P450 1B1 with IC50 values of 51 nM, 740 nM, and 590 nM respectively. Thus, diaryl triazenes should be further investigated as a potential chemopreventive agent.

Role of CYP2A6 in Methimazole Bioactivation and Hepatotoxicity.

Methimazole (MMI) is a widely used antithyroid drug, but it can cause hepatotoxicity by unknown mechanisms. Previous studies showed that the hepatic metabolism of MMI produces N-methylthiourea, leading to liver damage. However, the specific enzyme responsible for the production of the toxic metabolite N-methylthiourea is still unclear. In this study, we screened cytochromes P450 (CYPs) in N-methylthiourea production from MMI. CYP2A6 was identified as the key enzyme in catalyzing MMI metabolism to produce N-methylthiourea. When mice were pretreated with a CYP2A6 inhibitor, formation of N-methylthiourea from MMI was remarkably reduced. Consistently, the CYP2A6 inhibitor prevented MMI-induced hepatotoxicity. These results demonstrated that CYP2A6 is essential in MMI bioactivation and hepatotoxicity.

Novel Synthetic Analogues of 19(S/R)-Hydroxyeicosatetraenoic Acid Exhibit Noncompetitive Inhibitory Effect on the Activity of Cytochrome P450 1A1 and 1B1.

BACKGROUND AND OBJECTIVES: Cytochrome P450 (CYP) 1A1 and CYP1B1 enzymes play a significant role in the pathogenesis of cancer and cardiovascular diseases (CVD) such as cardiac hypertrophy and heart failure. Previously, we have demonstrated that R- and S-enantiomers of 19-hydroxyeicosatetraenoic acid (19-HETE), an arachidonic acid endogenous metabolite, enantioselectively inhibit CYP1B1. The current study was conducted to test the possible inhibitory effect of novel synthetic analogues of R- and S-enantiomers of 19-HETE on the activity of CYP1A1, CYP1A2, and CYP1B1. METHODS: The O-dealkylation rate of 7-ethoxyresorufin (EROD) by recombinant human CYP1A1 and CYP1B1, in addition to the O-dealkylation rate of 7-methoxyresorufin (MROD) by recombinant human CYP1A2, were measured in the absence and presence of varying concentrations (0-40 nM) of the synthetic analogues of 19(R)- and 19(S)-HETE. Also, the possible inhibitory effect of both analogues on the catalytic activity of EROD and MROD, using RL-14 cells and human liver microsomes, was assessed. RESULTS: The results showed that both synthetic analogues of 19(R)- and 19(S)-HETE exhibited direct inhibitory effects on the activity of CYP1A1 and CYP1B1, while they had no significant effect on CYP1A2 activity. Nonlinear regression analysis and comparisons showed that the mode of inhibition for both analogues is noncompetitive inhibition of CYP1A1 and CYP1B1 enzymes. Also, nonlinear regression analysis and Dixon plots showed that the R- and S-analogues have KI values of 15.7 ± 4.4 and 6.1 ± 1.5 nM for CYP1A1 and 26.1 ± 2.9 and 9.1 ± 1.8 nM for CYP1B1, respectively. Moreover, both analogues were able to inhibit EROD and MROD activities in a cell-based assay and human liver microsomes. CONCLUSIONS: Therefore, the synthetic analogues of 19-HETE could be considered as a novel therapeutic approach in the treatment of cancer and CVD.

Development of [18F]AldoView as the First Highly Selective Aldosterone Synthase PET Tracer for Imaging of Primary Hyperaldosteronism.

The purpose of this study was to synthesize a fluorine-18 labeled, highly selective aldosterone synthase (hCYP11B2) inhibitor, [18F]AldoView, and to assess its potential for the detection of aldosterone-producing adenomas (APAs) with positron emission tomography in patients with primary hyperaldosteronism (PHA). Using dibenzothiophene sulfonium salt chemistry, [18F]AldoView was obtained in high radiochemical yield in one step from [18F]fluoride. In mice, the tracer showed a favorable pharmacokinetic profile, including rapid distribution and clearance. Imaging in the adrenal tissue from patients with PHA revealed diffuse binding patterns in the adrenal cortex, avid binding in some adenomas, and "hot spots" consistent with aldosterone-producing cell clusters. The binding pattern was in good visual agreement with the antibody staining of hCYP11B2 and distinguished areas with normal and excessive hCYP11B2 expression. Taken together, [18F]AldoView is a promising tracer for the detection of APAs in patients with PHA.

Probing cytochrome P450 (CYP) bioactivation with chloromethylindoline bioprecursors derived from the duocarmycin family of compounds.

The duocarmycins belong to a class of agent which has great potential for use in cancer therapy. Their exquisite potency means they are too toxic for systemic use, and targeted approaches are required to unlock their clinical potential. In this study, we have explored seco-OH-chloromethylindoline (CI) duocarmycin-based bioprecursors for their potential for cytochrome P450 (CYP)-mediated cancer cell kill. We report on synthetic and biological explorations of racemic seco-CI-MI, where MI is a 5-methoxy indole motif, and dehydroxylated analogues. We show up to a 10-fold bioactivation of de-OH CI-MI and a fluoro bioprecursor analogue in CYP1A1-transfected cells. Using CYP bactosomes, we also demonstrate that CYP1A2 but not CYP1B1 or CYP3A4 has propensity for potentiating these compounds, indicating preference for CYP1A bioactivation.

The development of novel cytochrome P450 2J2 (CYP2J2) inhibitor and the underlying interaction between inhibitor and CYP2J2.

Human Cytochrome P450 2J2 (CYP2J2) as an important metabolic enzyme, plays a crucial role in metabolism of polyunsaturated fatty acids (PUFAs). Elevated levels of CYP2J2 have been associated with various types of cancer, and therefore it serves as a potential drug target. Herein, using a high-throughput screening approach based on enzymic activity of CYP2J2, we rapidly and effectively identified a novel natural inhibitor (Piperine, 9a) with IC50 value of 0.44 µM from 108 common herbal medicines. Next, a series of its derivatives were designed and synthesised based on the underlying interactions of Piperine with CYP2J2. As expected, the much stronger inhibitors 9k and 9l were developed and their inhibition activities increased about 10 folds than Piperine with the IC50 values of 40 and 50 nM, respectively. Additionally, the inhibition kinetics illustrated the competitive inhibition types of 9k and 9l towards CYP2J2, and Ki were calculated to be 0.11 and 0.074 µM, respectively. Furthermore, the detailed interaction mechanism towards CYP2J2 was explicated by docking and molecular dynamics, and our results revealed the residue Thr114 and Thr 315 of CYP2J2 were the critical sites of action, moreover the spatial distance between the carbon atom of ligand methylene and Fe atom of iron porphyrin coenzyme was the vital interaction factor towards human CYP2J2.

Binimetinib Is a Potent Reversible and Time-Dependent Inhibitor of Cytochrome P450 1A2.

Binimetinib is a selective MEK1/2 inhibitor, which is indicative of melanoma. We aimed to investigate the inhibitory effect of binimetinib on cytochrome P450 using human liver microsomes. Binimetinib was demonstrated to display reversible and time-dependent inhibitory effects on human CYP1A2. Binimetinib can inhibit the activity of phenacetin deethylation with IC50 of 5.6 µM. A 30 min preincubation of binimetinib with NADPH-supplemented human liver microsomes raised a significant left IC50 shift (6.5-fold), from 5.69-0.88 µM. The inactivation parameters Kinact and KI were 0.063 min-1 and 15.47 µM, and the half-life of inactivation was 11 min. Glutathione (GSH) and catalase/superoxide exhibited minor or no protective effect on binimetinib-induced enzyme inactivation. Trapping experiment by GSH induced a detection of GSH adduct, of which the formation was believed to be through the oxidation of electron-rich 1,4-benzenediamine to reactive 1,4-diiminoquinone species. Cytochrome P450 3A4, 2C9, and 2D6 were involved in the bioactivation of binimetinib. In conclusion, binimetinib was proven to display reversible and time-dependent inhibitory effect on CYP1A2, which may have implications for the toxicity of binimetinib.

Discovery of a novel potent cytochrome P450 CYP4Z1 inhibitor.

Human cytochrome P450 enzyme CYP4Z1 represents a promising target for the treatment of a multitude of malignancies including breast cancer. The most active known non-covalent inhibitor (1-benzylimidazole) only shows low micromolar affinity to CYP4Z1. We report a new, highly active inhibitor for CYP4Z1 showing confirmed binding in an enzymatic assay and an IC50 value of 63 ± 19 nM in stably transfected MCF-7 cells overexpressing CYP4Z1. The new inhibitor was identified by a systematically developed virtual screening protocol. Binding was rationalized using a carefully elaborated 3D pharmacophore hypothesis and thoroughly characterized using extensive molecular dynamics simulations and dynamic 3D pharmacophore (dynophore) analyses. This novel inhibitor represents a valuable pharmacological tool to accelerate characterization of the still understudied CYP4Z1 and might pave the way for a new treatment strategy in CYP4Z1-associated malignancies. The presented in silico model for predicting CYP4Z1 interaction provides novel mechanistic insights and revealed that the drug ozagrel interacts with CYP4Z1.

Pharmacodynamic and pharmacokinetic interactions of hydroalcoholic leaf extract of Centella asiatica with valproate and phenytoin in experimental models of epilepsy in rats.

ETHNOPHARMACOLOGICAL RELEVANCE: Centella asiatica (CA) is commonly used herbal medicine for treatment of epilepsy. CA has CYP2C9, CYP2D6 and CYP3A4 enzymes inhibition property and used as an adjuvant therapy with conventional antiepileptic drugs (AEDs). That may be responsible for herb-drug interaction. AIM OF THE STUDY: The present study was planned to evaluate interactions profile of hydroalcoholic extract Centella asiatica (HECA) with antiepileptic drugs in experimental models of epilepsy in rats. MATERIALS AND METHODS: Wistar rats (175-200 g) were used. In the pharmacodynamic interaction study, seizures were induced using pentylenetetrazole (PTZ) (60 mg/kg, i.p.) and maximal electroshock seizure (MES) (70 mA for 0.2 s). The therapeutic and sub-therapeutic doses of valproate (VPA) and phenytoin (PHT) were co-administrated with HECA in PTZ and MES model of seizures respectively. Behavioural parameters were assessed using elevated plus maze test and passive avoidance paradigm. Rat brain oxidative stress parameters were also assessed. In the pharmacokinetic interaction study, the serum levels of the VPA and PHT were estimated at different time intervals by HPLC and pharmacokinetic parameters were analyzed by WinNonlin software. RESULTS: The VPA and PHT produced complete protection against seizures in their therapeutic doses but not with sub-therapeutic doses. However, co-administration of HECA with a sub-therapeutic dose of VPA and PHT enhanced the protection of seizures and significantly (p < 0.001) attenuated the seizure induced oxidative stress and cognitive impairment. It also significantly increased (p < 0.001) serum levels of VPA and PHT. The alterations in pharmacokinetic parameters (maximum serum concentration, area under the curve, clearance) of AEDs were also found with co-administration of HECA. CONCLUSION: The results suggested that co-administration of HECA could improve the therapeutic efficacy of VPA and PHT. But, alteration in pharmacokinetic parameters revel that needs critical medical supervision to avoid any toxic reactions.

Discovery of heterocycle-containing α-naphthoflavone derivatives as water-soluble, highly potent and selective CYP1B1 inhibitors.

Cytochrome P450 1B1 (CYP1B1) has been well validated as an attractive target for cancer prevention and drug resistance reversal. In continuation of our interest in this area, herein, a set of forty-six 6,7,10-trimethoxy-α-naphthoflavone derivatives varying in B ring was synthesized and screened against CYP1 enzymes, leading to the identification of fluorine-containing compound 15i as the most potent and selective CYP1B1 inhibitor (IC50 value of 0.07 nM), being 84-fold more potent than that of the template molecule ANF. Alternatively, the amino-substituted derivative 13h not only possessed a potent inhibitory effect on CYP1B1 (IC50 value of 0.98 nM), but also had a substantially increased water solubility as compared with the lead ANF (311 µg/mL for 13h and <5 µg/mL for ANF). The current study expanded the structural diversity of CYP1B1 inhibitors, and compound 13h could be considered as a promising starting point with great potential for further studies.

Modified bile acids and androstanes-Novel promising inhibitors of human cytochrome P450 17A1.

Cytochromes P450 are key enzymes for steroid hormone biosynthesis in human body. They are considered as targets for the screening of novel high efficient drugs. The results of screening of bile acids and androstane derivatives toward human recombinant steroid 17α-hydroxylase/17,20-lyase (CYP17A1) are presented in this paper. A group of steroids, binding with micromolar or submicromolar affinity (in a range from 9 µM - less than 0.1 µM), was identified. Results presented here showed that these steroidal compounds are able to decrease rate of hydroxylation of essential CYP17A1 substrate - progesterone, while some compounds completely inhibited enzyme activity. Structure-activity relationship (SAR) analysis based on in vitro and in silico studies showed that high affinity of the enzyme to bile acids derivatives is correlated with side chain hydrophobicity and presence of hydroxyl or keto group at C3 position. From the other side, bile acid-derived compounds with more polar side chain or substituents at C7 and C12 positions possess higher Kd values. Among androstane-derived steroids couple of Δ5-steroids with hydroxyl group at C3 position, as well as 16,17-secosteroids, were found to be high affinity ligands of this enzyme. The data obtained could be useful for the design of novel highly efficient inhibitors of CYP17A1, since the bile acids-derived compounds are for first time recognized as effective CYP17A1 inhibitors.

Antimycobacterial activity of azepanobetulin and its derivative: In vitro, in vivo, ADMET and docking studies.

The antimycobacterial investigation of azepanobetulin and its amide derivative was performed. Both compounds showed increased in vitro antibacterial activity on the H37Rv MTB strain in aerobic and anaerobic conditions. Basing on differences between MIC and IC50 values a predominant bactericidal effect for amide in contrast to azepanobetulin with a bacteriostatic antibacterial mechanism is defined. Both compounds showed a strong antibacterial effect against resistant MTB strains with amide derivative being slightly more active. Amide derivative also showed a higher antibacterial potency against non-tuberculous mycobacterial strains (M. avium, M. abscessus). Molecular docking studies showed that the inhibition of tuberculosinyl adenosine transferase (Rv3378c) could constitute an antimycobacterial mechanism of action for these triterpenic azepane derivatives. The pharmacokinetic profile was evaluated by ADMET studies and azepanobetulin showing the better results was evaluated by in vivo experiments. This compound has demonstrated a statistically significant antimycobacterial activity compared to control, but inferior to isoniazid. Our findings show that pentacyclic triterpene derivatives holding a seven-membered azepane A-ring are the promising template for the development of new agents with high antibacterial potential against M. tuberculosis H37Rv, non-tuberculous mycobacterial and drug- resistant strains.

Dietary Polyphenols Inhibit the Cytochrome P450 Monooxygenase Branch of the Arachidonic Acid Cascade with Remarkable Structure-Dependent Selectivity and Potency.

The products of the cytochrome P450 monooxygenase (CYP)-catalyzed oxidation of arachidonic acid (AA), that is, epoxy- and hydroxy-fatty acids, play a crucial role in the homeostasis of several physiological processes. In a liver microsome-based multienzyme assay using AA as natural substrate, we investigated how polyphenols inhibit different oxylipin-forming CYP in parallel but independently from each other. The ω-hydroxylating CYP4F2 and CYP4A11 were investigated, as well as the epoxidizing CYP2C-subfamily and CYP3A4 along with the (ω-n)-hydroxylating CYP1A1 and CYP2E1. The oxylipin formation was inhibited by several polyphenols with a remarkable selectivity and a potency comparable to known CYP inhibitors. The flavone apigenin inhibited the epoxidation, ω-hydroxylation, and (ω-n)-hydroxylation of AA with IC50 values of 4.4-9.8, 2.9-10, and 10-25 µM, respectively. Other flavones such as wogonin selectively inhibited CYP1A1-catalyzed (ω-n)-hydroxylation with an IC50 value of 0.10-0.22 µM, while the isoflavone genistein was a selective ω-hydroxylase inhibitor (IC50: 5.5-46 µM). Of note, the flavanone naringenin and the anthocyanidin perlargonidin did not inhibit CYPs of the AA cascade. Moderate permeability of apigenin as tested in the Caco-2 model of intestinal absorption (Papp: 4.5 ± 1 × 10-6 cm/s) and confirmation of the inhibition of 20-HETE formation by apigenin in the colorectal cancer-derived cell line HCT 116 (IC50: 1.5-8.8 µM) underline the possible in vivo relevance of these effects. Further research is needed to better understand how polyphenols impact human health by this newly described molecular mode of action.

Calycosin Influences the Metabolism of Five Probe Drugs in Rats.

BACKGROUND: Calycosin (CAL), a type of O-methylated isoflavone extracted from the herb Astralagusmembranaceus (AM), is a bioactive chemical with antioxidative, antiphlogistic and antineoplastic activities commonly used in traditional alternative Chinese medicine. AM has been shown to confer health benefits as an adjuvant in the treatment of a variety of diseases. AIM: The main objective of this study was to determine whether CAL influences the cytochrome P450 (CYP450) system involved in drug metabolism. METHODS: Midazolam, tolbutamide, omeprazole, metoprolol and phenacetin were selected as probe drugs. Rats were randomly divided into three groups, specifically, 5% Carboxymethyl cellulose (CMC) for 8 days (Control), 5% CMC for 7 days + CAL for 1 day (single CAL) and CAL for 8 days (conc CAL), and metabolism of the five probe drugs evaluated using ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). RESULTS: No significant differences were observed for omeprazole and midazolam, compared to the control group. T max and t1/2 values of only one probe drug, phenacetin, in the conc CAL group were significantly different from those of the control group (T max h: 0.50±0.00 vs 0.23±0.15; control vs conc CAL). C max of tolbutamide was decreased about two-fold in the conc CAL treatment group (conc vs control: 219.48 vs 429.56, P<0.001). CONCLUSION: Calycosin inhibits the catalytic activities of CYP1A2, CYP2D6 and CYP2C9. Accordingly, we recommend caution, particularly when combining CAL as a modality therapy with drugs metabolized by CYP1A2, CYP2D6 and CYP2C9, to reduce the potential risks of drug accumulation or ineffective treatment.

Inhibition of human CYP1 enzymes by a classical inhibitor α-naphthoflavone and a novel inhibitor N-(3, 5-dichlorophenyl)cyclopropanecarboxamide: An in vitro and in silico study.

Enzymes in the cytochrome P450 family 1 (CYP1) catalyze metabolic activation of procarcinogens and deactivation of certain anticancer drugs. Inhibition of these enzymes is a potential approach for cancer chemoprevention and treatment of CYP1-mediated drug resistance. We characterized inhibition of human CYP1A1, CYP1A2, and CYP1B1 enzymes by the novel inhibitor N-(3,5-dichlorophenyl)cyclopropanecarboxamide (DCPCC) and α-naphthoflavone (ANF). Depending on substrate, IC50 values of DCPCC for CYP1A1 or CYP1B1 were 10-95 times higher than for CYP1A2. IC50 of DCPCC for CYP1A2 was 100-fold lower than for enzymes in CYP2 and CYP3 families. DCPCC IC50 values were 10-680 times higher than the ones of ANF. DCPCC was a mixed-type inhibitor of CYP1A2. ANF was a competitive tight-binding inhibitor of CYP1A1, CYP1A2, and CYP1B1. CYP1A1 oxidized DCPCC more rapidly than CYP1A2 or CYP1B1 to the same metabolite. Molecular dynamics simulations and binding free energy calculations explained the differences of binding of DCPCC and ANF to the active sites of all three CYP1 enzymes. We conclude that DCPCC is a more selective inhibitor for CYP1A2 than ANF. DCPCC is a candidate structure to modulate CYP1A2-mediated metabolism of procarcinogens and anticancer drugs.

Pregnenolonyl-α-glucoside exhibits marked anti-cancer and CYP17A1 enzymatic inhibitory activities.

We report here that pregnenolonyl-α-glucoside (2), a steryl glycoside synthesized directly from pregnenolone and glucose via a consecutive multienzyme-catalyzed process, exhibits marked dose-dependent cytotoxic activity against HT29, AGS, and ES-2 cells with IC50 values of 23.5 to 50.9 µM. An in vitro CYP17A1 binding pattern assay and protein-ligand docking model support that 2, like abiraterone, binds in the active site heme iron pocket of CYP17A1.

Combined Linear Interaction Energy and Alchemical Solvation Free-Energy Approach for Protein-Binding Affinity Computation.

Calculating free energies of binding (ΔGbind) between ligands and their target protein is of major interest to drug discovery and safety, yet it is still associated with several challenges and difficulties. Linear interaction energy (LIE) is an efficient in silico method for ΔGbind computation. LIE models can be trained and used to directly calculate binding affinities from interaction energies involving ligands in the bound and unbound states only, and LIE can be combined with statistical weighting to calculate ΔGbind for flexible proteins that may bind their ligands in multiple orientations. Here, we investigate if LIE predictions can be effectively improved by explicitly including the entropy of (de)solvation into our free-energy calculations. For that purpose, we combine LIE calculations for the protein-ligand-bound state with explicit free-energy perturbation to rigorously compute the unbound ligand's solvation free energy. We show that for 28 Cytochrome P450 2A6 (CYP2A6) ligands, coupling LIE with alchemical solvation free-energy calculation helps to improve obtained correlation between computed and reference (experimental) binding data.

In vitro and in silico studies of interaction of synthetic 2,6,9-trisubstituted purine kinase inhibitors BPA-302, BP-21 and BP-117 with liver drug-metabolizing cytochromes P450

An evaluation of possible interactions with enzymes of drug metabolism (cytochromes P450, CYP) is an important part of studies on safety and, in general, on the properties of any drug or biologically active compound. The article is focused on the preliminary metabolic study of selected 2,6,9-trisubstituted purine kinase inhibitors with significant anticancer activities which we have developed. The compounds BP-21 and BP-117 represent strong CDK inhibitors and the compound BPA-302 was developed as selective FLT3-ITD kinase inhibitor. Here, emphasis is placed on interactions of these compounds with the nine most important forms of CYP to evaluate the possibility of inhibition of these enzymes. The possibility of their inhibitory effect was studied in vitro on selected human liver microsomal CYP enzymes. The most affected enzyme was CYP2C19. Its activity dropped to 22 % of its original value by BPA 302, to 13 % by BP-21 and to 6 % by BP-117 at the highest concentration tested (250 µmol·l(-1)). The results suggest that the metabolism of concomitantly administered drugs should not be significantly affected at lower doses. Molecular docking of BPA-302 indicated that it can bind to active site of both CYP2C19 and CYP2D6 enzymes above the heme cofactor corroborating the experimental data.

Virtual Structural Similarity Elucidates Bioactivity of Fenchone: A Phytochemical Enriched in Fennel Essential Oil.

BACKGROUND: Fenchone is a natural monoterpene abundantly present in fennel essential oil. It is known for its wound healing properties but its other biological activities are less explored. METHODS: We used an in silico structural similarity searching approache to identify various biological activities of fenchone. The identified biological activities of fenchone (purchased from Sigma Aldrich) were validated by conducting DPPH free radical scavenging assay, MTT assay, well diffusion assay for antimicrobial activity and enzymatic assays to analyze the activity of different antioxidant enzymes. RESULTS: Camphor was found to possess maximum structural similarity with fenchone (similarityindex 100). Molecular docking demonstrated that the binding modes of fenchone were also similar to camphor against protein Cytochrome CYP101D1 (PDB ID: 4C9K). Fenchone also demonstrated to possess an antioxidant activity (IC50: 3.32±0.008mM), an antimicrobial activity (MIC: 0.49mM) and a very strong antifungal activity. Fenchone protects yeast cells from H2O2 induced cytotoxicity and is cytotoxic to cancerous Hela cells (IC50: 12.63±0.12 µM). Fenchone treatment also showed the reduced activity of antioxidant enzymes i.e glutathione-S-transferase, catalase and lipid peroxidase. CONCLUSION: To the best of our knowledge, this is the first report that used structural similarity searching to explore the biological activities of fenchone.