The immunomodulation potential of the synthetic derivatives of benzothiazoles: Implications in immune system disorders through in vitro and in silico studies

Benzothiazole and its natural or synthetic derivatives have been used as precursors for several pharmacological agents for neuroprotective, anti-bacterial, and anti-allergic activities. The objecctive of the present study was to evaluate effects of benzothiazole analogs (compounds 1–26) for their immunomodulatory activities. Eight compounds (2, 4, 5, 8–10, 12, and 18) showed potent inhibitory activity on PHA-activated peripheral blood mononuclear cells (PBMCs) with IC₅₀ ranging from 3.7 to 11.9 μM compared to that of the standard drug, prednisolone <1.5 μM. Some compounds (2, 4, 8, and 18) were also found to have potent inhibitory activities on the production of IL-2 on PHA/PMA-stimulated PBMCs with IC₅₀ values ranging between <4.0 and 12.8 μM. The binding interaction of these compounds was performed through silico molecular docking. Compounds 2, 8, 9, and 10 significantly suppressed oxidative burst ROS production in phagocytes with IC₅₀ values between <4.0 and 15.2 μM. The lipopolysaccharide (LPS)-induced nitrites in murine macrophages cell line J774 were found to be inhibited by compounds 4, 8, 9, and 18 at a concentration of 25 μg/mL by 56%, 91%, 58%, and 78%, respectively. Furthermore, compounds 5, 8, 12, and 18 showed significant (P < 0.05) suppressive activity on Th-2 cytokine, interleukin 4 (IL-4) with an IC₅₀ range of <4.0 to 40.3 μM. Interestingly compound 4 has shown a selective inhibitory activity on IL-2 and T cell proliferation (naïve T cell proliferation stage) rather than on IL-4 cytokine, while compound 12 displayed an interference with T-cell proliferation and IL-4 generation. Moreover compound 8 and 18 exert non-selective inhibition on both IL-2 and IL-4 cytokines, indicating a better interference with stage leading to humoral immune response and hence possible application in autoimmune diseases.     

Isolation of diverse bioactive compounds from Euphorbia balsamifera: Cytotoxicity and antibacterial activity studies

Antibacterial and cytotoxic activities of Euphorbia balsamifera, fractions and pure compounds were evaluated. The cytotoxic assays for HCT116, HePG2 and MCF7 showed a significant IC₅₀: 54.7 and 76.2 µg/mL of non-polar fraction “n-hexane” against HCT116 and HePG2, respectively. Antibacterial results revealed that plant fractions exhibited significant potential against the tested pathogens than the total extract where n-butanol and ethyl acetate fractions showed significant antibacterial activity (P < 0.05) against tested bacterial strains. Isolation and structure determination of compounds from n-hexane and n-butanol fractions were performed. From n-hexane fraction, 29-nor-cycloartanol (1), lanost-8-en-3-ol (2a), cycloartanol (2b) and kampferol-3,4'-dimethyl ether (3) were isolated and structurally identified, along with 24 compounds were tentatively identified by GC–MS. From the polar n-butanol fraction, 4-O-β-D-glucopyranosyl-2-hydroxy-6-methoxyacetophenone (4), 4-O-α-L-rhamnosyl-(1 → 6)-β-D-glucopyranosyl-2-hydroxy-6methoxy-acetophenone (5), quercetin-3-O-glucopyranoside (6) and isoorientin (7) were assigned. Structures of the obtained compounds were determined by nuclear magnetic resonance (NMR) spectroscopy and mass spectrometry. Except compounds 1 and 5, all reported compounds announced antibacterial efficiency. Compound 2 showed selectively the highest activity against Enterococcus faecalis (22 ± 0.13 mm), meanwhile 4-O-β-D-glucopyranosyl-2-hydroxy-6-methoxyacetophenone (4) showed broadly the highest antibacterial activity with MIC of 1.15–1.88 mg/mL against the test Gram-positive and Gram-negative bacteria. Cytotoxic assays indicated that kampferol-3,4'-dimethyl ether (3) exhibited the highest activity with matching IC₅₀ values to doxorubicin; 111.46, 42.67 and 44.90 µM against HCT116, HePG2 and MCF7, respectively, however, it is toxic on retina normal cell line RPE1.     

Cytotoxic cassaine diterpenoid–diterpenoid amide dimers and diterpenoid amides from the leaves of Erythrophleum fordii

Detailed phytochemical investigation from the leaves of Erythrophleum fordii resulted in the isolation of 13 compounds, including three cassaine diterpenoid–diterpenoid amide dimers (1, 3 and 5), and seven cassaine diterpenoid amides (6 and 8–13), together with three previously reported ones, erythrophlesins D (2), C (4) and 3β-hydroxynorerythrosuamide (7). Compounds 1, 3 and 5 are further additions to the small group of cassaine diterpenoid dimers represented by erythrophlesins A–D. Their structures were determined by analysis of extensive one- and two-dimensional NMR experiments and ESIMS methods. Cytotoxic activities of the isolated compounds were tested against HCT-8, Bel-7402, BGC-823, A549 and A2780 human cancer cell lines in the MTT test. Results showed that compounds 1 and 3–5 exhibited significantly selective cytotoxic activities (IC₅₀ < 10 μM) against these cells, respectively.     

Multisubstituted indole–acrylonitrile hybrids as potential cytotoxic agents

A series of multisubstituted indole–acrylonitrile hybrids were designed, synthesized and evaluated for their potential cytotoxic activities. The bio-evaluation results indicated that some of the target compounds (such as 3a, 3f, 3k, 3n) exhibited good to moderate cytotoxic effect on HepG2, BCG-823, BEL-7402, and HL-7702 cell lines. Especially, the compounds 3a and 3k also exhibited high cytotoxic activities (3a, 19.38 ± 3.38 μM; 3k, 15.43 ± 3.54 μM) against the BEL-7402 cell line resistant to Taxol (>25 μM) and 5-FU (>500 μM), which might be developed as novel lead scaffold for potential anticancer agents.     

New bioactive derivatives of nonactic acid from the marine Streptomyces griseus derived from the plant Salicornia sp.

Three new compounds, butyl homononactate (5), butyl nonactate (6), 8-actyl homononactic acid (7), along with four known compounds homononactic acids (1), nonactic acid (2), homononactyl nonactate (3), homononactyl homononactate (4) were isolated from the marine Streptomyces griseus RSH0407, derived from the plant Salicornia sp., Chenopodiaceae. Their structures were elucidated by extensive spectroscopic techniques and by comparison with data reported in the literature. The absolute configuration of 3 was first reported by using X-ray copper radiation. Compound 5 exhibited cytotoxic activities against the HCT-8, A2780, BGC-823, BEL-7402, and A549 cell lines in vitro, with IC₅₀ values of 2.87 ± 0.20, 4.90 ± 0.30, 2.19 ± 0.32, 5.07 ± 0.23 and 1.78 ± 0.18 μM, respectively, and compounds 4–7 showed weak antibacterial activities against four bacterials respectively.     

Chemical constituents of Ligularia alticola Worosch. leaves and their biological activities

Seven eremophilane-type sesquiterpenes (1–7), six cycloartane derivatives (8–13) and α-amyrin acetate (14) were isolated from the leaves of the far-eastern plant Ligularia alticola Worosch. (Family Asteraceae). (4S,5R,8S,10R)-8-Ethoxyeremophil-7(11)-en-12(8)-olide (1), 8α,11-epidioxy-8β-methoxyeremophil-6-ene (2) and 29-norcycloartan-3α-ol (8) have not been previously reported. Fukinone α-epoxide (3) was isolated for the first time from a natural source. The structures of all the compounds were established by the extensive analysis of their 1D and 2D NMR spectra and HR ESI mass spectrometry. The absolute stereochemistry of 1 was determined by comparison of theoretical and experimental ECD spectra with the application of B3LYP-TDDFT and B3LYP-GIAO calculations as well as by NMR spectroscopy. Compound 1 showed cytotoxic action against human cancer HL-60, Raji, and THP-1 cell lines (IC₅₀ 12.6, 6.0 and 6.9 μM, respectively). Compounds 2 and 4 demonstrated significant cytotoxic activities against HL-60 (IC₅₀ 2.8 and 5.8 μM, respectively) and Raji cells (IC₅₀ 2.9 and 4.2 μM, respectively). Compound 6 was cytotoxic against Raji cells (IC₅₀ 4.6 μM). None of tested compounds were cytotoxic against RAW 264.7 cells. Compounds 1 and 4–7 significantly decreased intracellular ROS levels, induced by endotoxic LPS from Escherichia coli in RAW 264.7 murine macrophages.     

(R)-3-Amino-1-((3aS,7aS)-octahydro-1H-indol-1-yl)-4-(2,4,5-trifluorophenyl)butan-1-one derivatives as potent inhibitors of dipeptidyl peptidase-4: Design,synthesis, biological evaluation,and molecular modeling

A series of (R)-3-amino-1-((3aS,7aS)-octahydro-1H-indol-1-yl)-4-(2,4,5-trifluorophenyl)butan-1-one derivatives was designed, synthesized, and evaluated as novel inhibitors of dipeptidyl peptidase-4 (DPP-4) for the treatment of type 2 diabetes. Most of the synthesized compounds demonstrated good inhibition activities against DPP-4. Among these, compounds 3e, 4c, 4l, and 4n exhibited prominent inhibition activities against DPP-4, with IC₅₀s of 0.07, 0.07, 0.14, and 0.17 μM, respectively. The possible binding modes of compounds 3e and 4n with dipeptidyl peptidase-4 were also explored by molecular docking simulation. These potent DPP-4 inhibitors were optimized for the absorption, distribution, metabolism, and excretion (ADME) properties, and compound 4n displayed an attractive pharmacokinetic profile (F = 96.3%, t_1/2 = 10.5 h).     

Design,synthesis and evaluation of 6-(4-((substituted-1H-1,2,3-triazol-4-yl)methyl)piperazin-1-yl)phenanthridine analogues as antimycobacterial agents

Focus in this Letter is made to design and synthesize a series of nineteen new 6-(4-((substituted-1H-1,2,3-triazol-4-yl)methyl)piperazin-1-yl)phenanthridine analogues employing click chemistry and evaluated for their anti-tubercular activity against Mycobacterium tuberculosis H₃₇Rv. Among the tested compounds, 7f and 7j exhibited good activity (MIC = 3.125 μg/mL), while 8a displayed excellent activity (MIC = 1.56 μg/mL) against the growth of M. tuberculosis H₃₇Rv. In addition, 7f, 7j and 8a compounds were subjected to cytotoxic studies against mouse macrophage (RAW264.7) cell lines and the selectivity index values are >15 indicating suitability of compounds for further drug development.     

Daphnane-type diterpenes with inhibitory activities against human cancer cell lines from Daphne genkwa

Four new daphnane-type diterpenes, genkwadanes A–D (1–4), together with 19 known ones, were isolated from ethanol extract of the flower buds of Daphne genkwa. Their structures were determined on the basis of extensive spectroscopic data. Among them, daphnane-type diterpene with a 1,10-double bond (1) was isolated from this plant for the first time. The cytotoxicity of all compounds 1–23 against the 10 selected human cancer cell lines was assayed. A number of compounds exhibited significant activities against the 10 cancer cell lines (IC₅₀ < 9.56 μM). and most interestingly, all the compounds revealed preferred cytotoxicities on the HT-1080 cell line and displayed much stronger inhibitory activities (IC₅₀ < 29.94 μM) compared with positive control 5-fluorouracil (IC₅₀ = 35.62 μM), particularly, compounds 9–11, 13, 16 and 19 exhibited the strongest cytotoxicity activities against the HT-1080 cell line (IC₅₀ < 0.1 μM).     

Cytotoxic triterpene saponins from the stem bark of Kalopanax pictus

Three new compounds, 3β,6β,23-trihydroxyolean-12-en-28-oic acid 3-O-α-l-arabinopyranoside (1), kalopanaxsaponin L (2), and kalopanaxsaponin M (13), as well as eleven known compounds (3–12 and 14), were isolated from the stem bark of Kalopanax pictus. Their structures were determined on the basis of extentive spectroscopic analyses and acid hydrolysis. The cytotoxicity of the compounds was evaluated in three human carcinoma cell lines, including HL-60, HCT-116, and MCF-7. Compounds 1, 5–8, 10, and 11 exhibited significantly cytotoxic activity toward HL-60 cells, with IC₅₀ values ranging from 0.1 to 6.9 μM. Compounds 4–7 and 14 showed significant cytotoxicity against HCT-116 cells, with IC₅₀ values ranging from 0.4 to 9.2 μM. Remarkably, the cytotoxic activities of compounds 5–7 against HCT-116 cells were greater than that of the anticancer chemotherapy drug, mitoxantrone (IC₅₀ = 3.7 μM). Compounds 1, 3, 5, and 14 were cytotoxic toward MCF-7 cells with IC₅₀ values in a range of 7.4–14.5 μM.     

Synthesis and biological evaluation of a novel series of pyrazole chalcones as anti-inflammatory,antioxidant and antimicrobial agents

A novel series of 1-(2,4-dimethoxy-phenyl)-3-(1,3-diphenyl-1H-pyrazol-4-yl)-propenone (3) have been prepared by the Claisen–Schmidt condensation of 1-(2,4-dimethoxy-phenyl)-ethanone (1) and substituted 1,3-diphenyl-1H-pyrazole-4-carbaldehydes (2). Substituted 1,3-diphenyl-1H-pyrazole-4-carbaldehydes (2) were prepared by Vilsmeir–Haack reaction on acetophenonephenylhydrazones to offer the target compounds. The structures of the compounds were established by IR, ¹H NMR and mass spectral analysis. All the compounds were evaluated for their anti-inflammatory (TNF-α and IL-6 inhibitory assays), antioxidant (DPPH free radical scavenging assay) and antimicrobial activities (agar diffusion method) against some pathogenic bacteria and fungi. Of 10 compounds screened, compounds 3a, 3c and 3g exhibited promising IL-6 inhibitory (35–70% inhibition, 10 μM), free radical scavenging (25–35% DPPH activity) and antimicrobial activities (MIC 100 μg/mL and 250 μg/mL) at varied concentrations. The structure–activity relationship (SAR) and in silico drug relevant properties (HBD, HBA, PSA, c Log P, molecular weight, E_HOMO and E_LUMO) further confirmed that the compounds are potential lead compounds for future drug discovery study. Toxicity of the compounds was evaluated theoretically and experimentally and revealed to be nontoxic except 3d and 3j.     

New phenolic glycosides with cyclooxygenase inhibition from the roots of Tecoma mollis

Three new phenolic glycosides (1–3) together with nine known ones were isolated from the roots of Tecoma mollis using DPPH radical scavenging bioassay-guided chromatographic separation. The structures of the new compounds were established using extensive spectroscopic data and HR-MS. The antioxidant, COX-2 inhibition, and cytotoxic activities were evaluated for the isolated compounds. Compound 4 displayed the strongest radical scavenging activity relative to ascorbic acid with IC₅₀ 8.7 μM. Compounds 5, 6, and 10 showed promising COX-2 inhibitory action, IC₅₀ values of 11.3 μM, 9.4 μM, and 13.4 μM, respectively. All compounds exhibited weak cytotoxic activity against Hela and A549 cancer cell lines.     

Tirucallane triterpenoids from the stem bark of Araliopsis synopsis

Two new tirucallane triterpenoids, 21-methoxy-21,23-epoxy-tirucalla-7,24-dien-3α-ol (1) and 21-methoxy-21,23-epoxy-tirucalla-7,24-diene-1α,3α-diol (2), together with thirteen known compounds were isolated from the CH₂Cl₂ extract of the stem bark of Araliopsis synopsis. The structures of the compounds were determined by comprehensive analyses of their 1D and 2D NMR, mass spectral (EI and ESI) data and comparison with previously known analogs. Compounds 1–10 were tested against bacteria, fungi and plant pathogen oomycetes by the paper disk agar diffusion assay resulting in missing to low activities corresponding with MICs > 1 mg/mL. However, compounds 5–10 exhibited high cytotoxic activity against the human Caucasian prostate adenocarcinoma cell PC-3 line, with IC₅₀ 8.5–12.5 μM compared to the standard Doxorubicin with IC₅₀ = 0.9 μM, while compounds 1, 3 and 4 showed low activity.     

Synthesis and biological evaluation of simple methoxylated chalcones as anticancer,anti-inflammatory and antioxidant agents

Chalcones have been identified as interesting compounds with cytotoxicity, anti-inflammatory and antioxidant properties. In the present study, simple methoxychalcones were synthesized by Claisen–Schmidt condensation reaction and evaluated for above biological activities. The structures of the compounds were established by IR, ¹H NMR and mass spectral analysis. The data revealed that compound 3s (99–100% at 10 μM concentration) completely inhibit the selected five human cancer cell lines as compared to standard flavopiridol and gemcitabine (70–90% at 700 nM and 500 nM concentrations, respectively), followed by 3a, 3n, 3o, 3p, 3q, 3r. Among the tested compounds 3l, 3m, 3r, and 3s exhibited promising anti-inflammatory activity against TNF-α and IL-6 with 90–100% inhibition at 10 μM concentration. DPPH free radical scavenging activity was given by the compounds 3o, 3n, 3l, 3r, 3m, 3a, 3p, 3c and 3s at 1 mM concentration. Overall, 3s was obtained as lead compound with promising anticancer, anti-inflammatory and antioxidant activities. Bioavailability of compounds were checked by in vitro cytotoxicity study and confirmed to be nontoxic. The structure activity relationship (SAR) and in silico drug relevant properties (HBDs, HBAs, PSA, c Log P, ionization potential, molecular weight, E_HOMO and E_LUMO) further confirmed that the compounds were potential candidates for future drug discovery study.     

The application of Heck reaction in the synthesis of guaianolide sesquiterpene lactones derivatives selectively inhibiting resistant acute leukemic cells

A series of guaianolide-type sesquiterpene lactones derivatives with arylation of α-methylene-γ-lactone moiety was synthesized using Heck reactions, and was evaluated for their activities against acute myelogenous leukemia (AML) cell line HL-60 and doxorubicin-resistant cell line HL-60/A. Although all compounds were significantly less active against HL-60 than the parent molecules, surprisingly, compounds 3a, 4c–4e, 5e, and 8d exhibited high potency against doxorubicin-resistant cell line HL-60/A (IC₅₀ = 6.2–19 μM), and their activities against HL-60/A were comparable to that of their parent molecules. In view of their novel activities against HL-60/A, compound 5e with inhibitory activity against HL-60/A (IC₅₀ = 6.2 ± 0.5 μM) was selected for study its preliminary mechanism. The result reveals that compound 5e can obviously induce apoptosis.     

Synthesis and antiproliferative activities of quebecol and its analogs

Simple and efficient synthesis of quebecol and a number of its analogs was accomplished in five steps. The synthesized compounds were evaluated for antiproliferative activities against human cervix adenocarcinoma (HeLa), human ovarian carcinoma (SK-OV-3), human colon carcinoma (HT-29), and human breast adenocarcinoma (MCF-7) cancer cell lines. Among all the compounds, 7c, 7d, 7f, and 8f exhibited antiproliferative activities against four tested cell lines with inhibition over 80% at 75 μM after 72 h, whereas, compound 7b and 7g were more selective towards MCF-7 cell line. The IC₅₀ values for compounds 7c, 7d, and 7f were 85.1 μM, 78.7 μM, and 80.6 μM against MCF-7 cell line, respectively, showing slightly higher antiproliferative activtiy than the synthesized and isolated quebecol with an IC₅₀ value of 104.2 μM against MCF-7.     

Triterpenoid saponins and C-glycosyl flavones from stem bark of Erythrina abyssinica Lam and their cytotoxic effects.

Six new compounds including two oleanane-type triterpenoid saponins (1, 2) and four C-glycosyl flavones (3–6), along with a known saponin (7), three di-C-glycosyl flavones (8–10) and a glycosyl auronol (11), were isolated from the stem bark of Erythrina abyssinica Lam. The structures of the new compounds, identified as 3-O-[α-l-rhamnopyranosyl-(1 → 2)-β-d-galactopyranosyl-(1 → 2)-β-d-glucuronopyranosyl]-22-O-β-d-glucopyranosyl sophoradiol (1), 3-O-[α-l-rhamnopyranosyl-(1 → 2)-β-d-glucopyranosyl-(1 → 2)-β-d-glucuronopyranosyl]-22-O-β-d-glucopyranosyl sophoradiol (2), 6-C-β-glucopyranosyl-8-C-β-quinovopyranosyl apigenin (3), 6-C-β-quinovopyranosyl-8-C-β-glucopyranosyl apigenin (4), 8-C-[6″-O-α-l-rhamnopyranosyl-(1‴ → 6″)]-β-glucopyranosyl 7,4′-dihydroxyflavone (5) and 8-C-[6″-O-β-d-xylopyranosyl-(1‴ → 6″)]-β-glucopyranosyl 7,4′-dihydroxyflavone (6), were determined by comprehensive spectroscopic analysis, including 1D and 2D NMR techniques, mass spectrometry and acid hydrolysis. These new compounds together with the known saponins 7 were evaluated for their cytotoxic activity against MCF-7 (estrogen dependent) and MDA-MB-231 (estrogen independent) cell lines. The new saponin 2 exhibited the highest cytotoxic activity among tested compounds, exerting a selective inhibitory effect against the proliferation of MCF-7 cells, with lower IC₅₀ value (12.90 μM) than that of the positive control, resveratrol (13.91 μM). Structure–activity relationship of these compounds is also discussed.     

Synthesis of novel 3,5-diaryl pyrazole derivatives using combinatorial chemistry as inhibitors of tyrosinase as well as potent anticancer,anti-inflammatory agents

In the present article, we have synthesized a combinatorial library of 3,5-diaryl pyrazole derivatives using 8-(2-(hydroxymethyl)-1-methylpyrrolidin-3-yl)-5,7-dimethoxy-2-phenyl-4H-chromen-4-one (1) and hydrazine hydrate in absolute ethyl alcohol under the refluxed conditions. The structures of the compounds were established by IR, ¹H NMR and mass spectral analysis. All the synthesized compounds were evaluated for their anticancer activity against five cell lines (breast cancer cell line, prostate cancer cell line, promyelocytic leukemia cell line, lung cancer cell line, colon cancer cell line) and anti-inflammatory activity against TNF-α and IL-6. Out of 15 compounds screened, 2a and 2d exhibited promising anticancer activity (61–73% at 10 μM concentration) against all selected cell lines and IL-6 inhibition (47% and 42% at 10 μM concentration) as in comparison to standard flavopiridol (72–87% inhibition at 0.5 μM) and dexamethasone (85% inhibition at 1 μM concentration), respectively. Cytotoxicity of the compounds checked using CCK-8 cell lines and found to be nontoxic to slightly toxic. Out of 15, four 3,5-diaryl pyrazole derivatives exhibiting potent inhibitory activities against both the monophenolase and diphenolase actions of tyrosinase. The IC₅₀ values of compounds (2a, 2d, 2h and 2l) for monophenolase inhibition were determined to range between 1.5 and 30 μM. Compounds 2a, 2d, 2h and 2l also inhibited diphenolase significantly with IC₅₀ values of 29.4, 21.5, 2.84 and 19.6 μM, respectively. All four 3,5-diaryl pyrazole derivatives were active as tyrosinase inhibitors (2a, 2d, 2h and 2l), and belonging to competitive inhibitors. Interestingly, they all manifested simple reversible slow-binding inhibition against diphenolase.     

Synthesis and cytotoxic activity of new azepino[3′,4′:4,5]pyrrolo[2,1-a]isoquinolin-12-ones

A series of azepino[3′,4′:4,5]pyrrolo[2,1-a]isoquinolin-12-ones (3a–f), that were conformationally restricted analogs of lead compound 2, were designed as potential cytotoxic compounds and synthesized using a radical oxidative aromatic substitution reaction as the key step. Compounds 3a–f were tested on five tumor cell lines to determine the conformational requirements for biological activity of compound 2. The results show that conformational restrictions on compound 2, generating the derivatives 3a–f, do not appreciably reduce the cytotoxic activity of 2, although compound 3d (R = Br) showed good activity against U-251 cells. Preliminary structure–activity relationship studies with these compounds revealed the importance of halogens bonded to the isoquinoline moiety. Additionally, derivatives 3f (R = NO₂) and 3b (R = F) were cytotoxic to PC-3 and K-562 cells. However, none of the azepino[3′,4′:4,5]pyrrolo[2,1-a]isoquinolinones inhibited the enzymatic activity of CDK1/cyclin B, CDK5/p25, or GSK-3.     

Antimicrobial activities of Dilobeia thouarsii Roemer and Schulte,a traditional medicinal plant from Madagascar

The leaves of Dilobeia thouarsii (Roemer and Schulte), a tree that is endemic to Madagascar (Proteaceae), are used in traditional Malagasy medicine to treat bacterial skin infections and wounds. This study investigated the in vitro antibacterial activities of D. thouarsii leaf extracts and identified the bioactive compounds with the aim of providing a scientific basis for its use against skin diseases. Using broth microdilution method for leaf crude extract and its compounds, we investigated inhibition of the growth of Bacillus cereus, Bacillus megaterium, Staphylococcus aureus, Enterococcus faecalis, Vibrio harveyi, Vibrio fisheri, Salmonella Typhimurium, Salmonella antarctica, Escherichia coli, and Klebsiella pneumoniae. The two purified phenolic compounds from leaf ethyl acetate extracts (1, 2) were found to be more active than the crude extract itself. The structure of the two compounds was elucidated by NMR and mass spectrometry: compound 1 was identified as 4-aminophenol and compound 2 as 4-hydroxybenzaldehyde. A marked inhibitory effect (MIC < 0.1 mg/ml) was found against S. aureus, which is a major agent in skin infections. We observed moderate activities (MIC values of between 0.1 and 0.5 mg/ml) for E. faecalis, Vibrio spp., and Bacillus spp. Neither compound was active against Salmonella spp., E. coli and K. pneumoniae (MICs > 1 mg/ml). To conclude, the high antimicrobial activity of D. thouarsii leaf extracts against S. aureus supports its traditional use to treat skin infections.