RESUMO
Continuing our search for bioactive compounds in species from the Juncaceae family, Juncus articulatus was investigated. Ten previously undescribed phenanthrenesâarticulins A-J (1-10)âand ten known compoundsâjuncuenin B, dehydrojuncuenin B, juncatrin B, ensifolins E, F, H, I, K, juncuenin D, and luzulin A (11-20)âalong with other compounds, have been isolated and identified. The isolated compounds were evaluated for antibacterial activity against Escherichia coli, Pseudomonas aeruginosa, methicillin-susceptible Staphylococcus aureus (MSSA), and methicillin-resistant Staphylococcus aureus (MRSA). Compounds 12 and 14 exhibited the most potent activity against planktonic and sessile MSSA and MRSA with minimum inhibitory concentration (MIC) values of 15.1 µM (12 for both bacterial strains) and 15.3 µM (14 for both bacterial strains). Compounds 15, 17, and 18 also exhibited activity against both strains, although to a lower extent, with MIC values ranging from 30.0 to 56.8 µM. The inhibition of biofilm formation of these compounds was observed at 15.1-114.3 µM. This study elucidates the phenanthrene composition of J. articulatus and the antibacterial effect of these compounds.
Assuntos
Antibacterianos , Biofilmes , Staphylococcus aureus Resistente à Meticilina , Testes de Sensibilidade Microbiana , Fenantrenos , Antibacterianos/farmacologia , Antibacterianos/química , Biofilmes/efeitos dos fármacos , Fenantrenos/farmacologia , Fenantrenos/química , Fenantrenos/isolamento & purificação , Estrutura Molecular , Staphylococcus aureus Resistente à Meticilina/efeitos dos fármacos , Escherichia coli/efeitos dos fármacos , Pseudomonas aeruginosa/efeitos dos fármacos , Staphylococcus aureus/efeitos dos fármacosRESUMO
Phenolic compounds are the main special metabolites of Cyperaceae species from phytochemical, pharmacological, and chemotaxonomical points of view. The present study focused on the isolation, structure determination, and pharmacological investigation of constituents from Carex praecox. Twenty-six compounds, including lignans, stilbenes, flavonoids, megastigmanes, chromenes, and phenylpropanoids, were identified from the methanol extract of the plant. Five of these compounds, namely, carexines A-E, are previously undescribed natural products. All compounds were isolated for the first time from C. praecox. The ACE-inhibitory activity of seven stilbenoid compounds was tested, and (-)-hopeaphenol proved to be the most active (IC50 7.7 ± 0.9 µM). The enzyme-kinetic studies revealed a mixed-type inhibition; therefore, domain-specific studies were also conducted. The in silico docking of (-)-hopeaphenol to the ACE affirmed some favorable interactions. In addition, the antiproliferative and antibacterial effects of some compounds were also evaluated.
Assuntos
Inibidores da Enzima Conversora de Angiotensina , Carex (Planta) , Simulação de Acoplamento Molecular , Compostos Fitoquímicos , Extratos Vegetais , Estilbenos , Estilbenos/química , Estilbenos/farmacologia , Compostos Fitoquímicos/química , Compostos Fitoquímicos/farmacologia , Extratos Vegetais/química , Extratos Vegetais/farmacologia , Carex (Planta)/química , Inibidores da Enzima Conversora de Angiotensina/química , Inibidores da Enzima Conversora de Angiotensina/farmacologia , Inibidores da Enzima Conversora de Angiotensina/isolamento & purificação , Humanos , Estrutura Molecular , Proliferação de Células/efeitos dos fármacos , Antibacterianos/farmacologia , Antibacterianos/química , FenóisRESUMO
Our research group previously identified graviquinone (1) as a promising antitumor metabolite that is formed inâ situ when the antioxidant methyl caffeate scavenges free radicals. Furthermore, it exerted a DNA damaging effect on cancer cells and a DNA protective effect on normal keratinocytes. To expand and explore chemical space around qraviquinone, in the current work we synthesized 9 new alkyl-substituted derivatives and tested their inâ vitro antitumor potential. All new compounds bypassed ABCB1-mediated multidrug resistance and showed highly different cell line specificity compared with 1. All compounds were more potent in MDA-MB-231 than on MCF-7 cells. The n-butyl-substituted derivatives 2 and 8 modulated the cell cycle and inhibited the ATR-mediated phosphorylation of checkpoint kinase-1 in MCF-7 cells. As a significant expansion of our previous findings, our results highlight the potential antitumor value of alkyl-substituted graviquinone derivatives.
RESUMO
The combination of compounds with complementary bioactivities into hybrid molecules is an emerging concept in drug discovery. In this study, we aimed to synthesize new hybrid compounds based on p53-MDM2/X protein-protein interaction spiropyrazoline oxindole-based inhibitors and ataxia telangiectasia and Rad3-related (ATR) protoflavone-based inhibitors through copper(i) catalysed azide-alkyne cycloaddition. Five new hybrids were prepared along with three representative reference fragments. The compounds were tested against human breast cancer cell lines MCF-7 (hormone-dependent, wild-type p53) and MDA-MB-231 (triple-negative, mutant p53). Most of the new hybrids were more cytotoxic than their reference fragments and several showed 2-4 times selective toxicity against MDA-MB-231 cells. Relevant pharmacological benefit gained from the hybrid coupling was further confirmed by virtual combination index calculations using the Chou method. Compound 13 modulated doxorubicin-induced DNA damage response through inhibiting the ATR-dependent activation of Chk-1, while increasing the activation of Chk-2. Our results suggest that the new hybrids may serve as new leads against triple negative breast cancer.
RESUMO
Common ragweed (Ambrosia artemisiifolia L.) is an invasive plant in Europe with spreading use in the contemporary folk medicine. The chemical composition of the above-ground parts is extensively studied, however, the metabolites of the roots are less discovered. By multiple chromatographic purification of the root extracts, we isolated thiophene A (1), n-dodecene (2), taraxerol-3-O-acetate (3), α-linoleic acid (4), (+)-pinoresinol (5), and thiophene E (7,10-epithio-7,9-tridecadiene-3,5,11-triyne-1,2-diol) (6). The 1H NMR data published earlier for 1 were supplemented together with the assignment of 13C NMR data. Thiophene E (6), which is reported for the first time from this species, exerted cytotoxic and antiproliferative effects on A-431 epidermoid skin cancer cells, whereas taraxerol-3-O-acetate (3) and α-linoleic acid (4) had slight antiproliferative effect on gynecological cancer cell lines. Thiophene E (6) and taraxerol-3-O-acetate (3) displayed antiproliferative and cytotoxic effects on MRC-5 fibroblast cells. Thiophene E (6) exerted weak antibacterial activity (MIC 25 µg/mL) on MRSA ATCC 43300, on Staphylococcus aureus ATCC 25923, Escherichia coli AG100 and E. coli ATCC 25922 both thiophenes were inactive. Although the isolated compounds exerted no remarkable cytotoxic or antiproliferative activities, the effects on MRC-5 fibroblast cells highlight the necessity of further studies to support the safety of ragweed root.
Assuntos
Ambrosia , Neoplasias , Humanos , Escherichia coli , Ácido Linoleico/farmacologia , Linhagem Celular , Tiofenos/farmacologia , Acetatos/farmacologiaRESUMO
Ginger (Zingiber officinale) is widely used as a spice and a traditional medicine. Many bioactivities have been reported for its extracts and the isolated compounds, including cardiovascular protective effects. Different pathways were suggested to contribute to these effects, like the inhibition of platelet aggregation. In this study, we synthesised fourteen 6-gingerol derivatives, including eight new compounds, and studied their antiplatelet, COX-1 inhibitor, and antioxidant activities. In silico docking of selected compounds to h-COX-1 enzyme revealed favourable interactions. The investigated 6-gingerol derivatives were also characterised by in silico and experimental physicochemical and blood-brain barrier-related parameters for lead and preclinical candidate selection. 6-Shogaol (2) was identified as the best overall antiplatelet lead, along with compounds 3 and 11 and the new compound 17, which require formulation to optimize their water solubility. Compound 5 was identified as the most potent antioxidant that is also promising for use in the central nervous system (CNS).
RESUMO
A new flexible germacranolide (1, lobatolide H) was isolated from the aerial parts of Neurolaena lobata. The structure elucidation was performed by classical NMR experiments and DFT NMR calculations. Altogether, 80 theoretical level combinations with existing 13C NMR scaling factors were tested, and the best performing ones were applied on 1. 1H and 13C NMR scaling factors were also developed for two combinations utilizing known exomethylene containing derivatives, and the results were complemented by homonuclear coupling constant (JHH) and TDDFT-ECD calculations to elucidate the stereochemistry of 1. Lobatolide H possessed remarkable antiproliferative activity against human cervical tumor cell lines with different HPV status (SiHa and C33A), induced cell cycle disturbance and exhibited a substantial antimigratory effect in SiHa cells.
Assuntos
Asteraceae , Sesquiterpenos , Humanos , Estrutura Molecular , Asteraceae/química , Espectroscopia de Ressonância Magnética , Imageamento por Ressonância Magnética , Sesquiterpenos/farmacologiaRESUMO
Resveratrol is a well-known natural polyphenol with a plethora of pharmacological activities. As a potent antioxidant, resveratrol is highly oxidizable and readily reacts with reactive oxygen species (ROS). Such a reaction not only leads to a decrease in ROS levels in a biological environment but may also generate a wide range of metabolites with altered bioactivities. Inspired by this notion, in the current study, our aim was to take a diversity-oriented chemical approach to study the chemical space of oxidized resveratrol metabolites. Chemical oxidation of resveratrol and a bioactivity-guided isolation strategy using xanthine oxidase (XO) and radical scavenging activities led to the isolation of a diverse group of compounds, including a chlorine-substituted compound (2), two iodine-substituted compounds (3 and 4), two viniferins (5 and 6), an ethoxy-substituted compound (7), and two ethoxy-substitute,0d dimers (8 and 9). Compounds 4, 7, 8, and 9 are reported here for the first time. All compounds without ethoxy substitution exerted stronger XO inhibition than their parent compound, resveratrol. By enzyme kinetic and in silico docking studies, compounds 2 and 4 were identified as potent competitive inhibitors of the enzyme, while compound 3 and the viniferins acted as mixed-type inhibitors. Further, compounds 2 and 9 had better DPPH scavenging activity and oxygen radical absorbing capacity than resveratrol. Our results suggest that the antioxidant activity of resveratrol is modulated by the effect of a cascade of chemically stable oxidized metabolites, several of which have significantly altered target specificity as compared to their parent compound.
RESUMO
Citrus trifoliata L. (Chinese or Japanese bitter orange) is a medicinal plant with furocoumarins and limonoids as characteristic secondary metabolites. The bitter taste of the fruit limits its use as food, however, it is applied in Asian traditional medicine for its antiphlogistic effect, to treat digestive ulcers and different gastrointestinal disorders and cancer. The phytochemical composition and pharmacological characteristics of this species have not been fully discovered, nevertheless its potential antiproliferative or cytotoxic effects might be related to furocoumarins or limonoids. Our aim was to isolate and identify secondary metabolites from C. trifoliata peel and seeds and to investigate their bioactivities that might be related to the supposed anticancer effect of the plant. By using different chromatographic methods, six pure compounds (phellopterin (2), scoparone (3), myrsellin (4), triphasiol (6), umbelliferone (7) and citropten (5,7-dimethoxycoumarin (8)) were isolated from the peel and four (imperatorin (1), auraptene (5), limonin (9) and deacetyl nomilin (10)) from the seeds of C. trifoliata fruits. These compounds are furocoumarin (1, 2), coumarin (3-8), and limonoid derivatives (9, 10). Scoparone (3) has been detected in this species for the first time. The furocoumarins (1-2) showed moderate activity on the human colorectal adenocarcinona tumor cell line COLO 320 in antiproliferative assays and 2 also had remarkable P-glycoprotein inhibitory activity and synergistic effect with doxorubicin. The coumarin 5 showed significant activity on the COLO 320 cell line in antiproliferative assays and P-glycoprotein inhibitory activity in the FACS (fluorescence activated cell sorting) assay.
RESUMO
Cytotoxic activities of methanolic crude extract of Stachys parviflora (Lamiaceae family) and its sub-fractions were primarily evaluated against human breast adenocarcinoma (MCF-7 and MDA-MB-231) and prostate (PC3) cell lines. The methanolic extract exhibited the highest activity, and was chosen for the isolation procedure. Four diterpenoid quinones, namely miltirone [1], tanshinone IIA [2], 1-hydroxy-tanshinone IIA [3], and cryptotanshinone [4] were isolated. Notably, this is the first report on the isolation and/or characterization of the mentioned diterpenoids from the Stachys genus. In this study, 1-hydroxy-tanshinone IIA [3] displayed the highest cytotoxicity among the isolated compounds. The mechanism of the cytotoxicity of methanolic extract and isolated compounds was further investigated by the utilization of propidium iodide staining (PI) assay. The results showed that the methanolic extract and 1-hydroxy-tanshinone IIA [3] enhanced DNA fragmentation in PC3 and MCF-7 cells. Moreover, the western blotting analysis demonstrated increasing and decreasing protein levels of Bax and Bcl2, respectively, and cleaved poly ADP-ribose polymerase (PARP). Further bioassay-guided phytochemical assessments of S. parviflora can be suggested as a promising approach for discovering potent bioactive secondary metabolites.
Assuntos
Antineoplásicos Fitogênicos , Neoplasias da Mama , Diterpenos , Stachys , Abietanos , Antineoplásicos Fitogênicos/química , Antineoplásicos Fitogênicos/farmacologia , Apoptose , Western Blotting , Neoplasias da Mama/metabolismo , Linhagem Celular Tumoral , Diterpenos/farmacologia , Humanos , Masculino , PróstataRESUMO
CONTEXT: Ambrosia artemisiifolia L. (Asteraceae) contains sesquiterpene lactones as characteristic secondary metabolites. Many of these compounds exert antiproliferative and cytotoxic effects. OBJECTIVE: To isolate the sesquiterpene lactones from the aerial part of A. artemisiifolia and to elucidate their cytotoxic, antiproliferative and antibacterial effects. MATERIALS AND METHODS: The compounds were identified by one-dimensional (1D) and 2D NMR, HR-MS spectroscopy from the methanol extract. Isolated compounds were investigated for their cytotoxic and antiproliferative effects on human colonic adenocarcinoma cell lines and human embryonal lung fibroblast cell line using MTT assay. The selectivity of the sesquiterpenes was calculated towards the normal cell line. To check the effect of drug interactions between compounds and doxorubicin, multidrug-resistant Colo 320 cells were used. RESULTS: A new seco-psilostachyinolide derivative, 1,10-dihydro-1'-noraltamisin, and seven known compounds were isolated from the methanol extract. Acetoxydihydrodamsin had the most potent cytotoxic effect on sensitive (Colo205) cell line (IC50 = 7.64 µM), also the strongest antiproliferative effect on Colo205 (IC50 = 5.14 µM) and Colo320 (IC50 = 3.67 µM) cell lines. 1'-Noraltamisin (IC50 = 8.78 µM) and psilostachyin (IC50 = 5.29 µM) showed significant antiproliferative effects on the multidrug-resistant Colo320 cell line and had moderate selectivity against human embryonal lung fibroblast cell line. Psilostachyin C exhibited cytotoxic effects on Colo205 cells (IC50 = 26.60 µM). None of the isolated compounds inhibited ABCB1 efflux pump (EP; P-glycoprotein) or the bacterial EPs. DISCUSSION AND CONCLUSIONS: Acetoxydihydrodamsin, 1'-noraltamisin, and psilostachyin showed the most remarkable cytotoxic and antiproliferative activity on tumour cell lines and exerted selectivity towards MRC-5 cell line.
Assuntos
Adenocarcinoma , Antineoplásicos , Sesquiterpenos , Adenocarcinoma/tratamento farmacológico , Ambrosia/química , Antineoplásicos/farmacologia , Linhagem Celular Tumoral , Humanos , Lactonas/farmacologia , Metanol , Compostos Fitoquímicos/farmacologia , Extratos Vegetais/química , Extratos Vegetais/farmacologiaRESUMO
Nine previously undescribed ingol-type diterpenoid polyesters with eighteen known ingol esters, two ent-atisane, and one stachane diterpenoid were isolated from the methanol extract of Euphorbia deightonii Croizat. The structures were established by extensive spectroscopic analysis involving 1D (1H, 13C J-modulation) and 2D NMR experiments, HRESIMS measurements, and the comparison of the spectroscopic data with reported literature values. The cytotoxic concentrations of 13 isolated compounds were determined, and the compounds were investigated for multidrug resistance modulating activity on an L5178 mouse lymphoma cell line using a rhodamin 123 accumulation assay. Six ingol esters demonstrated the significant inhibition of P-glycoprotein, while the two ent-atisane diterpenoids were found to be inactive. The measured activities allowed to establish some structure-activity relationships. Notably, lower and higher-type diterpenoids simultaneously occurred in E. deightonii.
RESUMO
From the aerial parts of Euphorbiagossypina var. coccinea Pax., eight new pregnane glycosides (euphogossypins A-H, 1-8) of the cynanforidine and deacetylmetaplexigenin aglycons, two new lignans (gossypilignans A and B, 9 and 10), and four known compounds, namely, the pregnane 12-O-benzoyldeaxcylmetaplexigenin (11), the lignan 9α-hydroxypinoresinol (12), and the flavonoids naringenin (13) and quercitrin (14) were isolated. The structure elucidation of the new compounds was carried out by a spectroscopic analysis, including HRMS, 1D (1H, 13C JMOD), and 2D NMR (HSQC, 1H-1H COSY, HMBC, and NOESY) experiments. The obtained pregnane glycosides were substituted with acetyl and benzoyl ester moieties, and sugar chains containing thevetose, cymarose, digitoxose, and glucose monosaccharides. All of the compounds are described for the first time from E. gossypina var. coccinea. The isolated pregnanes and lignans were tested for their antiproliferative activity on HeLa cells using the MTT assay; the compounds exerted no significant effect against the tumor cells.
RESUMO
Phenanthrenes are the main special metabolites of Juncaceae species from phytochemical, pharmacological, and chemotaxonomical points of view. The present study focused on the isolation, structure determination, and pharmacological investigation of phenanthrenes from Juncus ensifolius. Nineteen compounds, including 17 phenanthrenes, were identified from the methanol extract of the plant. Thirteen compounds, namely, ensifolins A−M (1−13), were obtained for the first time from natural sources. Four phenanthrenes [2-hydroxy-1,7-dimethyl-5-vinyl-9,10-dihydrophenanthrene (14), juncuenin B (15), juncatrin B (16), and sylvaticin A (17)], 4-hydroxybenzaldehyde (18) and luteolin (19) were isolated for the first time from J. ensifolius. Ensifolins A (1) and B (2) are structurally unique phenanthrenes, considering that they are flavonoid- (1) or benzaldehyde-adducts (2). The antiproliferative activity of all isolated compounds against HeLa, COLO 205, and COLO 320 cancer cells and a non-tumor (MRC-5) cell line was tested using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) viability assay. The luteolin-substituted phenanthrene ensifolin A (1) proved to be the most active against all three cancer cell lines (IC50 values 3.9−12.7 µM) and showed good selectivity (SI = 4.95) in the case of COLO 205. The best selectivity was recorded for ensifolins D (4, SI > 5.15, HeLa), H (8, SI > 8.13, HeLa), and 17 (SI > 9.43, HeLa). The synergistic activity of the compounds with doxorubicin was also tested on HeLa cells, and ensifolins E (5) and H (8) exhibited very strong synergism (CI < 0.1). In conclusion, these phenanthrenes are worthy of further investigation.
RESUMO
Two undescribed compounds, 3ß,7ß-dihydroxy-24-methylenelanosta-8-ene-11-one (1) and neolignane deightonin (4) were isolated from the aerial parts of Euphorbia deightonii Croizat together with six known compounds, namely, kansenone (2), euphorbol-7-one (3), dehydrodiconiferyl diacetate (5), marylaurencinol D (6), scoparon (7), and 3,4,3'-tri-O-methylellagic acid (8). The structures of the isolated compounds were determined by HRESIMS, 1D (1H, 13C JMOD) and 2D NMR (HSQC, HMBC, 1H-1H COSY, NOESY) spectroscopic analysis, and by comparison of the assignments with literature data. The anti-herpes simplex virus type-2 activity of the isolated compounds were investigated by qRT-PCR assay on Vero cells after determining cytotoxic concentration 50% (CC50). Compounds 1, 3, 4, and 7 exhibited inhibitory effects with respective IC50 values of 7.05, 2.42, 11.73, and 0.032 µM. Scoparon (7) showed the strongest anti-HSV activity with a selectivity index of 10.93.
RESUMO
Jacaranones are a small group of specific plant metabolites with promising biological activities. The occurrence of jacaranones is limited to only a few plant families, with Asteraceae being the most abundant source of these compounds. Therefore, jacaranones can also serve as chemotaxonomic markers. Our phytochemical investigation of Crepis pulchra L. (Asteraceae) resulted in three jacaranone derivatives (jacaranone, 2,3-dihydro-2-hydroxyjacaranone, 2,3-dihydro-2-methoxyjacaranone), and (6R,9S)-3-oxo-α-ionol-ß-d-glucopyranoside, fulgidic acid, 12,15-octadecadienoic acid methyl ester, scopoletin and apigenin-7-O-ß-d-glucoside. This is the first report on the isolation of jacaranones from a species belonging to the Cichorioideae subfamily of Asteraceae. Jacaranone derivatives were subjected to an in vitro antiproliferative assay against a panel of human cancer cell lines (MCF-7, MDA-MB-231, HeLa, and C33A), revealing high or moderate activities, with IC50 values ranging from 6.3 to 26.5 µM.
RESUMO
A new depside, olivieridepside (1), and a new secoiridoid, olivierigenin (2) were isolated from the aerial parts of Gentiana olivieri Griseb. along with four known compounds, gentiopicroside (3), olivierosides A (4) and B (5) and isoorientin (6). The structures of the isolates were determined by extensive 1 D and 2 D NMR spectroscopy and HR-MS analysis. This is the first report on the occurrence of a depside structure in the genus Gentiana. Moreover, a rare type of non-glycosidic secoiridoid (2) lacking an oxygenated group at C-1 is also being reported for the first time from this genus. The chemotaxonomic importance of the isolates was discussed in detail.
Assuntos
Gentiana , Depsídeos , Gentiana/química , Estrutura Molecular , Componentes Aéreos da Planta , TurquiaRESUMO
Seven new germacranolides (1-3, 5-8), among them a heterodimer (7), and known germacranolide (4), eudesmane (9) and isodaucane (10) sesquiterpenes were isolated from the aerial parts of Neurolaena lobata. Their structures were determined by using a combination of different spectroscopic methods, including HR-ESIMS and 1D and 2D NMR techniques supported by DFT-NMR calculations. The enantiomeric purity of the new compounds was investigated by chiral HPLC analysis, while their absolute configurations were determined by TDDFT-ECD and OR calculations. Due to the conformationally flexible macrocycles and difficulties in assigning the relative configuration, 13C and 1H NMR chemical shift and ECD and OR calculations were performed on several stereoisomers of two derivatives. The isolated compounds (1-10) were shown to have noteworthy antiproliferative activities against three human cervical tumor cell line with different HPV status (HeLa, SiHa and C33A). Additionally, lobatolide C (6) exhibited substantial antiproliferative properties, antimigratory effect, and it induced cell cycle disturbance in SiHa cells.
RESUMO
Euphorbia usambarica is a traditional medicine used for gynecologic, endocrine, and urogenital illnesses in East Africa; however, its constituents and bioactivities have not been investigated. A variety of compounds isolated from Euphorbia species have been shown to have activity against latent HIV-1, the major source of HIV-1 persistence despite antiretroviral therapy. We performed bioactivity-guided isolation to identify 15 new diterpenoids (1-9, 14-17, 19, and 20) along with 16 known compounds from E. usambarica with HIV-1 latency reversal activity. Euphordraculoate C (1) exhibits a rare 6/6/3-fused ring system with a 2-methyl-2-cyclopentenone moiety. Usambariphanes A (2) and B (3) display an unusual lactone ring constructed between C-17 and C-2 in the jatrophane structure. 4ß-Crotignoid K (14) revealed a 250-fold improvement in latency reversal activity compared to crotignoid K (13), identifying that configuration at the C-4 of tigliane diterpenoids is critical to HIV-1 latency reversal activity. The primary mechanism of the active diterpenoids 12-14 and 21 for the HIV-1 latency reversal activity was activation of PKC, while lignans 26 and 27 that did not increase CD69 expression, suggesting a non-PKC mechanism. Accordingly, natural constituents from E. usambarica have the potential to contribute to the development of HIV-1 eradication strategies.
RESUMO
Ingenol mebutate, isolated from Euphorbia peplus, is an ingenane-type diterpenoid, primarily used for the topical treatment of actinic keratosis, a premalignant skin condition. The aim of our work was to investigate other Euphorbia species to find structurally similar diterpenes that can be used as alternatives to ingenol mebutate. Pharmacological investigation of Euphorbia candelabrum, Euphorbia cotinifolia, Euphorbia ramipressa, and Euphorbia trigona revealed the potent keratinocyte (HPV-Ker cell line) inhibitory activity of these spurge species. From the methanolic extract of the aerial parts of Euphorbia trigona Miller, the most active species, five ingol (1-5) and four ingenane-type diterpenoids (6-9) were isolated by various chromatographic separation techniques, including open column chromatography, vacuum liquid chromatography, thin-layer chromatography, and high-performance liquid chromatography. The structures of the compounds were determined by NMR spectroscopic analysis and by comparison of the assignations with the literature data. The cytotoxic activity of the compounds against keratinocytes was tested in vitro by using ingenol mebutate as a positive control. Among the isolated compounds, two ingenane derivatives (6 and 7) exhibited remarkably stronger cytotoxic activity (IC50 values 0.39 µM and 0.32 µM, respectively) on keratinocytes than ingenol mebutate (IC50 value 0.84 µM). These compounds could serve as starting materials for further investigations to find alternatives to Picato® (with active substance ingenol mebutate), which was withdrawn from marketing authorization in the European Union.