Cristina Theoduloz

Preliminary pharmacological studies on Eugenia uniflora leaves: xanthine oxidase inhibitory activity

Eugenia uniflora is widely used in Paraguayan folk medicine. A hydroalcoholic extract of the leaves showed some central nervous system activity in hippocratic screening when given intraperitoneally, but little to no acute or subacute toxicity in doses up to 4200 mg/kg orally in BALB c mice. The LD50 of the extract was 220 mg/kg i.p. in mice. A decoction or infusion of the leaves is recommended for treating gout by native herbalists. The known flavonoids quercitrin, quercetin, myricitrin and myricetin were found to be responsible for the xanthine oxidase inhibitory action of the plant extract.

Free-radical Scavengers and Antioxidants from Peumus boldus Mol. ("Boldo")

The dry leaves of Peumus boldus (Monimiaceae) are used in infusion or decoction as a digestive and to improve hepatic complains. Preliminary assays showed free-radical scavenging activity in hot water extracts of boldo leaves, measured by the decoloration of a methanolic solution of the 1,1-diphenyl-2-picryl-hydrazyl radical (DPPH). Assay-guided isolation led to the active compounds. Catechin proved to be the main free-radical scavenger of the extracts. Lipid peroxidation in erythrocytes was inhibited by boldo extracts and fractions at 500 w g/ml with higher effect for the ethyl acetate soluble and alkaloid fractions. The IC 50 for catechin and boldine in the lipid peroxidation test were 75.6 and 12.5 w g/ml, respectively. On the basis of dry starting material, the catechin content in the crude drug was 2.25% while the total alkaloid calculated as boldine was 0.06%. The activity of boldine was six times higher than catechin in the lipid peroxidation assay. However, the mean catechin:total alkaloid content ratio was 37:1. The relative concentration of alkaloids and phenolics in boldo leaves and their activity suggest that free-radical scavenging effect is mainly due to catechin and flavonoids and that antioxidant effect is mainly related with the catechin content. The high catechin content of boldo leaves and its bioactivity suggest that quality control of Boldo folium has to combine the analysis of catechin as well as their characteristic aporphine alkaloids.

Gastroprotective effect of carnosic acid γ-lactone derivatives.

Carnosic acid (1) has been shown to possess gastroprotective activity in vitro and in vivo. However, little is known of the gastroprotective effect or cytotoxicity of carnosic acid gamma-lactone (3). To determine structure-activity relationships, a series of 17 esters of 3 were prepared including aliphatic, aromatic, and heterocyclic derivatives. Also, two units of 3 were coupled with succinic and phthalic acid as linkers. The compounds were assessed for their gastroprotective effect in the HCl/EtOH-induced gastric lesions model in mice and for cytotoxicity in human lung fibroblasts, human adenocarcinoma AGS cells, and Hep G2 hepatocellular carcinoma cells. At a single oral dose of 40 mg/kg, the gastroprotective effect increased moderately with the length of the alkyl chain. The best effects were observed for the butyrate (9) and chloroacetate (6) derivatives. Activity of fatty acid esters increased with chain length but decreased with unsaturation. The best gastroprotective effect, with lowest cytotoxicity, was found for the palmitate (11) and oleate (12) derivatives.

Studies on quinones. Part 44: Novel angucyclinone N-heterocyclic analogues endowed with antitumoral activity☆

In the search for new potentially anticancer drugs, series of angucyclinone aza-analogues containing pyridine and pyridopyridazine rings have been designed and synthesized by a highly efficient sequence involving a one-pot step for the synthesis of tricyclic quinone intermediate and highly regiocontrolled cycloaddition reactions with polarized 1,3-dienes. The new N-heterocyclic angular quinones were evaluated in vitro on normal human fibroblasts and on a panel of four distinct human cancer cell lines. All tested compounds showed high to moderate antitumor activity. Among the compounds, those with one and two pyridine moieties fused to the quinone system have shown the best effect. Structure-activity relationships established the main structural requirement for the activity of the new potential anticancer drugs.

Xanthine oxidase inhibitory activity of paraguayan myrtaceae

Nineteen Myrtaceae collections belonging to 15 species, 12 of which are used in Paraguayan folk medicine, were assayed for inhibitory activity towards the enzyme xanthine oxidase. Most leaf and stem extracts were active showing IC50 values ranging from 3.0 to 50 micrograms/ml. The reported activities support existing ethnobotanical data concerning their use for the treatment of gout.

Studies on quinones. Part 45: Novel 7-aminoisoquinoline-5,8-quinone derivatives with antitumor properties on cancer cell lines

A variety of 7-aminoisoquinoline-5,8-quinone derivatives were prepared from 2,5-dihydroxyacetophenone, methyl aminocrotonate, and the corresponding amines, through a highly efficient three-step sequence. The members of this series were tested on normal human fibroblasts and on a panel of three human cancer cell lines and their redox properties were determined by cyclic voltammetry in acetonitrile. Both the cytotoxicity and antitumor activity of 7-phenylaminoisoquinoline-5,8-quinone derivatives showed correlation with their half wave potentials and lipophilicities.

1,2,3-Triazole-Substituted Oleanolic Acid Derivatives: Synthesis and Antiproliferative Activity

Hybrid compounds are relevant products when searching for structure-activity relationships of natural products. Starting from the naturally occurring triterpene oleanolic acid, alkyl esters were prepared and treated with different aromatic azides using click chemistry to produce hybrid compounds. Some 18 new oleanolic acid derivatives were synthesized and the structures were confirmed by spectroscopic and spectrometric means. The antiproliferative activity of the new derivatives was evaluated towards normal lung fibroblasts (MRC-5), gastric epithelial adenocarcinoma (AGS), promyelocytic leukemia (HL-60), lung cancer (SK-MES-1) and bladder carcinoma (J82) cells. The alkyne esters 1 and 3 showed activity on all cell lines but without selectivity (19.6–23.1 μM and 14.1–56.2 μM, respectively), their respective methyl esters were inactive. Compounds with a benzene and p-anisole attached to the triazole ring, showed no antiproliferative effect. Introduction of a chlorine atom into the benzene ring (compound 9) elicited a selective effect against AGS cells (IC50 value: 8.9 μM). The activity was lost when the COOH function at C-28 was methylated. Better antiproliferative effect was found for compounds 11 and 15 bearing a p-toluenesulphonyl group, with values in the range of 10.8–47.1 μM and 11.5–22.2 μM, respectively. The effect, however, was not associated with selectivity.

Studies on quinones. Part 46. Synthesis and in vitro antitumor evaluation of aminopyrimidoisoquinolinequinones.

In the search of structure-activity relationship studies and to explore the antitumor effect associated with the pyrimidoisoquinolinequinone scaffold, several diversily substituted 8-aminopyrimido[4,5-c]isoquinolinequinones were regioselectively synthesized. Variation in the structure of the nitrogen substituent bonded to the 8-position of the pyrimidoisoquinolinequinone system led to a set of alkylamino-, phenylamino- and alkyphenylamino derivatives. The cytotoxic activity of the aminoquinone derivatives was evaluated in vitro using the MTT colorimetric method against one normal cell line (MRC-5 lung fibroblasts) and four human cancer cell lines (AGS human gastric adenocarcinoma; SK-MES-1 human lung cancer cells, and J82 human bladder carcinoma; HL-60 human leukemia) in 72-h drug exposure assays. Among the series, five compounds exhibited interesting antitumor activity against AGS human gastric adenocarcinoma and human lung cancer cells. The SAR studies revealed that both the nature of the nitrogen substituent into the quinone ring and the methyl group at the 6-position play key roles in the antitumor activity.

Free Radical Scavengers and Antioxidants from Tagetes mendocina

Tagetes mendocina (Asteraceae) is a medicinal plant widely used in the Andean provinces of Argentina. Preliminary assays showed free radical scavenging activity in the methanol extract of the aerial parts, measured by the decoloration of a methanolic solution of the 1,1-diphenyl-2-picrylhydrazyl radical (DPPH) and scavenging of the superoxide anion. Assayguided isolation led to 4′-hydroxyacetophenone (1), protocatechuic acid (2), syringic acid (3), patuletin (4), quercetagetin 7-O-β-d-glucoside (5), patuletin 7-O-β-d-glucoside (6) and axillarin 7-O-β-d-glucoside (7) as the free radical scavengers and antioxidant compounds from Tagetes mendocina. On the basis of dry starting material, the total phenolic content of the crude drug was 3.00% with 0.372% of flavonoids. The content of compounds 1-7 in the crude drug was 0.008, 0.015, 0.010, 0.029, 0.238, 0.058 and 0.017%, respectively. Quercetagetin 7-O-β-d-glucoside proved to be the main free radical scavenger of the extracts measured by the DPPH decoloration test as well as for quenching the superoxide anion and inhibition of lipoperoxidation in erythrocytes. In the lipid peroxidation assay the percentual inhibition was related with the number of methoxy groups in the molecule, ranging from 86% for the quercetagetin glucoside to 67% for the monomethoxylated and 31% for the dimethoxylated derivative. The compounds showed low cytotoxicity towards human lung fibroblasts with IC50 > 1mᴍ for compounds 1-3 and 0.24 to 0.52 mm for the flavonoids 4-7.

Antiproliferative Activity of the Diterpenes Jatrophone and Jatropholone and Their Derivatives

The antiproliferative activity of the diterpenes jatropholone A and B, 16 semi-synthetic derivatives thereof, and that of jatrophone and its three derivatives was assessed on human cell cultures. The cells used comprised normal lung fibroblasts (MRC-5), gastric adenocarcinoma (AGS), leukemia (HL-60), lung cancer (SK-MES-1), and bladder carcinoma (J82). Jatropholone A ( 1) was inactive against all the tumor cell lines; however, its acetylation rendered a compound with antiproliferative activity. The epimeric jatropholone B ( 8) was active against all the cancer cell lines, and its derivatives presented different effects on the selected cell lines. While jatrophone ( 19) showed strong anticancer activity, its derivatives 9beta,13alpha-dihydroxyisabellione and 13alpha-hydroxy-9 beta-acetoxyisabellione were less active.