M.C. Guerra

Partition data of penicillins determined by means of reversed-phase thin-layer chromatography

Abstract The RM values of II penicillins were measured by means of a reversed-phase thin-layer chromatographic method with various concentrations of acetone in the mobile phase. RM values were calculated by interpolation or extrapolation from the ranges of linearity between RM values and composition of the mobile phase. The influence of substituent groups on the RM values of the penicillins and disagreement with Σπ values are pointed out.

Comparison between Chinese medical herb Pueraria lobata crude extract and its main isoflavone puerarin: Antioxidant properties and effects on rat liver CYP-catalysed drug metabolism

Ge-gen (Radix Puerariae; RP) is used in traditional oriental medicine for various medicinal purposes. The drug is the root of a wild leguminous creeper, Pueraria lobata (Willd) Ohwi. It possesses a high content of flavonoid derivatives, the most abundant of which is puerarin (PU). Here, using the enhanced chemiluminescence technique based on horseradish peroxidase and a luminol-oxidant-enhancer reagent, we evaluated in vitro the antioxidant activity of PU and RP crude extract. Both biological samples inhibited the steady-state chemiluminescent reaction in a dose-dependent fashion. However, different inhibition mechanism were postulated, since only RP behaved like conventional antioxidants. This activity was supposed to be due the presence of compounds other than PU in the crude extract. Using each of the specific substrates to different cytochrome P450 (CYP) isoforms or the regio- and stereo-selective hydroxylation of testosterone as polyfunctional probe we found that when intragastrically administered in male Wistar rats, PU (100 or 200 mg/kg b.w.) and RP (700 or 1,400 mg/kg b.w.) significantly altered hepatic CYP-linked monooxygenases. While both CYP content and NADPH-(CYP)-c-reductase activity were significantly increased in all situations, a complex pattern of CYP modulation was observed, including both induction (PU: CYP2A1, 1A1/2, 3A1, 2C11; RP: CYP1A2, 3A1, 2B1) and inactivation (PU and RP: CYP3A, 2E1, 2B1), the latter being due to either parental agents or metabolites, as demonstrated by in vitro studies. Overall, these findings indicate that RP contains compounds with potent antioxidant activity and that both PU and RP impairs CYP-catalysed drug metabolism.

Anti-inflammatory and cicatrizing activity of Echinacea pallida Nutt. root extract

Among the different species belonging to the Echinacea family, largely used in traditional medicine, Echinacea pallida, Echinacea purpurea and Echinacea angustifolia were investigated. These different species, due to their difficult identification, were commonly confused in the past and probably used indifferently for the same therapeutic purposes. In fact, the three species have in common, some pharmacological activities, based on the presence of active compounds that act additively and synergistically. Nevertheless, the composition of each species has slight variation in the amount of each active component. In particular, echinacoside, a caffeoyl derivative, is present in E. pallida and only in traces in E. angustifolia. It seems to have protective effects on skin connective tissue and to enhance wound healing. The anti-inflammatory and wound healing activities of echinacoside, compared with the ones of the total root extract of E. pallida and E. angustifolia, were examined in rats, after topical application. The tissues of the treated animals were evaluated after 24, 48 and 72 h treatment and excised for histological observation at the end of the experiment. Results confirm the good anti-inflammatory and wound healing properties of E. pallida and of its constituent echinacoside, with respect to E. purpurea and control. This activity probably resides in the antihyaluronidase activity of echinacoside.

Cyanidin-3- O -β-glucopyranoside, a natural free-radical scavenger against aflatoxin B1- and ochratoxin A-induced cell damage in a human hepatoma cell line (Hep G2) and a human colonic adenocarcinoma cell line (CaCo-2)

Recent findings have suggested that oxidative damage might contribute to the cytotoxicity and carcinogenicity of aflatoxin B1 (AFB1). Induction of oxidative stress also plays an important role in the toxicity of another mycotoxin, ochratoxin A (OTA). In the present study, the protective effect of cyanidin-3-O-beta-glucopyranoside (C-3-G; an anthocyanin contained in oranges, blackberries, strawberries and cranberries) against AFB1- and OTA-induced cytotoxicity was investigated in a human hepatoma-derived cell line (Hep G2) and a human colonic adenocarcinoma cell line (CaCo-2). The ability of C-3-G to reduce the production of reactive oxygen species (ROS), the inhibition of protein and DNA synthesis and the apoptosis caused by the two mycotoxins was also investigated in both cell lines. Our experiments proved the significant cytoprotective effect of C-3-G in vitro against OTA- and AFB1-induced cell damage. In particular, 24 h of pretreatment with 50 microm-C-3-G inhibited the cytotoxicity of 10 microm-AFB1 (by 35 %) and of 10 microm-OTA (by 25 %) in Hep G2 cells (P < 0.001) and of 10 microm-AFB1 (by 10 %, P < 0.01) and of 10 microm-OTA (by 14 %, P < 0.05) in CaCo-2 cells. Moreover, 50 microm-C-3-G attenuated ROS production induced by the two toxins in both cell lines (P < 0.05). Inhibition of DNA and protein synthesis induced by the mycotoxins was counteracted by pretreatment with the antioxidant at 50 microm. Similarly, apoptotic cell death was prevented as demonstrated by a reduction of DNA fragmentation and inhibition of caspase-3 activation. The in vitro free-radical scavenging capacity of the anthocyanin was tested with the Briggs-Rauscher oscillating reaction. This system works at pH approximately 2. The results showed good scavenging power, in accordance with the observed inhibition of ROS production.

Oleuropein evaluated in vitro and in vivo as an antioxidant

Oleuropein is a phenolic compound extracted from the leaves of Olea europaea. The antioxidant activity of this natural product has been evaluated in vitro and in vivo by means of a chemiluminescent assay, based on a luminol‐horseradish peroxidase p‐iodophenol O2 mediated light emission system. In vitro, oleuropein had a remarkable antioxidant activity. Serum samples obtained from treated animals exhibited an antioxidant activity comparable to controls. Bile samples obtained from the same treated animals showed a significant inhibition (90%) of the light emission in the chemiluminescent assay, when compared with the control sample.

RM and log P values of 5-nitroimidazoles

Abstract The chromatographic RM values of a series of nitroimidazoles and their log P values were determined in view of a study of their structure-activity relationships as mutagenic agents. The equations describing the relationship between RM and log P values show a low correlation coefficient. The introduction of the molar refractivity of the R1 and R2 groups yields a significant improvement in the correlation coefficient. The molar refractivity could be an expression of the adsorption activity of the silica gel layer.

Study of the lipophilic character of xanthine and adenosine derivatives. I: RM and log P values

Abstract The RM values of a series of xanthine and adenosine derivatives were measured using silicone reversed-phase thin-layer chromatographic (TLC) and C18 reversed-phase high-performance TLC systems. The two series of data were well correlated. Both were compared with experimental log P and calculated CLOGP values. For xanthine derivatives a good linear relationship was shown between the RM values from the two chromatographic systems and the log P or CLOGP data. For adenosine derivatives the CLOGP values had to be corrected in order to fit the data to the same equation. The TLC data proved to be reliable parameters for describing the lipophilic properties of the test compounds.

Mutagenicity of a series of 25 nitroimidazoles and two nitrothiazoles in Salmonella typhimurium

Twenty-five 5-nitroimidazole and two 5-nitrothiazole derivatives were tested for mutagenicity as well as for antibacterial activity in Salmonella typhimurium TA-100 strain. Many of these compounds such as metronidazole, azanidazole, nimorazole, carnidazole, ornidazole, tinidazole, etc are extensively used in human chemotherapy, and some of them were recently synthetized for possible clinical trials as hypoxic cell specific radiosensitizers. Both mutagenic and antibacterial activity were shown for 22 of the test compounds. The high correlation between mutagenic and antibacterial activity supports the hypothesis of a same mechanism for both activities. The present results confirm that the mutagenicity of the nitroheterocyclic compounds is not separated from other biological activities, such as antimicrobial activity.

Phytochemical composition and antioxidant activity of Laurus nobilis L. leaf infusion.

Laurus nobilis L. (laurel) leaves are frequently used as a spice for cooking purposes. Folk medicine in many countries uses the infusion of the plant in stomachic and carminative remedies, as well as for the treatment of gastric diseases. Little information is available about the phytochemical composition of the infusion of dried leaves, which is a way to consume this aromatic and medicinal plant. Phytochemical investigations on the infusion were performed by high-performance liquid chromatography (HPLC) with a diode array detector (DAD) and direct electrospray ionization-tandem mass spectrometry. Several flavonoid derivatives were detected. Semipreparative HPLC from the infusion of laurel leaves isolated 10 flavonoid O-glycosides, one flavonoid C-glycoside, catechin, and cinnamtannin B1. Structures of the isolated compounds were computed on the basis of spectral measurements including high-resolution mass spectrometry spectroscopy and one- and two-dimensional nuclear magnetic resonance techniques. The amount of the flavonoids was also determined by HPLC-DAD. The antioxidant activity of the tea and the isolated compounds was also measured using two different in vitro methods: the Briggs-Rauscher oscillating reaction test, at a pH similar to that of the gastric juice, and the Trolox equivalent antioxidant capacity assay, at the pH of blood. For the infusion and the methanol extract the total phenolic content was also measured using the Folin-Ciocalteu reagent.

In vitro evaluation of the chemoprotective action mechanisms of leontopodic acid against aflatoxin B1 and deoxynivalenol-induced cell damage.

Several in vitro studies showed that free radical scavengers possess chemopreventive properties against mycotoxin‐induced cell damage which are at least partially associated with the induction of phase II detoxifying enzymes and antioxidant enzymes like glutathione S‐transferase (GST) and glutathione peroxidase (GPx). The aim of this project was to study the chemopreventive effects of leontopodic acid (LA), a potent natural occurring free radical scavenger isolated from the aerial parts of Leontopodium alpinum. Different mycotoxins were evaluated in two different cell lines on the basis of their specific toxicity: aflatoxin B1 (AFB1) on HepG2 cells and deoxynivalenol (DON) on U937 cells. Cell viability and reactive oxygen species concentration were determined, and the effects of pre‐treatment with LA on these parameters were investigated together with the GST and GPx activity as well as the concentration of reduced glutathione. The results show that LA protects U937 cells from DON‐induced cell damage but not HepG2 cells from AFB1. Moreover LA is able to enhance GPx activity in U937, but not GST activity in HepG2. We hypothesize that the increase in detoxifying enzymes is probably the main mechanism of antioxidant mediated chemoprevention. Copyright