Polyphenolic Secondary Metabolites Synergize the Activity of Commercial Antibiotics against Clinical Isolates of ß-Lactamase-producing Klebsiella pneumoniae.

Emergence of worldwide antimicrobial resistance prompted us to study the resistance modifying potential of plant-derived dietary polyphenols, mainly caffeic acid, ellagic acid, epigallocatechin-3-gallate (EGCG) and quercetin. These compounds were studied in logical combination with clinically significant antibiotics (ciprofloxacin/gentamicin/tetracycline) against Klebsiella pneumoniae, after conducting phenotypic screening of a large number of clinical isolates and selecting the relevant strains possessing extended-spectrum ß-lactamase (ESBL) and K. pneumoniae carbapenemase (KPC)-type carbapenemase enzymes only. The study demonstrated that EGCG and caffeic acid could synergize the activity of tested antibiotics within a major population of ß-lactamase-producing K. pneumoniae. In spectrofluorimetric assay, ~17-fold greater ciprofloxacin accumulation was observed within K. pneumoniae cells pre-treated with EGCG in comparison with the untreated control, indicating its ability to synergize ciprofloxacin to restrain active drug-efflux. Further, electron micrograph of ESBL-producing K. pneumoniae clearly demonstrated the prospective efficacy of EGCG towards biofilm degradation.

Inhibitory effect of Nymphaea pubescens Willd. flower extract on carrageenan-induced inflammation and CCl4-induced hepatotoxicity in rats.

Nymphaea pubescens Willd. is used as ingredient of ethnic diet and folk medicine in South-East Asia. The water (NPW), methanol (NPM) and chloroform (NPC) extracts of N. pubescens flowers were investigated for NO·, O2·â» and DPPH radical scavenging and iron chelating activities in vitro. NPW was found to be the most potent free radical scavenger (EC50<100 µg/mL) whereas NPC did not show EC50 at 500 µg/mL. Therefore, NPW was selected for further studies on anti-inflammatory and hepatoprotective activities, using standard in vitro and in vivo models. NPW exhibited inhibition of nitrogen radical generation in LPS-activated macrophages (IC50=75.5 µg/mL) through suppression of iNOS protein, with no associated toxicity in the cells. Further, 500 mg/kg of NPW reduced rat paw edema by ~50% after 6h of carrageenan administration. Hepatoprotective activity of NPW was also evaluated in vivo on CCl4-induced hepatotoxicity model in rats. NPW treatment (500 mg/kg/day for ten days) attenuated CCl4-induced increase in serum enzymes, viz. alanine and aspartate aminotransferases (ALT and AST) and bilirubin. Also, glutathione and superoxide dismutase (SOD)-levels were restored towards normalcy in the liver of CCl4-treated rats, indicating the hepatoprotective role of NPW, which was found to contain a fair amount of flavonoids, phenolics, and saponin constituents.

Pomegranate pericarp extract enhances the antibacterial activity of ciprofloxacin against extended-spectrum ß-lactamase (ESBL) and metallo-ß-lactamase (MBL) producing Gram-negative bacilli.

A methanolic extract of Punica granatum (pomegranate) fruit pericarp (PGME) was tested in combination with ciprofloxacin against extended-spectrum ß-lactamase (ESBL) producing Escherichia coli, Klebsiella pneumoniae, and metallo-ß-lactamase (MBL) producing Pseudomonas aeruginosa, which were screened for their resistance profile against fluoroquinolone antibiotics. The minimum inhibitory concentrations (MIC) of ciprofloxacin and PGME, alone, were determined, and synergy of ciprofloxacin-PGME combinations evaluated by checkerboard assay and fractional inhibitory concentration (FIC). Nineteen out of forty-nine strains exhibited synergy with ciprofloxacin (FIC of 0.125-0.5 for ciprofloxacin) further verified by agar-well assay. This could be due to the bacterial efflux pump inhibitor (EPI) activity of the polyphenolic constituents of PGME. However, the isolates exhibiting a high level of ciprofloxacin resistance did not respond to ciprofloxacin-PGME combinations, which could be due to target site modification not influenced further by EPI activity of PGME. Again, some strains were sensitive or weakly resistant to ciprofloxacin, which exhibited 'indifference' to the combination, probably due to a lack of over-expressed efflux mechanism. Thus, a synergy of a ciprofloxacin-PGME combination was demonstrated for the first time against ESBL- and MBL-producing Gram-negative bacilli, and the efficacy of an existing drug improved with the help of an inexpensive alternative therapy.

Antileishmanial activity of cryptolepine analogues and apoptotic effects of 2,7-dibromocryptolepine against Leishmania donovani promastigotes.

Cryptolepine (5-methyl-10H-indolo [3, 2-b] quinoline), an indoloquinoline alkaloid (1) isolated from a medicinal plant traditionally used in Western Africa for treatment of malaria, has been shown to possess broad spectrum biological activity in addition to its antiplasmodial effect. Here, the antileishmanial properties of 11 synthetic derivatives of cryptolepine against Leishmania donovani parasites have been evaluated for the first time. 2,7-Dibromocryptolepine (8; IC50 0.5 ± 0.1 µM) was found to be the most active analogue against the promastigote form of a classical L. donovani strain (AG83) in comparison to the natural alkaloid, cryptolepine (1; IC50 1.6 ± 0.1 µM). Further, 8 was found to substantially inhibit the intracellular amastigote forms of two clinical isolates, one of them being an SbV-resistant strain of L. donovani. Moreover, the toxicity of 8 against normal mouse peritoneal macrophage cells was markedly lower than that of 1 (IC50 values: 9.0 ± 1.2 and 1.1 ± 0.3 µM, respectively), indicating 8 to be a prospective "lead" towards novel antileishmanial therapy. This was supported by studies on the mechanism of cytotoxicity induced by 8 in L. donovani promastigotes (AG83), which revealed the cytoplasmic and nuclear features of metazoan apoptosis. Light microscopic observation demonstrated a gradual decline in the motility, cell volume, and survival of the treated parasites with increasing incubation time. Flow cytometric analysis of phosphatidylserine externalization and distribution of cells in different phases of cell cycle confirmed the presence of a substantial percentage of cells in early apoptotic stage. Disruption of mitochondrial membrane integrity in terms of depolarization of membrane potential, and finally degradation of chromosomal DNA into oligonucleosomal fragments - the hallmark event of apoptosis - characterized the mode of cell death in L. donovani promastigotes.

Valeriana wallichii root extracts and fractions with activity against Leishmania spp.

Leishmanial diseases, posing a public health problem worldwide, are caused by Leishmania parasites with a dimorphic life cycle alternating between the promastigote and amastigote forms. Promastigotes transmitted by the vector are transformed into amastigotes residing in the host tissue macrophages. Presently, new antiparasitic agents are needed against Leishmania donovani and Leishmania major, the respective organisms causing visceral and cutaneous leishmaniasis, since the available treatments are unsatisfactory due to toxicity, high cost, and emerging drug resistance. Over the years, traditional medicinal flora throughout the world enriched the modern pharmacopeia. Hence, roots of 'Indian Valerian' (Valeriana wallichii DC) were studied for its antileishmanial activity for the first time. The methanol and chloroform extracts showed activity against L. donovani promastigotes and both promastigotes and amastigotes of L. major. The most active fraction, F3, obtained from the chloroform extract, showed IC(50) at ∼ 3-7 µg/ml against both the promastigotes and 0.3 µg/ml against L. major amastigotes. On investigation of the mechanism of cytotoxicity in L. donovani promastigotes, the 'hall-mark' events of morphological degeneration, DNA fragmentation, externalization of phosphatidyl serine, and mitochondrial membrane depolarization indicated that F3 could induce apoptotic death in leishmanial cells. Therefore, the present study revealed a novel and unconventional property of V. wallichii root as a prospective source of effective antileishmanial agents.

The prospective role of plant products in radiotherapy of cancer: a current overview.

Treatment of cancer often requires exposure to radiation, which has several limitations involving non-specific toxicity toward normal cells, reducing the efficacy of treatment. Efforts are going on to find chemical compounds which would effectively offer protection to the normal tissues after radiation exposure during radiotherapy of cancer. In this regard, plant-derived compounds might serve as "leads" to design ideal radioprotectors/radiosensitizers. This article reviews some of the recent findings on prospective medicinal plants, phytochemicals, and their analogs, based on both in vitro and in vivo tumor models especially focused with relevance to cancer radiotherapy. Also, pertinent discussion has been presented on the molecular mechanism of apoptotic death in relation to the oxidative stress in cancer cells induced by some of these plant samples and their active constituents.

Anti-inflammatory and anticancer compounds isolated from Ventilago madraspatana Gaertn., Rubia cordifolia Linn. and Lantana camara Linn.

OBJECTIVES: The aim was to search for anti-inflammatory and anticancer compounds from three medicinal plants, viz. Ventilago madraspatana Gaertn., Rubia cordifolia Linn. and Lantana camara Linn. METHODS: The NO* scavenging potential of selected plant extracts was determined on LPS/IFN-gamma activated murine peritoneal macrophage cultures, and iNOS and COX-2 expression was evaluated by Western blot analysis. Bio-assay guided fractionation yielded four compounds: physcion and emodin from V. madraspatana, 1-hydroxytectoquinone from R. cordifolia, and oleanonic acid from L. camara. The anti-inflammatory activity of these compounds was tested through the carrageenan-induced rat-paw oedema model. They were then tested against a murine tumour (Ehrlich ascites carcinoma), and three human cancer cell lines, namely A375 (malignant skin melanoma), Hep2 (epidermoid laryngeal carcinoma) and U937 (lymphoma). KEY FINDINGS: All four compounds dose dependently inhibited NO* through suppression of iNOS protein without affecting macrophage viability. Physcion and emodin caused 65-68% reduction of oedema volume at 40 mg/kg, which validated their in-vivo anti-inflammatory effect. 1-Hydroxytectoquinone and oleanonic acid exhibited promising cytotoxicity against A375 cells. CONCLUSIONS: Ethnomedical reports on these traditional medicinal plants have been rationalised through an insight into the anti-inflammatory as well as anticancer potential of four constituents, characterised to be prospective candidates for designing novel therapeutic agents.