Antibacterial activity of (+/-) 6-benzyl-1-(3-carboxypropyl) indane; a possible way to identify leading novel anti-H. pylori agents

Reactive oxygen species, apoptosis, antimicrobial peptides and human inflammatory diseases

Excessive free radical generation, especially reactive oxygen species (ROS) leading to oxidative stress in the biological system, has been implicated in the pathogenesis and pathological conditions associated with diverse human inflammatory diseases (HIDs). Although inflammation which is considered advantageous is a defensive mechanism in response to xenobiotics and foreign pathogen; as a result of cellular damage arising from oxidative stress, if uncontrolled, it may degenerate to chronic inflammation when the ROS levels exceed the antioxidant capacity. Therefore, in the normal resolution of inflammatory reactions, apoptosis is acknowledged to play a crucial role, while on the other hand, dysregulation in the induction of apoptosis by enhanced ROS production could also result in excessive apoptosis identified in the pathogenesis of HIDs. Apparently, a careful balance must be maintained in this complex environment. Antimicrobial peptides (AMPs) have been proposed in this review as an excellent candidate capable of playing prominent roles in maintaining this balance. Consequently, in novel drug design for the treatment and management of HIDs, AMPs are promising candidates owing to their size and multidimensional properties as well as their wide spectrum of activities and indications of reduced rate of resistance.

Exploring alternative treatments for Helicobacter pylori infection

Helicobacter pylori (H. pylori) is a successful pathogen that can persist in the stomach of an infected person for their entire life. It provokes chronic gastric inflammation that leads to the development of serious gastric diseases such as peptic ulcers, gastric cancer and Mucosa associated lymphoid tissue lymphoma. It is known that these ailments can be avoided if the infection by the bacteria can be prevented or eradicated. Currently, numerous antibiotic-based therapies are available. However, these therapies have several inherent problems, including the appearance of resistance to the antibiotics used and associated adverse effects, the risk of re-infection and the high cost of antibiotic therapy. The delay in developing a vaccine to prevent or eradicate the infection has furthered research into new therapeutic approaches. This review summarises the most relevant recent studies on vaccine development and new treatments using natural resources such as plants, probiotics and nutraceuticals. In addition, novel alternatives based on microorganisms, peptides, polysaccharides, and intragastric violet light irradiation are presented. Alternative therapies have not been effective in eradicating the bacteria but have been shown to maintain low bacterial levels. Nevertheless, some of them are useful in preventing the adverse effects of antibiotics, modulating the immune response, gastroprotection, and the general promotion of health. Therefore, those agents can be used as adjuvants of allopathic anti-H. pylori eradication therapy.

Studies on anti-Helicobacter pylori agents. Part 2: new cephem derivatives

The synthesis and optimization of the anti-Helicobacter pylori activity of a novel series of cephem derivatives are described. Introduction of thio-heterocyclic groups containing N- and S-atoms to the 3-position and phenyl or thienyl acetamido groups to the 7-position of the cephem nucleus dramatically improved the activity. From this series of derivatives, compound 13i was found to have extremely potent in vitro anti-H. pylori activity, superior therapeutic efficacy compared to AMPC and CAM, no cross-resistance between CAM or MNZ and low potential for causing diarrhea due to instability to beta-lactamase.

Synthesis and anti-Helicobacter pylori activity of FR182024, a new cephem derivative

The synthesis and anti-Helicobacter pylori activity of a novel cephem derivative FR182024 (1) are described. FR182024 having a (5-methyl-1,3,4-thiadiazol-2-yl)-thio moiety at the 3-position and a phenylacetamido at the 7-position was found to have extremely potent in vitro anti-H.pylori activity, superior therapeutic efficacy to AMPC and CAM, and low potential for causing diarrhea.

Studies on anti-Helicobacter pylori agents. Part 1: Benzyloxyisoquinoline derivatives

The synthesis and optimization of the anti-Helicobacter pylori activity of a novel series of benzyloxyisoquinoline derivatives that was discovered by a random screening process, are described. In the in vitro assay, compound 10c containing a 3-acetamido-2,6-dichlorobenzyl substituent was found to have extremely potent activity against H. pylori and no activity against other common bacteria. The anti-H. pylori activity of 10c was superior to that of amoxicillin (AMPC) (1) and clarithromycin (CAM) (2). However, 10c did not show in vivo efficacy in a mouse infection model; a feature attributed to the lack of strong bactericidal activity at short contact times.

A critical comparison of the hemolytic and fungicidal activities of cationic antimicrobial peptides

The hemolytic and fungicidal activity of a number of cationic antimicrobial peptides was investigated. Histatins and magainins were inactive against human erythrocytes and Candida albicans cells in phosphate buffered saline, but displayed strong activity against both cell types when tested in 1 mM potassium phosphate buffer supplemented with 287 mM glucose. The HC50/IC50 ratio, indicative of the therapeutic index, was about 30 for all peptides tested. PGLa was most hemolytic (HC50 = 0.6 microM) and had the lowest therapeutic index (HC50/IC50 = 0.5). Susceptibility to hemolysis was shown to increase with storage duration of the erythrocytes and also significant differences were found between blood collected from different individuals. In this report, a sensitive assay is proposed for the testing of the hemolytic activities of cationic peptides. This assay detects subtle differences between peptides and allows the comparison between the hemolytic and fungicidal potency of cationic peptides.

In vitro susceptibility of Helicobacter pylori to trifluoromethyl ketones

Heteroaromatic trifluoromethyl ketones (TFMK's) showed strong inhibitory activity against Helicobacter pylori. The MIC50 observed for 2-trifluoroacetonylbenzoxazole (1) is 20-fold more active than metronidazole and is only twice as high as that of clarithromycin. The inhibitory mode of TFMK's on Hp growth was not related to inhibition of urease.

Discovery of a novel benzyloxyisoquinoline derivative with potent anti-Helicobacter pylori activity

The synthesis and in vitro optimization of the anti-Helicobacter pylori activity of a novel series of benzyloxyisoquinoline derivatives discovered by a random screening process, are described. FR180102 (7f), having a 3-acetamido-2,6-dichlorobenzyl moiety, was found to have extremely potent activity against H. pylori and no effect against a series of common Gram-positive and Gram-negative bacteria.