Current Bioactive Compounds - Volume 3, Issue 4, 2007

Photodynamic therapy (PDT) is an emerging treatment modality for cancer as well as non-cancer diseases. PDT involves administration of a photosensitizer in targeted tissues and photogeneration of cytotoxic reactive oxygen species that destroys tumor cells. Much effort has been paid to disperse hydrophobic photosensitizers molecularly in water, since self-aggregation of photosensitizers significantly reduces singlet oxygen yield. The self-aggregation and the particle formation have, however, been revaluated and extended in terms of passive tumor cell targeting and ongoing nanotechnology. Upon systemic administration, nanoparticles are preferentially taken up by tumor tissues due to EPR effect (Enhanced Permeability and Retention Effect). To improve therapeutic efficacy and suppress side effects, a variety of approaches has been explored by using photosensitizer nanoparticles such as dendrimers, quantum dots, liposomes, polymer micelles, peptide-conjugates, and hydrogel nanoparticles. Control of the size, surface property, and amphiphilicity are key factors in optimizing the nano-PDT-agents. In this article, the author will review recent progress in this growing field, including our approaches, from the viewpoint of supramolecular chemistry and nanotechnology. Future subjects will also be discussed.

In the past 20 years, photosensitisers have found a niche in the photodynamic treatment of accessible tumours (PDT). Most of the therapeutics involved in this approach are porphyrin-based natural products or derivatives. However, there is a range of other photodynamic agents derived from natural sources - either via direct extraction/purification, or via semisynthesis - currently being trialled both for anticancer PDT and the related antimicrobial application, covering areas such as wound disinfection and blood product sterilisation. The following review covers the advances made in the potential photoantimicrobial application of natural product photosensitisers and their derivatives.

The use of natural compounds has recently been reconsidered in modern clinical practice. A further advancement of these compounds is represented by the possibility of using innovative drug delivery systems that can improve the biopharmaceutical features of the delivered compounds. This review examines the recent developments in the field of delivery of natural drugs belonging to several therapeutic classes. In particular, the examined therapeutic classes are: antitumoral drugs, i.e. paclitaxel, doxorubicin, tea catechins and hypericin; anti-infective drugs, i.e. Melaleuca alternifolia and Artemisia arborescens L.; and antinflammatory/antioxidant drugs, i.e. cannabinoids and glycyrrhizinates used for topical application. In this review we highlight the utility of a suitable drug delivery system to improve the biopharmaceutical aspects of these drugs. The examined carriers are: vesicular carriers (liposomes, Ethosomes®, ultradeformable liposomes), nano- and microparticles, innovative gels, microemulsions.

Obesity and its comorbid conditions are increasing with an alarming rate throughout the world. The high incidence of obesity and scarcity of effective and reliable treatment have fuelled the development of anti-obesity drugs for many years. Different pharmacological approaches rely on four main lines of action- i) control of energy intake through modification of appetite; ii) control of energy expenditure through thermogenesis; iii) control of fat absorption in the gut through lipase inhibitors and iv) other pharmacological approaches. While many drugs have been introduced for the treatment of obesity, only two have so far been approved by the FDA for long term treatment - orlistat, which acts to prevent dietary fat absorption and sibutramine, which seems to affect both arms of energy balance equation i.e. energy intake as well as energy expenditure. However side effects have limited their use and both the medications have failed to gain a large market. A high proportion of current research is also centered on peptidic control of appetite and the modulation of signals from the adipose tissue. Hunger and satiety signals such as ghrelin, obestatin, peptide YY, the CB1 receptor antagonists such as rimonabant, CP-946,598, highly specific 5-HT2C receptor agonist such as APD356, pancreatic lipase inhibitor e.g. cetilistat (ATL-962) and GT389-255 are potentially attractive therapeutic strategies for treatment of obesity. Also, better understanding of human genetics can make an invaluable contribution to the study of human obesity, pointing toward more targeted and effective therapies. In addition to the analysis of current treatment strategies, this review also focuses on the areas of potentially high productivity in the future.

The effects of the aqueous extract of Khaya senegalenis (Desr) A. Juss. (Meliaceae) (EAKS) were evaluated on the contractile activity of the guinea-pig Taenia coli. EAKS in a range of concentrations from 10-8mg/ml to 10-2mg/ml induced an increase of the spontaneous rhythmic contractions and of basal muscular tone, in a concentration-dependent manner (EC50: 6.10-4 mg/ml). With 10- 2mg/ml of the extract, maximal stimulation was obtained. The effects of EAKS were comparable to those induced by acetylcholine (ACh). Moreover, the cholinoceptor antagonist, atropine, applied at a concentration of 10-6 mg/ml inhibited the stimulating effects of ACh. However, atropine did not inhibit the myostimulant action induced by EAKS. In calcium-free solution containing EDTA, a bivalent chelator, at a concentration of 10-3 mM, EAKS had no effect on the guinea-pig isolated Taenia coli. In the same conditions, ACh induced an increase of basal muscular tone. In conclusion, EAKS exerted a stimulating effect in the intestinal smooth muscle. Cholinergic mechanisms may not be involved. The myostimulating action of EAKS could be due to a mobilization of bivalent, mainly calcium flux.

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