Mini Reviews in Medicinal Chemistry - Volume 14, Issue 8, 2014

Background & Scope of the review: This review focuses on the UV radiation effects on skin, emphasizing the photoaging process, and the photoprotection conferred by tretinoin (all-trans retinoic acid or ATRA). Tretinoin is still the best tested retinoid to reverse photoaged skin. Major Conclusions: Tretinoin can be used for photoaging treatment or combined treatment by different mechanisms. It binds to and activates retinoic acid receptors, inducing changes in gene expression that leads to cell differentiation, decreased cell proliferation, and inhibition of tumourigenesis. It has been demonstrated that photoaging resulting from UV-B radiation can be treated by retinoid formulations. Pretreatment of human skin with tretinoin blocks dermal matrix degradation followed by sun exposure, inhibiting the induction of the activated protein-1 (AP-1) transcription factor and AP-1 regulated matrix-degrading metalloproteinases. General Significance and Interest: Tretinoin should be considered as a key factor as it is the most potent and best-studied retinoid. In addition, the development of advanced drug delivery systems, especially novel nanoformulations, has contributed to overpass some technical drawbacks besides the skin irritation potential. The triple combination of tretinoin, hydroquinone and corticosteroids is still considered the gold standard for melasma. Although there are other novel therapeutic approaches, more high-quality clinical trials are still needed.

AMP-activated protein kinase (AMPK) is a key energy sensor that regulates cellular energy homeostasis. AMPK activation is associated with decreased phosphorylation of mammalian target of rapamycin (mTOR) and S6 kinase and causes a general reduction in mRNA translation and protein synthesis. Therefore, AMPK is a novel target for anticancer therapy. Metformin and aspirin are two traditional drugs that are widely used as anti-diabetes and non-steroidal anti-inflammatory drugs (NSAIDs), respectively. Much evidence has confirmed that these two drugs demonstrated encouraging anti-cancer properties. Most importantly, both inhibited tumor proliferation and were mainly dependent on the AMPK/mTOR signaling pathway. In addition, several other drugs, such as resveratrol, berberine, statins, epigallocatechin gallate (EGCG) and capsaicin, have provided a similar capacity for tumor inhibition, and the anti-cancer effects of most of them were mainly the result of AMPK activation. In the current review, we summarize the literature on combination therapy based on these non-classical drugs and their potential mechanisms for activating AMPK. Combinations of these drugs will provide a novel cancer therapeutic regimen.

Androgen receptor has been shown to promote prostate cell growth and carcinogenesis of prostate cancer by up-regulating its target genes. Testosterone and dihydrotestosterone are two major hormones which bind to and activate androgen receptor. Targeting both the androgen receptor and the enzymes catalyzing the biosynthesis of testosterone and dihydrotestosterone has been shown to be clinically beneficial in the treatment of prostate cancer. Prostate cancer can become castration-resistant after long term treatment with chemo drugs, so efforts in finding compounds with improved efficiency to castration-resistant prostate cancer are urgently needed. In this review we summarized the studies on recent progress in the development of small molecular AR antagonists for the treatment of prostate cancer.

As important members of the terpenes family, sesquiterpenes represent a group of natural compounds with diverse skeletal types. Among them, the eremophilane-type sesquiterpenes, widely present in several genera (such as Ligularia, Senecio, Cacalia) of Asteraceae, account for a small number of natural compounds and form differently from other sesquiterpenes because they challenged the isoprene rule of biosynthesis. Due to the unique structural features and various functional groups, these compounds possess a number of biological activities such as anti-tumor, anti-bacterial and anti-inflammatory, having received increasing interest in the recent years. This review summarizes the occurrence of eremophilane-type sesquiterpenes and research progresses on their biological activities since the 1990s.

The emergence of drug resistant strains of important human pathogens has created an urgent necessity to find new targets and novel antitubercular agents. According to the literature survey, we noticed that enoyl ACP reductase is one of the most promising targets. This enzyme is the most important catalyst for the FAS II synthesis of mycolic acid, which is the most essential component of the mycobacterial cell wall. This review summarizes the progress made in the design of enoyl ACP reductase inhibitors and the role played by 3D-structure of the enzyme in drug design process.

Compounds derived from nature have played a major role in drug discovery. They became the basis for the development of new pharmaceuticals. In this scope, family Cucurbitaceae is a prominent source of secondary metabolites, mainly triterpenoids. In this paper, we provide a brief review of cucurbitane metabolites that exhibit an extensive range of biological actions specifically antidiabetic, anti-inflammatory, cytotoxic, hepatoprotective, and antiparasitic effects.