Potent P-glycoprotein inhibition of emodin derivative: synthesis and biological evaluation

Is Emodin with Anticancer Effects Completely Innocent? Two Sides of the Coin

Many anticancer active compounds are known to have the capacity to destroy pathologically proliferating cancer cells in the body, as well as to destroy rapidly proliferating normal cells. Despite remarkable advances in cancer research over the past few decades, the inclusion of natural compounds in researches as potential drug candidates is becoming increasingly important. However, the perception that the natural is reliable is an issue that needs to be clarified. Among the various chemical classes of natural products, anthraquinones have many biological activities and have also been proven to exhibit a unique anticancer activity. Emodin, an anthraquinone derivative, is a natural compound found in the roots and rhizomes of many plants. The anticancer property of emodin, a broad-spectrum inhibitory agent of cancer cells, has been detailed in many biological pathways. In cancer cells, these molecular mechanisms consist of suppressing cell growth and proliferation through the attenuation of oncogenic growth signaling, such as protein kinase B (AKT), mitogen-activated protein kinase (MAPK), HER-2 tyrosine kinase, Wnt/-catenin, and phosphatidylinositol 3-kinase (PI3K). However, it is known that emodin, which shows toxicity to cancer cells, may cause kidney toxicity, hepatotoxicity, and reproductive toxicity especially at high doses and long-term use. At the same time, studies of emodin, which has poor oral bioavailability, to transform this disadvantage into an advantage with nano-carrier systems reveal that natural compounds are not always directly usable compounds. Consequently, this review aimed to shed light on the anti-proliferative and anti-carcinogenic properties of emodin, as well as its potential toxicities and the advantages of drug delivery systems on bioavailability.

Synthesis and anti-inflammatory effects of novel emodin derivatives bearing azole moieties

Twelve azole derivatives of emodin were designed to possess anti-inflammatory activity and synthesized via a two-step sequence composed of the Williamson ether reaction and N-alkylation. The anti-inflammatory properties of these compounds were evaluated in RAW264.7 cells by measuring lipopolysaccharide (LPS)-induced nitric oxide (NO) production. The introduction of imidazole and four carbons into the scaffold of emodin led to the discovery of the potent compound 7e, which showed the best inhibition of NO production among twelve analogs. In our experiential setting, the IC₅₀ of compound 7e in NO production is 1.35 µM, which is lower than that of indomethacin. Mechanically, compound 7e effectively inhibited the protein and messenger RNA expressions of cyclooxygenase-2 and inducible NO synthase, as well as that of the proinflammatory cytokine interleukin-6, and the cytokines interleukin-1β and tumor necrosis factor-α in the LPS-stimulated RAW 264.7 macrophages. Compound 7e exerted inhibitory effects on the nuclear factor κB pathway by reducing the LPS-induced phosphorylation of the inhibitor of NF-κB and the nuclear translation of p-p65. These results suggest the potential of compound 7e in improving inflammatory conditions and diseases.

Anthraquinone derivative exerted hormetic effect on the apoptosis in oxygen-glucose deprivation-induced PC12 cells via ERK and Akt activated Nrf2/HO-1 signaling pathway

There were accumulated evidences that agents may attenuate neurological disorders through a hormetic effect. This study was designed to investigate hormetic effect of BME on the oxygen-glucose deprivation (OGD)-induced mitochondrial apoptosis in NGF-differentiated PC12 cells. The effect of BME on the intracellular reactive oxygen species (iROS) formation and pro-survival signals mediated by ERK and Akt as well as transcription factor nuclear factor-erythroid 2 p45-related factor 2 (Nrf2) pathways was also determined. The present results showed that, at low concentrations, pretreatment with BME triggered stress response by causing ROS production, then, activated survival-promoting signals via ERK and Akt activated Nrf2/HO-1 signaling pathway, resulting in decrease in cytotoxicity induced by the OGD. It may be accepted that mild pretreatment with BME stimulated transient and moderate ROS production, but activated hormetic signals and induced stress responsive genes. In contrast, high concentrations of BME displayed toxic action due to massive ROS production. These results suggested that the effect of BME on the OGD-induced PC12 cells may be hormetic mechanism including induction of oxidative stress and subsequent activation of stress response gene expression.