Embelin (2,5-Dihydroxy-3-undecyl-p-benzoquinone) for photodynamic therapy: study of their cytotoxicity in cancer cells.

Photodynamic therapy (PDT) involves the use of photochemical reactions mediated through the interaction of photosensitizing agent for the treatment of malignant tumor. The present study was carried out to evaluate the photosensitizing potential of embelin isolated from Embelia ribes. For PDT study, cells were grouped into four groups. Two types of control were used, one with Ehrlich's ascites carcinoma (EAC) cells alone (group 1) and one which received the illumination alone (group 2). Group 3 contains cells treated with different concentrations of embelin for 1 h at 37 °C. Another set of cells (group 4) after treatment with different concentrations of embelin was illuminated in ice for 4 min with a 1000-W halogen lamp. To study the mechanism of cell death, the following parameters such as reactive oxygen species (ROS), caspase-3, lactate dehydrogenase (LDH), and thiobarbituric acid reactive substances (TBARS) were analyzed both in the absence and presence of light after the treatment of embelin. PDT study clearly indicated that embelin alone recorded no cytotoxicity, but for light treatment alone with the different concentrations of embelin, there was a significant induction of cytotoxicity in a concentration-dependent manner. Level of ROS and LDH increased in cells treated with embelin. Moreover, caspase-3 also increased which clearly indicated that cell death is through caspase-dependent apoptosis. This is the first report on PDT, a novel modality, using embelin for cancer therapy in vitro. The novelty of the study depends on the fact that cytotoxicity was produced by the synergistic effect of the embelin and light.

Embelin (2,5-dihydroxy-3-undecyl-p-benzoquinone): a bioactive molecule isolated from Embelia ribes as an effective photodynamic therapeutic candidate against tumor in vivo.

The present study was carried out to assess the photosensitizing potential of embelin, the biologically active natural product isolated from Embelia ribes in photodynamic therapy (PDT) experiments in vivo. In vitro PDT clearly indicated that embelin recorded significant cytotoxicity in Ehrlich's Ascites Carcinoma (EAC) cells, which is superior to 5-aminolevulinic acid, a known photodynamic compound. For in vivo experiments solid tumor was induced using EAC cells in the male Swiss albino mice of groups I, II, III and IV. Group I served as the control (without solid tumor), group II served as tumor bearing mice without treatment and groups III and IV served as treatments. At the completion of 4 weeks of induction, the tumor bearing mice from group III and IV were given an intraperitoneal injection with embelin (12.5mg/kg body weight). After 24h, tumor area in the Group III and IV animals was exposed to visible light from a 1,000 W halogen lamp. The mice from groups I to III were sacrificed 2 weeks after the PDT treatment and the marker enzymes (myeloperoxidase [MPO], ß-d-glucuronidase, and rhodanese) were assayed and expression of Bcl-2 and Bax were analyzed in normal and tumor tissues. Animals from group IV were sacrificed after 90 days of PDT treatment and the above mentioned parameters were recorded. Reduction in tumor volume and reversal of biochemical markers to near normal levels were observed in the treated groups. This is the first report on PDT using a natural compound for solid tumor control in vivo. The uniqueness of the mode of treatment lies in the selective uptake of the nontoxic natural compound, embelin from the medicinal plant E. ribes used in Indian system of medicine, by the solid tumor cells and their selective destruction using PDT without affecting the neighboring normal cells, which is much advantageous over radiation therapy now frequently used.