Dobrina Tsvetkova’s research while affiliated with Medical University of Sofia and other places

Cannabis sativa L. is a medicinal plant from family Cannabaceae with many pharmacological activities. The recent appearance of a number of cannabis products in the pharmaceutical market has led to increased requirements for regulation and quality control. The control of Cannabis sativa L. is subject to the Psychotropic Substances Convention, which includes the addictive psychoactive delta-9-tetrahydrocannabinol (THC), and to the Narcotic Drugs Convention, which includes the illicit products: herbal and liquid cannabis, resin, extracts and tinctures of flowering or fruiting tops containing THC. Approved by the FDA for use in chemotherapy are Marinol caps. (THC) and Cesamet caps., containing the synthetic THC-derivative Nabilon. There is no harmonized European Union legislation on the use of cannabis and Cannabidiol (CBD), which antagonizes the THC-psychotropic effect. Legitimate products include seeds, oil, extracts, and seed tinctures of the industrial cannabis chemotype, containing primarily Cannabidiol and less than 0.2% THC. Sativex oral spray (THC/CBD = 1:1) is approved for muscle spasticity in multiple sclerosis. Cannabidiol was not used as a food ingredient in the European Union before 15.05.1997 and is a „novel food” according to Regulation 2015/2283. Flour; protein powder and cannabis seed oil are not „novel foods”. Cannabidiol as Epidiolex is FDA approved for epilepsy forms Lennox-Gastaut and Dravet.

In the current study, we investigated the effect of creatine monohydrate (CrM) and newly synthesized creatine lysinate (CrLys) in tail suspension (TST) and rotarod tests and their influence on the histology of the skeletal muscles. In the TST, a slight decrease in the immobility time from the 1 st to the 3 rd week was observed in the group treated with CrM at a dose of 1.5 g/kg/day and CrLys at a dose of 6 g/kg/day. The rotarod test revealed that CrM (1.5 g/kg/day) and CrLys (3 g/kg/day) lead to a significant improvement in motor coordination in the 3 rd week. The results from histology showed an increase in the muscle fiber diameter of soleus muscle in animals treated with CrM (3 g/kg/day) and CrLys (6 g/kg/day). The results showed that supplementation with creatine derivatives appears to be a generally effective nutritional ergogenic aid for an improvement of physical performance.

In our study we investigated the acute toxicity of а newly synthesized creatine lysinate as well as its effect on the biochemical parameters in mice. Creatine lysinate exerts better solubility in water (3.3%) in comparison to creatine monohydrate (1.4%) at 20 °C and it is determined as a non-toxic after intraperitoneal (LD50 – 4543 mg/kg) and oral administration (LD50 > 8000 mg/kg). Oral administration of creatine lysinate at doses of 3 g/kg/day and 6 g/kg/day for 2 weeks reduced the creatine kinase levels, which indicates muscle protection. An increased levels of liver enzymes like alanine aminotransferase (ALAT) and aspartate aminotransferase (ASAT) was observed after the supplementation with creatine lysinate at both administered doses and the level of lactate was comparable both in the studied and the control group.

Background: Cisplatin, a platinum complex discovered by Rosenberg in 1969, has long been known as the first metal-based anticancer agent. Since then, various similar derivatives of cisplatin have been investigated for pharmacological activity, and the approved complexes have been applied as drugs. Objectives: The aims of the current study are: 1) to summarize the advantages and dose-limiting effects of the approved and unapproved chemotherapy platinum cytostatics, 2) to develop new strategies for the development of platinum anticancer drugs, and 3) to clarify the important factors for the mechanism of action of platinum complexes. Methods: A search was conducted in the literature databases, and the obtained information was summarized and analyzed. Results: Myelosuppression is the main dose-limiting effect and the reason for the disapproval of platinum complexes, such as picoplatin, enloplatin, miboplatin, sebriplatin, zeniplatin, spiroplatin, iproplatin, and ormaplatin. From the basic point of view of inorganic coordination chemistry, such as theoretical calculations, crystal structures of model complexes, docking structures with nucleic acid molecules, spectroscopy, and biological aspects, the importance of physicochemical properties of inorganic platinum complexes for their mechanism of action has been indicated. Spectroscopic methods, such as FTIR, NMR, X-ray crystal structure analysis, and fluorescence microscopy, are important for the investigation of the conformational changes in the binding of platinum complexes and DNA. Conclusion: In the development of platinum complexes, strong anti-cancer drug activity, low toxicity, and resistance can be obtained by the application of polynuclear platinum agents, complexes with targeted activity, and nanoparticle formulations. Electronic structure, stereochemical, and thermodynamic properties are essential for understanding the reaction mechanism of platinum complexes.

The problems with anticancer therapy are resistance and toxicity. From 3000 Cisplatin derivatives tested as antitumor agents, most of them have been rejected, due to toxicity. The aim of current study is the comparison of therapeutic combinations of the currently applied in clinical practice: Cisplatin, Carboplatin, Oxaliplatin, Nedaplatin, Lobaplatin, Heptaplatin, and Satraplatin. The literature data show that the strategies for the development of platinum anticancer agents and bypassing of resistance to Cisplatin derivatives and their toxicity are: combination therapy, Pt IV prodrugs, the targeted nanocarriers. The very important strategy for the improvement of the antitumor effect against different cancers is synergistic combination of Cisplatin derivatives with: (1) anticancer agents—Fluorouracil, Gemcitabine, Cytarabine, Fludarabine, Pemetrexed, Ifosfamide, Irinotecan, Topotecan, Etoposide, Amrubicin, Doxorubicin, Epirubicin, Vinorelbine, Docetaxel, Paclitaxel, Nab-Paclitaxel; (2) modulators of resistant mechanisms; (3) signaling protein inhibitors—Erlotinib; Bortezomib; Everolimus; (4) and immunotherapeutic drugs—Atezolizumab, Avelumab, Bevacizumab, Cemiplimab, Cetuximab, Durvalumab, Erlotinib, Imatinib, Necitumumab, Nimotuzumab, Nivolumab, Onartuzumab, Panitumumab, Pembrolizumab, Rilotumumab, Trastuzumab, Tremelimumab, and Sintilimab. An important approach for overcoming the drug resistance and reduction of toxicity of Cisplatin derivatives is the application of nanocarriers (polymers and liposomes), which provide improved targeted delivery, increased intracellular penetration, selective accumulation in tumor tissue, and enhanced therapeutic efficacy. The advantages of combination therapy are maximum removal of tumor cells in different phases; prevention of resistance; inhibition of the adaptation of tumor cells and their mutations; and reduction of toxicity.