: Polymer-drug conjugates are polymers with drug molecules chemically attached to polymer side chains through a weak covalent bond (degradable bond) or a dynamic covalent bond. These systems are known as prodrugs in the inactive form of the drug passing into the blood circulation system. When the prodrug reaches to the target organ, tissue or cell, the drug is activated by cleavage of the bond between the drug and polymer under certain conditions existing in the target organ. The advantages of polymer-drug conjugates compared to other controlledrelease carriers and conventional pharmaceutical formulations are the increased drug loading capacity, the prolonged in vivo circulation time, the enhanced intercellular uptake, the better controlled release, the improved therapeutic efficacy and the enhanced permeability and retention effect. The aim of the present review is the investigation of polymer-drug conjugates bearing anticancer drugs. The polymer through its side chains is linked to the anticancer drugs via dynamic covalent bonds such as hydrazone/imine bonds, disulfide bonds and boronate esters. These dynamic covalent bonds are cleaved in conditions existing only in cancer cells and not in healthy ones. Thus, ensures the selective release of the drug to the targeted tissue, reducing in this way the frequent side effects of chemotherapy, leading to a more targeted application, despite the nature of the applied polymer, possessing the ability to aim selectively tumors via incorporation of a relative ligand.
This study aimed to determine the chemical composition of different types of tissue of Cedrus brevifolia Henry (Pinaceae) methanolic extracts, namely needles, twigs, branches, and bark. Cedrus brevifolia is a narrow endemic coniferous tree species of Cyprus, growing in a sole population in the mountainous area of Paphos Forest. Chemical analysis of the extracts was performed using liquid chromatography combined with time-of-flight high-resolution mass spectrometry (LC/Q-TOF/HRMS). The majority of the 36 compounds tentatively identified belonged to the flavonoids family. The extract of needles was the richest extract in terms of secondary metabolites. The extracts were studied for their antioxidant activity using the DPPH free radical scavenging assay. Additionally, the antibacterial activity was evaluated by determining both the minimum inhibitory concentration and the minimum bactericidal concentration against Staphylococcus aureus and Escherichia coli. All extracts demonstrated antioxidant property, while bark gave the highest antioxidant capacity (IC50 value of 0.011 mg/mL) compared to the other tissues. Antibacterial activity was observed against both types of bacteria, with the extract of branches presenting the strongest activity against S. aureus (MIC, 0.097 mg/mL and MBC, 0.195 mg/mL). This is the first time that extracts of needles, twigs, branches, and bark of C. brevifolia are compared regarding their chemical composition as well as their antimicrobial and antioxidant properties.
Hypericum perforatum is an herb whose use dates back centuries. Extracts of the plant are available as over-the-counter treatment options for depression. The genus consists of approximately 500 species, most of which have not yet been studied. Antimicrobial resistance has reached alarming levels, indicating a post-antibiotic era as many of the available treatment options become less effective. For this reason, nine Hypericum species were studied for their antimicrobial activity and their total phenolic and flavonoid content. Extracts were tested against Gram-negative and Gram-positive bacteria. Extracts inhibited the growth of Gram-positive bacteria (Staphylococcus aureus and Enterococcus faecalis). The lowest MIC and MBC values were calculated for the extract of H. perforatum against both microorganisms tested, reaching 0.06 mg/mL for S. aureus and 0.13 mg/mL for E. faecalis. Total phenolic content was the highest in the H. perforatum extract (86 ± 12.90 mg GAE/g dry plant material). H. tetrapterum presented the highest flavonoid content, equal to 1.58 ± 0.4 mg RE/g of dry plant material. The Hypericum species studied herein are less common or have not yet been examined compared to H. perforatum; therefore, our study adds new data to the knowledge of the genus Hypericum.
The purpose of this study was to identify the chemical components in root extracts of Saponaria cypria, an endemic species of Cyprus. Subsequently, the synergistic bioactivity of its root extracts through different extraction procedures was also investigated for the first time. A total of nine saponins, along with six phenolic compounds, were identified and quantified using the UHPLC/Q-TOF-MS method. Additionally, S. cypria root extracts demonstrated antibacterial potential against Escherichia coli, Staphylococcus aureus, Enterococcus faecalis and Salmonella enteritidis. S. aureus presented the highest susceptibility among all bacteria tested. These findings provide the first phytochemical data regarding the saponin, phenolic content and antimicrobial activity of S. cypria extracts, indicating that the Cyprus saponaria species is a rich natural source for bioactive compounds with a potentially wider bioactivity spectrum.
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