Structure-activity relationships of novel anti-diabetic ruthenium compounds : synthesis, characterization, mechanistic and in vitro studies = Uhlaka lokwenzeka kobudlelwane obusha bengxube iruthenium yokumelana nesifo sikashukela : izifundo zokwenza, ukulinganisa, ubuchwepheshe nocwaningo olwenziwa elebhu i-in vitro.

Abstract

Type 2 Diabetes Mellitus (T2DM) is a chronic metabolic disorder which is globally responsible for millions of fatalities per year. Management of T2DM typically involves orally administered anti-hyperglycaemic drugs in conjunction with dietary interventions. However, the current conventional therapy seems to be largely ineffective as patients continue to develop complications such as cardiovascular diseases, blindness and kidney failure. Existing alternative treatment entails the administration of organic therapeutic pharmaceuticals, but these drugs have various side effects such as nausea, headaches, weight gain, and respiratory and liver damage. Transition metal complexes have shown promise as anti-diabetic agents owing to their diverse mechanisms of activity. In particular, selected ruthenium compounds have exhibited intriguing biological behaviours as Protein Tyrosine Phosphatase (PTP) 1B and Glycogen Synthase Kinase 3 (GSK-3) inhibitors, as well as aggregation suppressants for the human islet amyloid polypeptide (hIAPP). The introduction chapter served as a survey on studies pertaining to ruthenium compounds as metallo-drugs for T2DM. Herein, we also provide perspectives on directions to fully elucidate in vivo functions of this class of potential metallopharmaceuticals. More specifically, there is still a need to investigate the pharmacokinetics of ruthenium drugs in order to establish their biodistribution patterns which will affirm whether these metal complexes are substitutionally inert or serve as pro-drugs. In addition, embedding oral-administered ruthenium complexes into bio-compatible polymers can be a prospective means of enhancing stability during drug delivery. This chapter was concluded with a descriptive rationale of the research study as well as specifying the specific research aims and objectives. Our prior studies have illustrated that the uracil ruthenium(II) diimino complex, [Ru(H3ucp)Cl(PPh3)] (1) (H4ucp = 2,6-bis-((6-amino-1,3-dimethyluracilimino)methylene)pyridine) displayed high hypoglycaemic effects in diet-induced diabetic rats. To rationalize the anti-diabetic effects of 1 in the first experimental chapter, three new derivatives have been prepared, cis-[Ru(bpy)2(urdp)]Cl2 (2) (urdp = 2,6-bis-((uracilimino)methylene)pyridine), trans-[RuCl2(PPh3)(urdp)] (3), and cis-[Ru(bpy)2(H4ucp)](PF6)2 (4). Various physicochemical techniques were utilized to characterize the structures of the novel ruthenium compounds. Prior to biomolecular interactions or in vitro studies, the stabilities of 1 – 4 were monitored in anhydrous DMSO, aqueous phosphate buffer containing 2% DMSO, and dichloromethane (DCM) via UV-Vis spectrophotometry. Time-dependent stability studies showed ligand exchange between DMSO nucleophiles and chloride co-ligands of 1 and 3, which was suppressed in the presence of an excess amount of chloride ions. In addition, the metal complexes 1 and 3 are stable in both DCM and an aqueous phosphate buffer containing 2% DMSO. In the case of compounds 2 and 4 with no chloride co-ligands within their coordination spheres, high stability in aqueous phosphate buffer containing 2% DMSO was observed. Fluorescence emission titrations of the individual ruthenium compounds with bovine serum albumin (BSA) showed that the metal compounds interact non-discriminately within the protein's hydrophobic cavities as moderate to strong binders. The metal complexes were capable of disintegrating mature amylin amyloid fibrils. In vivo, glucose metabolism studies in the liver (Chang) cell lines confirmed enhanced glucose metabolism as evidenced by the increased glucose utilization and glycogen synthesis in liver cell lines in the presence of complexes 2 – 4. The second experimental chapter, reports on the formation and characterization of new diamagnetic ruthenium uracil mono-imine compounds: [(η6-p-cymene)RuII(L)Cl] (L = urpda = 5-((pyridin-2-yl)methyleneamino)-6-aminouracil) for 1, urdpy = 6-amino-1,3-dimethyl-5-((pyridin-2-ylmethylene)amino)uracil) for 2 or urqd = 5-((quinolin-2-yl)methyleneamino)-6-aminouracil) for 3); cis-[RuII(L)(bipy)2] (L = urpy = 5-((pyridin-2-yl)methyleneamino)uracil) for 4 and H2dadp = 5,6-diaminouracil for 5); trans-[RuII(L)(PPh3)Cl2] (L = urpda for 6) are described. Various physicochemical techniques were utilized to characterize the structures of the novel ruthenium compounds. Furthermore, the DPPH and NO radical scavenging capabilities of metal complexes (2 – 10) were investigated. UV-Vis spectrophotometry data of the time-dependent (for 24 h) studies show that 4 and 5 are stable in aqueous phosphate buffer containing 2% DMSO. Similarly, the stabilities of 1 - 3 and 6 monitored in chloro-containing and non-coordinating solvent dichloromethane show that they are kinetically inert, whereas, in a high nucleophilic environment, the chloride co-ligands of 1 - 3 and 6 were rapidly substituted by DMSO. In contrast, the substitution of the labile ligand of the complexes by DMSO molecules from its solution with a high chloride content was suppressed. Solution chemical reactivities of the different metal complexes were rationalized by density functional theory computations. Furthermore, the binding affinities and strengths between BSA and the respective metal complexes were monitored using fluorescence spectroscopy. Mutually, these metal complexes showed comparable capabilities of denaturing mature BSA aggregates which was established by fluorescence spectroscopy and Transmission Electron Microscopy (TEM). The final experimental chapter entails the encapsulation of the ruthenium complexes 1 - 10 into separate organic chitosan (CS)-polyvinyl alcohol (PVA) blends and the subsequent nanofabrication of their electrospun nanofiber (ENF) conjugates, Ru-CS-PVA ENFs. Intravenous injections of insulin can be regarded as a primitive method for Diabetes Mellitus management which characteristically leads to patients developing insulin resistance while oral-administered anti-diabetic organodrugs such as Metformin have exhibited low bio-availability and typically induce gastrointestinal (GI) side-effects. Although the intravenous injections of selected metal compounds in Streptozocin (STZ)-diabetic results have delivered promising results, limited work has been done to evaluate their efficiencies during oral administration. Herein, the fabricated chitosan (CS)-polyvinyl alcohol (PVA) electrospun nanofibers (CS-PVA ENFs) of the leading insulin-enhancing ruthenium complex 1, cis-[Ru(bipy)2(H4ucp)](PF6)2 and its analogs: 2 – 10. The Ru-CS-PVA ENFs nanocomposites were characterized by using (SEM-EDX), powder X-ray diffraction, and FTIR spectroscopy. The Ru-CS-PVA ENF nanohybrids exhibited randomly oriented fiber mat morphology with mean diameters in the range of 118 - 280 nm. Metal-based drug release kinetics of 1 - 10 from the ENF polymer matrix were measured spectrophotometrically at pH 1.5 and 7.4, respectively. Electronic spectral trends and data analysis over a 24-hour data collection period reveals variable dissolution rates with first-order rate (kobs) constants ranging from 0.0146 to 2.74 μM h-1 with accompanying hyperchromism effects between 5.69 to 37.6% at a pH of 1.5 while at a pH of 7.4, kobs value limits were 0.0104 and 3.89 μM h-1 rendering corresponding 19.14 and 87.32% hypochromic shifts. The release kinetics data of 1 - 10 were spontaneously released into the aqueous media from the Ru-CS-PVA ENFs, with the highest and releasing rates recorded for complexes 8 and 4, respectively.

Iqoqa.

Uhlobo lweType 2 Diabetes Mellitus (T2DM) luyisifo sokuphazamiseka komzimba okuyisimbelambela ichronic metabolic disorder okutholakala emhlabeni jikelele okwenza izinkulungwane zigulele ukufa njalo ngonyaka. Ukwenganyelwa kweT2DM kuvame ukuthi kusebenze ngemishanguzo ephuzwayo eyihlisa izinga likashukela egazini i-anti-hyperglycaemic drugs kuhambisana nemizamo yokukhetha okudlayo idayethi .Yize-kunjalo , le mizamo ekhona yokwelapha okuvamile ibukeka ingenamthelela ogculisayo ngoba iziguli ziyaqhubeka zibe nezifo ezifana nesifo senhliziyo nesemithambo yegazi, ukungaboni nokukhathala kwezinso. Eminye yemizamo ihambisana nokukhishwa kwemishanguzo yokwelapha ngamakhambi emvelo i-organic therapeutic pharmaceuticals, kodwa le mithi inemiphumela eminingi engemihle, efana nesicanucanu senhliziyo , yikhanda elibuhlungu , ukukhuluphala , ukujuluka kanye nokulimala kwesibindi . Izakhiwo zetransition metal complexes zenyuse amathemba ukuba yizinhlobo zemithi yokwelapha isifo sikashukela ama-anti-diabetic agents wing kulokho okwenzeka ezinhlotsheni zezinto ezahlukene. Ikakhulu, ingxube enezingxenye zeruthenium iveze ukuziphatha okwaziwa nge-intriguing biological behaviours as Protein Tyrosine Phosphatase (PTP) 1B & Glycogen Synthase Kinase 3 (GSK-3) inhibitors, kanye ne aggregation suppressants for the human islet amyloid polypeptide (hIAPP). Isahluko sesethulo sisebenze njengohlolophenyo locwaningo mayelana nengxube yeruthenium njenge metallo-drugs yeT2DM. Lapho-kuphinde, kwabukwa imbonisamhlaba emhlahlandleleni ocacisa ngokusebenza ngokugcwele kwi-in vivo ezingeni lomthelela wemetallopharmaceuticals. Empeleni , sikhona isidingo sokucwaninga ukusebenzisana komzimba nemithi iruthenium ukuze kuzotholakala imikhuba yohlelo lokwedluliselwa emzimbeni kwamakhemikhali okuqinisekisa izakhiwo zemetal ukuthi zingakwazi ukumela ikhemikhali engasebenzi substitutionally inert noma osebenza njengomuthi owesekelayo ipro-drugs. Ngaphezu-kwalokho , ukufaka izakhiwo zeruthenium ephuzwayo efanele amapolymers aphilayo angasiza ukuthuthukisa uzinzo ekulethweni kwemishanguzo. Lesi sahluko siphethe ngokuchaza ubumqoka bocwaningo , izinhloso nezinjongo . Ucwaningo lwethu lwangaphambilini lweseke ukusebenza kwe uracil ruthenium(II) diimino complex, [Ru(H3ucp)Cl(PPh3)] (1) (H4ucp = 2,6-bis-((6-amino-1,3- dimethyluracilimino)methylene)pyridine) yaveza ukusebenza kwesimo sezinga elipansi kakhulu likashukela osegazini namandla asekudleni okunamafutha kwamagundane anesifo sikashukela. Ukulinganisela ukusebenza kwemiphumela ephikisana nesifo sikashukela okungokoku 1 kwesahluko sokuqala esiyilinge, okusukela kwenye ingxube elungiselelwe, cis- [Ru(bpy)2(urdp)]Cl2 (2) (urdp = 2,6-bis-((uracilimino)methylene)pyridine), trans- [RuCl2(PPh3)(urdp)] (3), and cis-[Ru(bpy)2(H4ucp)](PF6)2 (4). Amaqhingasu ahlukene aphathelene nomzimba namakhemikhali kwasetshenziswa ukwenza ingxube entsha yeruthenium. Ngaphambi kokulumbana kwamamolekhyuli aphilayo nezifundo ezenziwa elebhu ukuhlola uzinzo olusukela ku 1 – 4 lwahlolwa kwi-anhydrous DMSO, aqueous phosphate buffer containing 2% DMSO ozinzweni ngokwesikhathi kanye nedichloromethane (DCM) via UV-Vis spectrophotometry. Ucwaningo oluncike ozinzweni ngokwesikhathi luveze ukushitshana kweligandi phakathi kwe-DMSO nucleophiles ne chloride co-ligands of 1 and 3, eyacindezelwa kwipresence of an excess amount of chloride ions.

Ukwengeza , imetal complexes 1 & 3 izinzile kuzona zombili kwiDCM & an aqueous phosphate buffer containing 2% DMSO. Kulokhu , izingxube eyesi- 2 neyesi-4 with no chloride co-ligands ngaphakathi kwecoordination spheres, izinga eliphezulu lestability in aqueous phosphate buffer containing 2% DMSO uma ibukwa . IFluorescence emission titrations of the individual ruthenium compounds with bovine serum albumin (BSA) iveze ukuthi imetal compounds interact non-discriminately within the protein's hydrophobic cavities kusukela kwimoderate ukuya kwistrong binders. Amametal complexes enze lokhu okuyi disintegrating mature amylin amyloid fibrils. KwiIn vivo, izifundo zeglucose metabolism studies in the liver (Chang) cell lines iqinisekise i glucose metabolism as evidenced by the increased glucose utilization & glycogen synthesis in liver cell lines in the presence of complexes 2–4. Isahluko sesibili , imibiko ye formation & characterization of new diamagnetic ruthenium uracil mono-imine compounds: [(η6-p-cymene)RuII(L)Cl] (L = urpda = 5-((pyridin-2-yl)methyleneamino)-6-aminouracil) for 1, urdpy = 6- amino-1,3-dimethyl-5-((pyridin-2-ylmethylene)amino)uracil) for 2 or urqd = 5- ((quinolin-2-yl)methyleneamino)-6-aminouracil) for 3); cis-[RuII(L)(bipy)2] (L = urpy = 5-((pyridin-2-yl)methyleneamino)uracil) for 4 and H2dadp = 5,6-diaminouracil for 5); trans-[RuII(L)(PPh3)Cl2] (L = urpda for 6) are described. Various physicochemical techniques isetshenziselwe ukuhlunga izigaba zenovel ruthenium compounds. Ngaphezu-kwalokho , DPPH & NO radical scavenging capabilities of metal complexes (2 – 10) ahloliwe . Izifundo zeUV-Vis spectrophotometry data of the time-dependent (for 24 h) ziveze ukuthi that 4 and 5 azinzile kwi aqueous phosphate buffer containing 2% DMSO. Ngokufanayo , ama stabilities of 1 - 3 and 6 monitored kwi chloro-containing & non- coordinating solvent dichloromethane aveze ukuthi awuhlobo lwe kinetically inert, ekubeni, kumazinga aphezulu kwi nucleophilic environment, the chloride co-ligands of 1 - 3 and 6 were rapidly substituted by DMSO. Ngokuphambene , esikhundleni se labile ligand of the complexes by DMSO molecules from its solution with a high chloride content icindezelwe. Isixazululo se Solution chemical reactivities kuma metal complexes ahlukene alinganisiwe ngedensity functional theory computations. Ngaphezu kwalokho , ibinding affinities kanye namandla phakathi kwe BSA kanye ne respective metal complexes aqokwe ahlolwa kusetshenziswa ifluorescence spectroscopy. Ngokufanayo, lama metal complexes eveze ukuhambisana kwama capabilities edenaturing mature BSA aggregates asungulwe yifluorescence spectroscopy & Transmission Electron Microscopy (TEM). Isahluko sokugcina siqukethe iencapsulation of the ruthenium complexes 1 - 10 into separate organic chitosan (CS)-polyvinyl alcohol (PVA) blends & the subsequent nanofabrication of their electrospun nanofiber (ENF) conjugates, Ru-CS- PVA ENFs. I-Intravenous injections of insulin ingabukwa njengendlela endala yokwenza izinto kwi Diabetes Mellitus management evame ukuthi iziguli babe ne-insulin resistance ekubeni imishanguzo ephuzwa ngomlomo ye-anti-diabetic organodrugs afana ne Metformin aveze izinga eliphansi lebio-availability & typically induce gastrointestinal (GI) side-effects. Yize-ke noma intravenous injections ekhethekile emetal compounds in Streptozocin (STZ)-diabetic results elethe imiphumela ethembisayo ,umsebenzi okalelekile owenziwe ukuhlola ukusebenza kwayo ngesikhathi isetshenziswa ngomlomo . Lapha-kukhona , i fabricated chitosan (CS)-polyvinyl alcohol (PVA) electrospun nanofibers (CS-PVA ENFs) of the leading insulin-enhancing ruthenium complex 1, cis- [Ru(bipy)2(H4ucp)](PF6)2 and its analogs: 2 – 10. The Ru-CS-PVA ENFsnanocomposites aqokwe ngokusebenzisa i(SEM-EDX), powder X-ray diffraction, & FTIR spectroscopy. IRu-CS-PVA ENF nanohybrids iveze ukungahlelki kweoriented fiber mat morphology nezilinganiso ezincane zediameters in the range of 118 - 280 nm. Metal-based drug release kinetics of 1 - 10 from the ENF polymer matrix akalwe nge spectrophotometrically at pH 1.5 & 7.4, ngokufanayo. AmaElectronic spectral trends and data analysis okungaphezu kwamahora angama- 24 kuqoqwa imininingo aveza amavariable dissolution rates with first-order rate (kobs) constants ranging from 0.0146 to 2.74 µM h-1 ehambisana nomthelela wehyperchromism ophakathi kwamaphesenti angama 5.69 to 37.6% at a pH of 1.5 while at a pH of 7.4, kobs value limits isilinganiso sama 0.0104 and 3.89 µM h-1 rendering corresponding 19.1 & 87.3% hypochromic shifts. Imininingo yerelease kinetics data of 1 - 10 ikhishwe ngokungahlelekile kwi-aqueous media from the Ru-CS-PVA ENFs, ngesikalo esiphezulu ne releasing rates eqophe amacomplexes 8 and 4, ngokufanayo.