Browsing by Author "Sharma, Rajan"

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    Antimycobacterial Activity, Synergism, and Mechanism of Action Evaluation of Novel Polycyclic Amines against Mycobacterium tuberculosis
    (Advances in Pharmacological and Pharmaceutical Sciences, 2021-06) Kapp, Erika; Joubert, Jacques; Sampson, Samantha, L; Malan, Sarel, F; Sharma, Rajan; Warner, Digby, F; Seldon, Ronnett; Jordaan, Audrey; de Vos, Margaretha
    Mycobacterium tuberculosis has developed extensive resistance to numerous antimycobacterial agents used in the treatment of tuberculosis. Insufficient intracellular accumulation of active moieties allows for selective survival of mycobacteria with drug resistance mutations and accordingly promotes the development of microbial drug resistance. Discovery of compounds with new mechanisms of action and physicochemical properties that promote intracellular accumulation, or compounds that act synergistically with other antimycobacterial drugs, has the potential to reduce and prevent further drug resistance. To this end, antimycobacterial activity, mechanism of action, and synergism in combination therapy were investigated for a series of polycyclic amine derivatives. Compound selection was based on the presence of moieties with possible antimycobacterial activity, the inclusion of bulky lipophilic carriers to promote intracellular accumulation, and previously demonstrated bioactivity that potentially support inhibition of efflux pump activity. The most potent antimycobacterial demonstrated a minimum inhibitory concentration (MIC99) of 9.6 μM against Mycobacterium tuberculosis H37Rv. Genotoxicity and inhibition of the cytochrome bc1 respiratory complex were excluded as mechanisms of action for all compounds. Inhibition of cell wall synthesis was identified as a likely mechanism of action for the two most active compounds (14 and 15). Compounds 5 and 6 demonstrated synergistic activity with the known Rv1258c efflux pump substrate, spectinomycin, pointing to possible efflux pump inhibition. For this series, the nature of the side chain, rather than the type of polycyclic carrier, seems to play a determining role in the antimycobacterial activity and cytotoxicity of the compounds. Contrariwise, the nature of the polycyclic carrier, particularly the azapentacycloundecane cage, appears to promote synergistic activity. Results point to the possibility of combining an azapentacycloundecane carrier with a side chain that promotes antimycobacterial activity to develop dual acting molecules for the treatment of Mycobacterium tuberculosis.
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    Association between promoter methylation of MLH1 and MSH2 and reactive oxygen species in oligozoospermic men—A pilot study
    (Wiley, 2017) Gunes, S.; Agarwal, A.; Henkel, Ralf; Sharma, Rajan; Esteves, S.C.; Aljowair, A.; Emirzeoglu, D.; Alkhani, A.; Pelegrini, L.; Joumah, A.; Sabanegh, E.; Mahmutoglu, A.M.
    MLH1 and MSH2 are important genes for DNA mismatch repair and crossing over during meiosis and are implicated in male infertility. Therefore, the methylation patterns of the DNA mismatch repair genes MLH1 and MSH2 in oligozoospermic males were investigated. Ten oligozoospermic patients and 29 normozoospermic donors were analysed. Methylation profiles of the MLH1 and MSH2 promotors were analysed. In addition, sperm motility and seminal reactive oxygen species (ROS) were recorded. Receiver operating characteristic (ROC) analysis was conducted to determine the accuracy of the DNA methylation status of MLH1 and MSH2 to distinguish between oligozoospermic and normozoospermic men. In oligozoospermic men, MLH1 was significantly (p = .0013) more methylated compared to normozoospermic men. Additionally, there was a significant positive association (r = .384; p = .0159) between seminal ROS levels and MLH1 methylation. Contrary, no association between MSH2 methylation and oligozoospermia was found. ROC curve analysis for methylation status of MLH1 was significant (p = .0275) with an area under the curve of 61.1%, a sensitivity of 22.2% and a specificity of 100.0%. This pilot study indicates oligozoospermic patients have more methylation of MLH1 than normozoospermic patients. Whether hypermethylation of the MLH1 promoter plays a role in repairing relevant mismatches of sperm DNA strands in idiopathic oligozoospermia warrants further investigation.
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    Calibration of redox potential in sperm wash media and evaluation of oxidation–reduction potential values in various assisted reproductive technology culture media using MiOXSYS system
    (Wiley, 2018) Panner Selvam, M. K.; Henkel, Ralf; Sharma, Rajan; Agarwal, A.
    Oxidation–reduction potential describes the balance between the oxidants and antioxidants in fluids including semen. Various artificial culture media are used in andrology and IVF laboratories for sperm preparation and to support the development of fertilized oocytes under in vitro conditions. The composition and conditions of these media are vital for optimal functioning of the gametes. Currently, there are no data on the status of redox potential of sperm processing and assisted reproduction media. The purpose of this study was to compare the oxidation–reduction potential values of the different media and to calibrate the oxidation–reduction potential values of the sperm wash medium using oxidative stress inducer cumene hydroperoxide and antioxidant ascorbic acid. Redox potential was measured in 10 different media ranging from sperm wash media, freezing media and assisted reproductive technology one-step medium to sequential media. Oxidation–reduction potential values of the sequential culture medium and one-step culture medium were lower and significantly different (p < 0.05) from the sperm wash media. Calibration of the sperm wash media using the oxidant cumene hydroperoxide and antioxidant ascorbic acid demonstrated that oxidation–reduction potential and the concentration of oxidant or antioxidant are logarithmically dependent. This study highlights the importance of calibrating the oxidation–reduction potential levels of the sperm wash media in order to utilize it as a reference value to identify the physiological range of oxidation oxidation–reduction potential that does not have any adverse effect on normal physiological sperm function.
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    Chemical composition and cosmeceutical potential of the essential oil of oncosiphon suffruticosum (L.) Källersjö
    (MDPI, 2021) Adewinogo, Selena O.; Sharma, Rajan; Africa, Charlene W. J.
    The South African medicinal plant Oncosiphon suffruticosum (L.) Källersjö is an important remedy used to treat chronic, respiratory, and skin ailments. From the essential oil (EO) extracted by the hydrodistillation, sixteen constituent components were identified with oxygenated monoterpenes: camphor (31.21%), filifolone (13.98%), chrysanthenone (8.72%), 1,8-cineole (7.85%), and terpinen-4-ol (7.39%) as predominant constituents. In the antibacterial activity study, the EO was found most susceptible against Pseudomonas aeruginosa with an MIC of 6.4 mg/mL; however, it showed the same activity against Staphylococcus aureus and Escherichia coli with an MIC value of 12.8 mg/mL. The sun protecting factor (SPF) of the EO was found to be 2.299 and thus establishing it as a potentially important cosmeceutical for sunscreen applications. This is the first report investigating the essential oil of O. suffruticosum for its chemical composition and skin-related in vitro biological activities viz antibacterial, antioxidant capacity, antityrosinase, and sun protection factor.
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    Determination of seminal oxidation–reduction potential (ORP) as an easy and cost-effective clinical marker of male infertility
    (Wiley, 2017) Agarwal, A.; Henkel, Ralf; Sharma, Rajan; Tadros, N.N.; Sabanegh, E.
    Oxidative stress (OS) is an important contributing factor to male infertility. While previous methods to measure seminal OS are time-consuming and limited to the use of freshly produced semen, oxidation reduction potential (ORP) is easier and quicker to perform and can also be used in frozen semen. Therefore, this study evaluated the clinical utility of ORP as a potential marker of male infertility. ORP was measured in semen samples from 293 patients and 15 fertile controls and categorised according to WHO criteria as normozoospermic, oligozoospermic, asthenozoospermic, teratozoospermic and oligoasthenoteratozoospermic. Receiver operating characteristic (ROC) curves were generated to differentiate these categories. Semen parameters were significantly different when subjects were grouped as control and patients or between the patient and normozoospermic group for concentration and morphology. ORP levels were significantly different between the control and normozoospermic group. When subjects were grouped based on concentration, motility, morphology or a combination of these, the area under the ROC curve, sensitivity, specificity, positive predictive value and cut-off values were significantly different. These differences were significant when combined with ORP and grouped with any two sperm abnormalities. In conclusion, ORP is a quick, easy, cost-effective and reliable marker of semen quality as well as oxidative stress for use in a clinical setting.
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    Human sperm handling in intracytoplasmic sperm injection processes: In vitro studies on mouse oocyte activation, embryo development competence and sperm oxidation–reduction potential
    (Wiley, 2018) Roychoudhury, S.; Maldonado-Rosas, I.; Agarwal, A.; Esteves, S.C.; Henkel, Ralf; Sharma, Rajan
    Polyvinylpyrrolidone (PVP) and hyaluronic acid (HA) are routinely used in handling spermatozoa for intracytoplasmic sperm injection (ICSI). As there are still concerns about possible adverse effects on the embryo, this study investigated sperm handling in a mouse ICSI model to (i) evaluate oocyte activation after injection of spermatozoa selected for rotational or linear motion in PVP; (ii) assess the effect of sperm selection in PVP, HA and medium on oocyte activation; (iii) examine the effects of PVP and HA on parthenogenetic oocyte activation and embryo development; and (iv) assess the oxidation–reduction potential (ORP) of spermatozoa exposed to PVP, HA or medium. Oocyte activation was higher when spermatozoa exhibited rotational motion rather than linear motion (79% vs. 52%; p = .05). There was no difference in oocyte activation and embryo development after parthenogenetic oocyte activation after sperm injection using PVP, HA or medium-incubated spermatozoa. PVP-selected spermatozoa exhibited lower (p < .0001) ORP levels than using HA. Thus, results indicate that the sperm handling method and the type of medium used impact ICSI outcomes. Overall, sperm incubation in PVP, HA and medium yields similar outcomes with regard to oocyte activation and embryo development. However, PVP provides more antioxidative protection than HA and should therefore be preferred for sperm manipulation.
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    In vitro alpha-glucosidase and alpha-amylase inhibitory activities and antioxidant capacity of helichrysum cymosum and helichrysum pandurifolium schrank constituents
    (MDPI, 2022) Jadalla, Baraa M. I. S.; Moser, Justin J.; Sharma, Rajan
    Diabetes mellitus (DM) is a group of systemic metabolic disorders with a high rate of morbidity and mortality worldwide. Due to the detrimental side effects of the current treatment, there is a great need to develop more effective antidiabetic drugs with fewer side effects. Natural products are a well-known source for the discovery of new scaffolds for drug discovery, including new antidiabetic drugs. The genus Helichrysum has been shown to produce antidiabetic natural products.
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    Microwave-assisted methods for the synthesis of pentacyclo[5.4.0.02,6.03,10.05,9]undecylamines
    (Elsevier, 2013) Joubert, Jacques; Sharma, Rajan; Onani, Martin O.; Malan, Sarel F.
    Efficient methodologies for the preparation of pentacyclo[5..4.0.02,6.03,10.05,9]undecane (PCU) amine derivatives are described via microwave-assisted synthesis. The obtained results revealed that microwave-assisted synthetic procedures under controlled conditions (power, temperature and time) are very convenient, high yielding, efficient and low-cost methods for the preparation of PCU amine derivatives. The new methods show several advantages including operational simplicity, good performance, significant reduction in reaction time, less by-product formation and easier purification.
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    Synthesis & biological evaluation of neuroprotective molecules with polycyclic scaffolds
    (University of the Western Cape, 2017) Sharma, Rajan; Malan, Sarel F.; Joubert, Jacques
    Among neurological disorders, many of the most devastating disorders are neurodegenerative. Modern research associates excitotoxicity to a variety of neuropathological conditions, suggesting that the neurodegenerative diseases with distinct etiologies may have excitotoxicity as a common pathway. Excitotoxicity occurs through over-stimulation of receptors for excitatory neurotransmitters like the N-methyl-D-aspartate (NMDA) receptors. Due to the relevance of NMDA receptors and excitotoxic processes, the antagonism or modulation of NMDA receptors is used as a therapeutic tool against neurodegenerative diseases. NMDA receptor activity can be modulated by S-nitrosylation and this modulation of NMDA receptor activity can be utilised in the development of neuroprotective drugs.
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    Synthesis and biological evaluations of NO-donating oxa- and aza-pentacycloundecane derivatives as potential neuroprotective candidates
    (MDPI, 2018) Sharma, Rajan; Joubert, Jacques; Malan, Sarel F.
    In order to utilize the neuroprotective properties of polycyclic cage compounds, and explore the NO-donating ability of nitrophenyl groups, an array of compounds was synthesized where the different nitrophenyl groups were appended on oxa and aza-bridged cage derivatives. Biological evaluations of the compounds were done for cytotoxicity, neuroprotective abilities, the inhibition of N-methyl-D-aspartate (NMDA)-mediated Ca2+ influx, the inhibition of voltage-mediated Ca2+ influx, and S-nitrosylation abilities. All of the compounds showed low toxicity. With a few exceptions, most of the compounds displayed good neuroprotection and showed inhibitory activity for NMDA-mediated and voltage-gated calcium influx, ranging from high (>70%) to low (20–39%) inhibition. In the S-nitrosylation assay, the compounds with the nitro moiety as the NO-donating group exhibited low to good nitrosylation potency compared to the positive controls. From the biological evaluation of the tested compounds, it was not possible to obtain a simple correlation that could explain the results across all of the biological study domains. This can be ascribed to the independent processes evaluated in the different assays, which reiterate that neuroprotection is a result of multifactorial biochemical mechanisms and interactions. However, these results signify the important aspects of the pentacylcoundecylamine neuroprotectants across different biological study realms.