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    Abiotic stress of ZnO-PEG, ZnO-PVP, CuO-PEG and CuO-PVP nanoparticles enhance growth, sweetener compounds and antioxidant activities in shoots of Stevia rebaudiana Bertoni
    (Institution of Engineering and Technology, 2017) Javed, Rabia; Zia, Muhammad; Yücesan, Buhara; Gürel, Ekrem
    Nanoparticles are known to play remarkable role as abiotic stress elicitors in plants. This study reports the comparative analysis of effects produced by capped [zinc oxide (ZnO)-polyethylene glycol (PEG), ZnO-polyvinyl pyrrolidone (PVP), copper oxide (CuO)-PEG, CuO-PVP] and uncapped (ZnO and CuO) nanoparticles on the medicinal plant, Stevia rebaudiana raised in vitro for the production of commercially important sweetener compounds. In context of shoot organogenesis, ZnO-PEG, ZnO-PVP, CuO-PEG, CuO-PVP were employed to the growth medium that resulted in increased growth parameters, and larger content of steviol glycosides as compared to the shoots raised in medium containing ZnO and CuO, revealed by high-performance liquid chromatography. In the meanwhile, non-enzymatic antioxidant activities including total phenolic content, total flavonoid content, total antioxidant capacity, total reducing power and 2,2-diphenyl-1-picryl hydrazyl-free radical scavenging activity were calculated and showed comparatively greater amounts in shoots grown in medium containing capped ZnO or CuO nanoparticles. Furthermore, the ZnO and its derivatives revealed to be more reactive at 1 mg/l of concentration. Whereas, the CuO and its derivatives produced greater response on Stevia at 10 mg/l concentration of nanoparticles. This study paves the way for more such studies encompassing capped and uncapped nanoparticles and their ultimate effect on in-vitro grown plant tissues for the production of active metabolites on industrial scale. © The Institution of Engineering and Technology 2017.
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    Effect of zinc oxide (ZnO) nanoparticles on physiology and steviol glycosides production in micropropagated shoots of Stevia rebaudiana Bertoni
    (Elsevier France-Editions Scientifiques Medicales Elsevier, 2017) Javed, Rabia; Usman, Muhammad; Yücesan, Buhara; Zia, Muhammad; Gürel, Ekrem
    This study aims to address the effects of different concentrations (0, 0.1, 1.0, 10, 100 or 1000 mg L-1) of engineered zinc oxide (ZnO) nanoparticles (34 nm in size) on growth parameters, steviol glycosides (rebaudioside A and stevioside) production and antioxidant activities in the tissue culture grown shoots of Stevia rebaudiana Bertoni. The highest percentage of shoot formation (89.6%) at 1 mg L-1 of ZnO nanoparticles concentration suggests a positive influence of ZnO nanoparticles on S. rebaudiana growth as compared to other treatments with or without ZnO nanoparticles. Additionally, HPLC results illustrate a significant enhancement of steviol glycosides (almost doubled as compared to the control) in micro propagated shoots grown under an oxidative stress of 1 mg L-1 of ZnO nanoparticles. This finding is further affirmed by an increased 2,2-diphenyl-1-picryl hydrazyl (DPPH) scavenging activity, total antioxidant capacity, total reducing power, total flavonoid content and total phenolic content, with an ascending oxidative pressure and generation of reactive oxygen species (ROS). However, the antioxidant activities, formation of secondary metabolites and the physiological parameters showed a sudden decline after crossing a threshold of 1 mg L-1 concentration of ZnO nanoparticles and falls to a minimum at 1000 mg L-1, elucidating maximum phytotoxic effect of ZnO nanoparticles at this concentration. This is the first study evaluating both the favorable and adverse effects of ZnO nanoparticles employed to a highly valuable medicinal plant, S. rebaudiana. (C) 2016 Elsevier Masson SAS. All rights reserved.
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    Elicitation of Secondary Metabolites in Callus Cultures of Stevia rebaudiana Bertoni Grown Under ZnO and CuO Nanoparticles Stress
    (Springer India, 2018) Javed, Rabia; Yücesan, Buhara; Zia, Muhammad; Gürel, Ekrem
    Accumulation of secondary metabolites in medicinal plants by giving abiotic/biotic stress is, nowadays, an active area of research. This study reports the inoculation of ZnO and CuO nanoparticles in Murashige and Skoog (MS) medium having plant growth regulators for the regeneration of callus from leaf explants of medicinal plant, Stevia rebaudiana. Presence of ZnO and CuO nanoparticles in different concentrations results in conferring different kinds of physiology in different regenerants. 1 and 10 mg/L have been declared the best ZnO and CuO nanoparticles concentrations regarding various physiological parameters. Steviol glycosides have not been detected in any callus treatment. Moreover, the phytochemical characteristics of S. rebaudiana under different ZnO and CuO nanoparticles concentrations have been exploited. The highest amount of total phenolic content (TPC), total flavonoid content (TFC), total antioxidant capacity (TAC) and 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging activity has been obtained at 100 mg/L of ZnO nanoparticles, whereas TPC, TAC, TRP and DPPH free radical scavenging activity have been achieved highest at 10 mg/L concentration of CuO nanoparticles. However, the highest TRP in the context of ZnO and the highest TFC regarding CuO have been achieved at 50 and 100 mg/L, respectively. This clearly indicates that CuO nanoparticles are more toxic to Stevia callus as compared to ZnO nanoparticles, and opens avenues for future studies utilizing ZnO or CuO nanoparticles for the enhancement of commercially important secondary metabolites in different medicinal plants. © 2017, Society for Sugar Research & Promotion.
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    Nanoelicitation: A Promising and Emerging Technology for Triggering the Sustainable In Vitro Production of Secondary Metabolites in Medicinal Plants
    (Springer Nature, 2022) Javed, Rabia; Yucesan, Buhara; Zia, Muhammad; Gurel, Ekrem
    To obtain larger amounts of secondary metabolites is essentially needed by the global industrial market that is not feasible by traditional methods because these are time-consuming and result in eradication of plant stock by overexploitation. Therefore, in vitro culturing techniques are adopted to obtain the maximum quantity of secondary metabolites in a minimum time. Elicitors are key players for getting desired yields of secondary metabolites in plants. Eliciting the in vitro cell and tissue cultures is an efficient approach for the production of medicinally important plant secondary metabolites. Different parameters of optimized micropropagation protocols are exploited to be used as elicitors for further enhancement of secondary metabolites from medicinal plant species. The secondary metabolites produced by the plant cells include phenolics, flavonoids, alkaloids, terpenoids, and tannins. These metabolites are boosted under stressful conditions, whether biotic or abiotic in origin. The potential role of nanoparticles in the enhancement of secondary metabolic products in medicinal plants is a recent hot topic in the field of medicinal plant biotechnology. Nanoparticles have evolved as potent novel elicitors that significantly stimulate medicinal plant secondary metabolism. Various kinds of nanoparticles including metallic and metallic oxide nanoparticles and carbon-based nanomaterials are believed to induce abiotic stress to medicinal plants under in vitro conditions by which plant defense system is elicited, triggering biochemical as well as physiological responses, consequently producing enhanced and sustainable quantities of secondary metabolites. These industrially important bioactive metabolites are beneficial for the prevention of multiple diseases in the health-care system. Therefore, nanoelicitation should be applied as an effective tool for ameliorated stimulation and accumulation of secondary metabolites. However, in some cases, after the efficient uptake and translocation, nanoparticles produce deleterious effects causing phytotoxicity. © The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022.