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  • Author or Editor: Kalidas Shetty x
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The role of the antioxidant response system in association with the proline-associated pentose phosphate pathway for cold adaptation was investigated in three cool-season turfgrasses during a cold acclimation period. As phenolic biosynthesis and antioxidant stimulation is proposed to be linked to the proline-associated pentose phosphate pathway, this study was aimed to determine the active role of proline in metabolic regulation and its relationship with the cold stress tolerance mechanism of cool-season turfgrasses. In this study, significant accumulation of total soluble phenolics and higher total antioxidant activity was observed in creeping bentgrass (Agrostis stolonifera L.), kentucky bluegrass (Poa pratensis L.), and perennial ryegrass (Lolium perenne L.) during cold acclimation, confirming the direct and indirect role of phenolics to counter low temperature-induced oxidative stress. A positive correlation between high phenolic content and the proline-associated pentose phosphate pathway was also found in investigated turfgrass species during a cold acclimation period. Low succinate dehydrogenase activity along with the high glucose-6-phosphate dehydrogenase activity in cold-acclimated turfgrass species suggested a probable shift of carbon flux from the energy-consuming tricarboxylic cycle to the alternative energy-efficient proline-associated pentose phosphate pathway to induce a better cold stress tolerance mechanism in these cool-season turfgrasses. Higher proline accumulation in cold-acclimated turfgrass species also supported the above findings and a probable proline oxidation to support mitochondrial oxidative phosphorylation was observed in acclimated kentucky bluegrass based on the activity of proline dehydrogenase, which likely supports the active metabolic role of proline in stress-induced situations. Through this study, a significant variation in cold stress tolerance mechanisms was observed among three investigated cool-season turfgrass species during cold acclimation. Furthermore, a high cold stress tolerance characteristic was observed in kentucky bluegrass by adapting a more efficient pathway for an antioxidant response linked to proline accumulation.

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Grape (Vitis vinifera cv. Pok Dum) is a rich source of health relevant phenolic antioxidants and can be targeted to mitigate chronic oxidative stress commonly associated with noncommunicable chronic diseases (NCDs), such as cancer. Furthermore, improving health relevant phenolic bioactives and associated antioxidant properties of fruits by using chemical elicitation strategy has significant merit. Based on this biochemical rationale, chitosan and other chemical elicitors potassium dihydrogen phosphate (KH2PO4), potassium nitrate (KNO3), sodium selenite (Na2SeO3), and aluminum sulphate [Al2(SO4)3] were targeted to improve phenolic bioactive profiles and associated antioxidant and anticancer properties of cultured grape cells grown for 28 days. After chemical elicitor treatments, phenolic content, resveratrol content, antioxidant activity, phenylalanine ammonia-lyase (PAL) enzyme activity, and cytotoxicity (cell inhibition) against cancer cell lines of cultured grape cells were investigated using in vitro assay models. Overall, stimulation of phenolic bioactives and improvement in associated cytotoxicity against cancer cell lines were found in cultured grape cells after chemical elicitation treatments. Chitosan and other chemical elicitors resulted in lower growth of cultured grape cells; however, they enhanced phenolic biosynthesis on a cell weight basis when compared with the control. Chemical elicitor treatments, such as Na2SeO3 (50 mg·L−1 and 100 mg·L−1) and Al2(SO4)3 (50 mg·L−1), resulted in enhanced phenolic content at the end of 14 days of culture (1.7, 1.4, and 1.0-fold increase, respectively). Higher accumulation of resveratrol and higher antioxidant activity with Al2(SO4)3 (50 mg·L−1) and Na2SeO3 (100 mg·L−1) elicitation treatments were also observed. Enhanced phenolic bioactives in cultured grape cells in response to chemical elicitation treatment, such as Na2SeO3, also resulted in higher cytotoxicity against different cancer cell lines. Therefore, this study indicates that chemical elicitors, such as Na2SeO3 and Al2(SO4)3, as well as chitosan in select doses can be targeted to improve phenolic bioactives and associated antioxidant and anticancer properties in cultured grape cells and such strategy has relevance for wider applications with other phenolic antioxidant-enriched fruits.

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