The antioxidant and cellular effects of Withania somnifera alone and in combination with selenium
Year: 2014
Type: dissertation
Abstract: The respiratory system is a target for environmental oxidants from airborne pollution and \nother contaminants. Chronic exposure may result in inflammatory conditions such as \nallergies and asthma. The ability of the body to counteract oxidation is dependent on the \noxidative status of the individual, and can also benefit from the use of medicinal plant \npreparations such as Withania somnifera (WS), which is accredited with antioxidant and antiinflammatory \nproperties. Selenium is an important cofactor of antioxidant enzymes such as \nglutathione peroxidase. A deficiency of Se will result in decreased antioxidant enzymes \nlevels and a poor response to oxidative damage. The aim of this study was to determine the \nantioxidant content and activity of WS, as well as its in vitro effects with seleno-L-methionine \n(Se-Met), the major component of dietary selenium, in a physiologically relevant cell model \nsystem. Little is known about the combinational effects of non-enzymatic and enzymatic \nantioxidants i.e., WS in combination with Se-Met, and these effects were also quantified. \nThe antioxidant content (total phenolic (TPC) and flavonoid content (TFC)) and activity (2,2- \ndiphenyl-2-picrylhydrazyl (DPPH), trolox equivalent antioxidant capacity (TEAC)) and oxygen \nradical absorbance capacity (ORAC) of a water extract of WS, as traditionally prepared and \nused, was determined. The intracellular and total protection of WS alone (0-33.33 mg/ml) \nand in combination with Se-Met (0-33.33 pg/ml) (range: ½-100x RDA) was evaluated in a \nstandard cell line, the SC-1 fibroblast cell line and in physiologically relevant primary cultures \nof chick embryo lung cells (CELC) using the 2’,7’-dichlorofluorescein diacetate (DCFH-DA) assay. Water extracts of WS, as traditionally consumed, were found to possess significant \nantioxidant content and activity. For TPC and TFC, WS was found to contain 4.84 g CE/100 \ng DW, and 355 mg CE/100 g DW respectively. For DPPH, the IC50 of WS was 56.34 mg/ml, \nand the antioxidant activity of WS was 274.8 μmol TE/g. For TEAC, the IC50 of WS was 60.3 \nmg/ml, and the antioxidant activity of WS was 2.2 mmol TE/g. Using ORAC, the antioxidant \nactivity of WS was found to be 15.05 μM TE/g. \nWS and Se-Met exhibited both pro-oxidant and antioxidant effects in the DCFH-DA assay \nand this may be a function of concentration, as well as combinations of WS and Se-Met \nratios. Data indicates that both WS and Se-Met, alone and in combination, elicit protection \nvia the intracellular (at all concentrations) and extracellular (at higher concentrations) compartment of the SC-1 cell. A synergistic interaction is observed extracellularly between \nWS and Se-Met, with mostly additive effects occurring intracellularly. \nFor CELC, WS and Se-Met alone both demonstrated total protective effects at almost all \nconcentrations, and intracellular protective effects at higher concentrations. The combination \nof WS and Se-Met provided total and intracellular protection to the CELC at the highest \nconcentration combination. Antagonism between WS and Se-Met was observed at low \nconcentrations in the total protection assay, with weak synergism and antagonism occurring \nat higher concentrations. Synergism between WS and Se-Met was observed at low \nconcentrations intracellularly, with antagonistic interactions occurring at higher \nconcentrations. \nIn conclusion, WS and Se-Met, alone and in combination at non-cytotoxic concentrations, \ndisplayed significant cellular protection against oxidative damage and this was a function of \ncell line, concentration and ratios between WS and Se-Met.
Author: Claire Lynne Venter
Language: English
Subfield: Complementary and alternative medicine
Field: Medicine
Domain: Health Sciences
Open Access status: green
OpenAlex ID: W122348383