Screening for antioxidant and detoxification responses in Perna canaliculus Gmelin exposed to an antifouling bioactive intended for use in aquaculture

Polygodial is a drimane sesquiterpene dialdehyde derived from certain terrestrial plant species that potently inhibits ascidian metamorphosis, and thus has potential for controlling fouling ascidians in bivalve aquaculture. The current study examined the effects of polygodial on a range of biochemical biomarkers of oxidative stress and detoxification effort in the gills of adult Perna canaliculus Gmelin. Despite high statistical power and the success of positive controls, the antioxidant enzymes glutathione reductase (GR), glutathione peroxidase (GPOX), catalase (CAT), and superoxide dismutase (SOD); thiol status, as measured by total glutathione (GSH-t), glutathione disulphide (GSSG), and GSH-t/GSSG ratio; end products of oxidative damage, lipid hydroperoxides (LHPO) and protein carbonyls; and detoxification pathways, represented by GSH-t and glutathione S-transferase (GST), were unaffected in the gills of adult P. canaliculus exposed to polygodial at 0.1 or 1 × the 99% effective dose in fouling ascidians (IC₉₉). Similarly, GR levels, thiol status, and detoxification activities were unaffected in mussels exposed to polygodial at 10 × the IC₉₉, although GPOX, CAT, and SOD activities increased. However, the increases were small relative to positive controls, no corresponding oxidative damage was detected, and this concentration greatly exceeds effective doses required to inhibit fouling ascidians in aquaculture. These findings compliment a previous study that established the insensitivity to polygodial of P. canaliculus growth, condition, and mitochondrial functioning, providing additional support for the suitability of polygodial for use as an antifouling agent in bivalve aquaculture.     

Epibrassinolide ameliorates Cr (VI) stress via influencing the levels of indole-3-acetic acid, abscisic acid, polyamines and antioxidant system of radish seedlings

The present investigation determined the effects of epibrassinolide (EBL) on the levels of indole-3-acetic acid (IAA), abscisic acid (ABA), and polyamine (PA) and antioxidant potential of 7-d old Raphanus sativus L. cv. ‘Pusa chetki’ seedlings grown under Cr (VI) metal stress. Reduced titers of free (0.767 μg g⁻¹ FW) and bound (0.545 μg g⁻¹ FW) IAA in Cr (VI) stressed seedlings were observed over untreated control. Supplementations of EBL to Cr (VI) stressed seedlings were able to enhance both free (2.14-5.68 μg g⁻¹ FW) and bound IAA (2.45-7.78 μg g⁻¹ FW) concentrations in comparison to Cr (VI) metal treatment alone. Significant rise in free (13.49 μg g⁻¹ FW) and bound (12.17 μg g⁻¹ FW) ABA contents were noticed for Cr (VI) stressed seedlings when compared to untreated control. No significant increase in ABA contents were recorded for Cr (VI) stressed seedlings upon supplementation with EBL over Cr (VI) treatment alone. A significant increase in Put (18.40 μg g⁻¹ FW) and Cad (9.08 μg g⁻¹ FW) contents were found for 10⁻⁹ M EBL plus Cr (VI) metal treatments when compared to Cr (VI) treatment alone. Spermidine (Spd) contents were found to decline significantly for EBL treatment alone or when supplemented with Cr (VI) treatments over untreated controls and Cr (VI) treatment alone. Antioxidant levels were found to enhance, with glutathione (57.98 mg g⁻¹ FW), proline (4.97 mg g⁻¹ FW), glycinebetaine (39.01 μmol mL⁻¹), ascorbic acid (3.17 mg g⁻¹ FW) and phytochelatins (65.69 μmol g⁻¹ FW) contents noted for EBL supplemented to Cr (VI) metal solution over Cr (VI) treatment alone. Reduced activities of guaiacol peroxidase (0.391 U mg⁻¹ protein) and catalase (0.221 U mg⁻¹ protein) and enhanced activities of glutathione reductase (7.14 U mg⁻¹ protein), superoxide dismutase (15.20 U mg⁻¹ protein) and ascorbate peroxidase (4.31 U mg⁻¹ protein) were observed in seedlings treated with EBL plus Cr (VI) over Cr metal treatment alone. Reduced MDA (2.55 μmol g⁻¹ FW) and H₂O₂ (33.24 μmol g⁻¹ FW) contents were recorded for 10⁻⁹ M EBL supplemented to Cr (VI) stress over Cr (VI) treatment alone. Enhancement in free radical scavenging potential as indicated by higher values of 1,1-diphenylpicrylhydrazyl, deoxyribose and reducing power activity assays, and increased levels of phenols and soluble sugars also showed significant influence of EBL in alleviating Cr (VI) stress in radish seedlings.