Antioxidant Effects of Four Heartwood Extractives on Midgut Enzyme Activity in Heterotermes indicola (Blattodea: Rhinotermitidae)

Heterotermes indicola (Wasmann) (Blattodea: Rhinotermitidae) is a species of subterranean termite that is a destructive pest of wood and wood products in Pakistan. This study evaluated the antioxidant and antienzyme potential of heartwood extractives against H. indicola. Heartwood extractives of four durable wood species, Tectona grandis (L. f), Dalbergia sissoo (Roxb.), Cedrus deodara (Roxb.), and Pinus roxburghii (Sarg.) were removed from wood shavings via soxhlet extraction with an ethanol: toluene solvent system. The antioxidant potential of the extractive compounds was determined using the DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging test. Results showed maximum antioxidant activity for extractives of D. sissoo. D. sissoo had the lowest IC50 (the concentration where 50% inhibition of the DPPH radical is obtained) at 28.83 mu g/ml among the heartwood extractives evaluated. This antioxidant activity, however, was not concentration dependent as was observed in the other heartwood extractives tested. At the maximum test concentration, T. grandis showed the highest percent inhibition at 89.7%, but this inhibition was lower compared to the positive control antioxidant compounds butylated hydroxytoluene and quercetin. When termites were fed filter paper treated with IC50s of the extractives and control compounds, glutathione S-transferase activity in the guts of H. indicola workers was significantly reduced by T. grandis and D. sissoo extractives. Similarly, esterase activity was reduced more by P. roxburghii extractives compared to control antioxidant treatments and other tested extractives. However, none of the extractives examined significantly reduced the activity of catalase enzymes in H. indicola compared to treatments with the antioxidant control compounds.