Response of Some Biomarker Enzymes to Terpinolene Used as Repellent against Rhyzopertha dominica (Fab.) Infestation in Stored Food Grains

Abstract

The repellent activity of terpinolene and its effects on antioxidant, neurotransmitter and detoxifying enzymes of Rhyzopertha dominica was evaluated under laboratory condition. The terpinolene was made into 2% concentration and 0.2, 0.4, 0.6, 0.8 and 1.0ml dosages were made from it and replicated five times. The repellent activity of the compound was carried out by placing two a filter paper that have been divided into two equal parts into a Petri-dishes with one side been treated with the compound. The activities of SOD, CAT, GPx, AChE, CarEST and GST was determined in the larvae of the insect. The result showed that, only 1.0 ml dosage and the positive control achieved 100% repellency at 0-1 h and were significantly different from other treatments. The activity of SOD decreases with increase in dosage of the compound. The lowest SOD (0.29 µmol/min/ml) was recorded by the positive control but was not significantly different from the 1.0 ml dosage of the compound. CAT activity significantly reduced at higher dosage, while the positive control recorded the lowest CAT activity. GPx activity increased increased dosage. AChE activity decreased with increase in the compound dosage. DDVP recorded the lowest AChE activity 0.25 µmol/min/ml. CarEST and GST activities increased with increase dosage of 0.6 ml and drastically reduced at 0.8 and 1.0 ml of the compound. Terpinolene compound proven insecticidal and could be formulated to target SOD and AChE enzymes having shown significant effects on them. Thus, this could be the mode of action of the compound.