Rapid bioassay of pesticide residues in vegetable samples from Laguna, Philippines

Abstract

A rapid bioassay technique for the detection of pesticide residues was used in screening organophosphates and carbamate insecticides in vegetable samples from Laguna, Philippines. The rapid bioassay is based on the inhibition of the enzyme acetylcholinesterase (AChE) by organophosphate or carbamate insecticides. This enzyme is responsible for hydrolyzing acetylcholine, a chemical transmitter of stimuli from one nerve cell to another. Generally slightly lower sensitivities were obtained for the crude AChE than the purified enzyme. The activity of the crude AChE compared well with the Taiwan Agricultural Research Institute (TARI) purified acetylcholinesterase with activity of 1.09 x 10-2 mol/min/ml and 1.02 x 10-2 mol/min/ml, respectively. These results indicate that freshly prepared crude AChE may be used in screening for pesticide contamination in vegetables using the rapid bioassay method. A total of 168 vegetable samples were assayed and 11.3% gave more than 20% inhibition of acetylcholinesterase, a clear indication of the presence of insecticide residues. The higher the degree of enzyme inhibition, the higher the residues of insecticides. Gas chromatographic analysis revealed that samples which exhibited an inhibition >43% exceeded the maximum residue limit (MRL) set by FAO/WHO for methomyl, triazophos and diazinon. Samples which exhibited 20-40% inhibition contained residues of methyl parathion, chlorpyrifos and malathion at levels within the MRL set by FAO/WHO.

Source or Periodical Title

Philippine Agricultural Scientist

ISSN

317454

Page

2021-12-01

Document Type

Article

Subject

Acetylcholinesterase, Carbamates, Organophosphates, Pesticide residues, Rapid bioassay

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