Thermal Stability of Representative Bioactive Compounds in Biopesticide Derived from Castor Oil or Wormseed Extract under Controlled Temperature

Abstract

BACKGROUND:Castor oil and wormseed extract are important active ingredients for biopesticide, and ricinoleic acid in castor oil and three monoterpenes (ascaridole, carvacrol and p-cymene) in wormseed extract are known bioactive substances. However, their stabilities had not been studied, even though the stability was the core property for estimation of shelf-life of biopesticide. Aimed to investigate the thermal stabilities of the bioactive substances in castor oil and wormseed extracts. METHODS AND RESULTS:The contents of ricinoleic acid and three monoterpenes (ascaridole, carvacrol and p-cymene) were analyzed by gas chromatography (GC). The thermal stabilities of the bioactive substance were measured at 0 , 23 , 30 , 40 , 45 and 54 for 84 ℃ ℃ ℃ ℃ ℃ ℃ d. The half-lives of ricinoleic acid in biopesticides was ranged from 28.9 d to 57.8 d at 30 , and the stability of ℃ pure castor oil were located in the range (t 1/2 =46.2 d for Indian product and 27.7 d for Korean product) at the same temperature. The half-lives of the total monoterpenes in biopesticides were ranged from 3.9 d to 27.7 d at 30 . ℃ Among the monoterpenes, the stability ascaridole and p-cymene were decreased in acidic condition. All the bioactive substances showed similar stability on the different thermal conditions. CONCLUSION: The half-lives of most bioactive substance from castor oil and wormseed extracts were less than 100 d. To increase the stability of bioactive substance in biopesticide, stabilizing additives like antioxidant and oxygen remover should be considered to extend of the shelf-life.