The effect of preplanting gamma radiation on chemical constitutents of peppermint oil

Uniformly selected stem cuttings of peppermint (Mentha piperita L) were exposed to 0, 0.5, 1.0, 2.0 and 4.0 Krad of gamma rays from a Co60 source and subsequently grown in field. Irradiation dose of 1.0 Krad was the best stimulatory dose for enhancing herb fresh weight as it resulted in almost two folds yield as compared with control, whereas dose of 4.0 Krad did not affect plant growth. One Krad treated plants induced higher yield of essential oil as compared with other radiation treatments and control. The major chemical constitutents (menthol, menthone and menthyl acetate) were statistically affected by developmental stages, and by pre-planting irradiation treatments as expressed on the total content basis. Higher contents of menthol, menthone and menthyl acetate were found in plant cut during flowering stage. Pre-planting gamma irradiation did not seem to affect both chemical ''acid value, ester value and saponification value'' and physical properties ''specific gravity, solubility and refractive index'' of extracted mint oil