Application of EPR spectroscopy to identify irradiated Indian medicinal plant products

A study of gamma-irradiated Indian medicinal plant products was carried out using electron paramagnetic resonance (EPR) spectroscopy. Improved approaches like high-power measurement, microwave saturation, and thermal behavior of the radicals were explored for detection of irradiation. Aswagandha (Withania somnifera), vairi (Salacia reticulata), amla (Emblica officinalis), haldi (Curcumin longa), and guduchi (Tinospora cordifolia) exhibited a weak singlet at g = 2.005 before irradiation. Aswagandha, immediately after radiation treatment, revealed a complex EPR spectrum characterized by EPR spectrum simulation technique as superposition of 3 paramagnetic centers. One group of signal with organic origin was carbohydrate and cellulose radical and the other was isotropic signal of inorganic origin (g⟂ =2.0044 and g|| = 1.9980). However, other products did not exhibit any radiation-specific signal after irradiation. Power saturation and thermal behavior techniques were not suitable for these products. However, amongst all the 3 approaches, high-power measurement of EPR spectra emerged as a suitable technique in identification of the irradiated aswagandha.

Gamma-irradiation confirms hygienic quality and improves shelf life of food and other products. However, there is a lack of international consensus over considering this as a general application and different regulations are being enforced. EPR is one of the most promising techniques to identify irradiated foodstuffs for regulatory requirements but it has many limitations. Improved approaches based on the EPR technique explained in this study may be useful to identify irradiated products and become beneficial to food regulators and food irradiation enterprises to enhance confidence in irradiation technology.