Characterisation of phenolic compounds of Inca muña (Clinopodium bolivianum) leaves and the feasibility of their application to improve the oxidative stability of soybean oil during frying

Phenolic compounds from Inca muña leaves were, for the first time, qualitatively and quantitatively characterised. The main phenolic compounds encountered corresponded to flavanones, followed by flavones and hydroxycinnamic acid derivatives. Fractionation of Inca muña phenolic compounds revealed an ethyl acetate fraction (EaF) rich in phenolics and antioxidant activity. This EaF proved to be an efficient source of natural antioxidants for use against soybean oil oxidation during frying. Differential scanning calorimetry revealed higher induction periods for 600 ppm of EaF compared to 200 ppm of TBHQ and a negative control (no antioxidant added). During frying at ∼180 °C, 600 ppm of EaF showed the highest efficacy against oil oxidation in terms of p-anisidine values, conjugated dienes and trienes and polar compounds compared to 200 ppm of TBHQ and negative control. This study provides strong evidence for the antioxidant potential of Inca muña EaF phenolics against soybean oil oxidation. It suggests the possibility of incorporating these natural antioxidants from Inca muña leaves for use by the food industry.