Enhancing ferric-reducing antioxidant activity through terpene mixture optimization

The present study investigated the antioxidant potential of three terpenes p -cymene, thymol, and β-ionone—through their ferric reducing power (FRAP). Individually, p -cymene demonstrated the strongest activity with an EC 50 of 123.03 ± 2.05 µg/mL, followed by thymol (EC 50 = 153.16 ± 2.84 µg/mL), whereas β-ionone exhibited the lowest ferric reducing capacity (EC 50 = 931.46 ± 5.37 µg/mL), revealing significant variation in their antioxidant efficacy. To assess combinatorial effects, twelve randomized mixture trials were performed, each representing the mean of three independent repetitions, yielding FRAP EC 50 values ranging from 79.76 to 931.46 µg/mL. Statistical analysis identified significant contributions from linear terms (β 1 , β 2 , β 3 ), binary interactions (β 12 , β 13 ), and the ternary interaction term (β 123 ), indicating that both individual and combined effects shaped the overall antioxidant response. Analysis of 2D and 3D mixture plots suggested that an EC 50 around 79.70 µg/mL could be obtained by combining all three terpenes. Furthermore, desirability analysis predicted an optimal FRAP EC 50 of 58.23 µg/mL, achieved with a mixture comprising 17% β-ionone, 42% p -cymene, and 41% thymol, with a global desirability of 99.9%. These findings demonstrate that strategic blending of structurally related terpenes can substantially enhance ferric reducing capacity, providing a robust framework for the development of potent natural antioxidant formulations.