Comparison of methods for evaluation of the antioxidant capacity and phenolic compounds in common spices

- Ethanol/water is a better extraction solvent of TPC from spices than ethanol.
- Antioxidant capacity assays (CV, ABTS and PCL) were highly correlated.
- The ABTS and PCL methods provide about twice higher AC than CV assays.
- Spices were classified into low, medium and high antioxidant capacity.
- Clove, cinnamon and allspice had the highest AC among others.

The present study investigates the antioxidant capacity (AC) of ethanol and ethanol/water (1:1, v/v) extracts of selected spices, using cyclic voltammetry (CV), spectrophotometric and photochemiluminescence (PCL) methods. The ABTS test was used for the measurement of the scavenging capacity of the extracts against 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulphonate) radical cations whilst a photochemiluminescence technique was employed to measure the scavenging capacity against superoxide anion radicals (O2−). The cyclic voltammetry (CV) method provided the reducing capacity values of spices. The total phenolics (TPC) and total flavonoids (TF) were determined in both types of spice extracts.With the exception of vanilla, ethanol/water (1:1, v/v) was a better extraction solvent of TPC and TF in all spices when compared to ethanol alone. The order of AC values of spices determined by the applied methods was as follows: ABTS test > PCL assay > CV method. The obtained results were useful for classification of the tested spices into groups with high antioxidant capacity (clove, cinnamon and allspice), middle (star anise and nutmeg) and low AC (anise, ginger, vanilla, fennel, cardamom, white pepper and coriander). In conclusion, these findings may be useful for the selection of spices for further applications in different food formulations to support their function as antioxidants.