## 3 Results and Discussion
### Multivariate Analysis
#### 3.3.2 Hierarchical Cluster Analysis  
In order to evaluate the similarity measure, the spice extracts were classified using the methods of Wards and the Euclidean square. HCA was applied to quantify the correlations between all studied extracts and to display the similarities of 30 extracts based on their antioxidant characteristics determined by the modified DPPH, ABTS, FRAP, and F-C assays. The generated plots, called dendrograms, are presented in Figure 5.  
Similar to PCA, the 30 spice extracts were classified into three main clusters (Figure 5a). Twelve extracts of clove obtained from all prepared DESs (CloDES1, CloDES2, and CloDES3), extracts of nutmeg, ginger, and cinnamon prepared with DES3 (NutDES3, GinDES3, CinDES3), and extracts of these spices in ethanol and its mixture with water (70:30 \(v/v\)) (NutEt, GinEt, CinEt, NutEtW, GinEtW, and CinEtW) were arranged in one cluster characterized by similar moderate antioxidant properties. In addition, CloDES2, CloDES3, and CinEt with high AC were in the same inter-cluster, as shown in Figure 5a. However, a clear separation of two ethanolic clove extracts (CloEtW and CloEt) with the highest AC and TPC was observed. All investigated extracts of cardamom and coriander and extracts of nutmeg, ginger, and cinnamon obtained with two ecological solvents such  
Figure 5: Dendrograms of hierarchical cluster analysis for (**a**) spice extracts prepared using three deep eutectic solvents: DES1, DES2, and DES3 and common solvents: ethanol (Et) and ethanol:water (Et:W 70:30 \(v/v\)), and (**b**) the studied variables: DPPH, ABTS, FRAP, and F-C.  
as DES1 and DES2, having the lowest DPPH, ABTS, FRAP, and TPC values, formed an evidently distinct group. Moreover, the prepared cardamom extracts with the lowest AC and TPC created an inter-cluster (Figure 5a). HCA was also applied to four analytical methods (DPPH, ABTS, FRAP, and F-C), and they were grouped in clusters in terms of their similarity and discrepancy (Figure 5b). As can be seen, the analytical assays used formed two statistically significant clusters. The first cluster comprised two subgroups: (I) DPPH and (II) FRAP and F-C tests, while the second group contained only the ABTS method. This can be explained by the fact that the ABTS radical scavenging assay allows the determination of both hydrophilic and lipophilic antioxidants present in spice extracts. However, FRAP and F-C methods are based on the redox reaction principle and measure the ability of the spice extracts to reduce Fe(III) to Fe(II) and Mo(VI) to Mo(V), respectively. These two analytical methods are particularly suitable for hydrophilic antioxidants. Although the DPPH assay uses a radical dissolved in organic media and has a higher affinity toward lipophilic than hydrophilic antioxidants, it is more closely connected to the FRAP and F-C tests. It is noteworthy that AC and TPC in the studied spices were different from one another. The dendrograms revealed that the grouping of the 30 spice extracts was dependent on their origin and the properties of the extracting solvents, which would affect the total concentration of antioxidants. 3.3 Relationship between Antioxidant Capacity and Total Polyphenols in the Investigated Spice Extracts  
Presuming that the phenolic antioxidants might contribute to the AC of plant materials, the correlation coefficients between the AC, determined by the DPPH, ABTS, and FRAP methods, and the TPC measured by the F-C method were calculated and are visually presented in Figure 6.  
All [PERSON]'s correlation coefficients were found to be statistically significant with \(p\)-values less than 0.01. Correlation coefficients varied between 0.92 and 0.98, with the strongest correlation being between the ABTS and FRAP methods (r = 0.98, \(p\) < 0.01). Correlations between ABTS and F-C and FRAP and F-C assays were comparably high (r = 0.95, \(p\) < 0.01), while the correlation between DPPH and ABTS was 0.94 (\(p\) < 0.01).