# Relationship between Total Antioxidant Capacity, Cannabinoids and Terpenoids in Hops and Cannabis
## 3 Discussion  
Antioxidants may be hydrophobic (lipid-soluble) and hydrophilic (water-soluble) substances, yet plant-based antioxidants are mostly hydrophilic [18; 61]. Results obtained in this study showed an increased antioxidant activity in the pre-frozen samples, which can be attributed to the structural damage caused by the ice crystal formation reported previously in a preceding study; scanning electron microscopy analyses of cannabis samples showed that the cold temperature used during pre-freezing and consequent ice crystal formation caused wrinkling of cannabis trichome stalks and cannabis trichome heads to fall off [51]. Other research has shown that pre-freezing exerts positive effects on the quality and functional properties of plant material since a frozen state allows the release of bioactive compounds as bound phenolic acids and anthocyanins, resulting in increased antioxidant activity [13; 62]. [PERSON] and [PERSON] (2012) showed that pre-freezing apricots (_Prunus armeniaca_) at \(-20\)\({}^{\circ}\)C increased the concentration of vitamin C and \(\beta\)-carotene by 55.5% and 10.7%, respectively. The high temperature used during MAHD and freeze-drying caused a significant (\(p<0.05\)) reduction in the antioxidant activity in both hops and cannabis using the DPPH assay compared to the pre-frozen samples. This can be attributed to a reduction in free phenolic compounds present in the samples, as DPPH measures the scavenging activity of phenolic compounds [11; 30]. [PERSON] et al. (2019) observed a significant (\(p>0.05\)) reduction (5.7%) in the total free phenolic compounds in rice (_Oryza sativa_) when the drying temperature was increased from 20 \({}^{\circ}\)C to 80 \({}^{\circ}\)C. Significant (\(p<0.05\)) differences were not observed  
Figure 6: Concentration of terpen in hops in fresh undried, pre-frozen undried, microwave-assisted hot air dried, and freeze-dried hops (_H. lupulus_) biomass. Bars with the same letter are not significantly (\(p<0.05\)) different. between the antioxidant activity values for pre-frozen, freeze-dried and MAHD-dried cannabis samples using the FRAP method, likely due to the presence of iron-chelating compounds such as cannabinoids in the cannabis extract samples (Figure 3). Cannabinoids can interfere with the FRAP assay by chelating the Fe\({}^{3+}\) irons in the FRAP reagent mixture; [PERSON] et al. (2021) showed that cannabinoids are antioxidant agents as they can scavenge free radicals, and THC's antioxidant activity was greater by 35.3% with the FRAP assay when compared to DPPH assay. Given these data, the FRAP assay is recommended for determining antioxidant activity in cannabis and hop infloresences. Further studies using other antioxidant activity assays such as oxygen radical absorbance capacity (ORAC) and determining the presence of antioxidants in different cannabis and hop plant organs could be explored. The significant (\(p<0.05\)) increase in total THC and THCA concentrations can be attributed to the pre-freezing step. Pre-freezing causes structural damage to trichome structures and can be considered as an abiotic stressor [(51; 63)]. [PERSON] et al., (2013) reported that abiotic stresses increased total phenolic compounds (TPC) by 62.5% in barley (_Hordeum vulgare_) compared to the control upon harvest. Taking this into account, it is plausible that the structural damage incurred by trichomes during pre-freezing step helps release trapped secondary metabolites. Cannabinoid analyses showed a significant (\(p<0.05\)) increase in THC for MAHD-dried samples compared to fresh, undried (64.7%) and pre-frozen, undried samples (57%). This can be explained by the non-enzymatic decarboxylation process [(49)]. However, freeze-drying did not cause a significant change in the concentration of THC and THCA in the samples. Hence, freeze-drying can be used to preserve the secondary metabolites present in cannabis and these data support previous findings [(51)]. These findings are comparable to other crops preserved in this manner [(64; 65)]. [PERSON] et al.