# Relationship between Total Antioxidant Capacity, Cannabinoids and Terpenoids in Hops and Cannabis
## 5 Conclusions  
The effects of postharvest processing on hops and cannabis were evaluated to determine the relationship between antioxidant capacity and secondary metabolites. The study compared the efficiency of DPPH and FRAP assays to estimate total antioxidant activity in hops and cannabis extracts. The antioxidant activity of extracts derived from fresh, untreated samples were 3.6 TEAC (M) dry matter\({}^{-1}\) and 2.32 FRAP (M) dry matter\({}^{-1}\) for hops, and 2.29 TEAC (M) dry matter\({}^{-1}\) and 0.25 FRAP (M) dry matter\({}^{-1}\) for cannabis. The results showed that although freezing of inflorescences is a preservation technique, pre-freezing the hops and cannabis samples before drying increased the antioxidant values by 13% (DPPH assay) and 29.9% (FRAP assay) for hops, and by 7.7% (DPPH assay) and 19.4% (FRAP assay) for cannabis. Data showed that freeze-drying and MAHD significantly (\(p<0.05\)) reduced the antioxidant activity in hops by 79% and 80.2% [DPPH], respectively, and 70.1% and 70.4% [FRAP], respectively, compared to pre-frozen, undried hops. For cannabis, the DPPH assay showed that both freeze-drying and MAHD significantly (\(p<0.05\)) reduced the antioxidant activity of cannabis. However, there was no significant (\(p<0.05\)) difference between the antioxidant activity values for pre-frozen, freeze-dried, and MAHD cannabis samples using the FRAP method because of the presence of iron-chelating cannabinoids in the cannabis. Results showed that the FRAP assay accurately determines the antioxidant activities of cannabinoids compared to the DPPH assay and is a valuable assay for the cannabis industry. ANOVA analyses showed a significant (\(p<0.05\)) increase in the total THC (24.2 g 100 g dry matter\({}^{-1}\)) and THCA (27.2 g 100 g dry matter\({}^{-1}\)) concentrations in pre-frozen, undried samples compared to fresh, undried samples. Non-enzymatic decarboxylation was observed by the significant (\(p<0.05\)) increase in the THC inMAHD-dried samples compared to fresh, undried (64.7%) and pre-frozen, undried (57%). Although both drying systems showed a significant loss in the total terpene concentration, freeze-drying has higher terpene retention compared to MAHD. Freeze drying should be used as the drying system for medicinal plants to reduce the postharvest losses of secondary metabolites and decarboxylation of cannabinoids.  
Conceptualization, M.L., V.O. and V.R.; methodology, P.W.A. and Z.P.; software, M.S., N.T., P.W.A. and Z.P.; formal analysis, P.W.A.; visualization, P.W.A.; investigation, P.W.A. and Z.P.; writing--original draft preparation, P.W.A., Z.P. and S.M.; writing--review and editing, S.M., M.L., V.O., V.R., M.S. and N.T.; supervision, M.L.; funding acquisition, M.L. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the Natural Sciences and Engineering Research Council of Canada (NSERC) as part of the Collaborative Research and Development (CRDPF) 543704-19, in partnership with EXKA Inc. Mirabel, Canada) and Collaborative Research and Training Experience (CREATE 543319-2020; Quality Assurance and Quality Control for Cannabis Production, Products and Training or QAQCC) programs.  
Not applicable.  
We extend our sincere gratitude to the Schulich Graduate Fellowship Committee and [PERSON] for their support. The authors thank BloomLabs for providing laboratory support.  
The authors declare no conflict of interest.