Antioxidant activity, total phenolics, flavonoids, tannin content of cassava leaf (Manihot esculenta Crantz) with different cooking and drying methods

The effects of several cooking and drying methods on the total phenolics, total tannins, total flavonoids, and antioxidant activity of cassava leaf were examined in this study. The research employs a completely randomized design (CRD) with one factor, which is the processes included boiling for 5 and 10 minutes, steaming for 5 and 10 minutes, oven-drying and sun-drying. There are 6 treatments in total, and each treatment is replicated 3 times. The data are analyzed using Analysis of Variance (ANOVA), and if there are significant differences, further comparisons will be made using the DNMRT test at a significance level of α ≤ 5%. The antioxidant activity testing methods used were DPPH, ABTS, and FRAP. The results showed that the raw leaves possessed a considerable amount of total phenolics, tannins, flavonoids, and antioxidant activity. However, the steaming for 5 minutes led reduced to a loss in total phenolics and tannins but increased the total flavonoids content compared to the other wet methods, with 17,45 mg GAE/mL; 8,21 mg TAE/mL; and 163,39 mg RE/mL, respectively. The oven-drying reduced the loss of total phenolics, flavonoids, and tannins on cassava leaves compared to the sun-drying, with 22,25 mg GAE/mL; 113,31 mg RE/mL; and 8,21 mg TAE/mL, respectively. The DPPH, ABTS, and FRAP assays showed the reduced loss of antioxidant activities after steaming with 34.44 mg AAE/mL; 22.12 mg AAE/mL; and 27.32 µM Fe2+/mL respectively. The oven-drying also maintained the antioxidant activity compared to sun-drying with 42.22 mg AAE/mL; 23.57 mg AAE/mL; and 34.37 µM Fe2+/mL, respectively. In conclusion, the methods of heating cassava leaf had a significant effect on active compounds. It was recommended that steaming for 5 minutes is the preferred wet method, while oven-drying is the preferred dry method to maintain active compounds in cassava leaf.