## 3 Results and Discussion
### Antioxidant Activity of Leptadenia pyrotechnica Stem  
The effect of microwave and conventional heating on the antioxidant activity in terms of DPPH radical scavenging and reducing the power of the _L. pyrotechnica_ stem samples is shown in Figures 4 and 5. Before treatments, the DPPH of the _L. pyrotechnica_ stem was found to be 22.01%. Both microwave and conventional heating processes caused a significant (\(p<0.05\)) increment in the DPPH of the samples. However, it was observed that microwave-heated samples had significantly higher DPPH values than conventionally heated samples (Figure 3). The highest DPPH values were obtained in the samples treated with the microwave for 8 min (76.58%), followed by the samples microwave heated for 10 min (73.43%) and then the samples hot-air oven heated for 120 min (63.03%), respectively.  
A recent study applied various drying methods to dry blueberry fruits. It was found that microwave drying at 300 W for 82 min and 500 W for 64 min was the best way to increase the blueberry fruits' antioxidant capacity [31]. Coriander leaves dried in microwave ovens showed higher DPPH scavenging than those dried in conventional ovens [21]. Maillard reaction products might be produced during heating, contributing to the sample's increased antioxidant activity [31]. Although some phenolic compounds are destroyed, some new compounds like hydroxycinnamates and quinic acid are released, which play a role in the antioxidant activity of the material [32].  
Figure 4: Effect of microwave heating (MW) and hot-air heating (HA) methods on the DPPH scavenging of _Leptadenia pyrotechnica_ stem samples. The bars for the treatments bearing different letters are significantly different from each other at \(p<0.05\).  
The effect of heating processes on the reducing power (RP) of _L. pyrotechnica_ stem samples is depicted in Figure 5. The reducing power of the samples is measured in terms of its equivalent to the ascorbic acid. The microwave-treated samples showed a higher reducing power than the hot-air-treated samples. For instance, RPs of 23.18, 30.74, and 29.55 mg AAE/g were noticed for the samples that were microwave heated for 5, 8, and 10 min, respectively. However, the control sample showed a significantly (\(p<0.05\)) lower reducing power value (9.67 mg AAE/g DW) than all the samples. These results followed the findings for the TPC and TFC, which showed that the antioxidant activity of the _L. pyrotechnica_ samples was attributable to the phenolic compounds. Blueberry leaves dried under microwaves exhibited a higher ferric reducing power than oven-dried leaves, and their ferric reducing power was similar to that of freeze-dried blueberry leaves [21]. Microwave, vacuum, and oven-dried celery slices showed more antioxidant activity than the fresh sample. In short, microwave drying provides higher nutrients by increasing the antioxidant capacities [24]. [PERSON] [33] stated that the freeze-drying method gave the highest phenolic content and antioxidant activity in lemon myrtle, and no significant differences in phenolic compounds and antioxidant activity were observed among all the other drying methods, i.e., hot-air drying, microwave drying, vacuum drying, shade drying, and sun drying. However, microwave drying was suggested for the industrial-scale drying of lemon myrtle due to its time and/or energy efficiency.