## 3 Results and Discussion  
### Antioxidant Activities  
In this study, the DPPH, ABTS, nitric oxide and hydrogen peroxide scavenging activities have been used as in vitro models to evaluate the antioxidant capacity of the essential oil of _Hydnora africana_, in comparison with the standards BHT and Gallic acid. Figure 2 illustrates the DPPH radical scavenging activity of the essential oil of _Hydnora africana_ compared with BHT and Gallic acid. We observed weak DPPH inhibitory activities of the essential oil of _Hydnora africana_, compared with the reference compounds used. Previous studies have indicated that essential oils from different sources possess varying capacities to scavenge DPPH radicals, probably due to the differences in their composition. Factors like stereo-selectivity of the radicals or the solubility of the oil in the different testing systems have been reported to affect the capacity of essential oils in quenching different radicals [14]. Our result was similar to that of [PERSON] et al. [15] who also found weak DPPH radical scavenging activity using the essential oil of _P. brazzeana_ (RSA = 14% for 1 g/L, SC50 = 1.5 mg/mL and SC50 = 3.23 mg/mL). In contrast, [PERSON] et al. [16] showed that the essential oil of _Allium sativum_ was a more effective DPPH radical scavenger (SC50 = 7.67 mg/mL). It was observed that increasing the concentration of the oil or standards was not accompanied by any significant increases in their DPPH radical scavenging activities. It appears that the lowest concentrations tested (0.025 mg/mL) was sufficient, in each case, to produce the maximum antioxidant capacity of the standards. It is possible, therefore, that much higher doses of the oil than those tested in this study may produce higher DPPH radical scavenging activities. The IC\({}_{50}\) values could not be determined precisely for both standards as they were lesser than the lowest concentration tested (0.025 mg/mL). Similarly, IC\({}_{50}\) for the essential oil was greater than the highest concentration tested (0.5 mg/mL) and could not be precisely determined. The results observed in this study indicated that the _Hydnora africana_ essential oil hasa low effectiveness in donating a hydrogen proton to the lone pair electron for the radical. Figure 2: DPPH radical scavenging activity of the essential oil of _H. africana_. Bar graphs with different letters within the same concentration are significantly different (\(p<0.05\)). The ABTS radical scavenging activity of _H. africana_ essential oil is illustrated in Figure 3. The ABTS radical scavenging activity of the essential oil was also significantly lower (\(p>0.05\)) when compared to those of BHT and Gallic acid at all the concentrations investigated (Figure 3). The % inhibition of ABTS by the essential oil was found to be concentration- dependent. The IC\({}_{50}\) value for the ABTS radical scavenging activity of the essential oil was 0.55 mg/mL, while those of the standards could not be determined precisely as they were lower than the lowest concentration tested. This result here is similar to the work by [PERSON] et al. [17] who found that three _Uzbek Scutellaria_ species also exhibited weak ABTS radical scavenging activity. The nitric oxide radical scavenging activities of the essential oil and the reference compounds are presented in Figure 4. At all the concentrations tested, the essential oil produced a significantly higher (\(p<0.05\)) nitric oxide radical scavenging activity, when compared with both BHT and Gallic acid. However, the capacities of all the tested compounds to scavenge nitric oxide were largely concentration-dependent. Nitric oxide, in itself, can alter cell structure and function by modifying different signalling pathways. Its toxicity usually results when it combines with the superoxide anion to form peroxynitrite, which is a very strong oxidant [18]. The ability of the essential oil of _H.