## 3 Results and Discussion
### Anttimicrobial Activity
#### 3.4.1 Grapefruit Essential Oil (GF-EO)
\begin{table}
\begin{tabular}{c c c c c} \hline \hline  & \multicolumn{2}{c}{**DPPH**} & \multicolumn{2}{c}{**Nitric Oxide**} \\ \hline
**Concentration** & & & & \\
**(\(\mu\)g/mL)** & **GP-CE** & **GF-PE** & **Vit. C** & **GP-CE** & **GF-PE** & **Vit. C** \\ \hline
31.25 & 31.20 \(\pm\) 0.72 \({}^{\text{f}}\) & 2.97 \(\pm\) 0.82 \({}^{\text{f}}\) & 23.73 \(\pm\) 0.471 \({}^{\text{f}}\) & 27 \(\pm\) 1.31 \({}^{\text{f}}\) & 2.60 \(\pm\) 0.25 \({}^{\text{e}}\) & 43.32 \(\pm\) 0.32 \({}^{\text{f}}\) \\
62.5 & 46.06 \(\pm\) 0.53 \({}^{\text{e}}\) & 13.80 \(\pm\) 0.76 \({}^{\text{e}}\) & 41.08 \(\pm\) 0.68 \({}^{\text{e}}\) & 45.33 \(\pm\) 0.88 \({}^{\text{e}}\) & 9.62 \(\pm\) 0.71 \({}^{\text{d}}\) & 63.61 \(\pm\) 0.42 \({}^{\text{e}}\) \\
125 & 62.23 \(\pm\) 0.28 \({}^{\text{d}}\) & 21.27 \(\pm\) 0.44 \({}^{\text{e}}\) & 64.57 \(\pm\) 0.53 \({}^{\text{d}}\) & 65.67 \(\pm\) 0.33 \({}^{\text{d}}\) & 10.5 \(\pm\) 0.40 \({}^{\text{d}}\) & 77.83 \(\pm\) 0.51 \({}^{\text{d}}\) \\
250 & 71.13 \(\pm\) 0.33 \({}^{\text{c}}\) & 25.83 \(\pm\) 0.75 \({}^{\text{c}}\) & 71.85 \(\pm\) 0.52 \({}^{\text{c}}\) & 75.33 \(\pm\) 0.67 \({}^{\text{c}}\) & 28.86 \(\pm\) 0.52 \({}^{\text{c}}\) & 85.25 \(\pm\)0.32 \({}^{\text{c}}\) \\
500 & 88.96 \(\pm\) 0.52 \({}^{\text{b}}\) & 31.42 \(\pm\) 1.47 \({}^{\text{b}}\) & 86.09 \(\pm\) 0.59 \({}^{\text{b}}\) & 84.33 \(\pm\) 0.33 \({}^{\text{b}}\) & 44.04 \(\pm\) 0.76 \({}^{\text{b}}\) & 88.12 \(\pm\) 0.64 \({}^{\text{b}}\) \\
1000 & 92.26 \(\pm\) 0.54 \({}^{\text{a}}\) & 42.87 \(\pm\) 0.62 \({}^{\text{a}}\) & 96.09 \(\pm\) 46 \({}^{\text{a}}\) & 90 \(\pm\) 0.58 \({}^{\text{a}}\) & 55.30 \(\pm\) 0.51 \({}^{\text{a}}\) & 94.89 \(\pm\) 0.78 \({}^{\text{a}}\) \\ \hline IC\({}_{50}\) & 75.69 \(\pm\) 0.81 \({}^{\text{e}}\) & 1069.00 \(\pm\) 0.56 \({}^{\text{a}}\) & 118.16 \(\pm\) 0.78 \({}^{\text{c}}\) & 113.45 \(\pm\) 0.71 \({}^{\text{d}}\) & 791.40 \(\pm\) 0.52 \({}^{\text{b}}\) & 59.61 \(\pm\) 0.65 \({}^{\text{f}}\) \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Percentage inhibition (%) of the polyphenol-rich extracts from GF peels in terms of scavenged DPPH and nitric oxide free radicals at different concentrations (\(\mu\)g/mL) and their IC\({}_{50}\) values. Vitamin C was used as the standard. Values represent the mean \(\pm\) standard deviation. Different letters mean significant differences between concentrations (\(p\) < 0.05). _Candida albicans_ (16 mm), showing a better potential than amoxicillin (standard). For the Gm\(-\) bacteria, there was no inhibition. Our results align with most of the studies investigating the efficacy of EOs extracted from grapefruit peels against food spoilage organisms and foodborne pathogens. However, some studies reported different findings, mainly regarding Gram\(-\) bacteria inhibition. For instance, [PERSON] et al. (2019) reported the inhibition for _E. coli_ (26.86 mm) and _P. aeruginosa_ (8.57 mm). In addition, another recent study from [PERSON] et al. (2019) demonstrated that the GG-EO at 0.1 mg/mL could not inhibit _P. aeruginosa_ growth but inhibited its biofilm production in the range of 52-55%. The differences observed may be related to the method of EO extraction. This study used hydrodistillation, whereas other comparative studies used cold-pressing extraction. However, the previously reported studies agree that EOs are generally slightly more active against Gram\(+\) than Gram\(-\) bacteria. Gram\(+\) bacteria typically exhibit a higher susceptibility due to their thick peptidoglycan cell wall layer. Conversely, Gram\(-\) bacteria possess a thinner peptidoglycan layer along with an additional outer membrane composed of phospholipids and lipopolysaccharideaccharides (2019). The presence of non-oxygenated compounds and oxygenated sesquiterpenes, such as D-Limonene, \(\beta\)-pinene, \(\gamma\)-Terpinene, \(\alpha\)-pinene, and nookatome, contributes significantly to the antimicrobial activity.