## 3 Results and Discussion
### Chemical Characterization of C. australasia Peel Using HPLC-QTof-MS
\begin{table}
\begin{tabular}{c c c c c c c} \hline
**Peak** & **RT (min)** & \begin{tabular}{c} **[M –H] - \(m/z\)** \\ **Experimental** \\ \end{tabular} & \
\begin{tabular}{c} **[M –H] - \(m/z\)** \\ **Calculated** \\ \end{tabular} & **Molecular** & **Error (ppm)** &
\begin{tabular}{c} **MS/MS Fragment** \\ **ions (\(m/z\))** \\ \end{tabular} & **Proposed Compound** \\ \hline
1 & 1.3 & 191.0176 & 191.0192 & \(\mathrm{C_{S}H_{A}O_{9}}\) & \(-1.6\) & \(160,111,87\) & Citric acid * \\
2 & 3.8 & 145.0274 & 145.0290 & \(\mathrm{C_{S}H_{A}O_{9}}\) & \(-1.6\) & \(117\) & Coumarin * \\
3 & 6.1 & 179.0341 & 179.0344 & \(\mathrm{C_{S}H_{A}O_{4}}\) & \(-0.3\) & \(135\) & Caffe acid * \\
4 & 7.0 & 119.0496 & 119.0497 & \(\mathrm{C_{S}H_{S}O_{9}}\) & \(-0.1\) & \(101\) & **4-Vinylphenol** \\
5 & 7.3 & 609.1471 & 609.1456 & \(\mathrm{C_{S}H_{A}O_{16}}\) & \(1.5\) & \(301\) & Rutin * \\
6 & 7.6 & 463.0877 & 463.0877 & \(\mathrm{C_{S}H_{A}O_{9}}\) & \(0\) & \(301\) & **Hyperside * \\
7 & 8.0 & 579.1732 & 579.1714 & \(\mathrm{C_{S}H_{A}O_{9}}\) & \(3.1\) & \(271,151\) & Naringin * \\
8 & 8.4 & 315.0498 & 315.0505 & \(\mathrm{C_{S}H_{A}O_{9}}\) & \(-2.2\) & \(301,273,151\) & Isorhamnetin * \\
9 & 8.6 & 163.0407 & 163.0395 & \(\mathrm{C_{S}H_{A}O_{9}}\) & \(1.2\) & \(119\) & **2-Coumaric acid * \\
10 & 9.1 & 471.1268 & 471.1291 & \(\mathrm{C_{S}H_{A}O_{9}}\) & \(-4.9\) & \(267,205,163,59\) & **Ononin-O-acetate** \\
11 & 9.4 & 593.187 & 593.1870 & \(\mathrm{C_{S}H_{A}O_{9}}\) & \(0\) & \(431,285,163,\) & Didymin * \\
12 & 9.8 & 503.1871 & 503.1858 & \(\mathrm{C_{S}H_{A}O_{9}}\) & \(3.6\) & \(355,297\) & Unknown \\
13 & 9.9 & 491.2245 & 491.2222 & \(\mathrm{C_{S}H_{A}O_{9}}\) & \(4.7\) & \(373,329,285,165\) & Unknown \\
14 & 10.2 & 271.0612 & 27.10606 & \(\mathrm{C_{S}H_{A}O_{9}}\) & \(2.2\) & \(171,151\) & Naringin * \\
15 & 10.4 & 125.0229 & 125.0239 & \(\mathrm{C_{S}H_{A}O_{9}}\) & \(-1\) & \(81\) & **Pyrogallol * \\
16 & 10.8 & 499.1207 & 489.2125 & \(\mathrm{C_{S}H_{A}O_{9}}\) & \(-3.7\) & \(471,333,111\) & **Deacetylnomilinic acid** \\
17 & 11.3 & 517.2073 & 517.2074 & \(\mathrm{C_{S}H_{A}O_{9}}\) & \(-0.2\) & \(399,274,175,111\) & Unknown \\
18 & 11.7 & 469.1872 & 469.1862 & \(\mathrm{C_{S}H_{A}O_{9}}\) & \(2.1\) & \(381,229\) & **Limonin** \\
19 & 12.0 & 333.1355 & 333.1338 & \(\mathrm{C_{S}H_{A}O_{9}}\) & \(4.1\) & \(91,149\) & Unknown \\
20 & 12.5 & 445.2934 & 445.2954 & \(\mathrm{C_{S}H_{A}O_{9}}\) & \(-4.5\) & \(367,287,227\) & Unknown \\
21 & 12.8 & 425.2345 & 425.2328 & \(\mathrm{C_{S}H_{A}O_{9}}\) & \(4\) & \(410,381,335,311,283\) & Unknown \\
22 & 13.5 & 467.2452 & 467.2434 & \(\mathrm{C_{S}H_{A}O_{6}}\) & \(3.9\) & \(381,325,283,179,97\) & Unknown \\ \hline \end{tabular}  
* Compounds identified with commercial standards. Compounds identified for the first time in _C. australsica_ L. peel are in bold.  
\end{table} 
Table 1: Identification of phytochemicals in the ethyl acetate fraction of _C. australsica_ L. using HPLC-QTof-MS.  
an \([\text{M}-\text{H}]^{-}\) ion at \(m/z\) 469.1862 with MS/MS fragments at \(m/z\) 381 and 229, which have been previously reported in the literature [35], and characterized in the seeds of grapefruit and the pulp of _Citrus_ Sp. [37] and in _Citrus grandis_[35]. This limonoid, present in the _Rutaceae_ family in which citrus fruits are included, has been found to have anticancer properties [18]. Lastly, peak 1 (\([\text{M}-\text{H}]^{-}\) ions at \(m/z\) 191.0192) was characterized as one of the most well-known compounds present in all citrus fruits, i.e., citric acid [38]. The identification of this organic acid was confirmed by comparison with the authentic standard.