## 3 Results and Discussion
### Quantification of Phenolic acids and Flavonoids by HPLC  
Phenolic profile of different extracts of _Brassica_ species were identified by RP-HPLC method discussed in Table 2 and Figure 1. Cauliflower, red cabbage, Chinese cabbage, white cabbage and broccoli extracts showed a broad variation in polyphenic compounds. Catechine and quercetin were the major flavonoids while gallic acid, \(p\)-comaric acid, chlorogenic acid and benzoic acid were the major phenolic acids found in different _Brassica_ species. Red cabbage extract contained the highest gallic acid contents (113.21 mg/100 g DW) whereas Chinese cabbage showed the lowest contents of gallic acid (3.00 mg/100 g DW). However, \(p\)-comamic acid, chlorogenic acid and benzoic acid were also major phenolic compounds found in red cabbage extract (53.29, 25.7, 27.21 mg/100 g DW) correspondingly. \(P\)-hydroxyl benzoic acid was detected in all extracts of selected species of _Brassica_ genus cauliflower, broccoli, red cabbage, white cabbage and Chinese cabbage (18.35, 0.08, 3.22, 0.61 and 0.04 mg/100g DW), respectively. Ellagic (3.21 mg/100g DW) was only detected in red cabbage. Catechine was found in high concentration in red cabbage extract (151.8 mg/100 g DW). Different _Brassica_ vegetables contained different amounts of various phenolic acids and flavonoids and the variations were found to be significant (\(p\leq 0.05\)). \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Assays**} & \multicolumn{5}{c}{**Extracts**} & \multicolumn{2}{c}{**Butylated**} \\ \cline{2-7}  & **Cauliflower** & **Broccoli** & **Red Cabbage** & **White** & **Chinese** & **Hydroytoluene** \\  & & & & **Cabbage** & **Cabbage** & **(BHT)** \\ \hline Yield (g/100 g) & 12.8 \(\pm\) 0.64 \({}^{\text{a}}\) & 12.6 \(\pm\) 0.63 \({}^{\text{a}}\) & 12.7 \(\pm\) 0.63 \({}^{\text{a}}\) & 11.9 \(\pm\) 0.58 \({}^{\text{a}}\) & 11.6 \(\pm\) 0.59 \({}^{\text{a}}\) & — \\ TPC (mg/g dry material) & 29.9 \(\pm\) 1.7 \({}^{\text{c,d}}\) & 27.2 \(\pm\) 1.6 \({}^{\text{c}}\) & 32.8 \(\pm\) 1.9 \({}^{\text{d}}\) & 16.4 \(\pm\) 0.9 \({}^{\text{b}}\) & 9.7 \(\pm\) 0.6 \({}^{\text{a}}\) & — \\ TPC (mg/g dry material) & 20.9 \(\pm\) 1.2 \({}^{\text{c}}\) & 18.6 \(\pm\) 1.1 \({}^{\text{c}}\) & 23.7 \(\pm\) 1.1 \({}^{\text{d}}\) & 9.9 \(\pm\) 0.6 \({}^{\text{b}}\) & 7.7 \(\pm\) 0.4 \({}^{\text{a}}\) & — \\ DPPH IC\({}_{50}\) (mg/mL) & 3.1 \(\pm\) 0.18 \({}^{\text{c}}\) & 3.4 \(\pm\) 0.20 \({}^{\text{c}}\) & 2.3 \(\pm\) 0.13 \({}^{\text{b}}\) & 3.7 \(\pm\) 0.22 \({}^{\text{d}}\) & 4.6 \(\pm\) 0.27 \({}^{\text{a}}\) & 1.5 \(\pm\) 0.09 \({}^{\text{a}}\) \\ \hline \hline \end{tabular}  
* The values are mean \(\pm\) standard deviation of three independent observations. Different letters in superscript show significant differences among selected _Brassica_ species.  
\end{table} 
Table 1: Yield, total phenolic, total flavonoid contents and DPPH radical scavenging activity of ethanol extract of selected _Brassica_ species. All the species of _Brassica_ have sufficient amounts of phenolic acid and flavonoids that are potential antioxidants. [PERSON] et al. (2019) reported that _Brassica_ vegetables are good sources of phenolic acids and flavonoid compounds and their derivatives, such as red cabbage, consists of different acylated groups (sinapic acid and ferulic acid), whereas the white cabbage contains more than 20 phenolic compounds, such as caffe acid and _p_-coumaric acid.