## 3 Results
### Detection of Polyphenols in P. angustifolia and P. cupana Extracts and Intracellular Redox Status  
In plants, antioxidant activity is mainly due to the presence of phenolic compounds, including polyphenols and flavonoids. Flavonoids are also considered critical antioxidants in herbal medicine [39; 40]. Our data showed that _P. angustifolia_ and _P. cupana_ have high levels of phenolic, as well as flavonoid, contents (Figure 9A,B). Our study results confirmed that the fruits and seeds of _P. angustifolia_ and _P. cupana_ are good sources of phenols and flavonoids (polyphenols). Therefore, we postulated that both these extracts could have antioxidant potential. To test this possibility, we performed the DPPH scavenging assay, the reaction of which is based on the changing color of free radical solution with tested substances. The decline in absorption values after adding extracts to the radical solution is directly proportional to the quantity of produced DPPH [41]. DPPH measurement was conducted with two different concentrations of extracts, 40 and 320 ug\(\cdot\)mL\({}^{-1}\). Remarkably, the highest capacity for DPPH inhibition was observed using the 320 ug\(\cdot\)mL\({}^{-1}\) concentration with 73% and 48% in _Pyracantha_ and _Paullinia_ extracts, respectively (Figure 9C). These findings suggest the presence of phenolic and flavonoid compounds in both extracts. To further investigate whether the extracts of _Pyracantha_ and _Paullinia_ inhibit the growth of cancer cells by reducing ROS generation, we monitored  
Figure 6: _Pyracantha_ and _Paullinia_ stimulate cell cycle arrest in both cancer cell types. (**A** and **B**) PI/RNase A-stained cells treated with two different concentrations (40 or 320 ug\(\cdot\)mL\({}^{-1}\)) of _Pyracantha_ and _Paullinia_ were analyzed using flow cytometry. The cell populations are marked as sub-G1 (pink), G0/G1 (blue), S (green), and G2/M (brown) in histograms. (**C** and **D**) The representative graph shows the percentage of the cell population in the G2/M phase in MDA-MB231 and HEPG2 cancer cells, respectively. Untreated samples were used as controls for all tested plant extracts. the redox status of the HEPG2 extract-treated cells using the oxidation-sensitive fluorescent dye DCFDA. Both extracts showed the smallest effect on ROS generation at the lower concentration (40 \(\upmu\)g\(\cdot\)mL\({}^{-1}\)). Thus, _Pyracantha_ and _Paullinia_ extracts decreased ROS generation in HEPG2 cells in a concentration-dependent manner (Figure 9D,E). ROS generation decreased more significantly at the higher concentration (320 \(\upmu\)g\(\cdot\)mL\({}^{-1}\)), which may be due to increased apoptotic cell death. Earlier reports have suggested that various natural compounds present in plants are capable of combating cancer via inhibition of ROS generation in patients [42; 43]. Based on this finding, we further assessed the expression levels of antioxidant enzymes, such as catalase (CAT) and manganese-dependent superoxide dismutase (MnSOD or SOD2), in the extract-treated HEPG2 cells. The CAT and SOD2 levels were upregulated at the higher concentration (320 \(\upmu\)g\(\cdot\)mL\({}^{-1}\)) in HEPG2 cancer cells treated with both plant extracts (Figure 9F). These results suggest that antioxidants present in _Pyracantha_ and _Paullinia_ induce the inhibition of cancer cell proliferation through decreased ROS levels. Additionally, we have performed a cell viability test in HEPG2 cells in the presence of H\({}_{2}\)O\({}_{2}\) with both Pyracantha and Paullinia extracts to further validate our findings. Interestingly, H\({}_{2}\)O\({}_{2}\) blocked the effect of both plant extracts on the decrease in viability in cancer cells at the 50 \(\upmu\)M concentration (Supplementary Figure S1). Figure 7: _Pyracantha_ and _Paullinia_ induce apoptosis in cancer cells. (**A** and **B**) Caspase-3/7 activity was measured in MDA-MB231 and HEPG2 cells treated with two different concentrations (40 or 320 \(\upmu\)g\(\cdot\)ml\({}^{-1}\)) of _Pyracantha_ and _Paullinia_ extracts, respectively.