## 6 Biological Properties
### Antioxidant Activity  
Scientific research is interested in quantifying and using antioxidants mainly due to their potent biological activity. [47]. Although antioxidant compounds may be synthesized, there is a growing interest in the natural compounds from different plants [48; 49]. Taking this into account, [PERSON] et al. [50] performed a research to determine the phenolic, flavonoid, and total alkaloid content on four different extracts (methanolic, ethanolic, hydroalcoholic, and acetone) of _A. altissima_ (steams, stalks, and leaves) to establish a correlation to the antioxidant activity of these extracts. To assess their antioxidant activity, DPPH (2,2-diphenyl-1-picryl-hydraz) assay and the 6-carotene bleaching test were used.  
It was possible to quantify the total amount of phenolic compounds, 268.15 mg/g of dry extract in all extracts. The most important finding of this research is the potential antioxidant properties of _A. altissima_, since it is abundant in phenolic, flavonoid, and alkaloid compounds. [PERSON] et al. [51] have identified the presence of flavonoids (ranging around 5.34 to 5.41 g of rutin equivalents per 100 g of dry weight) in leaf extracts of _A. altissima_. The extraction method by reflux or ultrasound did not have a significant effect on the final concentration.  
Moreover, the antioxidant activity was performed by the DPPH assay and the 2,2-AzinoBis (3-ethylbenzothazoline-6-Sulphonic acid) (ABTS) radical scavenging assay. Once again, the extraction method did not affect the obtained concentrations, meaning that values are approximately 0.16 mM Trolox equivalent of extract for DPPH and around 9 mM Trolox equivalent when ABTS was used. In summary, results showed that flavonoids were in higher amounts than other compounds and are responsible for the antioxidant properties of the ethanolic leaf extracts [51]. Another study with leaves from different localities in Tunisia found that the main phenolic compounds in methanolic extracts were gallic acid, chlorogenic acid, HHDP-galloylglucose, epicatechin, rutin, hyperoside, and quercetin-3-galloyl hexoside [40]. Once again, the typical antioxidant activity assays (DPPH and ABTS) were used, as well as the ferric reducing antioxidant power (FRAP) assay and the 2-deoxyribose method, which was used for the determination of the scavenging effects of the methanolic extracts on hydroxyl (OH) radicals. Results showed good antioxidant activity of the methanolic extracts.  
Altogether, leaves from the Bousalem region showed better antioxidant activity than those from other regions, with EC\({}_{50}\) values of 14.78 ug/mL, 8.64 ug/mL, and 4.42 ug/mL when using the DPPH assay, ABTS assay, and the OH scavenging test, respectively. Regarding the leaf hydrodistilled residues, results were similar in efficacy to the DPPH and ABTS test. However, when using the OH radical test, the hydrodistilled residues showed a better antioxidant activity for the species that came from Bab Saadoun [40]. The DPPH test to assess the antioxidant activity of _A. altissima_ leaves was also used by [PERSON] et al. [39]. Methanolic extracts presented an IC\({}_{50}\) value of 35.46 ug/mL and its ethyl acetate fraction possessed an even lower IC\({}_{50}\) value (16.45 ug/mL). Recently, research was conducted to evaluate the physicochemical parameters and pharmacological bioactivity of _A. altissima_ seed oil. [PERSON] et al. [52] were able to show that the seed oil presents antioxidant activity. The DPPH assay determined that the IC\({}_{50}\) was 24.57 ug/mL, although the concentration of polyphenols was considered low (1.067 mg gallic acid equivalent/100 g oil). In addition, the study also showed that this seed oil presents moderate antimicrobial activity against Gram-positive bacteria.