## 7 Analytical Techniques for the Determination of Active Compounds
The samples from different sources revealed 19 similar compounds among the 10 different samples studied with a degree of similarity never exceeding 1.5%, with the predominance of compounds differing in accordance with the source. [PERSON] et al. [73] described for the first time the application of GC-MS to identify volatile compounds present in leaves of different ages. For extraction, Clevenger-type equipment was used for the hydrodistillation of the plant for 3 h, adding 1 mL of pentane to the graduated part, after which the pentane layer was separated and dried with sodium sulfate before analysis. The authors report that the composition of volatile compounds was dependent on the plant's age and its drying process. A higher prevalence of oxygenated aliphatic compounds was observed in younger plants while older plants revealed a greater prevalence of sesquiterpene compounds. To evaluate the herbicidal activity of ailanthone in _A. altissima_ bark, [PERSON] et al. [74] isolated this compound with solvents and purified it by Biogel P2. A higher concentration of ailanthone 92% \(w/w\) was obtained when dichloromethane was used. Three obtained fractions were subsequently fractionated by gel permeation chromatography using a Biorad Biogel P2 resin with a UV detector operating at 313 nm. Later, an HPLC coupled with a UV-VIS detector set at 256 nm was used to determine ailanthone in three different species. [PERSON] et al. [75] isolated cathn-6-one to evaluate its antifungal activity. This study was performed by quantifying the different protein expressions in _Fusarium oxysporum_ f. sp. _cucumerinum_ (Foc) by liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS). Extraction of the compound was carried out with three times ethanol (70%) at room temperature. The obtained extract was evaporated by vacuum and subsequently dissolved in water before partitioning with other solvents, namely n-hexane, ethyl acetate and butanol. Canthin-6-one present in 32 \(\upmu\)g/mL revealed an elevated downregulating effect on the expression of glutamine synthetase, thus affecting the synthesis of glutamine and glutamate, apart from downregulating the transport of amino acids, affecting the growth of the fungus. To characterise the volatile compounds from leaves and flowers, [PERSON] et al. [76] quantified them through a dynamic headspace sampling coupled with GC-MS. The compoundswere extracted with 150 mL of distilled water for 4 h by pumping air through a SuperQ volatile collection trap equipment and then eluted with 100 mL methylene chloride. The authors observed the presence of fifty-three compounds belonging to groups such as terpenoids, fatty acids, benzenoids, and nitrogen-containing compounds. The percentage of fatty acids present in the total emissions from the leaves was higher than in flowers, which were found to have a higher percentage of terpenoids in the overall emissions for volatile compounds compared to leaves, namely monoterpencids. To evaluate the phytotoxic activity of leaves, [PERSON] et al. [51] studied the composition of this species with GC-MS after extracting water-ethanol (\(70\%\); \(V/V\)) by reflux and ultrasound for one hour. The extract was then centrifuged, and the supernatant was filtered. Twenty-seven different compounds were identified, of which some fatty acids and polyphenols were estimated to contribute to the phytotoxic activity. [PERSON] et al. [77] identified the nematicidal activity of (E,E)-2,_A_-decadienal and (E)-2-decenal extracted from wood, leaf, bark, and root parts. These two compounds were extracted with methanol (1:10 \(w/w\)) with ultrasound for 15 min. After this process, the obtained solution was filtered and centrifuged. A GC-MS was used to determine the presence of these two compounds and the authors claimed their presence in wood parts only. The nematicidal activity revealed EC\({}_{50}\) values of 11.70 mg/L for (E,E)-2,_A_-decadienal and 20.43 mg/L for (E)-2-decenal when applied against the nematode _Meloidogyne javanica_. Additionally, [PERSON] et al.