## 3 Results and Discussions
### Effect of A. secundiramea Essential Oils on Bacterial Survival  
Essential oils extracted from _A. secundiramea_ leaves and flowers were tested against two gram-negative and one positive strains: _E. coli DH5\(\alpha\), P. aeruginosa PAOI_, and _S. aureus ATCC 6538P_, respectively. _E. coli_ represents a model strain to test antimicrobial activity, while _P. aeruginosa_ and _S. aureus_ are opportunistic pathogens. In particular, some bacterial strains of species _P. aeruginosa_ can cause infections in patients suffering from a disorder of the skin barrier [55]. _S. aureus_ is an important human pathogen that is responsible for most of the bacterial skin and soft tissue infections in humans too. This strain can also become more invasive and cause life-threatening infections, such as bacteremia, pneumonia, abscesses of various organs, meningitis, osteomyelitisitis, endocarditis, and sepsis. These infections represent a major public health threat because of their considerable number and spread [56]. As shown in Figure 4A, the oil extracted from flowers was able to inhibit the three strains: _E. coli_, _P. aeruginosa_, and _S. aureus_ growth, forming an inhibition halo. Figure 4B reports a quantitative analysis of inhibition halos (about 60, 35, and 38 AU/mL, respectively), almost comparable to the antibiotic control. We used ampicillin to inhibit _E. coli_ and _S. aureus_ cells growth, and colistin, a polymysin that acts on the bacterial membrane of gram-negative microorganisms, used as a positive control in the _P. aeruginosa_ experiment. The essential oil extracted from the _A. secundiramea_ leaves seems to be less efficient than that from flowers. A more sensitive method, shown in Figure 5, to calculate the efficiency of antimicrobial activity uses fixed concentration (500 \(\upmu\)g/mL). Figure S1 shows this at different concentrations (50, 100, and 250 \(\upmu\)g/mL, which confirms that _A. secundiramea_ flowers and leaves extracts have antimicrobial activity. The oil extracted from the flowers has a stronger antimicrobial activity than the one extracted from the leaves against the three bacterial strains tested. The antimicrobial activity of _A. secundiramea_ oil is probably due to a single molecule, the (_E_)-chrysanthenyl acetate, which is present in a pure form in the extract of flowers. Recent studies report that chrysanthenyl acetate, has been suggested as the active component. Chrysanthenyl acetate inhibits prostaglandin synthetase and might have analgesic properties [57]. Other studies suggest that compound analog chrysanthenyl acetate, may contribute to the antimigraine activity, due to its prostaglandin inhibition [58]. The antimicrobial activity of (_E_)-chrysanthenyl acetate, to the best of our current knowledge, is not well described in the literature. In general, this compound can be found in different plants and species of _Anthemis_, but never in pure form, as in the case of _A. secundiramea_ flowers [59]. This aspect is very promising, as with the extraction from the flowers, it is very easy to obtain, and the yield is very high, already making the oil available in good quantities for different applications. Both oil extracts are not cytotoxic against eukaryotic cells (HaCat line) tested for three different times (24, 48, and 72 h) at two different concentrations (100 and 500 \(\upmu\)g/mL), and the data is shown in Figure S2 (see Supplementary Materials).