# Novel Adamantane Derivatives: Synthesis, Cytotoxicity and Antimicrobial Properties
## 3 Results
### Antimicrobial Activity Assays  
The screening results obtained in vitro indicated that few of the analyzed compounds displayed antimicrobial activity (Table 1). The majority of the compounds exhibited an antibacterial effect towards Gram-positive bacteria, except substances numbered **3**, **11**, **16** and **23**, which were inactive towards them. The sensitivity of the other substances was varied. In the case of active compounds, the Minimal Inhibitory Concentrations (MICs) and Minimal Bactericidal Concentrations (MBCs) against these bacteria were within the scope of 62.5 \(\upmu\)g/mL to 1000 \(\upmu\)g/mL and from 250 \(\upmu\)g/mL to \(>\)1000 \(\upmu\)g/mL, respectively. Among them, derivatives **9**, **14**, **15** and **19** showed the highest antibacterial potential with MIC = 62.5-1000 \(\upmu\)g/mL towards all Gram-positive bacteria. _S. epidermidis_ ATCC 12228 was the most susceptible to compound **9** (MIC = 62.5 \(\upmu\)g/mL and MBC = 250 \(\upmu\)g/mL, MBC/MIC = 4) with a bactericidal effect. Other compounds displayed a moderate or mild effect (MIC = 250-1000 \(\upmu\)g/mL) or were inactive towards these bacteria.  
Schiff bases numbered as **9** substituted with 4-nitrophenyl and **14** with 3-nitrophenyl moiety as well as hydrazide **19** also inhibited growth of all Gram-negative bacterial strains (MIC = 125-1000 \(\upmu\)g/mL, MBC = 250 - \(>\) 1000 \(\upmu\)g/mL). Among them, hydrazide of 1-adamantancarboxylic acid **19** possessed the highest activity with a moderate effect (MIC = 125-500 \(\upmu\)g/mL and similar MBC = 250-1000 \(\upmu\)g/mL). This hydrazide showed a bactericidal effect towards all reference bacteria from this group (MBC/MIC = 1-4). The activity of other compounds was lower. Among these microorganisms, _B. bronchiseptica_ ATCC 4617 was the most sensitive to the tested substances (MIC = 125-1000 \(\upmu\)g/mL, MBC = 500 - \(>\) 1000 \(\upmu\)g/mL), except to derivatives **2**, **3**, **10**, **11**, **22** and **23** (which had no activity). Moreover, Schiff base **5** substituted with 3-ethoxy-2-hydroxyphenyl and hydrazide **19** were slightly active against some rods from the _Enterobacteriaceae_ family and _Pseudomonas aeruginosa_ ATCC 9027, respectively.  
The results included in Table 1 also indicated some antifungal effects of the tested compounds against yeasts from _Candida_ spp. Most of these substances were active at MIC and MFC (Minimal Fungicidal Concentration), ranging from 62.5 \(\upmu\)g/mL to 1000 \(\upmu\)g/mL and from 125 \(\upmu\)g/mL to \(>\)1000 \(\upmu\)g/mL, respectively. The compounds showed mainly moderate or mild effects. The activity of one of them--the Schiff base numbered **5**, which was substituted with 3-ethoxy-2-hydroxyphenyl--was good (MIC = 62.5 \(\upmu\)g/mL and MFC = 125 \(\upmu\)g/mL, MFC/MIC = 2) towards _C. albicans_ ATCC 10231 with a fungicidal effect. Compounds **5**, **9**, **14** and **15** exhibited a moderate fungicidal effect against all fungi (MIC = 62.5-500 \(\upmu\)g/mL, MFC = 125-1000 \(\upmu\)g/mL and MFC/MIC = 1-4). Compounds **2**, **8** and **10** had a slightly weaker effect. Moreover, derivatives **7**, **19** and **23** showed activity only towards some of yeasts. Compounds **16**, **20** and **22** had no anticandidal activity.