## 2 Results and Discussion
### Antimicrobial Screening  
The antibacterial activity of the pentacyclic compounds was screened against four bacteria strains, namely _Staphylococcus aureus_ ATCC 25,923 (S.A.), _Microoccus luteus_ NCIMB 8166 (M.L), _Escherichia coli_ ATCC 25,922 (E.C.) and _Pseudomonas aeruginosa_ ATCC 27,853 (P.A.). Tetracycline (Tet. [[https://en.wikipedia.org/wiki/Tetracycline](https://en.wikipedia.org/wiki/Tetracycline)]([https://en.wikipedia.org/wiki/Tetracycline](https://en.wikipedia.org/wiki/Tetracycline)), accessed on 13 December 2021) was used as standard antibacterial agent. Furthermore, the antifungal activity of the products was tested against two pathogenic reference yeasts, namely _Candida albicans_ ATCC 90,028 (C.A.) and _Candida brucei_ ATCC 6258 (C.K.). Amphotericin B (Amp B [[https://en.wikipedia.org/wiki/Amphotericin_B](https://en.wikipedia.org/wiki/Amphotericin_B)]([https://en.wikipedia.org/wiki/Amphotericin_B](https://en.wikipedia.org/wiki/Amphotericin_B)), accessed on 13 December 2021.) has been used as a standard antifungal agent. The determinations of the minimal inhibition concentrations (MIC) and the minimal bactericidal/fungicidal concentrations (MBC/MFC) were conducted following the technique of dilution in liquid medium, as described by [PERSON] et al. [47]. When tested on different microorganism strains, the compounds were found to display significant activity. The potencies were qualitatively assessed by the presence or the absence of an inhibition zone diameter (Figures 6 and 7). The MIC, MBC and MFC values are presented in Tables 4-6, respectively. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multicolumn{6}{c}{**Bacterial Strains**} \\ \hline \multicolumn{6}{c}{**Gram-Positive Bacteria**} & \multicolumn{2}{c}{**Gram-Negative Bacteria**} & \multicolumn{2}{c}{**Yeast Strains**} \\ \hline \multirow{2}{*}{**Comp.**} & \multicolumn{2}{c}{_S. aureus_} & **M. luteus** & _E. coli_ & _P. aeroginosa_ & _C. albicans_ & _C. Krusei_ \\  & **ATCC 25923** & **NCIMB 8166** & **ATCC 25922** & **ATCC 27853** & **ATCC 90028** & **ATCC 6258** \\ \hline
**5a** & 31.5 & 1000 & 500 & 250 & 7.8 & 31.5 \\
**5b** & 1000 & >1000 & >1000 & 1000 & 125 & 500 \\
**5c** & NA & >1000 & NA & NA & 62.5 & NA \\
**5d** & 62.5 & >1000 & NA & NA & 125 & 125 \\
**5e** & 500 & >1000 & 1000 & NA & NA & NA \\
**5f** & NA & >1000 & NA & NA & 250 & 250 \\
**5g** & 500 & >1000 & NA & NA & 250 & 250 \\
**5h** & 1000 & >1000 & NA & NA & 125 & 250 \\
**5i** & >1000 & >1000 & NA & NA & 125 & 250 \\
**5j** & 1000 & >1000 & NA & NA & NA & NA \\
**5m** & 1000 & >1000 & >1000 & NA & 1000 & 500 \\
**5n** & NA & >1000 & NA & NA & NA & NA \\
**5o** & 1000 & >1000 & NA & NA & 500 & 500 \\
**5p** & 500 & >1000 & NA & NA & 250 & 250 \\
**5q** & 1000 & >1000 & NA & NA & 125 & 250 \\
**Tet.** & 24 \(\pm\) 0 & 12 \(\pm\) 0.1 & 9 \(\pm\) 0 & 11 \(\pm\) 1.1 & NT & NT \\
**Amp. B** & NT & NT & NT & NT & 15 \(\pm\) 0.58 & 14 \(\pm\) 0.1 \\ \hline \end{tabular}
\end{table} 
Table 6: Antibacterial and antifungal activity (MBC and MFC in \(\mathrm{\SIUnitSymbolMicro g}/\mathrm{mL}\)). \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multicolumn{6}{c}{**Bacterial Strains**} \\ \hline \multirow{2}{*}{**Comp. **} & \multicolumn{2}{c}{_S. aureus_} & **M. luteus** & _E. coli_ & _P. aeroginosa_ & _C. albicans_ & _C. krusei_ \\  & **ATCC 25923** & **NCIMB 8166** & **ATCC 25922** & **ATCC 27853** & **ATCC 90028** & **ATCC 6258** \\ \hline
**5a** & 31 \(\pm\) 0.03 & NA & NA & 9 \(\pm\) 0 & 12 \(\pm\) 0 & 11 \(\pm\) 0 \\
**5b** & 17 \(\pm\) 0 & 10 \(\pm\) 0 & 8 \(\pm\) 0 & NA & 14 \(\pm\) 0 & 11 \(\pm\) 0 \\
**5c** & NA & 10 \(\pm\) 0 & NA & NA  
The highest antibacterial activity of the cycloadducts is display against gram-positive bacteria (_Staphylococcus aureus_ ATCC 25,923 and _Microococcus luteus_ NCIMB 8166), whereas towards gram-negative bacteria (_Escherichia coli_ ATCC 25,922 and _Pseudomonas aeruginosa_ ATCC 27853), the probed compounds are in general less active compared to gram-positive ones.