## 3 Results
### In Vitro Anti-Inflammatory Activity  
The denaturation of proteins is an indicator for the presence of an inflammatory process. During this process, the secondary and tertiary structures of proteins are destroyed and a disturbance in their biological functions is observed. The ability of a certain substance (natural or synthetic) to reduce inflammation is associated with an anti-inflammatory effect [39]. Some anti-inflammatory drugs have been shown to inhibit the thermally induced protein denaturation in a dose-dependent manner [40].  
The _in vitro_ anti-inflammatory activity was evaluated as inhibition of albumin denaturation, assessing the degree of resistance to thermal denaturation of the human albumin molecule in the presence of SJW EO. The results are presented as the percentage of inhibition of albumin denaturation (Figure 3A), as well as a half-maximal inhibitory concentration or IC\({}_{50}\) (Figure 3B).  
The SJW EO at concentration of 1 mg/mL exhibited the highest anti-inflammatory effect, expressed as inhibition of the thermally induced albumin denaturation (44.9 \(\pm\) 0.08%). This value was higher than those of the conventional anti-inflammatory drugs used as controls (22.57 \(\pm\) 0.12% for acetylsalicylic acid or Aspirin and 43.62 \(\pm\) 0.04% for Prednisolon Cortico) at the same concentration. SJW showed the lowest IC\({}_{50}\) value (1.11 \(\pm\) 0.01 mg/mL), compared to those of the controls (2.22 \(\pm\) 0.02 mg/mL for acetylsalicylic acid and 1.15 \(\pm\) 0.01 mg/mL for Prednisolon Cortico).  
The non-steroidal and steroidal anti-inflammatory drugs (NSAIDs and SAIDs) also effectively inhibit inflammation, which, from a medical point of view, is a normal healing process; however, these drugs cause many adverse effects, especially with high dosages and prolonged intake. NSAIDs can cause gastric ulcers, stomach irritation and lower gastrointestinal disorders [41, 42], while SAIDs increase the risk of hyperglyaemia, predisposition to infections,  
\begin{table}
\begin{tabular}{l c c} \hline \hline  & \multicolumn{2}{c}{**Inhibition Zones (IZ), mm**} \\ \cline{2-3}
**Test Microorganisms** & \multicolumn{2}{c}{**St. John’s Wort EO**} \\  & **(10 mg/mL)** & **Control (MeOH)** \\ \hline _Bacillus subtilis_ ATCC 6633 & 9 \(\pm\) 0.00 & - \\ _Bacillus cereus_ NCTC 11145 & 9 \(\pm\) 0.00 & - \\ _Staphylococcus aureus_ ATCC 25923 & 8 \(\pm\) 0.00 & - \\ _Listeria monocytogenes_ NBIMCC 8632 & 9 \(\pm\) 0.00 & - \\ _Enterococcus faecalis_ ATCC 29212 & 8 \(\pm\) 0.00 & - \\ _Salmonella enteritidis_ ATCC 13076 & 9 \(\pm\) 0.00 & - \\ _Klebsiella pneumoniae_ ATCC 13883 & 12 \(\pm\) 0.71 & - \\ _Escherichia coli_ ATCC 25922 & 9 \(\pm\) 0.00 & - \\ _Proteus vulgaris_ ATCC 6380 & - & - \\ _Pseudomonas aeruginosa_ ATCC 9027 & 11 \(\pm\) 0.00 & - \\ _Candida albicans_ NBIMCC 74 & 8 \(\pm\) 0.00 & - \\ _Saccharomyces cerevisiae_ ATCC 9763 & 10 \(\pm\) 0.00 & - \\ _Aspergillus niger_ ATCC 1015 & - & - \\ _Aspergillus flavus_ * & - & - \\ _Penicillium chrysogeum_ * & 10 \(\pm\) 0.00 & - \\ _Pusarium monilforme_ ATCC 38932 & 8 \(\pm\) 0.00 & - \\ \hline \hline \end{tabular}
* plant isolates.  
\end{table}
Table 4: Antimicrobial activity of Bulgarian St John’s Wort (_H. perforatum_ L.) essential oil.  
peptic ulcer disease, glaucoma, cataracts, psychosis, depression, adrenal insufficiency, diabetes and osteoporosis [43]. Consequently, the results in the present study reveal the great anti-inflammatory potential of SJW EO that can find application in the development of new medical formulations as alternatives to conventional anti-inflammatory drugs.