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Investigation of the antimicrobial and anti-inflammatory effects of phytochemical compounds derived from Haberlea rhodopensis (Master thesis)

Μπουρλάκης, Δημήτρης/ Bourlakis, Dimitris/ Λοιμώδη Νοσήματα-Διεθνής Ιατρική: από το Εργαστήριο στην Κλινική Πράξη

The endemic resurrection plant Haberlea rhodopensis Friv. is remarkable for its ability to survive and recover after prolonged periods of drought and environmental stress upon rehydration. The present study evaluated the antimicrobial and anti-inflammatory activities of ethanolic extracts derived from H. rhodopensis, including the whole crude extract (Ex1), a combination of the active compounds myconoside (M) and paucifloside (P) (Ex2), and the individual compounds M and P. The primary aim was to validate the antimicrobial potential of these extracts and compounds against clinically relevant bacterial pathogens. Antimicrobial activity was assessed using disc diffusion and biofilm formation assays. The results showed that none of the tested extracts significantly inhibited the growth of selected Gram-positive and Gram-negative bacterial strains, including Escherichia coli, Salmonella enterica, and Staphylococcus aureus. To further investigate whether these extracts could mitigate infection through secondary mechanisms, their anti-inflammatory potential was evaluated in both murine and human macrophage cell models. Cytotoxicity was assessed by Sulforhodamine B (SRB) and Alamar Blue assays, revealing no significant cytotoxic effects at the tested concentrations. Moreover, treatment with the crude extract appeared to enhance macrophage viability under certain conditions. Anti-inflammatory activity was evaluated by quantitative Real-Time PCR analysis of a panel of pro-inflammatory and anti-inflammatory cytokines and transcription factors. Treatment of macrophages with M or P, either before or after inflammatory stimulation, resulted in a marked reduction in the expression of key pro-inflammatory markers, including IL-6 and COX-2. Furthermore, expression of the anti-inflammatory cytokine IL-10 was enhanced following all treatments and was particularly upregulated in response to treatment with M. Although Ex1 and Ex2 also showed some capacity to reduce inflammatory responses, their effects were generally less pronounced than those of the individual compounds. Overall, these findings suggest that while the H. rhodopensis ethanolic extracts display limited direct antimicrobial activity against the tested bacterial pathogens, their bioactive constituents, myconoside and paucifloside, possess promising anti-inflammatory properties. Their potential to mitigate inflammatory responses associated with infection and disease warrants further investigation.