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. 2023 Jan 18;13(2):274.
doi: 10.3390/life13020274.

Outstanding Antibacterial Activity of Hypericum rochelii-Comparison of the Antimicrobial Effects of Extracts and Fractions from Four Hypericum Species Growing in Bulgaria with a Focus on Prenylated Phloroglucinols

Yana Ilieva  1 , Teodor Marinov  2 , Iliyan Trayanov  3   4 , Mila Kaleva  1 , Maya Margaritova Zaharieva  1 , Lyubomira Yocheva  5 , Zlatina Kokanova-Nedialkova  2 , Hristo Najdenski  1 , Paraskev Nedialkov  2
Affiliations

Outstanding Antibacterial Activity of Hypericum rochelii-Comparison of the Antimicrobial Effects of Extracts and Fractions from Four Hypericum Species Growing in Bulgaria with a Focus on Prenylated Phloroglucinols

Yana Ilieva et al. Life (Basel). .

Abstract

Microbial infections are by no means a health problem from a past era due to the increasing antimicrobial resistance of infectious strains. Medicine is in constant need of new drugs and, recently, plant products have had a deserved renaissance and garnered scientific recognition. The aim of this work was to assess the antimicrobial activity of ten active ingredients from four Hypericum species growing in Bulgaria, as well as to obtain preliminary data on the phytochemical composition of the most promising samples. Extracts and fractions from H. rochelii Griseb. ex Schenk, H. hirsutum L., H. barbatum Jacq. and H. rumeliacum Boiss. obtained with conventional or supercritical CO2 extraction were tested on a panel of pathogenic microorganisms using broth microdilution, agar plates, dehydrogenase activity and biofilm assays. The panel of samples showed from weak to extraordinary antibacterial effects. Three of them (from H. rochelii and H. hirsutum) had minimum inhibitory concentrations as low as 0.625-78 mg/L and minimum bactericidal concentrations of 19.5-625 mg/L against Staphylococcus aureus and other Gram-positive bacteria. These values placed these samples among the best antibacterial extracts from the Hypericum genus. Some of the agents also demonstrated very high antibiofilm activity against methicillin-resistant S. aureus. Ultra-high-performance liquid chromatography-high-resolution mass spectrometry revealed the three most potent samples as rich sources of biologically active phloroglucinols. They were shown to be good drug or nutraceutical candidates, presumably without some of the side effects of conventional antibiotics.

Keywords: Hypericum; MRSA; S. aureus; bacterial biofilm; extracts; microbes; phytochemicals.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Total ion chromatogram (TIC) chromatographic profile of the samples with the highest antibacterial effect. The conditions and the time frame were the same for (A–C). (A) CH2Cl2 extract of aerial parts of Hypericum rochelii (RochD); (B) CO2 extract of aerial parts of H. rochelii (RochC); (C) fraction eluted with 90% MeOH on Diaion HP20 of CH2Cl2 extract of the aerial parts of H. hirsutum (HirDM90).
Figure 2
Figure 2
Phloroglucinols found in H. rochelii and H. hirsutum.
Figure 3
Figure 3
Metabolic activity of S. aureus after treatment with decreasing concentrations of three of the tested samples. The metabolic activity of untreated control was normalized as 100%. These samples, due to their high activity, were tested in a lower range of concentrations in order to obtain the antibacterial parameters.
Figure 4
Figure 4
Metabolic activity of S. aureus after treatment with decreasing concentrations of seven of the tested samples. The metabolic activity of untreated control was normalized as 100%.
Figure 5
Figure 5
Metabolic activity of MRSA after treatment with decreasing concentrations of the tested samples. The metabolic activity of untreated control was normalized as 100%.
Figure 6
Figure 6
Metabolic activity of E. faecalis after treatment with decreasing concentrations of the tested samples. The metabolic activity of untreated control was normalized as 100%.
Figure 7
Figure 7
Metabolic activity of S. pyogenes after treatment with decreasing concentrations of the tested samples. The metabolic activity of untreated control was normalized as 100%.
Figure 8
Figure 8
Metabolic activity of E. coli after treatment with decreasing concentrations of the tested samples. The metabolic activity of untreated control was normalized as 100%.
Figure 9
Figure 9
Metabolic activity of P. aeruginosa after treatment with decreasing concentrations of the tested samples. The metabolic activity of untreated control was normalized as 100%.
Figure 10
Figure 10
Metabolic activity of Yersinia enterocolitica after treatment with decreasing concentrations of the tested samples. The metabolic activity of untreated control was normalized as 100%.
Figure 11
Figure 11
Biofilm inhibition of MRSA after exposure to four samples. (a) Sample RochD; (b) Sample HirDM90; (c) Sample HirDM100; (d) Sample RumDKo.
Figure 12
Figure 12
Microscopic evaluation of the biofilm inhibition using four samples—40× magnification.
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