Growth-Inhibiting and morphostructural effects of constituents identified in Asarum heterotropoides root on human intestinal bacteria

Abstract

BackgroundThe growth-inhibiting and morphostructural effects of seven constituents identified in Asarum heterotropoides root on 14 intestinal bacteria were compared with those of the fluoroquinolone antibiotic ciprofloxacin.MethodA microtiter plate-based bioassay in sterile 96-well plates was used to evaluate the minimal inhibitory concentrations (MICs) of the test materials against the organisms.Resultsδ-3-Carene (5) exhibited the most potent growth inhibition of Gram-positive bacteria (Clostridium difficile ATCC 9689, Clostridium paraputrificum ATCC 25780, Clostridium perfringens ATCC 13124, and Staphylococcus aureus ATCC 12600) and Gram-negative bacteria (Escherichia coli ATCC 11775 and Bacteroides fragilis ATCC 25285) (minimal inhibitory concentrations (MIC), 0.18–0.70 mg/mL) except for Salmonella enterica serovar Typhimurium ATCC 13311 (MIC, 2.94 mg/mL). The MIC of methyleugenol (2), 1,8-cineole (3), α-asarone (4), (−)-asarinin (6), and pellitorine (7) was between 1.47 and 2.94 mg/mL against all test bacteria (except for compound 2 against C. difficile (0.70 mg/mL); compounds 1 (23.50 mg/mL) and 4 (5.80 mg/mL) against C. paraputricum; compounds 2 (5.80 mg/mL), 4 (12.0 mg/mL), and 7 (0.70 mg/mL) against C. perfringens); compound 1 against E. coli (7.20 mg/mL) and S. enterica serovar Typhimurium (12.0 mg/mL). Overall, all of the constituents were less potent at inhibiting microbial growth than ciprofloxacin (MIC, 0.063–0.25 mg/ mL). The lactic acid-producing bacteria (four bifidobacteria and two lactobacilli) and one acidulating bacterium Clostridium butyricum ATCC 25779 were less sensitive and more susceptible than the five harmful bacteria and two nonpathogenic bacteria (B. fragilis and E. coli) to the constituents and to ciprofloxacin, respectively. Beneficial Gram-positive bacteria and harmful and nonpathogenic Gram-negative bacteria were observed to have different degrees of antimicrobial susceptibility to the constituents, although the antimicrobial susceptibility of the harmful Gram-positive bacteria and the harmful and nonpathogenic Gram-negative bacteria was not observed. Scanning electron microscopy observations showed different degrees of physical damage and morphological alteration to both Gram-positive and Gram-negative bacteria treated with α-asarone, δ-3-carene, pellitorine, or ciprofloxacin, indicating that they do not share a common mode of action.ConclusionA. heterotropoides root-derived materials described merit further study as potential antibacterial products or lead molecules for the prevention or eradication from humans from diseases caused by harmful intestinal bacteria.

Morphological and ultrastructural changes in bacterial cells as an indicator of antibacterial mechanism of action

“…Nomenclature in the literature varies, some authors referring to them as'round forms' [76,100], 'round cells' [63, 101,102], 'spherical forms', 'spherical cells' [54,78,103], or 'coccoid forms' [104,105]. In a few papers, these descriptors are used interchangeably with the term 'spheroplast' [54,101,102] but this is incorrect.…”

Phylogenetic relationships in Asarum: Effect of data partitioning and a revised classification

“…Li et al, 2013; X.‐W. Li et al, 2013; Perumalsamy et al, 2013; Williamson et al, 2013). Several genera have been segregated from Asarum (i.e., Asiasarum F.Maek., Geotaenium F.Maek., Heterotropa Morren & Decne., Hexastylis Raf., Japonasarum Nakai), but in recent treatments these have been treated as infrageneric taxa (Shumei et al, 2003; Sugawara, 2006).…”

Frontiers in antibiotic alternatives for Clostridioides difficile infection

“…Zingerone (derived from ginger) and menthol (derived from peppermint) inhibited C. difficile at the same inhibition concentration of 9.4 mg/mL, whereas trans-cinnamaldehyde, an active constituent found in cinnamon bark, exhibited strong inhibitory activity with an MIC of 0.2 mg/mL[ 52 ]. δ-3-Carene, a monoterpene derived from the root of Asarum heterotropoides , exhibited anticlostridial activity with an MIC of 0.7 mg/mL with a less potential of suppressing beneficial intestinal bacteria[ 53 ]. Moreover, an essential oil extract that contains 16.5% of δ-3-carene exhibited antimicrobial activity against C. difficile at a concentration of 0.25% (v/v)[ 54 ].…”