Antibacterial and Antifungal Activity of Propyl-Propane-Thiosulfinate and Propyl-Propane-Thiosulfonate, Two Organosulfur Compounds from Allium cepa: In Vitro Antimicrobial Effect via the Gas Phase

Abstract

Propyl-propane thiosulfinate (PTS) and propyl-propane thiosulfonate (PTSO) are two volatile compounds derived from Allium cepa with a widely documented antimicrobial activity. The aim of this study was to evaluate their anti-candidiasis activity and the ability of its gaseous phase to inhibit bacterial and yeast growth in vitro. The minimum inhibitory concentration of various antifungal products (including PTS and PTSO) was determined versus 203 clinical isolates of Candida spp. through broth microdilution assay. Additionally, the antimicrobial activity through aerial diffusion of PTS and PTSO was evaluated over the growth of a collection of bacteria and yeasts cultivated in agar plates. All yeasts were susceptible to the antifungals tested, except C. glabrata and C. krusei, that showed azole resistance. PTSO (MIC50 and MIC90 ranged from 4 to 16 mg/L and 8 to 32 mg/L, respectively) was significantly more active against yeasts than PTS (MIC50 and MIC90 ranged from 16 to 64 mg/L and 32 to 64 mg/L). Values were higher than those obtained for antifungal drugs. Gaseous phases of PTS and PTSO generated growth inhibition zones whose diameters were directly related to the substances concentration and inversely related to the microbial inoculum. The quantification of PTS and PTSO levels reached in the growth media through aerial diffusion displayed a concentration gradient from the central zone to the periphery. Only P. aeruginosa ATCC 27853 showed resistance, while yeasts (C. albicans ATCC 200955 and C. krusei ATCC 6258) presented the higher susceptibility to both compounds. These results suggest that PTS and PTSO display antibacterial and anti-candidiasis activity in vitro through aerial diffusion, having potential use in human therapy.

Antifungal Activity of Propyl-Propane-Thiosulfinate (PTS) and Propyl-Propane-Thiosulfonate (PTSO) from Allium cepa against Verticillium dahliae: In Vitro and in Planta Assays

“…However, the D pathotype appeared to be somewhat less affected to the gas phase of PTS and PTSO during the volatility-linked activity test, while the antifungal effect was quite more noticeable against the isolates of the ND pathotype. In line with our results, other authors have recently reported the antimicrobial activity of PTS and PTSO against bacteria and yeast through their gas phase [14].…”

“…To study the antifungal activity of the compounds associated with their gas phase, the methodology described in Section 2.3.1 was carried out with some modifications [14,42].…”

“…In recent years, the antimicrobial activity of several organosulfur compounds such as thiosulfinates and thiosulfonates, obtained from Allium genus plants such as onion ( Allium cepa L.), Welsh onion ( Allium fistulosum L.) or garlic ( Allium sativum L.), has been extensively studied [ 10 , 13 , 14 , 15 , 16 ]. In onion, the most common organosulfur compounds are isoalliin (S-propenyl-L-cysteine sulfoxide) and propiin (S-propyl-L-cysteine sulfoxide).…”

Beneficial Effects of Organosulfur Compounds from Allium cepa on Gut Health: A Systematic Review

“…On the contrary, Lactobacillus and Bifidobacterium were the most resistant populations to these compounds. In line with these results, other articles reported the antibacterial activity of PTS and, especially, PTSO, against Gram-positive and Gramnegative human clinical isolates [52,87]. The results highlighted the special sensitivity of E. coli or Salmonella strains, regardless of their resistance to antibiotics such as cefotaxime or cefazidime, or their capacity to produce Extended-Spectrum Beta-Lactamase.…”

“…The results highlighted the special sensitivity of E. coli or Salmonella strains, regardless of their resistance to antibiotics such as cefotaxime or cefazidime, or their capacity to produce Extended-Spectrum Beta-Lactamase. Moreover, the activity against Gram-positive bacteria such as methicillin-resistant Staphylococcus aureus, Enterococcus faecalis and Streptococcus agalactiae was higher than the one observed against enterobacteria, especially in the case of PTSO [52,87].…”