Characterization of the Inclusion Complexes of Isothiocyanates with γ-Cyclodextrin for Improvement of Antibacterial Activities against Staphylococcus aureus

Abstract

The aim of this study was to develop inclusions formed by γ-cyclodextrin (γ-CD) and three isothiocyanates (ITCs), including benzyl isothiocyanate (BITC), phenethyl isothiocyanate (PEITC), and 3-methylthiopropyl isothiocyanate (MTPITC) to improve their controlled release for the inhibition of Staphylococcus aureus (S. aureus). These inclusion complexes were characterized using X-ray diffraction, Fourier-transform infrared, thermogravimetry, and scanning electron microscopy (SEM), providing appropriate evidence to confirm the formation of inclusion complexes. Preliminary evaluation of the antimicrobial activity of the different inclusion complexes, carried out in vitro by agar diffusion, showed that such activity lasted 5–7 days longer in γ-CD-BITC, in comparison with γ-CD-PEITC and γ-CD-MTPITC. The biofilm formation was less in S. aureus treated with γ-CD-BITC than that of BITC by using crystal violet quantification assay and SEM. The expression of virulence genes, including sarA, agr, cp5D, cp8F, clf, nuc, and spa, showed sustained downregulation in S. aureus treated with γ-CD-BITC for 24 h by quantitative real-time polymerase chain reaction (qRT-PCR). Moreover, the growth of S. aureus in cooked chicken breast treated with γ-CD-BITC and BITC was predicted by the Gompertz model. The lag time of γ-CD-BITC was 1.3–2.4 times longer than that of BITC, and correlation coefficient (R2) of the secondary models was 0.94–0.99, respectively. These results suggest that BITC has a more durable antibacterial effect against S. aureus after encapsulation by γ-CD.

A Bioactive Chitosan−Based Film Enriched with Benzyl Isothiocyanate/α−Cyclodextrin Inclusion Complex and Its Application for Beef Preservation

“…BITC−α−CD displayed a quite similar spectrum to that of α−CD, except for the existence of characteristic peaks at 2140–2040 cm −1 . In recent studies, BITC was reported to have absorption bands at 2140–2040 cm −1 attributed to the thiocyanate group and at 1600–1345 cm −1 ascribed to the benzene ring [ 10 , 38 ]. Moreover, the benzene ring of BITC was suggested to be entrapped in the cavity of γ−CD, whereas the thiocyanate moiety was exposed outside [ 38 ].…”

“…In recent studies, BITC was reported to have absorption bands at 2140–2040 cm −1 attributed to the thiocyanate group and at 1600–1345 cm −1 ascribed to the benzene ring [ 10 , 38 ]. Moreover, the benzene ring of BITC was suggested to be entrapped in the cavity of γ−CD, whereas the thiocyanate moiety was exposed outside [ 38 ]. Another study entrapping BITC to β−CD reported a resemble inclusion complex pattern [ 39 ].…”

“…XRD analysis is a common and desirable method to measure and characterize the crystal structures of the test samples [ 42 ]. Since BITC under ambient temperature is at aqueous status, the XRD information of which is difficult to acquire [ 38 ]. The diffraction patterns of α−CD and BITC−α−CD were displayed in Figure 2 b.…”

Functional Chitosan-Based Composite Film Incorporated with 3-(Methylthio) Propyl Isothiocyanate/α-Cyclodextrin Inclusion Complex for Chicken Meat Preservation

“…In Figure 1 a, the feature absorption bands of α-CD appear at 3400 cm −1 , 2926 cm −1 , 1156 cm −1 , 1078 cm −1 , and 1028 cm −1 , which belonged to the O-H symmetric stretching vibration, C-H stretching vibration, C-O-C glycosidic bridge stretching vibration, and C-O/C-C stretching vibrations, respectively [ 29 , 30 ]. The FTIR spectrum of pure MTPITC has been illustrated in our recent report, in which the prominent peak, displayed at around 2140–2040 cm −1 , corresponded to the thiocyanate group (N=C=S) [ 31 ]. In the current study, after being encompassed in the α-CD, the characteristic absorption peaks of MTPITC at 2140–2040 cm −1 were still observed, suggesting that MTPITC exists in the inclusion complex.…”

Comparative Transcriptomic Analysis of Staphylococcus aureus Reveals the Genes Involved in Survival at Low Temperature

“…Staphylococcus aureus is a Gram-positive bacterium that infects the human body and produces enterotoxins [ 1 , 2 ]. According to a report by the Centers for Disease Control and Prevention [ 3 , 4 ], approximately 241,000 foodborne diseases are caused by S. aureus each year in the United States, and it is the third most prevalent foodborne disease in the world [ 5 ], as it is often present in frozen and refrigerated food, such as meat, aquatic products, and ice cream [ 6 ].…”