Encapsulating within zein/trehalolipid nanoparticles (Z/TL) via NaOH/phytic acid-driven method (PAPD) can improve water solubility and stability of carvacrol (CAR). However, this technique still has limitations including empirically determined parameters and potential risk of core material degradation. In this respect, we introduced a strategy of positioning dual critical pH based on specific attributes of wall and core materials. The finest alkalization endpoint for Z/TL was determined by monitoring conformational changes across pH 7–12. Meanwhile, the suitable pH of deprotonation was identified by assessing pH-dependent water solubility and chemical stability of CAR. Obtained information was applied to modify PAPD into PAPD’. The colloidal properties, encapsulation efficiency (EE), loading capability (LC), environmental stress resistance, and in vitro release behavior of nanoparticles prepared using PAPD’ and PAPD were systematically compared. The optimal alkalinization endpoint for Z/TL was determined to be pH 11.25. where the degree of hydrolysis would not increase further, but the acceleration of increase in aqueous solubility would reach its maximum. The optimal pH of deprotonation for CAR was pH 11, balancing high solubility with controllable degradation. PAPD’-nanoparticles exhibited a smaller size (99.36 nm), higher ζ-potential (−43.91 mV), and improved EE/LC (97.95 %/29.39 %). Enhanced stability, along with a sustained release profile were demonstrated. Consumption of NaOH/PA was also reduced while maintaining required efficacy. Overall, customized PAPD’ not only improves the processing adaptability and flexibility of fabricating protein-based nanoparticles but also provides a theoretical framework and practical paradigm for the rational design of nanocarriers for bioactive compounds.
Summary Temperature-sensitive polyurethane (TSPU) films incorporated with carvacrol and cinnamyl aldehyde were prepared for the potential use of food packaging. The antimicrobial properties and sustained release kinetics of carvacrol and cinnamyl aldehyde in TSPU film were investigated. Results indicated that cinnamyl aldehyde and carvacrol had favourable antimicrobial properties at relatively low addition ratio. The diffusion and release of carvacrol were linearly related to temperature and its addition ratio. The release rates of carvacrol from TSPU film increased from 0.6% to 2.2% with the increase of addition ratio and temperature. The first-order kinetic equation could be used to describe its diffusion and sustained release process. TSPU films could significantly prolong the shelf life of Cantonese-style moon cakes by effectively inhibiting microbial growth and decreasing lipid oxidation comparing with commonly used polyethylene food packaging. Results obtained in the present work can provide technical guide of sustained release food packaging films with antimicrobial properties.
Carvacrol expresses a wide range of biological activities, but the studies of its mechanisms focused on bacteria, mainly involving the destruction of the plasma membrane. In this study, carvacrol exhibited strong antifungal activities against several phytopathogenic fungi and determined a novel antifungal mechanism against Lasiodiplodia theobromae. RNA sequencing indicated that many genes of L. theobromae hyphae were predominately induced by carvacrol, particularly those involved in replication and transcription. Hyperchromic, hypsochromic, and bathochromic effects in the UV-visible absorption spectrum were observed following titration of calf thymus DNA (ctDNA) and carvacrol, which indicated the formation of a DNA–carvacrol complex. Circular dichroism (CD) spectroscopy indicated the response of DNA to carvacrol was similar to 4’, 6-diamidino-2-phenylindole (DAPI), but different from that of ethidium bromide (EB), implying the ionic bonds between carvacrol and ctDNA. Fluorescence spectrum (FS) analysis indicated that carvacrol quenched the fluorescence of double-stranded DNA more than single-stranded DNA, indicating that carvacrol mainly bound to double-stranded DNA. A displacement assay showed that carvacrol reduced the fluorescence intensity of the DNA–DAPI complex through competing with DAPI, but this did not occur for DNA–EB. FS assay revealed that carvacrol bound to AAA sequence on the minor groove of ds-oligonucleotides. The hydroxyl of carvacrol was verified to bind to ctDNA through a comparative test in which structural analogs of carvacrol, including thymol, 4-ethyl-1,2-dimethyl, etc. were analyzed. The current study indicated carvacrol can destruct plasma membranes and bind to the minor groove of DNA, which inhibited the fungal proliferation by disturbing the stability of dsDNA.
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