Abstract
Oregano essential oil (EO) enteric release powder was formulated by spray drying feed emulsions stabilized with polysaccharides (PSC) and Eudragit® L100 (PLM). Different modified starches were used in the PSC component. Spray-dried powders were evaluated for particle size and morphology, dynamic packing, flowability, chemical interactions, reconstitution, and gastric protection. Feed emulsions were stable, indicating the good emulsification ability of the PLM/PSC combination. The presence of polymer in the encapsulating wall neutralized electrostatic charges indicating physical attraction, and FTIR spectra showed peaks of both PLM and PSC without significant shifting. Furthermore, the presence of polymer influenced spray drying, resulting in the elimination of surface cavities and the improvement of powder packing and flowability, which was best when the surface-active, low-viscosity sodium octenyl succinate starch was used (angle of repose 42°). When a PLM/PSC ratio of 80/20 was used in the encapsulating wall, the spray-dried product showed negligible re-emulsification and less than 15% release in pH 1.2 medium for 2 h, confirming gastric protection, whereas at pH 6.8, it provided complete re-emulsification and release. In conclusion, (1) polymer–PSC physical interaction promoted the formation of a smoother particle surface and product with improved technological properties, which is important for further processing, and (2) the gastro protective function of Eudragit® L100 was not impaired due to the absence of significant chemical interactions.
Highlights
Essential oils are widely exploited as natural antimicrobials due to their accepted safety and efficacy profiles [1,2]
Later studies have demonstrated antiviral activity of essential oil (EO) against a range of human/animal viruses: Gilling et al [6] and Sánchez et al [7] demonstrated that EO inactivated murine norovirus (MNV) and other enteric viruses such as the picornaviruses, caliciviruses, astroviruses, and hepatitis by acting directly on the viral capsid; Pilau et al [8] demonstrated the activity of EO against bovine viral diarrhea virus (BVDV); Choi et al [9] showed activity against anti-enterovirus
From the above published data, it seems that the EO activity is exerted on pathogens that mainly reside in the intestine, and this has been demonstrated in vivo: Zou et al showed that EO-treated pigs had lower E. coli population in the jejunum, ileum, and colon due to the promotion of intestinal barrier integrity [11]
Summary
Essential oils are widely exploited as natural antimicrobials due to their accepted safety and efficacy profiles [1,2]. Katsoulos et al showed that the administration of oregano EO in calves prevented neonatal diarrhea syndrome and reduced mortality by inhibiting coliform bacterial overgrowth in the small intestine due to its antibacterial activity against E. coli [12]. These results prove that in order to release its full potency, EO should be delivered directly to the intestine. Since its main constituent carvacrol, which is responsible for the antimicrobial activity, is partly absorbed in the gut after oral administration [13], less amount reaches the intestine, reducing the therapeutic efficacy. A microencapsulated EO oral formulation is needed to provide gastric protection and enteric release, besides masking the bitter taste and protecting the EO bioactive ingredients during processing, transportation, and storage
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