The objective of this work was the recovery of chitosan by ultrasound-assisted extraction (UAE) from white shrimp (Litopenaeus vannamei) chitin, and the physicochemical and structural characterization of the obtained biopolymer, as well as its antimicrobial effect on Pythium ultimum growth. A 2³ factorial design was used to evaluate chitosan extraction conditions. Instrumental analysis techniques for chitosan characterization and radial growth inhibition, as an antifungal activity test, were performed. The ultrasonically extracted chitosan (UC) reached a yield of 86.96% with 100% solubility, a degree of deacetylation (DDA) >78%, molecular weight (M_W) of 3.928 × 10⁵ g mol⁻¹, and a crystallinity index (Icr) of 87%, calculated through nuclear magnetic resonance (¹H NMR) and Fourier transform infrared spectroscopy (FTIR), size exclusion chromatography (SEC), and X-ray diffraction (XRD), respectively. The inhibitory activity of the chitosan was evaluated against the oomycete Pythium ultimum, observing a 93% radial inhibition over 24 h. UAE proved to be an excellent alternative to the conventional deacetylation, reducing reaction time and obtaining a UC with higher M_W and (Icr) than the commercial one, which could potentiate its applications.

The physicochemical properties, proximate composition, minerals, total polyphenols, carotenoids, phenolic compounds, antioxidant, and antibacterial activities of ciricote (Cordia dodecandra A. DC.) tropical fruit were investigated. Minerals were quantified by using micro-Energy Dispersive X-Ray Fluorescence. Lutein and β-carotene were identified in ciricote fruit by using UPLC-PDA analysis. The highest values of the total polyphenols content and antioxidant activity were presented in ethanolic crude extracts obtaining by the ultrasonic-assisted method with freeze-dried fruit. The phenolic acids profile was identified and quantified by UPLC-PDA-ESI-MS. The main phenolic acids were caffeoyl hexoside, rufescenolide, quercetin 3-O-rutinoside, and rosmarinic acid. The ciricote extracts presented antibacterial activity against Staphylococus aureus (Gram+) and Salmonella typhymurium (Gram−). In conclusion, the ciricote (Cordia dodecandra A. DC.) tropical fruits could be very useful source of biological macromolecules, micro-elements, and phytochemical compounds for the food and pharmaceutical industry.