Nanoencapsulation of thymol in zein by simple coacervation for enhancement of free-radical scavenging and antimicrobial activities

Date

10-2013

Degree

Bachelor of Science in Chemistry

College

College of Arts and Sciences (CAS)

Adviser/Committee Chair

Evelyn B. Rodriguez

Restrictions

Restricted: Not available to the general public and to those bound by the confidentiality agreement. Access is available only after consultation with author/thesis adviser.

Abstract

Thymol, a naturally occuring bioactive compound, has benefits in nutraceutical, cosmeceutical, and post-harvest applications owing to its antioxidant, antibacterial, and antifungal properties. However, its use is limited by violatility and poor water solubility which decrease its bioactivity. In this study, thymol was encapsulated in zein to enhance free radical scavenging, antibacterial, and antifungal activities and to control its release. Extraction of milled yellow corn grits by 70% ethanol followed by defatting and decolorization afforded zein in 6.99% yield. The zein isolate had a specific gravitiy of 1.19 +0.03 and emulsifying activity of 59.73 + 2.71%. Emulsion stability determination revealed that zein can stabilize coconut oil emulsion by 89.08 + 0.34% after 15 days of storage. These properties indicated that zein could be an ideal wall material for encapsulation. Encapsulation of thymol in zein by simple coarvation allowed an encapsulation efficiency and loading efficiency of 67.99 + 0.22% and 15.22 + 0.05% respectively. Atomic force microcopy (AFM) showed that thymol particles had an average size of 99.84 + 22nm. The thymol nanoparticles were found to be stable after 40 days of storage under refrigerated condition (98.34 + 0.25%) and room temperature (97.35 + 0.27%). In vitro release studies in surfactant solution showed an initial burst release for the first hour (49.30 + 3.10%) followed by a controlled release up to 24 hours (77.58 + 0.16%). DPPH assay revealed that encapsulation promoted a 2-fold increase in free-radical scavenging activity of thymol. Encapsulation also enhanced the antimicrobial activity of thymol against gram-negative Escherichia coli, gram-positive staphylococcus aerus, and fungus Colletotrchum musae as shown by disc diffusion assay. E. coli was found to be more susceptible to thymol compared to S. aureus while fungus C. musae was the most resistant. At lower concentration of the core material, the activity of the nanoparticles was comparable to high concentration of spectinomycin. Results of the antifungal assay using banana fruits showed that thymol can be developed as a fingicidal agent for post-harvest applications. The encapsulated thymol was found to be more effective compared to non-encapsulated form as shown by the reduction of rot, fungal growth, and black spots after 10 days of storage at room temperature.

Language

English

Location

UPLB Main Library Special Collections Section (USCS)

Call Number

LG 993.5 2013 C42 /P86

Document Type

Thesis

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