Date of Completion

2024

Document Type

Thesis

Degree Name

Bachelor of Science in Biochemistry

Keywords

Aggregation-Induced Emission fluorogens (AIEgens), Citrus Maxima

Abstract

Aggregation-induced emission (AIE) fluorogens exhibit enhanced and stable fluorescence upon aggregation, in contrast to conventional fluorophores, which typically undergo fluorescence quenching under similar conditions. In this study, various parts of the pomelo fruit (Citrus maxima), specifically the pulp, lamella, and peel, were screened for potential AIE activity. Among the three, only the peel extract demonstrated fluorescence, warranting its selection for further compound isolation and characterization. The crude extract was obtained via ethanol extraction and subsequently subjected to column chromatography using a 7:3 ethyl acetate–hexane solvent system to isolate and purify the target compound. Fractions 4 and 5 (Rf = 0.854) and fractions 29 to 32 (Rf = 0.882) exhibited bright blue fluorescence, consistent with the emission observed in the crude extract. Fractions 4 and 5 were more pronounced and better resolved, indicating a potentially higher concentration of the target compound and lower contamination from other constituents. Fractions 4 and 5 were analyzed using proton NMR and carbon NMR for structural elucidation. The proton NMR spectra did not match known compounds typically found in pomelo peel, suggesting the presence of a compound mixture. The carbon NMR spectra primarily showed signals corresponding to ethyl acetate, likely due to low analyte concentration relative to the solvent, which may have masked the carbon signals of the target compound. The UV-Vis spectroscopy of the isolated fraction revealed a maximum absorption (λmax) at 323 nm, indicating the presence of non-extensive conjugation. Fluorescence measurements using a microplate reader showed a decrease in fluorescence intensity with increasing hexane concentration, suggesting that the isolated compounds do not exhibit typical AIE behavior. Further characterization using high-resolution mass spectrometry (LC-MS QTOF) is recommended to determine the exact molecular composition and confirm the identity of the compounds present in fractions 4 and 5.

First Advisor

Margel C. Bonifacio, RCh, PhD

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