Chemical Profiling and Geographic Differentiation of Ugandan Propolis by GC-MS Through Chemometric Modelling

Area of Science:

• * Analytical Chemistry
• * Natural Product Chemistry
• * Chemotaxonomy

Background:

• * Propolis, a bee-derived resin, possesses known bioactivity, necessitating detailed compositional analysis.
• * Geographical origin is hypothesized to influence propolis chemical makeup, but data remains limited.
• * Understanding regional variations is crucial for standardizing propolis quality and efficacy.

Purpose of the Study:

• * To comprehensively characterize the volatile and semi-volatile chemical constituents of Ugandan propolis.
• * To investigate geographical variations in propolis composition across nine agro-ecological zones.
• * To establish chemometric models for regional differentiation and identify chemical markers.

Main Methods:

• * Headspace gas chromatography-mass spectrometry (HS-GC-MS) for volatile compounds.
• * Derivatisation-based GC-MS for semi-volatile and non-volatile compounds.
• * Multivariate statistical analyses, including partial least-squares discriminant analysis (PLS-DA) and orthogonal PLS-DA (oPLS-DA), for data interpretation.

Main Results:

• * Identification of 213 volatile and 169 non-volatile compounds, including terpenes, triterpenoids, phenolic acids, and alkylresorcinols.
• * Significant geographical discrimination of propolis samples demonstrated by chemometric modelling (Q² > 0.90).
• * Identification of specific chemical markers differentiating propolis from various Ugandan districts, notably Nakasongola, Bushenyi, and Adjumani.

Conclusions:

• * The study provides the first extensive chemical profile of Ugandan propolis, highlighting regional chemical diversity.
• * Combined GC-MS techniques and multivariate analysis are effective tools for differentiating propolis by geographical origin.
• * This research supports the standardization of propolis preparations and the development of quality control measures for its pharmacological use.