Chemical characterization of Brazilian propolis using automated direct thermal desorption–gas chromatography–mass spectrometry

Abstract

Background Propolis, produced by honey bees, is used around the world, displaying several corroborated biological activities. Brazil is one of the leading producers of propolis, with a great diversity of types, each with a characteristically chemical fingerprint influenced by the flora of the local region. The secondary metabolite's composition of propolis strongly impacts its biological properties, and its chemical characterization is of great importance for its quality control. Several chromatographic techniques have been applied to characterize propolis, highlighting the extraction of its volatiles and its analysis through gas chromatography. Fourteen Brazilian propolis samples collected in five states, including brown, green and red propolis types, were chemically characterized using the automated direct thermal desorption–gas chromatography-mass spectrometry (DTD-GC-MS). Results Red propolis type was characterized by acyclic saturated hydrocarbons, fatty alcohols, terpenes, and phenylpropanoids as nonacosane, α-copaene, β-amyrin acetate, anethole, and 7-O-methylvestitol. Brown propolis presented hydrocarbons, mono, and sesquiterpenes, as α-pinene and α-bisabolol. Brazilian green propolis presented polycyclic aromatic hydrocarbons and sesquiterpenes, including 1-methyl-octahydroanthracene, 2,5-dimethyl-γ-oxo-benzenebutanoic acid, nerolidol, and spathulenol. Principal component analysis (PCA) was performed, allowing for clustering brown and red propolis types, indicating a divergence with the chemical composition of the green propolis samples. The Hierarchical Cluster Analysis (HCA) allowed differentiating the chemical fingerprint of each propolis type. Conclusions Red propolis was characterized by sesquiterpenes, pterocarpans, and isoflavans; brown propolis was characterized by hydrocarbons, aldehydes, and monoterpenes, while green propolis samples were characterized by the presence of polycyclic aromatic hydrocarbons, sesquiterpenes, and naphthalene derivatives.