Comprehensive Study of Mediterranean (Croatian) Propolis Peculiarity: Headspace, Volatiles, Anti‐Varroa‐Treatment Residue, Phenolics, and Antioxidant Properties

Abstract

Eight propolis samples from Croatia were analyzed in detail, to study the headspace, volatiles, anti-Varroa-treatment residue, phenolics, and antioxidant properties. The samples exhibited high qualitative/quantitative variability of the chemical profiles, total phenolic content (1,589.3-14,398.3 mg GAE (gallic acid equivalent)/l EtOH extract), and antioxidant activity (11.1-133.5 mmol Fe(2+) /l extract and 6.2-65.3 mmol TEAC (Trolox® equivalent antioxidant capacity)/l extract). The main phenolics quantified by HPLC-DAD at 280 and 360 nm were vanillin, p-coumaric acid, ferulic acid, chrysin, galangin, and caffeic acid phenethyl ester. The major compounds identified by headspace solid-phase microextraction (HS-SPME), simultaneous distillation extraction (SDE), and subsequent GC-FID and GC/MS analyses were α-eudesmol (up to 19.9%), β-eudesmol (up to 12.6%), γ-eudesmol (up to 10.5%), benzyl benzoate (up to 28.5%), and 4-vinyl-2-methoxyphenol (up to 18.1%). Vanillin was determined as minor constituent by SDE/GC-FID/MS and HPLC-DAD. The identified acaricide residue thymol was ca. three times more abundant by HS-SPME/GC-FID/MS than by SDE/GC-FID/MS and was not detected by HPLC-DAD.

Mediterranean Propolis from the Adriatic Sea Islands as a Source of Natural Antioxidants: Comprehensive Chemical Biodiversity Determined by GC-MS, FTIR-ATR, UHPLC-DAD-QqTOF-MS, DPPH and FRAP Assay

“…The major compounds reported in most samples of Croatian propolis were phenolic acids (ferulic, p-coumaric acid) and flavonoids (galangin, pinocembrin, chrysin) [16,18,[76][77][78]. These findings are very similar to the profiles of RP, K1P and K3P from the current study.…”

“…Comparison of the obtained results with other reports on Croatian propolis was not possible, due to the different extraction, methodology or way of data presentation [18,78,125,126].…”

“…Thymol was the most abundant in K3P HS (10.1-39.9%). However, thymol is not a typical propolis constituent and can be connected with anti-Varroa treatment [18,59]. Typical sesquiterpenes were found in EO (K1P;…”

“…These findings are very similar to the profiles of RP, K1P and K3P from the current study. However, Croatian samples that did not contain these compounds were also reported, demonstrating occurrence of different propolis types in Croatia [16,18]. Saftić et al recently reported LC-MS analysis of propolis from different regions of Croatia, including Mediterranean samples.…”

Comparative analysis of volatile compound profiles of propolis from different provenances

“…A mixture of aliphatic hydrocarbons (C7–C30) in n ‐hexane (Sigma–Aldrich) was coinjected under the same chromatographic conditions to calculate the linear retention index or Kovats index of each compound. The percentage relative amount of the individual components was expressed as per cent peak area relative in agreement with previous papers on the gas chromatography (GC) composition of propolis . The compounds were quantified by the external standard method.…”