Phytochemical Screening and Antioxidant Activity of Selected Estonian Galium Species

Abstract

The aim of the present study was to examine three different <i>Galium</i> species from the native population of Estonia, <i>Galium verum</i>, <i>Galium aparine</i>, and <i>Galium mollugo</i>, to characterise their non-volatile and volatile phytochemical composition and antioxidant activity. The main groups of bioactive compounds in the plants were quantified by colorimetric tests, showing high concentrations of polyphenols (up to 27.2 ± 1.5 mg GAE/g), flavonoids (up to 7.3 ± 0.5 mg QE/g) and iridoids (up to 40.8 ± 2.9 mg AE/g). The species were compared using HPLC-DAD-MS/MS, revealing some key differences in the phytochemical makeup of the extracts. The most abundant compound in the extracts of <i>Galium verum</i> blossoms and herb was found to be asperuloside, in <i>Galium aparine</i> herb, asperulosidic acid, and in <i>Galium mollugo</i> herb, chlorogenic acid. Additionally, the composition of volatile compounds was analysed by SPME-GC-MS. The degree of variability between the samples was high, but three volatiles, hexanal, anethole, and <i>β</i>-caryophyllene, were quantified (≥1%) in all analysed samples. The antioxidative activity of all extracts was evaluated using the ORAC_FL method, demonstrating that the <i>Galium</i> species from Estonia all exhibit strong antioxidant capacity (up to 9.3 ± 1.2 mg TE/g). Out of the extracts studied, <i>Galium verum</i> blossoms contained the highest amounts of bioactives and had the strongest antioxidant capacity.