Phytochemical Screening and Antioxidant Activity of Selected Estonian Galium Species

The aim of the present study was to examine three different Galium species from the native population of Estonia, Galium verum, Galium aparine, and Galium mollugo, 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 Galium verum blossoms and herb was found to be asperuloside, in Galium aparine herb, asperulosidic acid, and in Galium mollugo 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 β-caryophyllene, were quantified (≥1%) in all analysed samples. The antioxidative activity of all extracts was evaluated using the ORAC_FL method, demonstrating that the Galium species from Estonia all exhibit strong antioxidant capacity (up to 9.3 ± 1.2 mg TE/g). Out of the extracts studied, Galium verum blossoms contained the highest amounts of bioactives and had the strongest antioxidant capacity.