Valorisation of Roman chamomile (Chamaemelum nobile L.) herb by comprehensive evaluation of hydrodistilled aroma and residual non-volatile fractions

Valorization of botanicals for the development of natural food-grade ingredients is an important task in terms of sustainability and processing waste reduction. In this study, Roman chamomile (Chamaemelum nobile L.) herb was collected at six different vegetation phases in the period 26 May - 23 August 2019 and subjected to biorefining into the several valuable fractions. The yield of hydro-distilled essential oil (EO) was in the range of 0.22% (intensive vegetative growth) to 0.80% (full flowering). Angelic, isobutyric, butyric and methacrylic acid esters and some monoterpene and sesquiterpene derivatives were the major EO constituents: 3-methylpentyl angelate (20.11-27.56%), methallyl angelate (7.28-10.33%), isoamyl angelate (5.57-9.02%), isobutyl angelate (4.84-6.79%), 2-methylbutyl angelate (3.11-6.32%), 3-methylamyl methacrylate (5.04-6.17%), 3-methylpentyl isobutyrate (4.29-6.64%), 3-methylamyl isobutyrate (4.29-6.64%), α-pinene (1.61-6.37%) and pinocarvone (1.46-4.67%). In order to valorize water soluble and solid EO distillation residues their antioxidant potential was evaluated by several in vitro assays: water extracts were considerably stronger antioxidants than acetone extracts isolated from the solid residues. Water extracts of the plants collected at flowering phases were the strongest antioxidants; their TPC, FRAP and ORAC values were up to 143.2 mg gallic acid equivalents/g, 650, and 5601 μmol TE/g dry extract, respectively, while effective concentrations (EC₅₀) of DPPH^• and ABTS^•+ scavenging, were down to 0.59 and 0.49 mg/mL, respectively. Among 7 tentatively identified by UPLC/Q-TOF/MS phenolic constituents the intensity of molecular ion of 3,5-dicaffeoyl quinic acid was the largest. The results obtained may assist for developing flavorings, antioxidants and health beneficial preparations from C. nobile extracts.