Seasonal effect on bioactive compounds recovery using aqueous extraction, antioxidant activities, and volatile profiles of different parts of S.maritima (Scabiosa atropurpurea sub. maritima L.)

The Scabiosa genus of the family Caprifoliaceae comprises around 100 species distributed mainly in the Mediterranean. Studies on Scabiosa species, incentivized by their wide use in folk medicine, highlighted their interesting phytochemical contents and biological activities. In this study, we investigated the antioxidant activity and phenolics contents of the aqueous extracts obtained from the different parts of Scabiosa maritima at four stages of development. Extraction was conducted by maceration, infusion, and decoction methods. Total phenolic content (TPC), total flavonoids content (TFC), condensed tannin content (CTC), flavonols content, ferric reducing power (RP), total antioxidant activity (TAC), and ABTS and DPPH scavenging activity were evaluated. Pigments (b-carotene, chlorophyll a, chlorophyll b, leukopene) contents of the different plant parts were also investigated as well as the chemical composition of essential oils obtained from leaves collected during April (pre-flowering stage) and inflorescence collecting during May (flowering stage). Mixed effect models were fitted to the different datasets, to elucidate the effect of the different intervening factors (organs, sampling date, and extraction method). The studied parameters have shown an organ-dependent variation, with leaves exhibiting in general the highest values. The analysis of random effect plots revealed an opposite behavior of leaves vs. stem and roots across time. Pigments, phenolics contents, and antioxidant activities were the highest in leaves during March, while they attained their peak during either April or June for stem and roots. The extraction method did not drastically affect the variation pattern of different variables across plant parts and sampling date, however, a significant effect on deviation magnitude was recorded. Infusion extraction generally assures the best recovery of phenolics from the different plant parts. Leaves and inflorescence essential oils exhibited a distinct chemical composition with only hexahydrofarnesyl acetone as the common compound. Leaves essential oil composition was dominated by apocarotenoid derivatives while pyridine derivatives were the group of the major compounds identified in inflorescence essential oil. Inflorescence essential oil was also characterized by a considerable amount of mescalin (5.66%). Repeated measure correlation (rmcorr) and multivariate analysis (MFA) highlighted respectively a moderate to strong correlation between extracts’ antioxidant activities and phenolics contents and confirm the opposite time evolution pattern displayed by roots and leaves regarding the different analyzed variables. The extreme position on the second axes of the factorial map, occupied by stems collected during June and roots collected during May highlighted the distinctively high antioxidant activities of their decoctions.