Variations in phenolic composition and antioxidant activities of Scabiosa maritima (Scabiosa atropurpurea sub. maritima L.) crude extracts and fractions according to growth stage and plant part

This study aimed to assess for the first time how growing stage and plant part affect the phytochemical contents and antioxidant capacities of extracts and fractions of Scabiosa Atropurpurea sub. Maritima L. (S.maritima). An experiment was conducted on the different parts (leaves, stem, roots, inflorescences, and fruits) of plants collected from the Zaghouan region, Tunisia, at different growing stages: vegetative stage (March), early budding stage (April), late flowering stage (May) and late maturing stage (June). The various plant parts were subjected to hydro-methanolic extraction and sequential solvent fractionation (Chloroform and Acetate). For each extract or fraction, content of total phenolics (TPC), flavonol, tannin (CTC) and total flavonoids (TFC) were quantified. The antioxidant activity of different extracts was assessed using total antioxidant capacity (TAC), ferric reducing power (FRAP), 1, 1-diphenyl-2-picryl hydrazyl (DPPH) and 3-ethylbenzothiazoline-6-sulfonic acid (ABTS) radical scavenging activities. A Multiple Factor Analysis (MFA) and hierarchical clustering were done on the data set obtained from the various measurements. Additionally, the chemical composition of five selected crude extracts was determined by high performance liquid chromatography coupled with a diode array (HPLC-DAD). Phytochemical compounds (phenolic, flavonoids, flavonol and tannin) and antioxidant activities (TAC, FRAP, ABTS and DPPH) of S.maritima extracts and fractions differ among plant parts and change throughout the growing stages. The highest phytochemical content and antioxidant activities of plant parts during the different growing stages were mainly recorded in acetate fractions. Leaves generally exhibited higher phytochemical content and antioxidant activity compared to other plant parts. Their highest values were reached during flowering season (plants collected in May). Unlike leaves and stem, roots exhibited their highest phytochemical content and antioxidant activity in June. The MFA results distinguished leaf samples from the other plant parts and highlighted a strong correlation between phytochemical content and antioxidant capacity. High levels of catechin hydrate (ranging from 1951.86 to 6748.97 mg/100 g of extract) were recorded in all samples. Leaf samples were found to contain high amounts of luteolin-7-O glucoside and kaempferol-3-O-rutinoside while particularly high contents of resorcinol and catechol (226.00 and 57.71 mg/100 g of extract, respectively) were observed in the stem sample.