Chemical variability of Centaurium erythraea essential oils at three developmental stages and investigation of their in vitro antioxidant, antidiabetic, dermatoprotective and antibacterial activities

This work is aimed the study of volatile compounds of Centauruim erythraea Raphin at three developmental stages (vegetative, flowering and post-flowering) and the investigation of their in vitro antioxidant, antidiabetic, dermatoprotective and antibacterial properties. The chemical composition of Centauruim erythraea essential oils (CEEO) was determined using GC/MS analysis. 39 volatile compounds were identified, belonging mainly to oxygenated monoterpenes, 51.63%, 44.10% and 53.69% at the vegetative, flowering and post-flowering stage, respectively. Menthol, carvacrol and tricosane were the main compounds of CEEO at the three developmental stages. The antioxidant effects of CEEO were determined by DPPH, FRAP and ABTS assays. CEEO at the flowering stage showed the best antioxidant effects by an IC50 = 47.18 ± 3.62 μg/mL, IC50 = 53.25 ± 2.19 μg/mL, IC50 = 65.34 ± 3.71 μg/mL determined by DPPH, FRAP and ABTS assays, respectively. The in vitro antidiabetic effect was evaluated by α-amylase and α-glucosidase enzymes inhibitory. CEEO at vegetative stage demonstrated a remarkable α-amylase (IC50 = 31.91 ± 0.336 μg/mL) and α-glucosidase (IC50 = 56.77 ± 1.02 μg/mL) inhibitory activities. Moreover, CEEO at the flowering and post-flowering stage strongly inhibited the tyrosinase enzyme with IC50 of 41.863 ± 0.031 μg/mL IC50 = 49.183 ± 0.298 μg/mL, respectively. The antibacterial effects were evaluated by determining the diameters of inhibition, the minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC). CEEO showed important antibacterial inhibition at three seasonal stages and particularly against Staphylococcus aureus and Listeria monocytogenes. Moreover, CEEO at post-flowering stage presented bactericidal effects especially against S. aureus (MIC = MBC = 0.125% (v/v)), L. monocytogenes (MIC = MBC = 0.125% (v/v)), and Proteus mirabilis (MIC = MBC = 0.125% (v/v)). The results obtained in this study show that the biological properties of CEEO are mainly depending to phenological stages, during which volatile bioactive synthesis occurs.