Effect of phenological stages on yield, chemical composition and biological properties of essential oil from Thymus maroccanus Ball.

Abstract

The effects of phenological stages on the composition, antioxidant, insecticidal and allelopathic properties of essential oils (EOs) obtained from the aerial parts of Thymus maroccanus Ball. were evaluated. The GC-MS analysis identified that analyzed EOs were dominated by carvacrol (63.70 - 68.19 %) followed by p-cymene (6.09 - 9.67 %) and γ-terpinene (3.67 - 8.49 %). When carvacrol and p-cymene gradually increased from the lowest values (63.70% and 6.09%) at the pre-flowering stage to reach the highest ones (68.19% and 9.67%) at post-flowering stage, γ-terpinene gradually decreased from the highest proportion (8.49%) to the lowest (3.67%). EO from post-flowering aerial parts showed higher scavenging ability on DPPH radicals (% inhibition: 25.19 - 95.75 %; IC50 = 0.26 mg/mL), in contrast, the essential oil from pre-flowering stage exhibited the highest Fe³⁺ reducing power ability (Absorbance:  0.329 - 0.812; IC50 = 0.14 mg/mL). Insecticidal properties showed no substantial difference between T. maroccanus EO extracted at different growth stages. The LD50 and LD90 values were ranged from 0.15 to 0.17 µL/cm², and from 0.37 to 0.47 µL/cm², respectively in contact assays, as well as from 318.93 to 362.84 µL/L air, and from 725.08 to 739.12 µL/L air, respectively in fumigant assays. The results indicated that allelopathic activity of Eos is not greatly affected by growth developmental stages.