Phenolic content, antioxidant and allelopathic activities of various extracts of Thymus numidicus Poir. organs

- The polyphenol contents of various extracts of Thymus numidicus organs were studied.
- The highest amounts of polyphenol, flavonoid, flavonol and proanthocyanidin were shown by the leaf methanolic extracts.
- The level of antioxidant activity of all extracts was high.
- A significant correlation between radical scavenging capacities with total phenolic was revealed.
- The root extracts presented high shoot and root growth inhibition of M. sativa and T. æstivum plantlets.

Total phenol content, antioxidant and allelopathic properties of roots, steems and leaves extracts of Tunisian endemic T. numidicus were studied. Three solvent systems with varying polarities (petroleum ether, ethyl acetate and methanol) were used. The highest amounts of polyphenols (98.66 ± 3.17 mg EAG/g DW), flavonoids (54.28 ± 1.6 mg RE/g DW), flavonols (27.23 ± 1.71 mg RE/g DW) and proanthocyanidins (5.12 ± 0.8 μg cyanidin chloride/g DW) were shown by the polar subfraction of the leaf methanolic extracts. The efficiency of the solvents used to extract phenols from the three organs varied considerably. The level of antioxidant activity estimated by DPPH and ABTS test systems was high for leaf (IC50 = 11.06 ± 0.33 μg/ml; 235.46 ± 2.14 μg TE/mg DW) and stems (IC50 = 15.29 ± 0.9 μg/ml; 233.75 ± 1.2 μg TE/mg DW) methanolic extracts. A significant correlation between radical-scavenging capacities of extracts with total phenolic compound content was observed. The results also indicate that the root extracts inhibited the shoot and root growth of Medicago sativa and Triticum æstivum seedlings. Thus, the T. numidicus extracts may be used as a natural herbicide.