Variability of phenolic contents, antioxidant and antimicrobial activities of Inula crithmoides from Tunisia

Inula crithmoides L. is a spontaneous halophyte thriving on waterlogged zones. This species is harnessing edible, medicinal, aromatic and economic potentialities. In fact, this plant is known for its richness on bioactive compounds, mainly on essential oils. In this study, we tried to carry out the richness of this species on phenolic compounds and to evaluate their biological activities. Different parts of the plant were collected from Kairouan (center of Tunisia) air dried, grounded to a fine powder then subjected to a selective extraction with petroleum ether, acetone 60% then ethyl acetate in order to have a phenolics enriched fraction. Dried extracts were dissolved in methanol to be used in the colorimetric quantification of phenolics and to estimate their antioxidant activities (DPPH, total antioxidant activity, reducing power and inhibition of the β-carotene bleaching tests) and antibactrial activity against four human pathogenic bacteria. Results revealed that I. crithmoides extracts contain interesting amounts of these phytochemicals, significantly variable within the different plant parts, with highest amounts recorded in flower extracts. Besides, the entire investigated antioxidant test showed that I. crithmoides extracts exhibited high antioxidant activities, especially flower extracts. The effect of I. crithmoides extracts on the degree of inactivation of selected food borne pathogenic bacteria was variable and depended on the strains in question and on the part of the plant. These finding suggest that I. crithmoides is an interesting source of phenolics having antioxidant and antibacterial potentialities allowing them to be used as preservative ingredients in the food, pharmaceutical, and cosmetic industry.

Keywords: Inula crithmoides, phenolic compounds, biological activities