Chemical composition and evaluation of antioxidant and antimicrobial activities of Tunisian Thymelaea hirsuta with special reference to its mode of action

In the present study, we evaluated in vitro antimicrobial and antioxidant properties of Thymelaea hirsuta extracts as well as its phytochemical composition. Total phenolic and flavonoid contents were highest in acetone and ethyl acetate extracts respectively. The different extracts were tested against a panel of microorganisms, food-borne bacteria and spoilage fungi, in order to evaluate the antimicrobial properties of this plant. Among the tested extracts, only the ethyl acetate one exhibited antibacterial and antifungal activities. Acetone extract showed only an antibacterial activity. The investigation of the mode of action of the active ethyl acetate extract by the time-kill curve showed a drastic bactericidal effect after 5 min using a concentration of 624 μg/ml. Also, it appears that the ethyl acetate extract is an antifungal agent with a cellular target includes the pump H+-ATPase. The antioxidant activities of the different extract were evaluated using DPPH, lipid peroxidation and hydroxyl radical scavenging methods. From the obtained results it can be noticed that ethyl acetate and acetone extracts exhibited the best performance. The major phenolic compounds of the ethyl acetate extract of T. hirsuta were identified by Gas chromatography–mass spectrometry (GC–MS). A total of 16 compounds were characterized including p-hydroxybenzoic, p-coumaric, ferulic and caffeic acids known to have various biological activities.

► T. hirsuta ethyl acetate extract showed strong antimicrobial activity.
► The time-kill kinetics showed a bactericidal effect against Bacillus cereus.
► The fungicidal action for A. flavus showed an inhibition of the H+-ATPase.
► Ethyl acetate and acetone extracts exhibited strong antioxidant activities.
► GC-MS analysis of the active extract revealed the presence of 13 phenolic acids.