Exploring the antifungal properties of tannin extracts from Olea europaea var. rougette leaves against Aspergillus spp.

Abstract

Due to significant health risks associated with chemical antifungal agents in food storage, safe and natural sources are now one of the most frequently demanded ingredient for food preservation. Byproducts from olive trees provide an affordable and sustainable source of bioactive chemicals. This study will examine the mycelial growth and germination-inhibitory properties of Olea europaea var. rougette leaves and characterize their phytochemical makeup.The phytochemical screening revealed the presence of polyphenolics compounds mainly tanins.The chemical composition was analyzed by gas chromatography mass spectrometry (GCMS). Total polyphenolic content (TPC), hydrolysable tannins content (HTC) and condensed tannin content (CTC) were assessed using Foilin ciocalteu, potassium iodide and vanilline methods, respectively. The mycelial growth and germination inhibition properties were examined on soft wheat based solid and liquid media. Tannic extract (ethyl acetate extract) revealed highest amounts in polyphenols, hydrolysable tanins and condensed. GC–MS profile of tannic extract showed the presence of 26 bioactive molecules known for their antifungal potential, mainly: Guaiacol (0.12%), 2-methoxy-4-vinylphenol (1.52%), Syringol (0.18%), p-tyrosol (4.70%), homovanillyl alcohol (1.32%), 4-propylresorcinol (1.07%), β-camphor (0.17%), β-turmerone (1.57%) and 4-phenyl-quinolin-2-ol (6.58%). The tannic extract (ethyl acetate fraction) showed significant mycelial growth and germination inhibition activities in contrast to hydro-acetonic and dichloromethanic extracts. Furthermore, myelial growth inhibition showed more effectiveness in comparison to germination inhibition technique.The results suggested that byproducts of Olea europaea var. rougette leaves are a substantial natural source of bioactive compounds, especially tannins with potent antifungal characteristics in vitro which make it interesting to investigate its effectiveness in vivo.