Structural characterization of phytochemical content, antibacterial, and antifungal activities of Juglans regia L. leaves cultivated in Algeria

Abstract

Many microorganisms cause diseases to plants, animals and humans. Recently, natural compounds extracted from different medicinal and officinal plants have had a promising antimicrobial potential. In this present study, the antifungal and antibacterial activities of Juglans regia leaves cultivated in Algeria have been evaluated. The chemical composition was analyzed by GCMS spectroscopy . 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 antibacterial activity was tested against five bacterial strains and the antifungal activity was tested against seven fungal strains . The GC-MS profile of ethyl acetate fraction (tannic extract) revealed the presence of many interesting biomolecules we note: Phenol (0.19%), gaiucol (0.16%), catechol (0.65%), 2-Methoxy-4-vinylphenol (1.77%), eugenol (0.78%), (E)-coniferol (0.66%), 1, 5-naphthalenediol (2.01%) and 5-hydroxy-1, 4-naphthalenedione or juglone (0.18%). The tannic extract (ethyl acetate fraction) presented a high antifungal activity on Aspergillus terreus , Aspergillus ochraceus and Aspergillus Brasilliensis ATCC 16404 with percentage of growth inhibition of 77,033 ± 3,395, 73,327 ± 3,851 and 71,850 ± 0,641 respectively for the highest concentration. It also showed an interesting antibacterial activity against Klebseilla pneumoniae ATCC 70063 with minimal inhibitory concentration of 3.125 μg/ml comparing to the hydro-acetonic extract(MIC value). Our finding provides for the first time the chemical profiling of this species grown in Algeria and also an efficient and targeted natural approach to the discovery of classes of antibacterial and antifungal compounds for various applications. • Juglans regia 's leaves harvested from Blida north, center, Algeria. • Preparation of alcoholic extracts: crude and tannic extract. • The extracts are a rich source of secondary metabolites such as: polyphenols and tannins. • Both extracts have an antibacterial and antifungal potential. • Tannic extract has a stronger effect comparing to the crude extract. • GC-MS analysis of the tannic extract showed the presence of a variety of biochemical components known for their biological effects.