Phenolic composition and biological activity of endophytic fungi isolates inhabited Acacia nilotica

This study aimed to screen the phenolic profile, antimicrobial and antiradical activities of endophytic fungi residing in the tissues of Acacia nilotica grown in Sudan. Isolates of endophytic fungi were isolated from fruit, leaf and twig. Methanolic extracts were prepared by maceration. Antimicrobial activity was determined by the disc diffusion method. Antiradical activity was evaluated by the 1, 1-diphenyl-2-picryl hydrazyl (DPPH) assay. Ten endophytic fungi were recovered from the twig (6), leaf (2) and fruit (2) of A. nilotica. Extracts revealed better antifungal activity, with isolates T3, L1 and F1 exerting the highest inhibition zones (20.6, 20 and 18.3 mm, respectively) against Aspergillus niger. Isolates T4 and T5 revealed the highest antiradical effect with IC50 values of 302 and 478 µg/mL respectively. Chemical analysis revealed that gallic acid and naringenin were the dominant compounds. Their pattern divided the endophytic fungi into two categories; gallic acid- rich endophytes including isolates L1 and L2 (isolated from the leaf) as well as isolates T4 and T2 (isolated from the twig). The other category was naringenin- rich endophytes comprised isolates F1 and F2, which were isolated from the fruit, and isolates T1, T3, T5 and T6 isolated from the twig. Moreover, extracts accumulated gallic acid were devoid of naringenin and the opposite was true. This behavior was not detected in the host plant where these two compounds coexist and identified in all extracts.