Isolation and Identification of Endophytic Fungi with Acetylcholinesterase Inhibitory Potential from Bacopa Monnieri

Abstract

Endophytic fungi are the source of potent bioactive compounds resides in medicinal plants with various bioactivities like anti-acetylcholinesterase, antifungal, antibacterial, and antioxidant etc. In the current study, the medicinal plant Bacopa monnieri was selected for the isolation of the endophytic fungi. A total of seven endophytic fungi isolated from B. monnieri. The crude extracts from these fungal isolates have been evaluated for preliminary acetylcholinesterase inhibitory and antioxidant activities. Among the seven crude extracts the maximum acetylcholinesterase inhibitory activity of 64.10% was shown by the fungal extract BM-16 at 250 μg/ml followed by BM-6, with inhibitory activity of 60% at 125 μg/ml, in comparison to DPZ, which was used as a reference compound. The fungal crude extracts were also tested for antioxidant activity. Among these 7 selected fungal isolates, BM-6 showed maximum antioxidant activity of 75.51% and BM-16 58.29 % at 250 μg/ml. The fungal extract BM-6 revealed the presence of condensed tannins, alkaloids, flavonoids, steroids, glycosides, and triterpenoids, and the fungal extract BM-16 showed the presence of alkaloids, steroids, glycosides, saponins, and triterpenoids. BM-6 and BM-16 were selected for further analyses. TLC was done by selecting an appropriate solvent system. Column chromatography was also performed for the selected fungal isolates. After purification via column chromatography, total of 11 fractions obtained, 4 from BM-6 and 7 from BM-16. Out of these fractions, fraction F-4 from fungal extract BM-6 and fractions F-6 and F-7 from fungal extract BM-16 showed maximum acetylcholinesterase inhibitory activity of 61.75%, 71.70%, and 73.17% at 160 μg/ml of concentration, respectively. Out of these 3 selected fractions, fraction F7 of BM-16 showed the maximum acetylcholinesterase inhibitory activity of 73.17%. The same fraction was analyzed using UV-spectroscopic, HRMS and FTIR analyses. Endophytic fungus BM-16 was identified through microscopic and molecular techniques and it was observed that BM-16 showed morphology similar to Alternaria tenuissima. Molecular and phylogenetic analysis confirmed that BM-16 was Alternaria tenuissima.