Identification and Bioactivity Analysis of Endophytic Fungi Isolated from Mangrove Plant (Sonneratia caseolaris)

Abstract

Endophytic fungi, or endophytes, exist widely inside the healthy tissues of living plants and are important components of plant micro-ecosystems. Microorganisms that live within the intracellular tissues of plants asymptomatically while maintaining a symbiotic relationship are referred to as endophytic fungi. Endophytes and their host plants have established a special relationship with one another, which can significantly influence the formation of metabolic products in plants and consequently affect the quality and quantity of crude drugs derived from medicinal plants. The purpose of this study was to isolate and identify endophytic fungi from the leaf tissues of Sonneratia caseolaris to determine their antibacterial, antioxidant, and cytotoxic activities. Six endophytic fungi—Wardomyces moseri, Simplicillium clavatum, Alternaria destruens, Alternaria porri, Diaporthe recera, and Apicoccum nigrum—were isolated from the leaves of the mangrove plant Sonneratia caseolaris. Among all the extracts, CHL 01, CHL 03, CHL 04, CHL 05 (EtOH/ethyl acetate), and CHL 08 (MeOH) showed very good antioxidant activity, with the lowest IC₅₀ values compared with ascorbic acid (10.9730 μg/ml), which was used as the standard. Other extracts showed mild to moderate activity with higher IC₅₀ values. All the crude extracts of the endophytic fungi from Sonneratia caseolaris were tested for antibacterial activity against two Gram-positive and Gram-negative bacteria. A standard erythromycin disc (10 μg/disc) was used for comparison. The results showed high zones of inhibition at concentrations of 500 μg/disc and 1000 μg/disc, while the concentration of 100 μg/disc showed a poor zone of inhibition. Among all the extracts, good activity with low LC₅₀ values was observed against nauplii. Among them, CHL 01 (Wardomyces moseri spp.), CHL 03 (Alternaria destruens), and CHL 08 (Apicoccum nigrum) showed the maximum activity with low LC₅₀ values against the nauplii.