Antimicrobial and antioxidant activity of extracts from native strains of Trichoderma afroharzianum isolated from soil in Argentina

CALUMBY, R.J.N. ; ROCHA, F. ; BUTASSI, E. ; SVETAZ, L. A., .; SORTINO, M. A.; RIUS, S. ; CAMPOS-BERMUDEZ, V.A.

Congreso; 32 Congresso Brasileiro Microbiologia; 2023

In recent years, the increase in antimicrobial resistance has become a global health concern, driving the search for therapeutic alternatives. Natural products have emerged as valuable sources in the discovery of new drugs. Among them, filamentous fungi stand out as promising candidates due to their ability to synthesize various bioactive compounds. Specifically, the genus Trichoderma is recognized for producing a wide variety of secondary metabolites, many of which exhibit antibacterial, antifungal, anticancer, antioxidant, larvicidal, and anti-inflammatory activities. However, despite these remarkable characteristics, comprehensive research on the biological potential of metabolites derived from Trichoderma has not yet received the proper attention. Therefore, the objective of this study was to evaluate the antimicrobial and antioxidant potential of crude extracts from three native strains of Trichoderma afroharzianum isolated from soil in Argentina. For the preparation of the extracts, each strain of Trichodermawas cultivated in 200 mL of potato dextrose brothat 28°C with agitation (180 rpm) for a period of 20 days. After the cultivation time, the fermented material was filtered using a vacuum system to separate the mycelium from the culture supernatant. The obtained supernatants were subjected to liquid-liquid partitioning with ethyl acetate (three times) in a 1:1 ratio, while the mycelia were macerated with methanol for 72 hours, renewing the eluent solution every 24 hours. After the extraction process, the extracts were filtered and placed in a rotary vacuum evaporator at 40°C to obtain crude extracts. The antimicrobial activity of these extracts was tested against Staphylococcus aureus(ATCC 25923), Escherichia coli(ATCC 25922), and Candida albicans(ATCC 90028) using the disk diffusion and broth microdilution methods to determine the minimum inhibitory concentration (MIC).To evaluate the antioxidant activity, the DPPH (2,2-diphenyl-1-picrylhydrazyl) free radical scavenging method was employed.The results demonstrated that the majority of organic extracts obtained from the mycelium and culture supernatants of the three strains of T. afroharzianumexhibited a broad-spectrum antimicrobial activity, inhibiting Gram-positive bacteria (S. aureus), Gram-negative bacteria (E. coli), and the fungus C. albicans, resulting in inhibition zones ranging from 7 to 16 mm in the disk diffusion assay. Regarding the MIC, the extracts showed moderate activity against S. aureusand C. albicans, and low activity against E. coli. The lowest MICs were obtained from the culture supernatant extracts, with values of 125 µg/mL for S. aureusand 500 µg/mL for E. coli, while the mycelium extract of one of the strains presented a MIC of 250 µg/mL against C. albicans. In the antioxidant activity assay, the percentage of DPPH radical scavenging activity at different concentrations (7.8–1000 µg/mL) ranged from 12.88±0.45% to 39.67±0.78%, with the culture supernatant extracts exhibiting superior antioxidant activity compared to those obtained from the mycelium. These findings confirm the antimicrobial and antioxidant activity of T. afroharzianumand reinforce its biological potential as a source of active metabolites, which hold promise for future therapeutic applications. Furtherstudies are required to identify and characterize the key metabolites of Trichodermaassociated with its antimicrobial and antioxidant activities.