Atividade biológica em fungos endofíticos : análise cienciométrica da produção científica global e bioprospecção em espécies associadas a Palicourea rigida Kunth, uma planta medicinal do Cerrado

Abstract

Endophytic fungi inhabit the interior of vegetables, asymptomatically, establishing a mutualistic relationship with the host. It has been verified that this group of microorganisms produces metabolites and enzymes with great biological activity produced for biotechnology. The objective of this work was to promote a review of this global scientific on the biological activity in endophytic fungi and to prospect these properties in endophytic fungi associated with Palicourea rigida Kunth leaves. Popularly known as “bate-caixa”, “gritadeira” or “douradão”, this native plant from the Cerrado is considered medicinal, as it is popularly used to treat urinary disorders, female reproductive system and inflammation. From a search on the Web of Science platform, considering the terms (Fung* AND Endophytic) AND (Bioprospection OR Bio-prospection OR Prospecting OR Bioactivit* OR “Biological Activit*”) in the title, abstract or keywords, in the interval from 1997 to 2019, 458 scientific papers were found that meet the search criteria. The highest production occurred in 2018 (70 articles) and the highest average of citations per year occurred in 2006 (156 citations/article). The most frequent journal for Marine Drugs (16 publications) and the one with the highest H index (13) was found in the European Journal of Organic Chemistry. The largest amount of publication is in the area of Microbiology (52 articles). The most frequent keyword for natural products (cited 95 times). The most frequent authors were Barbara Schulz and Siergfried Draeger (16 articles each), both from the Braunschweig University of Technology in Germany. The affiliation of authors and co-authors is thought, China was the most frequent country to host research, cited in 412 articles, followed by Brazil (189 articles) and India (160 articles). Most of the bioassays took place in 2014, with 2018 being the year with the highest number of records (81 trials). Almost half of the articles (43%) proved antimicrobial properties, 29% proved anti-tumor properties, 9% proved enzymatic properties, 8% proved antioxidant properties, and 11% other activities. The temporal distribution of articles increased since the 2000s. With regard to the experimental component of the dissertation, there were four endophytic fungi, Colletotrichum sp. SXS649, Pestalotiopsis sp. SXS650, Botryosphaeriales SXS651 and Diaporthe sp. SXS652, from the leaves of three specimens of P. rigida, selected at the Ecological Reserve of the State University of Goiás (REC-UEG), for bioprospecting assays of biological activity. Among the secondary metabolites, the presence of phenols and flavonoids was found in all crops, in addition to the production of the enzymes amylases, cellulases, proteases and tanases. Thus, lower and moderate levels of antioxidant were detected by asking Colletotrichum sp., Pestalotiopsis sp., Botryosphaeriales and Diaporthe sp., corresponding to 5.6804; 22.4748; 11.8528; 27.4803 mg.mL-1, respectively, when free radical scavenging (DPPH) and 8.0917; 47.0602; 0; 32.2691 mol Fe2+.mg-1, respectively, when a reduction of ferrous sulfate (FRAP) is considered. The Botryosphaeriales isolate has a minimum inhibitory concentration (IMC) of 23.20 mg.mL-1 against Staphylococcus epidermidis and Pseudomonas aeruginosa; Diaporthe sp. 27.00 mg.mL-1 IMC against Escherichia coli. In the antitumor evaluation, Colletotrichum sp. presents 69% inhibition of tumors in potato discs at the concentration of 9.70 mg.mL-1. In the verification of bioremediation in soil contaminated with soybean oil, all isolates proved to be efficient in the treatment by inducing a reduction in phytotoxicity above 20% of Lactuca sativa. In the preliminary toxicity evaluation, all aggregates with high toxicity (LC50 <100 mg.mL-1) to the microcrustacean Artemia salina. Without plaque antagonism, all those present inhibited phytopathogenic fungi Aspergillus niger, Inonotus rickii, Pestalotiopsis mangiferae and Coniophora puteana, with percentages between 34.17 to 76.93%. The results obtained reveal that the studied endophytic fungi are promising candidates to be used in biotechnological processes, as therapeutic agents; in soil bioremediation processes; and in agriculture for the biological control of phytopathogenic fungi. However, further tests are needed to verify toxicity.