Evaluation of in vitro alpha-glucosidase inhibitory, antimicrobial, and cytotoxic activities of secondary metabolites from the endophytic fungus, Nigrospora sphaerica, isolated from Helianthus annuus

Preuttiporn Supaphon,Sita Preedanon

doi:10.1007/s13213-019-01523-1

Abstract

PurposeThis study aimed to evaluate alpha-glucosidase inhibition and antimicrobial activity as well as cytotoxic activity of extracts from the endophytic fungus, Nigrospora sp., isolated from leaves of Helianthus annuus, which is widely cultivated for food and used as a medicinal plant.MethodsThe fungus (TSU-CS003) was identified based on internal transcribed spacer ribosomal DNA sequences and fungal biomass, and fermentation broth was subjected to extraction by solvents (hexane and ethyl acetate). All extracts were tested for their antimicrobial activity, alpha-glucosidase inhibition, and cytotoxicity activity. In addition, the active extract was analyzed by using gas chromatography mass spectrometry (GC-MS)ResultsTSU-CS003 was identified as Nigrospora sphaerica. The fermentation broth extract (BE) showed strong antimicrobial activity against Staphylococcus aureus and methicillin-resistant S. aureus (Gram-positive bacteria) with minimum inhibitory concentration (MIC) values in the range of 16–32 μg/mL and a few yeasts with MIC values ranging from 64 to 128 μg/mL, especially Talaromyces marneffei with an MIC value of 4 μg/mL. The effects of BE were observed by SEM. The results showed that this extract affected the cell morphology of T. marneffei. The half-maximal inhibitory concentration (IC50) of BE from alpha-glucosidase inhibition was recorded as 17.25 μg/mL and also showed significant cytotoxicity against A549 human cancer cell lines with an IC50 value of 22.41 μg/mL. Furthermore, BE was analyzed by using GC-MS and divided into three main compounds, including 5-pentyldihydrofuran-2(3H)-one, (Z)-methyl 4-(isobutyryloxy)but-3-enoate, and 2-phenylacetic acid.ConclusionThis was the first report of the endophytic fungus N. sphaerica from H. annuus. It is a potential source of active metabolites, which gave the strong antifungal activity, antioxidant activity, and cytotoxicity to A549 cancer cell lines.

Highlights

The side effects of common standard agents are a critical point for patients and have become a serious medical concern worldwide
Plant samples were further cut into six 0.5 × 0.5 cm2 segments and placed in potato dextrose agar (PDA) supplemented with penicillin G and streptomycin (50 mg/mL) to suppress bacterial growth
The phylogenetic trees were constructed by maximum parsimony (MP) and maximum likelihood (ML) analyses

Summary

Introduction

The side effects of common standard agents are a critical point for patients and have become a serious medical concern worldwide. Many side effects of drugs have been reported (Shobha et al 2014; Al-Dhabi et al 2015). There is need to survey new sources of active metabolites. Plants have been screened for their biological activities (Katiyar et al 2012; Atanasov et al 2015). The discovery of many active metabolites from plants has occurred during the last decade, health problems are still a major concern and effective. Ann Microbiol (2019) 69:1397–1406 approaches are needed. One of the strategies to solve this issue is finding alternative sources of active secondary metabolites

Objectives

Methods

Results

Discussion

Conclusion