Antimicrobial constituents of Hypocrea virens, an endophyte of the mangrove-associate plant Premna serratifolia L.

Abstract

Emergence of multidrug-resistant pathogenic microorganisms has prompted a worldwide search for new antibiotics from various sources. Endophytic fungi from unique habitats are considered as potential sources of novel bioactive compounds. Sri Lankan mangrove ecosystem is such a distinctive and unexploited resource for the discovery of structurally diverse and biologically active metabolites including antimicrobials. Nine endophytic fungi were isolated from the leaves and twigs of Premna serratifolia L. from a mangrove habitat in the Negombo lagoon and the antimicrobial activities of their laboratory cultures were evaluated. The most promising antimicrobial activity was exhibited by the endophytic fungus Hypocrea virens. Bioassay guided fractionation of the organic extract of this fungus led to the isolation of two known metabolites; the antimicrobial epidithiodioxopiperazine, gliotoxin (1), and the closely related but less active bisdethiobis(methylthio)gliotxin (2). The chemical structures of the two compounds were determined by spectroscopy and confirmed by comparison of mass and nuclear magnetic resonance (NMR) spectral data with the reported values for these molecules. The minimum inhibitory concentration (MIC) values obtained for gliotoxin (1) in the current study are 0.13 µg mL -1 for Bacillus subtilis, 16 µg mL -1 for Staphylococcus aureus, 32 µg mL -1 for Methicillin Resistant Staphylococcus aureus (MRSA) and Escherichia coli, 64 µg mL -1 for Pseudomonas aeruginosa and Candida albicans fungus. This is the first study to report the isolation of endophytic fungi from P. serratifolia and their antimicrobial activities.

Antimicrobial potentials of natural products against multidrug resistance pathogens: a comprehensive review

“… 110 The antimicrobial epidithiodioxopiperazine, gliotoxin 206, and bisdethiobis (methylthio)gliotxin 207, were isolated from the endophytic fungus Hypocrea virens , from Premna serratifolia , showed MIC 32–35 μg mL −1 against MRSA. 111 Terrenolide S 208, isolated from the endophytic fungus Aspergillus terreus isolated from the roots of Carthamus lanatus , displayed a potent activity towards MRSA with IC 50 2.29 μM. 112 (22E, 24R)5, 8-epidioxy-5α,8α-ergosta-6,22E-dien-3β-ol 209, isolated from Chinese mangrove Ceriops tagal endophytic Cytospora sp., showed weak anti-MRSA with MIC 233 μM.…”

Antibacterial activities of endophytic fungi isolated from six Sri Lankan plants of the family Cyperaceae

“…Healthy disease-free plants were brought to the laboratory within 10-24 hours of collection and were processed as follows: First, the soil, dust and dirt were removed by washing well with tap water and the plant parts were separated into aerial sections and roots. These were surface sterilized by sequentially immersing and agitating in 70% ethanol for 1 min, 5.3% sodium hypochlorite solution for 3 min and again in 70% ethanol for 30 sec (Ratnaweera et al, 2016). To remove any remaining solvents, the plant parts were washed thoroughly with sterilized distilled water and air-dried inside a biosafety cabinet (BIOBASE) under aseptic conditions.…”

Antifeedant, contact toxicity and oviposition deterrent effects of phyllostine acetate and phyllostine isolated from the endophytic fungus Diaporthe miriciae against Plutella xylostella larvae

“…UWU/SCT/JMNMJ/01) of the plant used for the current study was deposited in the Department of Science and Technology, Uva Wellassa University. Collected plants were washed thoroughly using tap water, the aerial and root parts were separated and surface sterilized sequentially by agitating with 70% EtOH for 1 min, 0.5% NaOCl for 3 min, 70% EtOH for 30 s and finally rinsing with sterile distilled water . Sterilized aerial and root parts were air dried inside a biosafety cabinet (BIOBASE, Jinan, China), cut into small segments and placed on antibiotic enriched (10 mg mL −1 ) potato dextrose agar (PDA; HiMedia) dishes under aseptic conditions and incubated at room temperature until fungi emerged from the exposed tissues.…”