Production, HPLC analysis, and in situ apoptotic activities of swainsonine toward lepidopteran, Sf‐21 cell line

Abstract

Swainsonine, a secondary metabolite from Metarhizium anisopliae has been extensively studied in the complementary areas of therapeutics and toxicology. This work aims to develop a simple UV-HPLC method of analyses for swainsonine in Metarhizium fermentation broth and to explore its in situ entomotoxic activities. The partially purified broth was quantitatively analyzed using middle UV (205 nm)-reverse phase HPLC method with different mobile phases and gradient programmes. Swainsonine was eluted as single peak at (te ) 6.0-6.9 min with average concentration of 4.04 ± 0.52 μg/mL using optimal mobile phase (0.1% trifluoroacetic acid in water and acetonitrile). The mass spectrometry analysis further indicated the characteristic MS1 species for swainsonine, [M+H](+) 174.30 in corresponding HPLC peaks. The antiproliferative effects of swainsonine on lepidopteran, Sf-21 cells were determined through 3-(4, 5-dimethylthia-zol-2-yl)-2, 5-diphenyl tetrazolium bromide (IC50 standard = 3.90 μM and IC50 purified = 5.27 μM) and trypan blue dye exclusion (IC50 standard = 6.91 μM and IC50 purified = 8.67 μM) assays. The fluorescence activated cell sorting evaluation of Sf-21 cells showed nearly 35% and 42% of population in various apoptotic stages at 36 h, when treated with standard and purified swainsonine, respectively. The morphodimensional field emission scanning electron and atomic force microscopic analyses further confirmed the characteristic apoptotic features like membrane blebbings, ruptures and volume shrinkage in the lepidopteran cells after 24-36 h of post-treatment incubation. The study describes the potential entomotoxic activities of swainsonine and its role in the virulence of Metarhizium spp.

Secondary metabolites from hypocrealean entomopathogenic fungi: novel bioactive compounds

“…Eight acyl isocoumarins, meromusides A-H (79-86), were discovered as a result of the deletion of the histone acetyltransferase (HAT) gene in M. robertsii (previously known as M. anisopliae). 29 M. robertsii has been investigated for SM production under various culture conditions and in different developmental stages, 2, 3 yielding nonribosomal peptides (NRPs) such as the destruxins, 112 serinocyclins 113,114 and metachelins; 115 hybrid PK-NRP products such as NG39x 116 and the cytochalasins; 29 terpenoids such as helvolic acid 117 and ovalicin; 118 and alkaloids such as swainsonine 119,120 and tyrosine betaine. 121 Modulation of histone acetylation provides an additional avenue to map the parvome of this economically important HEF biopesticide.…”

“…123 A series of isocoumarins were isolated from various strains of the scale insect pathogen Conoideocrella tenuis. These included 6,8-dihydroxy-3-methylisocoumarin (106), 6,8dihydroxy-3-hydroxymethylisocoumarin ( 109) and the isocoumarin glucosides 105, 107, and 108 from strain BCC 12732; 72 the isocoumarin glycoside (110) from BCC 18627; 71 and the new (111)(112)(113)(114)(115) and known (116)(117)(118)(119) isocoumarin analogues from BCC 44534. 61 These compounds may derive from a collaborative hrPKS-nrPKS system where the hrPKS partner is lost, nonfunctional or at least not competent for chain extension, hence the nrPKS utilizes a simple acetate unit for chain initiation.…”

Is the Insect Cuticle the only Entry Gate for Fungal Infection? Insights into Alternative Modes of Action of Entomopathogenic Fungi

“…produce mainly destruxins (Dtx) [5,12] (Figure 1). Secondary metabolites pose antibacterial and antifungal properties, preventing the growth of opportunistic saprophytic bacteria and fungi [23].…”

Perplexing Metabolomes in Fungal-Insect Trophic Interactions: A Terra Incognita of Mycobiocontrol Mechanisms

“…Most notable genera are the Metarhizium, Beauveria , and Aspergilli etc. which relies upon the polyketides, alkaloids, and NRP’s (non-ribosomal peptides) as their chemical shield or offensive tools of metabolites ( Rohlfs and Obmann, 2009 ; Döll et al, 2013 ; Singh and Kaur, 2014a ). Further, the in vivo expression of the toxin metabolite types and their relative quantities depends upon the respective insect host and numerous other factors ( Skrobek et al, 2008 ).…”

“…Although many studies have described the therapeutic potentials of swainsonine, its entomotoxic properties and role in the entomopathogenic virulence of Metarhizium are still largely unexplored. Recently, Singh and Kaur (2014a) have reported the in vitro entomotoxic properties of swainsonine isolated from M. anisopliae against the lepidopteran target host ( Spodoptera sp.) through the induction of apoptotic cell death mechanisms.…”