Abstract
Members of the millipede order Julida rely on dominantly quinonic defensive secretions with several minor, non-quinonic components. The free radical-scavenging activities of ethanol, methanol, hexane, and dichloromethane extracts of defensive secretions emitted by Pachyiulus hungaricus (Karsch, 1881) and Megaphyllum unilineatum (C. L. Koch, 1838) were investigated using the ABTS, DPPH, and total reducing power (TRP) tests. The obtained extracts were also tested for inhibition of acetylcholinesterase and tyrosinase activity. Finally, the antifungal potential of both julid extracts was evaluated against seven Fusarium species. Secretions of both species showed activity against free radicals, acetylcholinesterase, tyrosinase, and all of the selected fungal species. The secretions of P. hungaricus exhibited a more potent antioxidative effect than did those of M. unilineatum, while there were no significant differences of antiacetylcholinesterase activity between the tested extracts. Only the hexane extract of M. unilineatum showed an effect on tyrosinase activity stronger than that of P. hungaricus. Fusarium sporotrichioides, F. graminearum, and F. verticillioides were the fungi most resistant to secretions of both julids. The Fusarium species most susceptible to the secretion of P. hungaricus was F. avenaceum, while the concentrations of M. unilienatum extracts needed to inhibit and completely suppress fungal growth were lowest in the case of their action on F. lateritium. Our data support previous findings that julid defensive secretions possess an antimicrobial potential and reveal their antioxidative and antineurodegenrative properties. Bearing in mind the chemical complexity of the tested defensive secretions, we presume that they can also exhibit other biological activities.
Highlights
With more than 1.2 million species [1], arthropods are arguably the most speciose and abundant group in the animal kingdom
In order to explore and expand our knowledge about the antifungal potential of these exudates, we evaluated properties of defensive secretions of the latter two mentioned species against seven Fusarium species
The highest antioxidative capacities were noticed for the MetOH extract of P. hungaricus defensive secretions in both the ABTS assay (0.972 ± 0.036 mg/mL) and the DPPH assay (0.114 ± 0.002 mg/mL), values which were only 3.7-fold and 2.8-fold lower, respectively, than that of the commercial
Summary
With more than 1.2 million species [1], arthropods are arguably the most speciose and abundant group in the animal kingdom Their impressive and unique evolutionary success is reflected in the remarkably great morphological, physiological, developmental and ecological diversity of arthropods [2]. The first body fossils of millipedes (Diplopoda) can be traced to the Silurian, molecular data indicate that their diversification dates from the Middle Ordovician or earliest Silurian [5,6,7] This group of animals is among the oldest of terrestrial arthropods. One of the most conspicuous peculiarities of millipedes is the presence of defensive glands (ozadenes) along the trunk (Fig 1A) These exocrine organs are segmentally arranged and variable, both in morpho-anatomic features and in the nature of secreted chemicals. The major compounds secreted by millipedes can be roughly listed as quinones, phenolics, cyanogenetic compounds, and alkaloids [12,14]
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