Hydroquinones from defensive secretion of a giant Pacific millipede, Acladocricus setigerus (Diplopoda: Spirobolida)

Abstract

The presence of considerable quantities of hydroquinones including hydroquinone, 2-methylhydroquinone, 2,3-dimethoxyhydroquinone, 2-methoxy-3-methylhydroquinone, and 2,3-dimethoxy-5-methylhydroquinone renders the defensive secretion of Acladocricus setigerus (Silvestri, 1897) significantly different from that of other quinone-producing millipedes. In addition, two hitherto undescribed compounds, namely, 2,3-dimethoxy-5-methylhydroquinone and 2-methyl-3,4-methylenedioxyphenol, were characterized from the defensive secretion. However, it is uncertain if the latter compound is formed after the release of the secretion. The two major compounds, 2-methyl-1,4-benzoquinone and 2-methoxy-3-methyl-1,4-benzoquinone, constitute about 75% of the defensive fluid. Furthermore, hydrocarbons, which are typically present in the secretions of most other arthropods that use benzoquinones as repellents, are notably absent in the secretion of A. setigerus.

Composition of the Defensive Secretion in Three Species of European Millipedes

“…No differences in the composition of the secretions from males vs. females were noted. Moreover, the two main compounds found in the exudates of the analyzed species, 2-methoxy-3-methyl-1,4-benzoquinone (IV) and 2-methyl-1,4-benzoquinone (II), also are the major components in other julids (Huth, 2000), as well as in some spirobolids (Attygalle et al, 1993;Wu et al, 2007). Generally these two compounds are the most common components of the defensive secretions of juliformian millipedes.…”

“…The scan range was m/z 35-550 in EI mode, and m/z 60-550 in CI mode. The identification of the compounds was based on comparison of their EI mass spectra with the NIST MS Search 2.0 computerized mass spectral libraries Wiley7 and Nist05, and with the available literature EI-MS data of the compounds previously identified in the defensive secretions of millipedes (Attygalle et al, 1993;Wu et al, 2007). Further, CI-MS spectra of all twelve compounds showed characteristic base peaks at m/z values numerically equal to their respective nominal masses plus one values.…”

Harvestman Phenols and Benzoquinones: Characterisation and Biosynthetic Pathway

“…The alkyl and methoxybenzoquinones are also often components of millipede defensive secretions alongside their corresponding hydroquinones [38][39][40][41]. Some millipede species in the families Spirostreptidae and Harpagophoridae secrete benzoquinones 6 and 7, the hydroquinone 15 and several methoxy substituted benzo-and hydroquinones.…”

Exploring the global animal biodiversity in the search for new drugs – Spiders, scorpions, horseshoe crabs, sea spiders, centipedes, and millipedes

“…This held particularly true for the benzoquinones [51,237,247,248]. Notably, the two dominant quinones in the defensive secretion of Pachyiulus hungaricus (Karsch, 1881) (Julida, Julidae) (Figure 12), 2-methyl-1,4,-benzoquinone and 2-methoxy-3-methyl-1,4-benzoquinone, elicited meaningful antibacterial and antifungal activity, including activity against methicillin-resistant Staphylococcus aureus [249].…”

“…Different taxonomic groups also produce a variety of other defensive chemicals such as alkaloids (by the orders Glomerida and Polyzoniida [231,232]); phenolic compounds (by the orders Callipodida [233] and Julida [234,235]); as well as benzoquinones (particularly the orders Spirobolida, Spirostreptida [236,237] and Julida [234,235]). …”