Antimicrobial Diterpene from the Brazilian Termite Nasutitermes macrocephalus (Isoptera: Termitidae: Natutitermitinae)

Abstract

Termites are insects with a complex social organization on castes among which soldiers are the only responsible for the colony defense. The soldiers of the Nasutitermes genus use chemical defense, which comprises a mixture of mono, sesqui and mainly diterpenes. The new diterpene 2b,3a-dihydroxy-trinervita-1(15),11-diene, found in Nasutitermes macrocephalus, was isolated using preparative high performance liquid chromatography (HPLC) and identified by gas chromatography-mass spectrometry (GC-MS) and nuclear magnetic resonance (NMR) techniques. The absolute stereochemistry determined was supported by ab initio calculations and by comparison of the experimental circular dichroism data with the theoretical results. The isolated diterpene was evaluated against the bacteria Staphylococcus aureus (Gram-positive) and Escherichia coli (Gram-negative), and the fungi Candida albicans and Aspergillus brasiliensis. The isolated diterpene presented minimal inhibitory concentrations of 62.5 and 62.5 µg mL -1 against S. aureus and C. albicans, respectively. Keywords: Nasutitermes macrocephalus, biological activities, HPLC IntroductionTermites are insects present all over the world, with about 2750 species living in tropical and subtropical regions.1 They are social insects with castes responsible for distinct functions: workers are tasked to build the mound and to feed the others castes; king and queen respond for reproduction, resulting in eggs that become larvae that may become workers, soldiers or winged (secondary breeding).2,3 Soldiers are responsible for the defense of the mound and, depending on the species they will present mechanical and/or chemical defense.1,2,4,5 The Nasutitermes genus (Isoptera: Termitidae: Nasutitermitinae) is the most evolved among the termites since their soldiers use only chemical defense, avoiding contact with the enemies. 5They produce and storage a mixture of mono, sesqui and diterpenes in the frontal gland, resulting in a sticky secretion that is ejected against the enemies.6-10 The great success of the Nasutitermes evolution has been attributed to this defense method.2 The monoterpenes are the same compounds found in plants, like a-pinene, b-pinene, limonene and terpinolene, and they are associated with the protection of the colony from fungal infections. 11Sesquiterpenes are in minor quantity, as found in N. gracilirostris, N. torresi, N. triodiae, N. octopilis and N. macrocephalus. 9,12,13 The skeletons of the diterpenes found in termites (trinervitanes, kempanes and rippertanes) are broadly described in all species, 14 and are related to both species communication, as they are blind, and to defense. 15 Although there are several studies on the identification of these diterpenes, just a few of them focused on the biological activities of those substances. For example, one study presented five compounds with antibacterial activity against Bacillus subtilis and Escherichia coli.16 Therefore, several molecules with interesting biological activities produced by species in the Nasutitermes ...

Termites as human foods—A comprehensive review

“…Seventeen diffferent termite species of three different families consist of aldehydes, alcohols, and diterpenes (Mitaka & Akino, 2021). In other species, Nasutitermes macrocephalus contained α‐pinene, limonene, β‐trans‐caryophyllene, α‐selinene, rippertane, trinervitane diterpenes (De La Cruz et al., 2013). The most prevalent compounds in M. bellicosus were hydroquinone, methylhydroquinone, 3,4‐dihydroxyphenethyl glycol, N ‐acetyldopamine, and niacinamide.…”