Bioactivities and modes of action of VUAA1

Abstract

BACKGROUND The compound 2‐((4‐ethyl‐5‐(pyridin‐3‐yl)‐4H‐1,2,4‐triazol‐3‐yl)thio)‐N‐(4‐ethylphenyl) acetamide (VUAA1) is reported to be an odorant receptor co‐receptor (Orco) agonist in insects with potential use as an insect repellent. For this study, the biological activity of VUAA1 was investigated in several bioassays with Aedes aegypti, including adult contact, spatial repellency, and larval repellency assays, as well as topical, injection, and feeding toxicity assays. Neurophysiological action was further explored by analysis of fruit fly central nervous system firing, cockroach axon recordings, patch clamp analysis of Kv2 potassium channel, and acetylcholinesterase inhibition studies. Finally, the metabolic impact on the toxicity of VUAA1 was explored by applying it in combination with established metabolic synergists. RESULTS In repellency and bite protection screens, VUAA1 showed little activity against adult mosquitoes, apparently due to its low volatility, since its effectiveness was increased by heating or mixing with transfluthrin acid and citronella oil. It did produce measurable repellency of mosquito larvae that was more potent than N,N‐diethyl‐m‐toluamide (DEET). Overall, VUAA1 showed low acute toxicity to both insects and mice, and it was weakly synergized by triphenyl phosphate. There was no observed cross‐resistance in a pyrethroid‐resistant strain of Anopheles gambiae. VUAA1 showed a two‐phase effect on the central nervous system, with neuroexcitation at 1 μmol L‐1 and an inhibitory effect at 100 μmol L‐1 that may relate to block of Kv2 potassium channels. CONCLUSIONS VUAA1 presented low toxicity, similar to other insect repellents. Its limited solubility, low volatility, and resulting poor adult repellency without additional adjuvants may restrict the utility of VUAA1 in typical public health applications. © 2020 Society of Chemical Industry

Repellent activity of essential oils to the Lone Star tick, Amblyomma americanum

“…However, innovation in the field of arthropod repellents has been relatively low and continues to rely heavily on DEET, which some are hesitant to use even though it has been accepted as safe when used correctly [ 9 , 10 , 51 ], IR3535 or picaridin. Considering this, recent efforts have been made to develop novel repellents that can be integrated into the current rotation of insecticides and personal protectants for protection from arthropod-vectored pathogens [ 52 – 55 ].…”

Understanding the biological action of insecticides is the key to their continuous improvement

“…Yang et al . characterize the effects of a known compound, VUAA1, in a variety of repellency and toxicity bioassays on three mosquito species 9 . Overall bio‐activity of VUAA1 alone was reported as low, but significant larval repellency was observed, as well as enhanced adult repellency when mixed with other known repellents.…”

The future of microbial bioherbicides

“…Sixteen of the articles in this issue are from conference participants 2–17 . Four related articles from non‐participants are also included 18–21 . The article by Duke gives the rationale for the meeting, discussing the many microbial bioherbicides that have failed and detailing the technical and economic reasons for lack of success 2 .…”

“…as potential herbicides. The mode of action of the microbial compound radulanin A as a photosystem II (PSII) inhibitor was elucidated, 19 and the action of citrinin, a secondary product of Penicillium and Aspergillis species on PSII was determined by Yang et al 21 …”