# Antibacterial Activity of Defensive Secretions from the Lace Bug Stephanitis svensoni (Drake) (Hemiptera: Tingidae)

## TL;DR

This study identifies antibacterial compounds in secretions from lace bug nymphs, which could be useful for developing new antibiotics.

## Contribution

The study identifies novel antibacterial compounds in lace bug secretions, including ones with broad-spectrum activity.

## Key findings

- Eleven compounds were identified in the secretions of S. svensoni nymphs.
- Three compounds showed antibacterial activity against both Gram-positive and Gram-negative bacteria.
- 1-(2,6-dihydroxyphenyl)dodecan-1-one showed strong antibacterial activity even at low concentrations.

## Abstract

All developmental stages of Stephanitis svensoni (Drake) (Hemiptera: Tingidae) are found on the underside of Japanese star anise Illicium anisatum leaves, and nymphs of the species possess glandular setae on their dorsal abdomen, from which droplets are secreted. Secretions from nymphs of the genera Stephanitis and Corythucha, belonging to the family Tingidae, are suggested to function as defensive substances against predators in a previous study. In this study, secretions from nymphs of S. svensoni were demonstrated to contain 11 compounds, including aliphatic aldehydes, aliphatic ketones, and aromatic polyketides. Antibacterial activity examination of the 10 identifiable compounds using the paper disk method showed that four compounds exhibited antibacterial activity against the Gram-positive bacterium Staphylococcus aureus, while two compounds exhibited antibacterial activity against the Gram-negative bacterium Escherichia coli. Of the two compounds that showed antibacterial activity against both bacteria, one compound showed significant antibacterial activity even at low concentrations, indicating a stronger and wider antibacterial spectrum.

Nymphs of Stephanitis svensoni (Drake) (Hemiptera: Tingidae) have numerous glandular setae on their dorsal abdomens. Chemical analysis of the exudates from these setae revealed the presence of 11 compounds, including aliphatic aldehydes, aliphatic ketones, and aromatic polyketides. Among them, 3-oxododecanal, 5-hydroxy-2-heptylchromanone, and 5-hydroxy-2-undecanylchromanone were identified for the first time in the family Tingidae. Previous research has suggested that secretions from nymphs of the genus Stephanitis, belonging to the family Tingidae, function as defensive substances against predators. The exudates of S. svensoni showed antibacterial activity against the Gram-positive bacterium Staphylococcus aureus. Antibacterial tests conducted using preparations of the 10 identified compounds showed antibacterial activity in 3-oxododecanal, 2,6-dihydroxyacetophenone, and 1-(2,6-dihydroxyphenyl)dodecan-1-one. In addition, antibacterial tests against the Gram-negative bacterium Escherichia coli showed activity in 2,6-dihydroxyacetophenone and 1-(2,6-dihydroxyphenyl)dodecan-1-one. Therefore, 2,6-dihydroxyacetophenone and 1-(2,6-dihydroxyphenyl)dodecan-1-one exhibited a wide antibacterial spectrum. Particularly, 1-(2,6-dihydroxyphenyl)dodecan-1-one, which showed antibacterial activity even at low concentrations, holds promise as lead drug compound.