Active compounds of stem bark extract from Schima superba and their molluscicidal effects on Pomacea canaliculata

Abstract

Pomacea canaliculata is an invasive snail that can adversely affect biodiversity, agricultural crop yields and human health. Schima superba, which belongs to the Theaceae family, exhibits insecticidal and antibacterial activity, but few studies have focused on its potential molluscicidal activity. In this study, we systematically evaluated the molluscicidal activity of S. superba extract against P. canaliculata in a variety of conditions, including multiple exposure intervals (24, 48 and 72 h), temperatures (15, 20 and 25 °C) and shell diameters (1.5 ± 0.2, 2.5 ± 0.2 and 3.5 ± 0.2 cm). The molluscicidal activities of a 10% microemulsion of S. superba extract were tested on rice in plastic pots filled with mud at different exposure intervals (1, 3, 5 and 7 days). In addition, we isolated and purified the active components from S. superba extract and described them. S. superba was highly toxic to P. canaliculata; the LC₅₀ values for the crude extract at 72 h were 12.25 mg L⁻¹ (15 °C), 11.31 mg L⁻¹ (20 °C), 8.33 mg L⁻¹ (25 °C) with 2.5 ± 0.2 cm shell diameter and 9.43 mg L⁻¹ (1.5 ± 0.2 cm shell diameter), 9.48 mg L⁻¹ (2.5 ± 0.2 cm shell diameter), 10.06 mg L⁻¹ (3.5 ± 0.2 cm shell diameter) at 25 °C. There was a positive correlation between the molluscicidal activity of the extract and treatment temperature after 24 h of treatment, but there was no clear correlation beyond 24 h. In addition, there was no statistically significant correlation between the molluscicidal activity of the extract and shell diameters. Pot trials showed that the crude extract effectively controlled P. canaliculata at 8 and 10 mg L⁻¹. We isolated and characterized two pentacyclic triterpenoid saponins from S. superba, maetenoside B and sasanquasaponin III, which had high molluscicidal activity. This study provides an important foundation for future research on the potential value of S. superba as a molluscicide.