Sarniensine, a mesembrine-type alkaloid isolated from Nerine sarniensis, an indigenous South African Amaryllidaceae, with larvicidal and adulticidal activities against Aedes aegypti

Abstract

A new mesembrine-type alkaloid, named sarniensine, was isolated together with tazettine, lycorine, the main alkaloid, and 3-epimacronine from Nerine sarniensis, with the last two produced for the first time by this plant. This Amaryllidaceae, which is indigenous of South Africa, was investigated for its alkaloid content, because the organic extract of its bulbs showed strong larvicidal activity with an LC₅₀ value of 0.008μgμL^-1 against first instar Aedes aegypti larvae and with an LD₅₀ value 4.6μg/mosquito against adult female Ae. aegypti, which is the major vector for dengue, yellow fever and the Zika virus. The extract did not show repellency at MED value of 0.375mgcm² against adult Ae. aegypti. Sarniensine was characterized using spectroscopic and chiroptical methods as (3aR,4Z,6S,7aS)-6-methoxy-3a-(2'-methoxymethyl-benzo [1,3]dioxol-1'-yl)-1-methyl-2,3,3a,6,7,7a-hexahydro-1H-indole. It was less effective against larva at the lowest concentration of 0.1μgμL^-1, however it showed strong adulticidal activity with an LD₅₀ value of 1.38±0.056μgmosquito^-1.

Keywords: Aedes aegypti; Amaryllidaceae alkaloids; Larvicide and adulticide activities; Natural pesticide; Nerine sarniensis; Sarniensine.