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 0.008 mu g mu L-1 against first instar Aedes aegypti larvae and with an LD50 value 4.6 mu g/mosquito against adult female Ac. aegypti, which is the major vector for dengue, yellow fever and the Zika virus. The extract did not show repellency at MED value of 0375 mg cm(2) 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,6,7,7-hexahydro-1H-indole. It was less effective against larva at the lowest concentration of 0.1 mu g mu L-1, however it showed strong adulticidal activity with an LD50 value of 138 +/- 0.056 mu g mosquito(-1). (C) 2016 Elsevier B.V. All rights reserved.