Antimicrobially Active Isoquinoline Alkaloids from Litsea cubeba

Abstract

Bioassay-guided fractionation of the alkaloidal extract of the aerial part of Litsea cubeba led to the isolation of two new isoquinoline alkaloids, (+)-N-(methoxycarbonyl)-N-norboldine (1) and (+)-isoboldine β-N-oxide (2), together with 11 known analogues (3 – 13). Their structures were established by extensive spectroscopic techniques and by comparing spectroscopic data with those in the literature. Compounds 1 and 4 showed antimicrobial activities. This is the first report on the presence of compounds 1, 2, 6, 8, 9, 11, and 12 in this plant and on the antimicrobial activities of 1 and 4. The bioactivities of isoquinoline alkaloids are also at least partly responsible for the pharmacological function of the folk medicinal plant Litsea cubeba.

Key words

Litsea cubeba - Lauraceae - isoquinoline alkaloids - antimicrobial activity - (+)-N-(methoxycarbonyl)-N-norboldine - (+)-isoboldine β-N-oxide

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