Amaryllidaceae andSceletiumalkaloids

Abstract

Recent progress on the isolation, identification, biological activity and synthetic studies of Amaryllidaceae alkaloids, as well as the structurally close alkaloids from the Sceletium genus, published from July 2015 to June 2017 are reviewed.

Antiplasmodial Lycorane Alkaloid Principles of the Plant Family Amaryllidaceae

“…The bulbous flowering plant family Amaryllidaceae is recognizable for its unique chemical character, due primarily to its isoqui-noline alkaloid constituents [8]. Apart from their significant array of structural diversity, these alkaloids are also characterized by a wide range of biological properties, particularly in the cancer and motor neuron disease arenas [9].…”

“…In the microbial area, promising antibacterial and antifungal activities have been described for several members of the family [10,11]. The lycorine alkaloids are the largest of the nine alkaloid groups discernible for the Amaryllidaceae [8]. Biologically, they have shown the most promise as potential anticancer agents [12].…”

“…Traub remains the only species that has, to date, been examined for antiplasmodial lycorane alkaloid components [25]. In the event, the α-dihydro analogs zephyranthine (7) and 1,2-O-diacetylzephyranthine (8) were identified in ethanolic bulb extracts of the plant, but were shown to be inactive against the P. falciparum strain NF54 compared to the reference standard chloroquine (IC 50 of 0.004 µg/mL) [25].…”

“…The other two compounds that stood out were also both natural, 1,2-O-diacetyllycorine (6) (IC 50 of 0.097 µg/mL against the F-32 strain) and ungeremine (14) (IC 50 of 0.088 µg/mL against the K1 strain) [31,34]. Given that the A-ring of the lycorane template is, by convention, a 1,2,4,5-tetrasubstituted aryl system, little can be achieved by way of further structural modification [8]. This is in contrast to the crinane alkaloids, who, like lycorane alkaloids, are also a major alkaloid group of the Amaryllidaceae, where a C-7 methoxyl group is common for many of its representatives [8].…”

“…Given that the A-ring of the lycorane template is, by convention, a 1,2,4,5-tetrasubstituted aryl system, little can be achieved by way of further structural modification [8]. This is in contrast to the crinane alkaloids, who, like lycorane alkaloids, are also a major alkaloid group of the Amaryllidaceae, where a C-7 methoxyl group is common for many of its representatives [8]. Whilst the A-ring methylenedioxy moiety is a mainstay of lycorane alkaloids, several of its members, such as pseudolycorine (16), are discernible, wherein this feature has been modified [8].…”