Structure-activity studies on the lycorine pharmacophore: A potent inducer of apoptosis in human leukemia cells

The direct chemoselective differential functionalization of the ring-C hydroxyl groups present in the Amaryllidaceae alkaloid lycorine is described allowing for selective manipulation of the 1,2-hydroxyl groups. A mini-library comprised of synthetic and natural lycorane alkaloids was prepared and their apoptosis-inducing activity investigated in human leukemia (Jurkat) cells. Further insights into the nature of this interesting apoptosis-inducing pharmacophore are described, including the requirement of both free hydroxyl groups in ring-C.     

Alkaloids of Crinum pratense

From the bulbs of Crinum pratense, collected at flowering, lycorine, 1,2-diacetyllycorine, ambelline, narcissidine, and three phenanthridone alkaloids, viz. hippadine, pratorinine and anhydrolycorin-7-one, were isolated and characterized on the basis of comprehensive spectral analyses (UV, IR, ¹H NMR, ¹³C NMR, MS, [α]_D) and chemical evidence. Among the phenanthridone alkaloids (1–3, only the natural occurrence of hippadine was previously known. Pratorinine is a new phenanthridone alkaloid and anhydrolycorin-7-one was known before only as a synthetic compound. The physiological significance of hippadine is appraised.     

Synthetic S-alk(en)yl-L-cysteine sulphoxides-alliinase fission products: Simulation of flavour components of Allium species

The preparation and properties (especially those of the respective alliinase-fission products) of synthetic flavour precursors as found in Allium species are described. Alliinase-fission products of mixtures of appropriate pairs of the precursors, after reduction with sodium borohydride, yielded volatile products which were substantially identical to the corresponding natural products.     

Three chromones from bulbs of Pancratium biflorum

Two polyoxygenated chromones, 5,7-dihydroxy-2-methylchromone (1) and 5,6-dihydroxy-7- methoxy-2-methylchromone(2), and a glucosyloxychromone, 7     

Interspecific variation in floral fragrances within the genus Narcissus (Amaryllidaceae)

To improve our understanding of the floral biology, pollination, and systematics of the genus Narcissus, a comparative study was made of flower volatiles from nine species native to southern Spain using headspace collection and GC-MS analysis. The species fell into three fragrance types based on the identity of their major volatiles. In all but one species the fragrances consisted mainly of monoterpene isoprenoids mixed with benzenoids: in six species trans-ß-ocimene occurred in high proportions, in two others it was lacking; the last species had a fragrance dominated by fatty acid derivatives, mixed with terpenoids. Two of the species showed marked intraspecific variation in many of their volatiles. When the volatile data matrix of all species was subjected to cluster analyses and the resulting phenetic trees compared with currently recognized taxonomic groups, there was no congruence at the subgeneric level. However, there was considerable agreement at the sectional level, although in most sections we studied only a single species. This apparent agreement was stronger when the volatiles were analyzed according to shared biosynthetic pathways rather than treated individually, pointing to the higher value of using biosynthetic pathways for uncovering and confirming phenetic, and probable evolutionary, relationships among species. In terms of possible selective pressures from pollinators in shaping fragrance chemistry, available information on the pollination of our species suggested an association between fragrance and types of pollinators. Two pollinator-fragrance groups were apparent: (1) species pollinated by insects that include butterflies and moths displayed fragrances containing volatiles typical of moth-pollinated flowers, most particularly indole combined with high amounts of esters, and (2) species visited exclusively by insects other than butterflies and moths, especially by bees and flies, had fragrances lacking this combination of volatiles. Narcissus assoanus was unusual among our species in having both fragrance chemotypes. Future pollination studies of Narcissus in the field are needed to test the reliability and predictability of the proposed fragrance-pollinator associations.