The Alkaloids: Chemistry and Biology, Vol. 64

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From the journal: Natural Product Reports. The lycopodium alkaloids. The first page of this article is displayed as the abstract. You have access to this article. Please wait while we load your content Something went wrong. Try again?

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Cited by. Back to tab navigation Download options Please wait Article type: Review Article. DOI: Download Citation: Nat.

Volume 83. The Alkaloids

The lycopodium alkaloids W. Ayer, Nat.

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Search articles by author W. Back to tab navigation Fetching data from CrossRef. The ten homoerythrinan-type alkaloids found in Colchicaceae, see Fig. The alkaloid 3-epischelhammericine as well as other alkaloids from Dysoxylum have shown molluscicidal activity and cardiac effects [ 67 , 79 ], and dyshomoerythrine from Manoao is reported to have insecticidal activity [ ].

Five alkaloids, see Fig. They are all isolated from different species of Colchicum [ , , , ]. Structural diversity of miscellaneous phenethylisoquinoline alkaloids in Colchicaceae. A phylogenetic hypothesis of plant relationships is dependent on sampling size, which is a function of the number of investigated plant species and the number of characters in the matrix. In molecular systematic studies based on nuclear sequences the characters will equal the number of nucleotides in the sequence used for analysis.

For Colchicaceae a family wide investigation based on chloroplast gene sequences, representing fourteen out of fifteen genera the single species of Kuntheria was not sampled has been published [ 47 ]. A genus-level tree based on those results, with Kuntheria placed together with Schelhammera and Tripladenia , is shown in Fig.

The phylogenetic hypothesis and classification for Colchicaceae modified from Vinnersten and co-workers [46, 47]. The dendrogram clearly shows that the groups not traditionally associated with phenethylisoquinoline alkaloids constitute the basal clades of the family. As further discussed in the text this highlights them as potential new sources of Colchicaceae alkaloids, or even new structural types of phenethylisoquinoline alkaloids. Chemosystematic prediction is likewise dependent on sampling size, here as a function of the number of investigated plant species and the limits of detection for the compounds of interest using a specific method.

As the Colchicaceae alkaloids span from alkaline compounds, over aprotic or quaternary nitrogen compounds insensitive to pH-changes, to phenolic alkaloids even within the different structural types the isolation method may bias the detection of compounds [ ]. Another bias in reviewing Colchicaceae alkaloids may be the strong focus on detection of colchicine itself in the literature. This alkaloid is by far the most commonly reported compound, and it has been shown to be present in all investigated genera of the family by nanospray-MS again with the single species of Kuntheria unsampled [ 49 ].

However, the similarities between the systematic and chemical sampling on genus level makes Colchicaceae a good case study in evolution of chemical characters. The genera Uvularia and Disporum have been treated as part of the now defunct family Uvulariaceae, which by some authors also have included Schelhammera including the later segregated Kuntheria and Tripladenia , though these latter genera have also been placed in the former Convallariaceae [ 46 , ].

Burchardia has been reported to be devoid of tropolonic alkaloids [ ], and its relationship to the rest of Colchicaceae have been questioned and sometimes it is instead treated in a monogeneric family Burchardiaceae [ ]. The alkaloid chemistry of the early diverging lineages, Burchardieae and Uvularieae, has not been investigated in any detail according to standard literature searches, but the three genera are confirmed to contain colchicine [ 49 ].

The chemistry of the tribe Tripladenieae, which is restricted to eastern Australia extending to New Guinea, have in comparison been fairly extensively investigated. The genera Schelhammera and Kuntheria are unique in Colchicaceae by producing homoerythrinan instead of colchicine-type alkaloids as major components [ , , , , ]. Further investigations are needed to see if this is the case for Tripladenia as well. However, as stated above a plant under the name of Kreysigia multiflora has been shown to contain appreciable amount of homoaporphine, homoproaporphine and colchicine-type alkaloids [ 50 , , ], and this plant is either Tripladenia or a species of Schelhammera.

The collection data for the material used by Badger and Bradbury [ ] indicate that their original isolation is done on Tripladenia cunninghamii. Our nanospray mass spectrometry screening has confirmed the presence of colchicine in both Schelhammera and Tripladenia [ 49 ]. The three remaining tribes constitute the classical subfamily Wurmbaeoideae [ 45 ] or Colchicaceae in its strict sense [ 46 ] and several reviews of their alkaloid contents have been published [ 41 , 44 , 52 , , ].

Besides colchicine- and lumicolchicine-type alkaloids Iphigenieae also contain homoaporphine and homomorphine alkaloids [ , , , ], while only colchicine- and lumicolchicine-type alkaloids have been reported from the few species investigated from the tribe Anguillarieae [ 44 , ]. The most species-rich tribe is Colchiceae, which also contains Colchicum and Gloriosa the two most studied genera, and it is reported to contain all structural types present in Colchicaceae except for homoerythrinan alkaloids [ 97 , , , , , , , , , , , , , , , , , , , , , , ].

Combining this distribution data with the hypothetical biosynthetic network in Fig. Since this pathway contains the androcymbine-type alkaloids as an intermediate, these are also expected to have a family-wide distribution. The homoaporphine and homoproaporphine alkaloids are both present in the tribe Colchiceae, while only homoaporphines are present in the tribe Iphigenieae.

This could indicate that the two types are biosynthesized by independent pathways, and that homoproaporphines are not precursors for homoaporphines as would be suggested by analogy with benzylisoquinoline alkaloids. There is some experimental evidence that this is the case [ 57 ]. The homoerythrinan alkaloids are often discussed together with their erythrinan counterparts [ , , ], and their biosynthesis is considered to be analogous to these.

The two possible pathways to homoerythrinan alkaloids in Fig. A pathway analogous to that proposed for erythrinan alkaloids [ , ] would include androcymbine-type intermediates, while a pathway from diarylazahexenoid-type precursors would by-pass these and directly produce dibenzo[ d,f ]azecines.

Regardless of the validity of any of these hypotheses, the large structural variation and the high proportion and wide range of biological activities associated with alkaloids make them a highly interesting compound-type for medicinal chemists. However, the research focus is often limited to a very small number of compounds with extraordinary activity, such as colchicine in the present example. This might be due to presence of low concentrations of minor components, bias in selection of screening assays for biological activity, or skewed sampling of plant material.

We argue that by accepting the notion that natural products are prevalidated for biological activity and taking evolutionary aspects into account, these potential problems can be attenuated and open new avenues of interesting research. Of the phenethylisoquinoline alkaloids of Colchicaceae only colchicine-type alkaloids have been, and is still, extensively investigated and the activity under scrutiny has almost exclusively been that of cytotoxicity. This leaves seven structural groups of alkaloids within the family for which we today have very little information on possible biological activities and roles.

Especially interesting from this perspective are the homoerythrinan alkaloids, seemingly absent in most of the family and replacing colchicine-type alkaloids in Tripladenieae. With the presence of these alkaloids in several distantly related plant groups it is imperative to predict that they have biological activities of potential for human use, and the reported molluscicidal and insecticidal activities can be considered as a starting point and need further investigations. From an evolutionary standpoint it is also obvious that the sampling of Colchicaceae has been very skewed.

This is notable for the early lineages as well as the second most species rich genus Wurmbea. Compared to the structural diversity of known benzylisoquinoline and Amaryllidaceae alkaloid types, which have at least analogous biosynthesis patterns, the phenethylisoquinoline alkaloids of Colchicaceae is a small group. This could be the result of undersampling of different phylogenetic lineages within the family. It has been argued that we only take advantage of a very small fraction of the plant biodiversity around us. As an example De Luca and co-workers propose in depth collaborative investigations of plant metabolomes, using new technologies to elucidate and modify biosynthetic pathways to create larger yields or new chemically diverse biological active compounds [ ].

Another option for finding new compounds or activities, as argued here, is taking advantage of evolutionary evidence in selection of the plants or compounds to be studied. The phylogenetic distribution of specific compounds predicts at least one of either presence of biosynthetic pathways or advantageous biological activity, thus identifying less known or unstudied chemistry. Based on the known phylogenetic hypothesis in Fig. In conclusion we have shown how thinking about evolution can influence selection of plant material in drug lead discovery, and how knowledge about phylogenetic relationships may be used to evaluate predicted biosynthetic pathways and identify priority species for further study.

The author s confirm that this article content has no conflicts of interest. Europe PMC requires Javascript to function effectively. Recent Activity. The snippet could not be located in the article text. This may be because the snippet appears in a figure legend, contains special characters or spans different sections of the article.

Bentham Science Publishers. Curr Top Med Chem. Published online Jan.

PMID: S, Copenhagen DK, Denmark. This article has been cited by other articles in PMC.

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