The Flavonoidal Alkaloids

Details of the extraction methods for ficine (4) and isoficine (5) were not given. Phyllospadine (6) was isolated from the flavonoid-containing n-butanol-soluble extract from dried plant material (4). The alkaloids from Vochysia and Buchenavia were isolated by conventional procedures, utilizing acid-base extraction and subsequent column or thin-layer chromatography using silica gel or alumina (5,6). 

The fiavonoidal moiety of ficine was deduced from its UV spectrum, which was very similar to chrysin (37), and the bathochromic shift indicated a saturated alkyl substituent on ring A. Treatment with Gibb s reagent to detect the presence of a proton para to a phenolic OH (17) gave a positive result for 5 but not 4. Although no molecular ion could be seen in the mass spectrum, the peaks obtained were equivalent to the sum of the individual spectra of chrysin (37) and 

A -methylpyrrole. It was assumed that pyrolysis occurred at the inlet temperature and that ficine and isoficine consisted of chrysin substituted with M-methylpyr-role at positions 8 and 6, respectively. The presence of chrysin as part of the molecule was confirmed by its formation from 4 by alkaline hydrolysis. 

Phyllospadine was characterized as its triacetate. Its alkaloidal nature was detected by a positive Dragendorff s reaction and its flavonoidal nature by its UV spectrum and the co-occurrence of the parent flavonoid hispidulin (38). The H-NMR spectrum showed signals identical to those of 38 apart from the lack of the signal at 8 7.22 attributed to 8-H. The attachment of the nitrogenous ring was therefore reckoned to be at this position. The characterization of the ring as N- 

The phenolic nature of vochysine was deduced from the bathochromic shift in the presence of alkali observed in the UV spectrum. The UV spectrum showing peaks at 215 and 275 nm together with peaks at m/z 272, 153, and 120 in the mass spectrum indicated the presence of a 4 -OH flavan. The peak at m/z 69 was indicative of pyrrolidine substituent. 

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The flavonoidal alkaloids have thus been found widely scattered throughout the higher plants. In view of the ubiquitous occurrence of flavonoids and the simplicity of the nitrogenous component in the compounds so far isolated, it is quite possible that they may occur in more species. The occurrence of the flavonoid alkaloids in Buchenavia but not Terminalia has been used to confirm the taxonomic distinction between these genera (6). 

No studies have been carried out on the biosynthesis of the flavonoidal alkaloids. It is assumed, however, that the flavonoid moiety is formed by the usual... 

This sea grass49 contains the flavones hispidulin and luteolin as well as the flavonoidal alkaloid phyllospadine (45). 

Tables 1,2 summarise the compounds of this type so far isolated from the plant kingdom and it can be seen that there is no discernible pattern in the distribution of chromone alkaloids in the flowering plants. The flavonoidal alkaloids have been isolated from several different plant families but often only from one genus of a family. Many genera and species related to those yielding this type of alkaloid have not been investigated so further studies may enable patterns to be discerned.

The only other novel flavonoidal alkaloid reported, named lilialine (4), was isolated from the flowers of Lilium candidum from Slovakia [12]. This molecule consists of a flavone linked at C-8 to a 2-oxo-pyrrole ring, this latter ring being unique amongst the flavonoidal alkaloids so far... 

The discovery of the ability of the flavonoid alkaloids to inhibit kinase aroused particular interest because kinases are produced by oncogenes and... 

Some of the potential uses of the fats and oils found in plants have been reviewed and some uses of carbohydrate-based polymers briefly discussed. Plants contain a whole variety of other chemicals including amino acids, terpenes, flavonoids, alkaloids, etc. When the potential for these naturally occurring materials are combined with the secondary products that can be obtained by fermentation or other microbial processes or by traditional chemical transformations, the array of chemicals that can readily be created from renewable resources is huge. In this section a few of the more interesting examples are considered. 

Mancini 1988). Flavonoids vary across the ontogenic cycle, with the highest concentration of isovitexin occurring between preflowering and flowering stages. The indole alkaloids are small amounts (up to 0.01%), including harman, harmine, harmaline, and harmalol (Tyler 1994). Mechanisms of Action... 

Quinolizidine alkaloids are non-toxic to the legumes which produce them. On the other hand, the quinolizidine alkaloids can be toxic and in some cases very toxic to other organisms. The biotoxicity of alkaloids has for some time been considered to be connected with their bitter taste" ° ". The quinolizidine alkaloids are certainly bitter in taste to humans. However, not all alkaloids are. Literature states that some pyrrolizidine and indolizidine alkaloids are not bitter in their pure forms" Furthermore, there are many non-alkaloid compounds, such as flavonoids, that are bitter in taste but non-toxic. Therefore, although quinolizidine alkaloids are bitter, the connection between biotoxicity and bitter taste is not absolute. 

The structures used for the alkaloids in this chapter are numbered conventionally for the flavonoid or noreugenin moiety. The carbon atoms of the nitrogen-containing ring are numbered separately T, 2, etc. These alkaloids are of interest due to their amphoteric nature, being both bases and phenols, and also because of the reputed biological activity of some of the plants which contain them. 

The first flavonoidal alkaloids to be isolated were ficine (4) and isoficine (5) in 1965 from Ficus pantoniana King. (Moraceae) (i). These alkaloids have not... 

Most recently a series of piperidinyl-flavonoid alkaloids have been isolated from two Buchenavia spp. (Combretaceae) (6). The leaves of B. macrophylla Eichl. yielded buchenavianine (8) and iV-demethylbuchenavianine (9). The fruits... 

The flavonoidal moiety in Buchenavia alkaloids was deduced from their UV spectra. The more detailed structure determination for individual alkaloids is outlined below. 

The UV spectra of all flavonoidal alkaloids is related entirely to the flavonoid part of the molecule. Table I lists the data reported for each alkaloid. Flavones exhibit maxima in the region of 270-325 nm whereas the flavanones show maxima at about 250-320 nm. The flavan vochysine shows an absorbtion only at 275 nm since there is no conjugation system in ring C. 

The molecular ions of some of the alkaloids isolated more recently have been obtained and have been useful indicators of the substituents present on a common nucleus, particularly for the Buchenavia alkaloids (6). All spectra so far reported have been obtained using electron impact fragmentation. Table III lists the fragmentation patterns reported. Thus far no studies have been made on the breakdown mechanisms, but the cleavage of the flavonoid and nitrogenous rings is obviously an important process. 

C-NMR spectral data have been recorded for vochysine (7) (5) and the Buchenavia alkaloids (8-16) (6) (Table V). In both cases comparison of the spectra with those of the parent flavonoid enabled the identity of this part of the molecule to be established. The chemical shifts of the A ring carbon atoms in some of the Buchenavia alkaloids have also been used to determine the point of substitution of the piperidine ring as described above, e.g., for buchenavianine (8). 

Auzi, A.A., Hartley, T.G., and Waterman, P.G., Distribution of flavonoids, alkaloids, acetophenones and phloroglucinols in the genus Bosistoa (Rutaceae), Biochem. Syst. EcoL, 25, 611, 1997. 

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