Biflavonoid

Fig. 4. Two 4,6-linked biflavonoid units linked to each other through a methylene ether bridge formed by reaction with formaldehyde.

See D. M. Smith, 1980, for a study of flavonoid profiles of the varieties.) The overall flavonoid profile of P. triangularis is fully in accord with the uifique status of the species. A detailed discussion of the chemistry of this system, which is beyond the scope of the present treatment, can be found in a paper by Wollenweber and Dietz (1980). An example of the complexity of flavonoid biosynthesis in this species can be found in a description of biflavonoids present in the farinose exudate (linuma et al., 1994). 

The family Caprifoliaceae comprises approx 400 species, of which Lonicera japonica Thunb., Lonicera affinis Hook and Arn, Lonicera confusa DC, Sambucus javanica Reinw. ex. Bl, Sambucus sieboldiana (Miq.) Graebn, and Weigela floribunda (Sieb. and Zucc.) K. Koch, are used to treat inflammatory conditions in Asia and the Pacific. There is an expanding body of evidence to suggest that biflavonoids from this family might hold some potential as phospholipase A2 inhibitors. One such compound is ochnaflavone from Lonicera japonica Thunb. 

Chang HW, Baek SH, Chung KW, Son KH, Kim HP, Kang SS. Inactivation of phospholipase A2 by naturally occurring biflavonoid, ochnaflavone. Biochem Biophys Res Commun 1994 205 843-849. 

Nielsen M, Frokjaer S, Braestrup C. (1988). High affinity of the naturally-occurring biflavonoid, amentoflavon, to brain benzodiazepine receptors in vitro. Biochem Pharmacol. 37(17) 3285-87. 

Another biflavonoid named amentoflavone (Fig. 21) was also isolated from this species, S. tamariscina. Several studies demonstrated that... 

Kaikabo AA, Samuel BB, Elfo JN. (2009) Isolation and activity of two antibacterial biflavonoids from leaf extracts of Garcinia livingstonei. Nat Prod Commun 4 1363-1366. 

Free-living primates respond to plant chemistry black-and-white colobus monkeys, Colobus polykomos, avoid plant leaves with alkaloids, biflavonoids, and milky latex and prefer to eat leaves with a better ratio of nutrients to digestion inhibitors (McKey et al, 1981). The howler monkey, Alouatta palUata, a generalist herbivore, depends on more than one factor in its choice... 

Biflavonoids from Garcinia kola Isoflavones from Astragalus membranaceus... 

Other online HPLC techniques (such as LC-CD or LC-IR) are likely to be exploited. For example, a mixture of diastereoisomeric biflavonoids from the African plant Gnidia involucrata (Thymelaeaceae) could not be separated on a preparative scale by HPLC or crystallization. However, their analytical separation on a Cig column was sufficient to run an online LC-CD investigation and provide stereochemical information about the individual isomers. 

Nunome, S. et al.. In vitro antimalarial activity of biflavonoids from Wikstroemia indica, Planta Med., 70, 76, 2004. 

Kapadia, G.J., Oguntimein, B., and Shukla, Y.N., High-speed countercurrent chromatographic separation of biflavonoids from Garcinia kola seeds, J. Chromatogr. A, 673, 142, 1994. 

Ferrari, J. et al., Isolation and on-line LC/CD analysis of 3,8"-linked biflavonoids from Gnidia involucrata, Helv. Chim. Acta, 86, 2768, 2003. 

Li, X.-C. et al.. Absolute configuration, conformation, and chiral properties of fiavanone-(3 8")-flavone biflavonoids from Rheedia acuminata. Tetrahedron, 58, 8709, 2002. 

Mayer, R., Calycopterones and calyflorenones, novel biflavonoids from Calycopteris floribunda, J. Nat. Prod, 61, 1274, 1999. 

Hemingway, R.W., Biflavonoids and proanthocyanidins, in Natural Products of Woody Plants 1 Chemicals Extraneous to the Lignocellulosic Cell Wall, Rowe, J.W., Ed., Springer Verlag, New York, 1989, chap. 7.6. 

Geiger, H., Biflavonoids and triflavonoids, in The Flavonoids — Advances in Research Since 1986, Harborne, J.B., Ed., Chapman Hall, London, 1994, chap. 4. 

Baba, K., Taniguchi, M., and Kozawa, M., Three biflavonoids from Wikstroemia sikokiana, Phytochemistry, 37, 879, 1994. 

Baba, K. et al., Biflavonoids from Daphne odora, Phytochemistry, 38, 1021, 1995. 

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