Naturally occurring polyphenols – rationale for drug development

The development of new drugs involves a multi-step process that seeks to identify aspects such as efficacy, stability and toxicity of candidate compounds, before their application in clinical settings (Ting 317 – 323). Naturally occurring polyphenols comprise a wide-range of compounds and sub-groups of phenolic compounds that differ in their “stability, bioavailability and physiological functions” (Tsao 1232). In subsequent paragraphs, the review highlights how structures of specific polyphenols relate to their biological activities.

One of the naturally occurring groups of polyphenols with potential health benefits is flavonoids. The chemical structure of flavonoids (figure 1) is comprised of a C6-C3-C6 (flavan) backbone, with the C6 units (ring A and B) being phenyl groups (Tsao 1233). Variations in the third ring, which connects the two phenyl rings, and different hydroxylation patterns in the phenyl rings results into subgroups such as anthocyanins, flavones, flavonols, flavan-3-ols, and flavanones (Tsao 1233). Most flavonoids have their B ring attached to C2 position of the C ring, but compounds such as isoflavones and neoflavonoids attach to C3 and C4 positions (Tsao 1233). Additionally, compounds such as Chalcones, classified as flavonoids, lack the heterocyclic ring (ring C) present in other flavonoids (Tsao 1233). Such structural diversity in flavonoids and different glycosylation patterns account for their different biological activities (Tsao 1233). In plants, flavonoids occur as polymers with complex polymers forming tannins and complex compounds present in foods such as grapes, black tea and red wine (Heim, Tagliaferro and Bobilya 573). Go to part four here.

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