Vasodilators for Biological Research

Anthony Robert Butler, Russell James Pearson 

With the discovery that N O plays a role in vasodilation it has become important that nitrovasodilators (i.e. substances that act as vasodilators by the release of NO) are well-characterised. This includes a clear understanding of the mechanism of NO release. The use of an inappropriate agent may give non-reproducible or false data. At least three crucial factors must be considered when an NO-donor drug is selected  

Substances regularly used in biological and physiological research will be examined in the light of these three criteria with the aim of providing researchers with the relevant information to aid in the selection of an NO-donor suitable for the experiments being undertaken. 

Undoubtedly sodium nitrite is a vasodilator [1]. This is seen from anecdotal evidence when nitrite is used as an antidote to cyanide poisoning hypotension is a major hazard. However, in ex vivo experiments the effect of nitrite is small but the situation in vivo is more difficult to assess, for reasons that will be clear shortly. It is now generally assumed that nitrite acts as a vasodilator because it can undergo a spontaneous reaction to give NO. The termolecular equation (Eq. (1)) sometimes given for this process is certainly incorrect as termoleculer reactions very rarely occur. 

In fact the process occurs in two steps and the correct equations are  

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Biflavonoids comprise a group of the flavonoid family that possesses a variety of structures, and biological activities of high relevance, sueh as anticancer, antibacterial, antifungal, antiviral, anti-inflammatory, antinociceptive, antioxidant, vasodilator, anticlotting, among others, regardless of the bioactivity of each monomer unit. The chemistry of biflavonoids is very important in many fields of research, especially because these compormds are structurally different bioactive molecules with potential for biomedical application. 

These minor components of cocoa have become an intense focus of research interest because of their demonstrated beneficial effect on health. The interest has been recently reinforced by the scientific opinion on the substantiation of a health claim related to cocoa flavanols and the maintenance of normal endothelium-dependent vasodilation issued by the European Food Safety Authority (EFSA) Panel on Dietetic Products, Nutrition and Allergies (NDA) [3], In order to obtain the claimed effect, 200 mg of cocoa fiavanols should be consumed daily. This amount could be provided by 2.5 g of high-fiavanol cocoa powder or 10 g of high-flavanol dark chocolate. This reinforces the scientific interest in the development of sensitive and rapid analytical methods for determining these minor components in cocoa, cocoa products, and chocolate. Another important aspect is related to the development of analytical methodologies for sensitive and selective identification and quantification of the main metabolites of cocoa polyphenols in biological samples in order to understand their bioavailability and their contribution to health. 

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