Calluna vulgaris (L.) Hull (heather) is the only species within the genus Calluna (Ericaceae). It is a dominant species of heather communities and can be found in most parts of Europe and Northern America from lowland up to alpine regions. Common heather is traditionally used to treat urinary tract disturbances and inflammatory related disorders. This review covers the current knowledge on phytochemical investigations of C. vulgaris which revealed a complex pattern of flavonoid glycosides including acetylated compounds as well as other classes of phenolics (chromones, procyanidins and simple phenols). Recently, an acetophenone (rodiolinozide) was identified. C. vulgaris occurs in habitats comprising several altitudinal zones which makes it an attractive species to study the variation of its metabolic profiles in wild populations growing under different climatic conditions. Within phenolic compounds, flavonols showed significant differences in samples collected at different altitudes with increased levels of quercetin glycosides at higher altitudes whereas no significant correlation could be found for caffeoyl quinic acids and the dihydroflavonol glycoside callunin. Expanding such investigations to different species and different geographical areas should give a more accurate picture of suitable marker compounds within the group of phenolics in order to detect adaptive processes in high altitude plants. Furthermore, investigations on the specific patterns of phenolics at cellular and subcellular level and their variation due to factors like enhanced solar radiation and low temperature should be expanded.

The influence of galloyl residues on the antioxidant mechanism of polyphenols to prevent hemoglobin-promoted lipid oxidation was investigated by using polyphenolic fractions with different degrees of galloylation: nongalloylated structures from pine bark (IVP), medium-galloylated from grape pomace (IVG), and high-galloylated from witch hazel bark (IVH). Hemoglobin (Hb) from the pelagic fish horse mackerel (Trachurus trachurus) was employed as a Hb standard. In vitro experiments showed an important increase in the deoxygenation and autoxidation of horse mackerel Hb at acidic pH values. All polyphenolic fractions significantly reduced the redox stability of Hb in buffer solutions, showing a greater deoxygenation and methemoglobin (metHb) formation in the presence of IVH, followed in decreasing order by IVG and IVP. However, galloylated polyphenols (IVH and IVG) were efficient to inhibit the oxidation of the oxygenated Hb (OxyHb) and the formation of lipid oxidation products in chilled washed fish muscle. This antioxidant activity of galloylated proanthocyanidins showed a positive relationship with the phenolic concentration. Polyphenols devoid of galloyl groups (IVP) were less active to prevent either Hb oxidation or lipid oxidation in fish muscle. The results draw attention to the potential role of galloyl residues to lessen Hb-catalyzed lipid oxidation in muscle and to maintain Hb in reduced and oxygenated states, which exhibit lower pro-oxidant activity as compared to the metHb and deoxyHb species.