Semipreparative Chromatographic Procedure for the Isolation of Dimeric and Trimeric Proanthocyanidins from Barley

Abstract

A semipreparative chromatographic method for the isolation of small amounts (10−20 μg) of dimeric and trimeric proanthocyanidins from barley is described. Concentrated extracts of barley were injected onto a high-performance gel filtration column (Superdex 75 HR), and were eluted with methanol. This procedure resolved the dimeric proanthocyanidins (prodelphinidin B3 and procyanidin B3), as well as the trimeric procyanidin C2 and three other trimeric prodelphinidins. The separated flavanoid peaks were collected and their contents were estimated by UV spectrophotometry, reaction with p-dimethylaminocinnamadehyde, and reversed phase HPLC with electrochemical detection. This method produced proanthocyanidins in sufficient amounts to calibrate a system for direct injection chromatographic analysis of beers and barley extracts. The method described may be optimized for the isolation of dimeric proanthocyanidins only, in which case the preparation can take as little as 3 h; alternatively, by extending the chromatographic separation to 9 h, the four major trimeric proanthocyanidins of barley can be recovered also in a chromatographically pure state. Keywords: Analysis; barley; beer; calibration standard; high-performance liquid chromatography; proanthocyanidin

Study of Some Qualitative and Quantitative Characters of the Grapes of Indigenous Greek Grapevine Varieties (Vitis vinifera L.) using HPLC and Spectrophotometric Analyses

“…The total flavanol content was estimated using the pdimethylaminocinnamaldehyde (DMACA) method (Vivas et al, 1994;Li et al, 1996;McMorrough et al, 1996). Extract (0.2 mL), diluted 1:50 with methanol, was introduced into a 15-mL tube and added 1mL DMACA solution (0.1% in 1 N HCl in MeOH).…”

A comparison of Czech and Chinese varieties of barley with regards to technologically important polyphenolic substances.

“…Spektrum jejich vlastností, týkajících se pivovarské technologie a zejména vlastností hotového produktu, je velice široké. V minulosti se studium polyfenolových sloučenin soustřeďovalo zejména na jejich roli v procesu tvorby polyfenol-bílkovinných komplexů, a tím i na vliv polyfenolů na koloidní stabilitu piva (McMurrough et al, 1996a;McMurrough et al, 1996b;Parker, 2007, Aron a Shellhammer, 2010Rehmanji et al, 2005) a možnosti selektivního odstraňování prekursorů vzniku zákalu (Leiper et al, 2005). Po zavedení moderních stabilizačních postupů, schopných odstranit z piva velkou část polyfenolů, byla tato problematika poměrně dlouhou dobu považována za vyřešenou a pozornost se posunula směrem k antioxidačním vlastnostem polyfenolů (Rice-Evans et al, 1996;Pietta, 2000; Dvořáková et al, 2008a), ať už s ohledem na tvorbu senzoricky nežádoucích produktů, zejména karbonylů (Vandehaegen et al, 2006;Mikyška et al, 2011) The aim of this study was to find differences in the quantity and presence of selected polyphenolic substances in barley grown in the Czech Republic and in the People's Republic of China.…”

“…Vzhledem k tomu, že některé skupiny polyfenolových sloučenin, zejména flavan-3-oly a proanthokyanogeny, jsou spoluodpovědné za zhoršo-vání koloidní stability piva (McMurrough et al,1996a;McMurrough et al, 1996b;Parker, 2007;Aron a Shellhammer, 2010), mohla by znalost vztahu mezi odrůdou, agrotechnickými parametry a obsahem polyfenolových sloučenin v budoucnu významně přispět k zajištění vysoké kvality vyráběného produktu. ■ ■ 2 MATERIÁL A METODY…”

“…Considering the fact that different groups of polyphenolic compounds (particularly flavan-3-ols and proanthocianidins) have a negative impact on the colloidal stability of beer (McMurrough et al, 1996a;McMurrough et al, 1996b;Parker 2007;Aron and Shellhammer, 2010), knowledge about the relationship between the variety, the agrotechnological parameters and the contents of polyphenols in barley could add considerably to a higher quality of the product.…”

“…The range of their properties with regards to beer technology and especially to the quality of the final product is wide. In the past, polyphenols were often studied mainly with regards to their significance in the process of the formation of polyphenols-protein complexes which influence the colloidal stability of beer (McMurrough et al, 1996a;McMurrough et al, 1996b;Parker, 2007;Aron and Shellhammer, 2010;Rehmanji et al, 2005) and to the possible a selective removal of these haze-active precursors from beer (Leiper et al, 2005). This matter was considered as solved with the introduction of modern stabilization methods able to remove a large part of the polyphenols.…”