On-line HPLC analysis of the antioxidant activity of phenolic compounds in brewed, paper-filtered coffee

Abstract

Caffeoyl-, feruloyl-and dicaffeoylquinic acids (chlorogenic acids) in infusions from green and medium roasted coffee beans were identified and quantified by reverse phase HPLC with photodiode array and MS 3 detection prior to assessment of the antioxidant activity using an HPLC system with post-column on-line antioxidant detection based on 2,2'-azinobis-3-ethylbenzothiazoline-6-sulphonic acid radical scavenging activity. Caffeoylquinic acids were the most abundant antioxidants and roasting induced isomerisation with a decline in 5-O-caffeoylquinic acid and concomitant increases in the 3-and 4-Oderivatives. This did not affect the level of caffeoylquinic acid-derived antioxidant activity in the roasted coffee. Roasting did, however, result in the appearance of additional unidentified HPLC peaks with antioxidant activity. Because of this and an increase in the antioxidant activity of components that did not elute from the reversed phase HPLC column, the antioxidant capacity of the beverage derived from medium roast beans was double that of the unroasted coffee. The antioxidant activity of coffees that have undergone different degrees of roasting would, therefore, appear to be due to combinations of different components. The effect of roasting on chlorogenic acids in coffee beans is considered, and the possible contribution of Maillard reaction products to the antioxidant capacity of roasted coffees is discussed. Key words: Coffea, ABTS + , chlorogenic acids, hydroxycinnamates, HPLC-MS n .Análise por HPLC "on-line" da atividade antioxidante de compostos fenólicos em café preparado por infusão e filtrado em papel: Ácidos cafeoil-, feruloil-e dicafeoilquínicos (ácidos clorogênicos) em infusões de sementes de café verde e sementes medianamente torradas foram identificados e quantificados por cromatografia líquida de alta eficiência (HPLC) em fase reversa com detecção em fotodiodo e MS 3 , antes da avaliação da atividade antioxidante usando um sistema HPLC com detecção antioxidante "on-line", baseada na eliminação de radicais pelo ácido 2,2'-azinobis-3-etilbenzotiazolina-6-sulfônico. Ácidos cafeoilquínicos foram os mais abundantes antioxidantes e a torração induziu a isomerização, com declínio do ácido 5-O-cafoilquínico e concomitante aumento dos derivados 3-e 4-O-cafeoilquínicos. Isto não afetou o nível da atividade antioxidante derivada de ácidos cafeoilquínicos no café torrado. Torração, no entanto, resultou no aparecimento de picos adicionais nas corridas cromatográficas, com atividade antioxidante. Por causa disto e de um aumento na atividade antioxidante dos componentes que não eluíram da coluna cromatográfica de fase reversa da HPLC, a capacidade antioxidante da bebida preparada de grãos de café medianamente torrados foi o dobro daquela de grãos não torrados, verdes. Portanto, a atividade antioxidante de cafés que tenham sofrido diferentes graus de torração parece ser devido a combinações de diferentes componentes. O efeito da torração sobre os ácidos clorogênicos nas sementes de café é discutido, assim como as ...

Methods for Total Antioxidant Activity Determination: A Review

“…The antioxidant contributions of individual HPLC peaks were added to give the total HPLC-derived antioxidant activity. The total antioxidant capacity of the green coffee determined with the on-line HPLC system was 760 ± 2.5µmol Trolox/l and 984 ± 25.8µmol Trolox/l for the roasted coffee [117].…”

“…The ABTS cation radical was The antioxidant activity using a HPLC system with postcolumn on-line antioxidant detection, based on 2,2'-azinobis-3-ethylbenzothiazoline-6-sulphonic acid radical scavenging activity. The method was applied to the determination of antioxidant content of coffee [117]. Following separation of the coffee samples on the HPLC column, the eluate was directed to a PDA (photodiode array) detector and then mixed with a stabilised solution of the ABTS cation radical and the solution was directed to a detector monitoring absorbance at 720 nm.…”

Determination of Caffeine Content and Antioxidant Activity of Coffee

“…Antioxidants [34] are substances that when present at low concentrations, compared with those of the oxidizable substrate significantly delay or inhibit oxidation of that substrate [30], [32], [43]. In living system, antioxidants have played an important role in scavenging excessive free radicals [35] such as reactive oxygen species (ROS) and reactive nitrogen species (RNS) [36]- [39] which are formed during normal cellular metabolism in high concentration [33], [40].…”

“…Among those dietary species, coffee is a major source of antioxidants and is estimated to provide half of total antioxidant intake in several populations [20], [41], [42]. Thus, coffee extracts have received a lot of attention in recent years and numerous studies have proven that the biologically active components of the extracts such as chlorogenic acids (caffeoylquinic acids [29], dicaffeoylquinic acids [29], feruloylquinic acids [29], [30], [31]), [34] and pcoumaroylqunic acids [29]), melanoidns [37], [39], [44] and lipid soluble heterocyclic compounds (alkaloids) [45], [46] play significant role for its antioxidant behavior in both vitro and vivo [32].…”

Atividade antioxidante in vitro e in vivo de café bebida mole

“…Stalmach et al (2006) também verificaram que a capacidade antioxidante da bebida, preparada com grãos submetidos à torração média, foi o dobro daquela dos grãos verdes.…”