Isolation of high molecular weight components and contribution to the protective activity of coffee against lipid peroxidation in a rat liver microsome system.

One of the most extensively studied and best-established properties of coffee is its antioxidant activity. We have shown that coffee brew has the ability to inhibit lipid peroxidation completely in a rat liver microsome biological system. The inhibitory activity was mainly due to the high molecular weight (HMW) fraction; this consisted of five components that were isolated, purified, and seen to occur in different amounts in the brew. Each component had different spectra and element compositions, although they all contained nitrogen. HMW, nitrogen content, and brown color enabled three components to be attributed to the melanoidin family; the two nonbrown components could not be considered as melanoidins. Each melanoidin and nonmelanoidin component contributes to a different extent to the protective action exerted by coffee brew. None of the isolated components completely inhibited microsomal lipid peroxidation alone, suggesting that each acts at different sites and/or possesses different mechanisms of action. The protective activity of coffee brew is thus underpinned by the antiradical properties, reducing power, and metal chelating ability of the individual components, each contributing to a different extent.

Hydroxycinnamic acid derivatives occurring in Cichorium endivia vegetables.

The hydroxycinnamic acid derivatives found in Chicorium endivia var. crispum and var. latifolium polyphenolic extracts were detected and characterized by high-performance liquid chromatography (HPLC) combined with photodiode array detector (DAD) and electrospray ionization-tandem mass spectrometry (ESI-MS/MS). The method provides data (molecular weight and diagnostic fragment ions) on the molecular structure of compounds. The combined approach enabled identification of four hydroxycinnamic derivatives in each chicory extract; three derivatives (5-O-caffeoylquinic acid, 3,4-di-O-caffeoylquinic acid, and 5-O-feruloylquinic acid) were found in both chicories, while 3,5-di-O-caffeoylquinic acid was typical of var. crispum and cis-caftaric acid of var. latifolium.

Isolation and determination of alpha-dicarbonyl compounds by RP-HPLC-DAD in green and roasted coffee.

Glyoxal, methylglyoxal, and diacetyl formed as Maillard reaction products in heat-treated food were determined in coffee extracts (coffee brews) obtained from green beans and beans with different degrees of roast. The compounds have been reported to be mutagenic in vitro and genotoxic in experimental animals in a number of papers. More recently, alpha-dicarbonyl compounds have been implicated in the glycation process. Our data show that small amounts of glyoxal and methylglyoxal occur naturally in green coffee beans. Their concentrations increase in the early phases of the roasting process and then decline. Conversely, diacetyl is not found in green beans and forms later in the roasting process. Therefore, light and medium roasted coffees had the highest glyoxal and methylglyoxal content, whereas dark roasted coffee contained smaller amounts of glyoxal, methylglyoxal, and diacetyl. For the determination of coffee alpha-dicarbonyl compounds, a reversed-phase high performance liquid chromatography with a diode array detector (RP-HPLC-DAD) method was devised that involved the elimination of interfering compounds, such as chlorogenic acids, by solid phase extraction (SPE) and their derivatization with 1,2-diaminobenzene to give quinoxaline derivatives. Checks of SPE and derivatization conditions to verify recovery and yield, respectively, resulted in rates of 100%. The results of the validation procedure showed that the proposed method is selective, precise, accurate, and sensitive.