Studies on extraction and antioxidant potential of green coffee

Green coffee conserves were prepared from the species Coffea arabica and Coffea robusta by flaking, powdering and extraction with solvent mixtures of isopropanol and water in different ratios and their antioxidant properties were investigated. The yields of conserves were highest 27% for C. arabica and 29% for C. robusta, when isopropanol and water in ratio of 60:40 was employed. The total polyphenol content was determined and found to be higher (31.7–32.2%) in these conserves. At a concentration of 200 ppm, coffee conserves from Arabica and Robusta, exhibited 92% and 88% antioxidant activity respectively in comparison to 95% for BHA. The conserves were analyzed by HPLC and three phenolic compounds could be identified. The chlorogenic acid, the major compound in the purified extracts (56 ± 10%), was isolated and characterized by 1H and 13C NMR spectral data. While the caffeic acid part of the molecule was confirmed from the signals for aromatic protons and olefenic protons, the quinic acid group was evident from the signals for methine protons α to hydroxyl groups as well as for the methylene protons of the cyclohexane moiety. Similarly, 13C spectra showed signals for two carbonyl carbons, apart from eight signals corresponding to six aromatic and two olefenic carbons and signals for the six carbons in the cycloalkane side chain.