The chemical composition of green coffee from different geographical origins is characterized by the presence of several chlorogenic acids, including esters of trans - cinnamic acids and quinic acid (Table 1). Caffeic acid (1), p - coumaroylquinic acid (2), p - coumaroylN - tryptophan (3), chlorogenic acid (3 - O - caffeoylquinic acid) (4), neochlorogenic acid (5 - O - caffeoylquinic acid) (5), cryptochlorogenic acid (4 - O - caffeoylquinic acid) (6), caffeoyl- N - tryptophan (7), 3 - O - feruloylquinic acid (8), 5 - O - feruloylquinic acid (9), 3,4 - O - dicaffeoylquinic acid (10), 3,5 - O - dicaffeoylquinic acid (11), 4,5 - O - dicaffeoylquinic acid (12), 3 - O- feruloyl- 4 - caffeoylquinic acid (13), 3 - O - feruloyl- 5 - caffeoylquinic acid (14), 4 - O - feruloyl- 5 - caffeoylquinic acid (15), and caffeine (16) were isolated (Fig. 1), as is typical of the C. arabica and C. canephora species (Alonso-Salces et al., 2009; Clifford, 1999; Clifford and Knight, 2004; Del Rio et al., 2010). Among phenolic compounds, neochlorogenic acid (5) was the most abundant compound in all samples analyzed, followed by chlorogenic acid (4) (Table 1). Caffeine (16) was the second most abundant compound in all analyzed samples (Table 1). The total amount of identified compounds shows a clear and significant distinction between C. canephora from Uganda and Vietnam and all other C. arabica accessions. Among the latter, C. arabica from Ethiopia showed the lowest amount (Fig. 2). These data are in agreement with the literature data, confirming a higher content of chlorogenic acids and caffeine in the C. canephora accessions (Alonso-Salces et al., 2009; Correia et al., 1995; Guerrero and Suarez, 2001). One of the crucial parameters for the use of green coffee in dietary supplements is the ratio between caffeine and total chlorogenic acids, the latter being responsible for most of the antioxidant capacity of green coffee extracts. Moreover, concentrations of phenolic compounds and methylxanthines are considered reliable geographical indicators, as well as chemotaxonomical markers (Alonso-Salces et al., 2009). The plot of caffeine against total chlorogenic acids shows a clear distinction between C. canephora accessions from Uganda and Vietnam and all the other C. arabica accessions (Fig. 3). In particular, C. canephora (robusta) shows high levels of both caffeine and total chlorogenic acids, which agrees with the highest total content of extracted compounds (Fig. 2). With the sole exception for Honduras accessions, a clear separation was found among C. arabica accessions according to their geographical origin, with a narrow differentiation based on caffeine and a broad differentiation based on their content of total chlorogenic acids (Fig. 3). In particular, the accessions from Ethiopia and Mexico show the lowest content of both caffeine and chlorogenic acids, whereas the accessions from Kenya have a relatively low caffeine content and the highest content of chlorogenic acids (Fig. 3).
