Análisis fitoquímico comparativo de tres variedades de Coffea arabica.

Abstract

Coffee husk is an agro-industrial residue from coffee processing that, according to studies referred to by other authors, could be a raw material of commercial interest. Studies show that it has antioxidant capacity, which benefits human health. Therefore, this research aimed to evaluate the chemical composition and biological activity of the husk from three varieties of C. arabica: Acawa (A), Sarchimor (S), and Bourbon Sidra (B), using chromatographic and spectroscopic methods, to support its potential use in the pharmaceutical and food industries. A bromatological analysis of the coffee husks was conducted through determinations that evidenced the nutritional value and quality of the plant material, highlighting variety B for its higher protein and total fiber content. However, the other varieties also demonstrated good quality. Thin-layer chromatography (TLC) analysis showed that varieties A and S have similar chromatographic profiles regarding the presence of chemical compounds with conjugated chromophore groups, phenolic metabolites, and antioxidant capacity. Additionally, the existence of amino acids and caffeine with very similar planar chromatographic appearance was evidenced for the three raw materials. Column chromatography coupled with mass spectrometry (HPLC/MS) allowed the identification of the main specialized metabolites, suggesting the presence of a variety of compounds, highlighting caffeine and other phenolic nature compounds such as caffeoylquinic derivatives. It is noteworthy that the S variety exhibited the greatest diversity of chemical components by both methods. These results are related to the quantification of phenolic compounds and tannins by the Folin-Ciocalteu method and precipitation with gelatin, where varieties A and S showed the highest values of total phenols and tannins. Caffeine levels, also quantified spectrophotometrically with the help of a calibration curve, were also higher in these varieties. The antioxidant capacity was quantified using the 2-diphenyl-1-picrylhydrazyl (DPPH) method and by measuring the ferric reducing antioxidant power (FRAP), with the results referred to as equivalent to the Trolox standard. Although all three raw materials have antioxidant capacity by both mechanisms of action, the previously mentioned varieties stand out as the most effective, results that strongly correlate positively with the level of determined phenolic compounds. The in vivo assay to identify the hypoglycemic capacity of the S variety coffee husk was promising. Although the effect significantly differed from glibenclamide, the oral administration of the husks managed to reduce basal glucose levels compared to the negative control. This assay is considered preliminary, taking into account that some details regarding the administration of the husk need to be corrected, in addition to the need to evaluate the dose-response effect using more than one treatment group with husk. Finally, it was concluded that the analyzed coffee husks can be considered as raw materials of interest in the pharmaceutical or food industry, taking advantage of the synergistic effect provided by their antioxidant and hypoglycemic capacity.