Influencia del secado de la cascarilla de coffea arábica (café) variedad catucai amarillo en la composición química y actividad biológica

Abstract

The coffee agroindustry in Ecuador generates a considerable volume of waste, which is generally discarded without prior treatment, representing an environmental challenge and an opportunity for the valorisation of these by-products. Among these is the husk, a valuable raw material due to its antioxidant potential. However, its use as a functional ingredient in pharmaceutical and food products depends largely on the methods used for its processing, including drying, a key step that can influence its chemical composition and biological activity. For this reason, the aim of this research was to evaluate the influence of the drying method (freeze-drying and oven drying) on the chemical composition and biological activity of C. arabica yellow Catucaí husks, using qualitative and quantitative methods, in order to use them for the benefit of human health. Thin layer chromatographic evaluation (TLC) showed that both hydroalcoholic extracts obtained by both drying methods presented similar chromatographic behaviour. Metabolites with conjugated chromophore groups, compounds of phenolic nature and antioxidant capacity, as well as amino acids and caffeine were identified. The determination of specialised metabolites by high-performance liquid chromatography coupled to mass spectrometry (HPLC/MS) showed that both extracts have a similar chemical composition. Alkaloids (caffeine and trigonelline), chlorogenic acid derivatives, along with other phenolic compounds such as procyanidins, flavonoids, xanthones and simple phenols were identified. These findings correlate with the quantification of phenols and tannins developed by the Folin-Ciocalteu method and gelatin precipitation, as well as the spectrophotometric determination of caffeine, revealing that there are no statistically significant differences between both drying methods, which evidences the presence of these metabolites of interest. However, individual quantitative analysis of the identified compounds is recommended to rule out possible variations. Antioxidant capacity was measured as equivalent to trolox by the iron reducing antioxidant power (FRAP) and free radical scavenging (DPPH) assays. This suggests that the content of total phenols, the main metabolites contributing to this biological activity, remains stable regardless of the drying method used. Glucose tolerance activity in albino mice (Mus musculus) using a C. arabica husk extract showed an appreciable reduction in basal glucose levels and a superior effect to glibenclamide treatment at any of the three doses tested (100, 200 and 400 mg/kg bw). The lowest dose administered showed the most acceptable behaviour, while at the 400 mg/kg bw dose, further acute toxicity studies are recommended. It is concluded that the drying method does not significantly influence the chemical composition and biological activity studies carried out for coffee husks, which suggests their use as a source of bioactive compounds with antioxidant and hypoglycaemic properties, representing a promising alternative for the development of functional or therapeutic food products.