Polyphenol content and free radical scavenging activity of bee pollen collected in Castelo Branco, Portugal

The aim of this work is to evaluate the methodology to obtain an extract rich in caffeic acid (CAD) derivatives in spent coffee ground (SCG) and evaluate its free radical scavenging activity. Eighteen SCG samples and coffee beverage were collected from different brands and coffee shops. The SCG extracts were prepared by three methods: A) ethanol 96o according Campos et al [1]; B) extracts prepared in A were hydrolysed with HCl 37% (1:10), according Markham [2]; C) water extraction. All samples were screened by HPLC/DAD for phenolic profile characterization and structural identification and quantification of CAD [1]. Among caffeine the majority of the compounds found in the coffee beverage were CAD and in the SCG the compounds remaining the same. The hydrolysed extracts confirmed its existence, possible as glycosides (Fig. 1). The matrix resulting from the hydrolysis of the SCG can also be used to explore further bioactivities for therapeutic consideration once the released aglycones are in general more active. Method A was the most efficient (4.305 mg CAD/g SCG). Nevertheless the results were different according to the products. The caffeine ratio between SCG and expresso coffee was 17% and the ratio of CAD in both samples was 8%. A significant free radical scavenging potential (activity of DPPH) was founded yet in SCG (EC50 = 1.857 µg/mL) comparing with the coffee beverage (EC50 = 0.172 µg/mL) around 10% lower. The results show that the SCG has potential for future biological screening showing a stable compound profile and constitutes a much simpler matrix than the beverage, simplifying its analysis and further studies for potential bioactivities.