Abstract
The phytochemical compositions of green coffee beans (GB), roasted coffee (RC), and the solid residue known as spent coffee grounds (SCG) have been associated with beneficial physiological effects. The objective of this study was to analyze the total phenolic compounds, antiradical scavenging ability, antibacterial activity, and antiproliferative activity on cancer cells of aqueous and ethanolic extracts of GB, RC, and SCG samples. The total phenolic content was quantified by Folin–Ciocalteu assay, while the antiradical activity was evaluated by ABTS●+ and DPPH radical assays, antibacterial activity was determined using the microtiter broth dilution method, and antiproliferative activity was evaluated by MTT assay in lung carcinoma cells (A549) and cervical cancer cells (C33A); furthermore, apoptosis and cell cycle arrest were evaluated by flow cytometry. Ethanolic extracts of RC and SCG showed the highest content of total phenols. The SCG ethanolic extract exhibited the lowest inhibitory capacity 50 (IC50) values for free radicals. The SCG extracts also had the lowest MIC values in bacteria. In antiproliferative assays, SCG extracts exhibited a significant decrease in viability in both cell lines, as well as increased apoptotic cells and promoted cell cycle arrest. The higher content of total phenols and antiradical activity of SCG ethanolic extracts was related to their antiproliferative activity in cancer cells, as well as their antibacterial activity against clinical isolates; therefore, the utilization of SCG adds value to an abundant and inexpensive residue.
Highlights
Coffee, an infusion of ground, roasted coffee beans, has been reported as being one of the most widely consumed beverages in the world [1]
The content of total phenolic (TPC) compounds in ethanolic extracts had the greatest phenolic content, while lower phenolic contents were found in aqueous extracts
The results demonstrate that spent coffee grounds (SCG) extracts exhibited an ability to inhibit the growth of clinically isolated methicillinresistant strains at the concentration range of 2–8 mg·mL−1, where the most effective extract against these strains was ethanolic SCG extract (2 mg·mL−1)
Summary
An infusion of ground, roasted coffee beans, has been reported as being one of the most widely consumed beverages in the world [1]. Along the coffee value chain, a huge number of by-products are generated annually and, in many cases, residues from the coffee industry are not properly handled For this reason, applications such as the production of mushrooms, enzymes, organic acids, biofuels, and fertilizers have been proposed for the value addition of coffee by-products [4]. Due to the functional properties of SCG, its utilization can be viewed, for the food and pharmaceutical industries, as an economically advantageous alternative to the development of foods, drugs, and therapies for the prevention and treatment of diseases In this context, the bioactive compounds in green coffee (GB), roasted coffee (RC), and spent coffee grounds (SCG) have all been shown to possess antioxidant, antiproliferative, and antibacterial effects. Jiménez-Zamora et al [10], Hernández-Arriaga et al [11], and Balzano et al [12] reported the antiproliferative effect of bioactive compounds from SCG extracts on human colon cancer cells (HT-29) and lung carcinoma cells (A549)
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