Compostos bioativos obtidos da casca de maçã da variedade Royal Gala (Malus domestica).

Abstract

The apple (Malus domestica) is a fruit from the Rosaceae family, known for its medicinal properties present in the pulp, seeds and peel. Apple extracts have various biological activities, including antioxidant, anticancer and antimutagenic, attracting interest for their use as food additives and nutraceutical supplements. This study aimed to analyze the bioactive constituents and the antioxidant, cytotoxic and antimicrobial activities of extracts from the peel of the Royal Gala variety. The extracts were obtained by two extraction methods, maceration and Soxhlet, using hexane, ethyl acetate, methanol, ethanol and a mixture of ethanol and water (50:50). The antioxidant activity was determined using the DPPH radical scavenging method and expressed as IC50, while the phenolic compounds were quantified using the Folin-Ciocalteu method. The cytotoxic activities were tested in vitro on HepG2 and HCT116 tumor cells using the Alamar Blue assay, expressed in terms of inhibition of cell proliferation (IPC). In addition, the antimicrobial activity was assessed by broth microdilution, testing bacteria (Gram-positive and Gram-negative) and fungi, in order to determine the minimum inhibitory concentration (MIC). The extracts obtained by maceration showed antioxidant activity ranging from 17.83 ± 2.53 μg.mL-1 (ethanol and water 50:50) to 353.10 ± 2.79 μg.mL-1 (ethanol II). The soxhlet extracts showed antioxidant activity ranging from 36.75 ± 1.23 μg.mL-1 (ethanol and water 50:50) to 358.66 ± 73.44 μg.mL-1 (ethyl acetate). The content of total phenols in the maceration extracts ranged from 13.34 ± 0.06 mgEA/extract (ethanol) to 153.00 ± 0.82 mgEA/extract (ethanol and water 50:50). For the soxhlet extracts, the total phenol content ranged from 6.97 ± 0.64 mgEA/extract (ethyl acetate) to 113.81 ± 0.05 mgEA/extract (ethanol and water). The cytotoxic activity against HCT116 ranged from 8.22 ± 3.61% (ethyl acetate) to 20.22 ± 1.79% (ethanol II), while the cytotoxic activity against HepG2 ranged from 0.59 ± 0.17% (methanol) to 23.35 ± 2.07% (ethanol and water). None of the extracts showed significant antimicrobial activity. These findings highlight that apple peel extracts are promising in terms of antioxidant and cytotoxic activity. Among the extraction methods tested, the extracts obtained with a mixture of ethanol and water (50:50) showed the best results in terms of antioxidant activity and phenolic content. The CMEA extract (ethanol and water) showed the greatest inhibition on the HepG2 strain. The research highlights that several factors, such as extraction method, solvents and apple variety, influence the biological activities of the extracts. This study contributes to understanding the potential of apples as a source of bioactive compounds with applications in health and nutrition. The results encourage further research into the use of apple extracts in food and pharmaceutical products, promoting greater exploitation of the fruit's properties in public health and well-being issues. Furthermore, the research suggests that the combination of extraction methods and the use of suitable solvents can maximize the recovery of the beneficial compounds present in apples, broadening the possibilities for their application in the food industry and medicine.