Citation: Nascimento, R.d.P.d.; Rizzato, J.S.; Polezi, G.; Boughanem, H.; Williams, N.G.; Borguini, R.G.; Santiago, M.C.P.d.A.; Marostica Junior, M.R.; Parry, L. Myrciaria jaboticaba Fruit Peel: Bioactive Composition as Determined by Distinct Harvest Seasons and In Vitro Anti-Cancer Activity. Plants 2024, 13, 2907. https://doi.org/10.3390/ plants13202907 Academic Editor: Carlos Gamarra- Luques Received: 22 August 2024 Revised: 9 October 2024 Accepted: 15 October 2024 Published: 17 October 2024 Copyright: © 2024 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). plants Article Myrciaria jaboticaba Fruit Peel: Bioactive Composition as Determined by Distinct Harvest Seasons and In Vitro Anti-Cancer Activity Roberto de Paula do Nascimento 1,2, * , Julia Soto Rizzato 1 , Gabriele Polezi 1 , Hatim Boughanem 2,3,4,5 , Non Gwenllian Williams 2 , Renata Galhardo Borguini 6 , Manuela Cristina Pessanha de Araujo Santiago 6 , Mario Roberto Marostica Junior 1,† and Lee Parry 2,† 1 Laboratório de Nutrição e Metabolismo, Departamento de Ciência de Alimentos e Nutrição, Faculdade de Engenharia de Alimentos, Universidade Estadual de Campinas, Campinas 13083-862, SP, Brazil; jsotorizzato@gmail.com (J.S.R.); gpolezi@gmail.com (G.P.); mmarosti@unicamp.br (M.R.M.J.) 2 Prevention and Early Detection Laboratory, European Cancer Stem Cell Research Institute, School of Biosciences, Cardiff University, Cardiff CF24 4HQ, UK; h.b.boughanem@gmail.com (H.B.); williamsng1@cardiff.ac.uk (N.G.W.); parryl3@cardiff.ac.uk (L.P.) 3 Department of Endocrinology and Nutrition, Virgen de la Victoria University Hospital, 29010 Malaga, Spain 4 Unidad de Gestión Clinica Medicina Interna, Lipids and Atherosclerosis Unit, Maimonides Institute for Biomedical Research in Córdoba (IMIBIC), Reina Sofia University Hospital, University of Córdoba, 14004 Córdoba, Spain 5 Spanish Biomedical Research Center in Physiopathology of Obesity and Nutrition (CIBERObn), Instituto de Salud Carlos III, 28029 Madrid, Spain 6 Empresa Brasileira de Pesquisa Agropecuária, Embrapa Agroindustria de Alimentos, Rio de Janeiro 23020-470, RJ, Brazil; renata.borguini@embrapa.br (R.G.B.); manuela.santiago@embrapa.br (M.C.P.d.A.S.) * Correspondence: roberto_beto1@hotmail.com; Tel.: +55-32988287447 † These authors contributed equally to this work. Abstract: Jaboticaba (Myrciaria jaboticaba) is a recognizable and unique crop from Brazil. The fruit’s byproducts are currently being studied, given their bioactive composition and promising anti-cancer potential. It is not evident, however, if different harvesting seasons can modify the chemical profile and antioxidant capacity of jaboticaba fruit fractions. Furthermore, as there is limited data for jaboticaba’s anti-proliferative effects, additional assessments are required to improve the robustness of these findings. Therefore, this study aimed to determine the composition of the peel of jaboticaba collected in two periods (May—off-season, sample 1—and August–October—peak season, sample 2) and test the peel’s richest anthocyanin sample against colorectal cancer (CRC) cell lines. To accomplish this, proximate, spectrophotometric, and chromatographic analyses were performed in two freeze-dried samples; and anti-proliferative and/or colony-forming assays were carried out in Caco-2, HT29, and HT29-MTX cells. As a result, sample 2 showed the highest levels of polyphenols overall, including flavonoids and anthocyanins. This sample displayed significative higher contents of cyanidin-3-O-glucoside (48%) and delphinidin-3-O-glucoside (105%), in addition to a superior antioxidant capacity (23% higher). Sample 1 showed higher amounts of total protein, gallic acid (20% higher), and specific carotenoids. An aqueous extract from sample 2 was tested against CRC, showing anti-proliferative effects for Caco-2 cells at 1 and 2 mg/mL concentrations, with IC50 values of 1.2–1.3 mg/mL. Additionally, the extract was able to inhibit cell colony formation when tested at both low and high concentrations. In conclusion, jaboticaba collected in the main season stands out regarding its polyphenol composition and holds potential against cancer cell growth. Keywords: agro-industrial byproduct; anthocyanins; anti-colony-forming activity; anti-proliferative action; Caco-2 cells; colorectal cancer; cyanidin-3-O-glucoside; delphinidin-3-O-glucoside; gallic acid; phenolic compounds Plants 2024, 13, 2907. https://doi.org/10.3390/plants13202907 https://www.mdpi.com/journal/plants