Phytochemical Profile, Toxicity, and Pharmacological Potential of Peels from Four Species of Tropical Fruits

Tropical fruit peels are generally discarded as waste, yet they contain bioactive substances that could have various uses; in addition, their pharmacological potential remains unexplored. This study aims to characterize the phytochemical profile, toxicity, and pharmacological potential of methanol extracts obtained from the peels of the following tropical fruit species: Annona squamosa L. (purple sugar apple), Annona reticulata L. (custard apple), Chrysophyllum cainito L. (green star apple), and Melicoccus bijugatus Jacq. (mamoncillo). Methanol peel extracts were obtained by maceration. All extracts contained flavonoids, anthraquinones, and triterpenoids as determined by colorimetric methods. A. squamosa and C. cainito exhibited the highest content of total phenols as assayed by the Folin-Ciocalteu method. M. bijugatus showed the highest content of total sugars (fructose, glucose, and sucrose) as determined by high-performance liquid chromatography. A. squamosa and C. cainito presented the highest antioxidant capacities (according to 2,2'-diphenyl-1-picrylhydrazyl, 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid, and cupric reducing antioxidant capacity assays), displayed moderate toxicity against HCT-116 cells, and increased the vinblastine susceptibility of MCF-7/Vin . A. squamosa and M. bijugatus extracts demonstrated modulation of acetylcholinesterase activity, whereas those of A. reticulata showed anti-inflammatory activity by inhibiting protein denaturation. These results confirm that tropical fruit peels can be valuable sources of bioactive compounds, and our findings provide new information about their pharmacologic potential so that they can be used as raw material for the development of new drugs aimed at treating a variety of ailments.