BIOACTIVE AND TOXIC COMPOUNDS IN SEEDS OF CARICA PAPAYA USING ANALYTICAL TECHNIQUES AND ARTEMIA SALINA BIOASSAY

The study of fruit by-products, such as seeds and peels, with a view to their use as food supplements, involves not only the assessment of their nutritional composition but also the investigation of bioactive and potentially toxic compounds. The objective of this study was to evaluate the presence of bioactive and toxic compounds in papaya peel, pulp, and seeds, as a part of a broader project aimed at developing a traditional Mozambican white maize flour porridge enriched with papaya seeds. The analysis of bioactive compounds included antioxidant capacity assays (DPPH, ABTS⁺, and FRAP), as well as the determination of total phenolic compounds, flavonoids, and carotenoids. Toxic potential was assessed using an Artemia salina bioassay, measuring the survival rate of ten organisms in triplicate after 6, 12, and 24 hours of exposure to extract concentrations ranging from 0.08 mg/mL to 4 mg/mL. Aqueous seed extracts exhibited concentration-dependent toxicity, ranging from 100% survival at 0.16 mg/mL to 0% survival at 3.2 mg/mL, with an estimated LC₅₀ of 2.4 mg/mL. Papaya peel exhibited the highest antioxidant capacity in both ABTS (2389.7 μM Trolox/g extract) and FRAP (11.02 μM Fe²⁺/g extract) assays, and high levels of total flavonoids (190.71 mg QE/100 g) and total carotenoids (376.4 μg/g). In contrast, the pulp showed the highest antioxidant activity (15.18 μM DPPH), as well as the highest concentrations of total phenolic compounds (424.41 mg GAE/100 g) and total carotenoids (472.3 μg/g). Seeds displayed the lowest levels of bioactive compounds, with total phenolics of 89.58 mg GAE/100 g, total flavonoids of 33.02 mg QE/100 g, and total carotenoids of 36.4 μg/g, alongside the lowest antioxidant capacity in the FRAP (1.53 μM Fe²⁺/g extract) and ABTS (1803.6 μM Trolox/g extract) assays. Therefore, the toxic effect observed in seed extracts may be associated with the presence of other bioactive secondary metabolites, such as glucosinolates and their enzymatic derivatives, isothiocyanates, previously reported in papaya seeds. These promotes toxic effects in aquatic organisms, including crustaceans, where they can compromise essential physiological processes. In humans, however, the toxicity is considerably lower, possibly due to metabolic differences, more efficient detoxification mechanisms, and the low levels of exposure normally observed in the diet. The potential functional benefits of the seeds should be interpreted with caution, considering both the limited antioxidant contribution and the presence of metabolites with potential toxic effects in sensitive organisms, as well as the dilution effect when used as a food supplement.

Financing Bodies: Fundação de Amparo à Pesquisa do Estado de Goiás (FAPEG) 201210267000885; Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); Coordenação de Aperfeiçoamento de Pessoal de Nível Superior-CAPES.