Soluble melanins of the Randia echinocarpa fruit – Structural characteristics and toxicity

Abstract

The water-soluble melanins (SM) of Randia echinocarpa fruit possess interesting biological activities and have been scarcely characterized. In this study, SM were obtained at boiling (SMBT) and room (SMRT) temperatures and characterized by UV-Vis, IR, thermogravimetric analysis, and GC-MS of the hydrolysis products of the SM; besides, the solid-state 13 C NMR, elemental analysis, and acute and sub-acute toxicity of the SMBT were determined. SMBT and SMRT contain organic acids and carbohydrates and their spectroscopic signals and thermograms were similar, but the SMBT yield was higher.The SMBT were characterized by their elemental composition (C 48.260 ± 0.011%, N 3.693 ± 0.009% and H 6.093 ± 0.076%) consistent with the presence of aromatic rings and eumelanins, degradation temperature at 300°C, 13 C NMR signals supporting melanin-bonding with carbohydrates and organic acids, and innocuity in Balb/C mice (acute assay, LD 50 > 5 g/kg b.w.; sub-acute assay, no lethality at 500 mg/kg b.w. for 30 days). Practical applicationsThe consumption of melanins has been associated with health benefits because of their biological activities (e.g., antioxidant, immunostimulatory, UV-and radiationprotective). Randia echinocarpa is employed in Mexican traditional medicine against chronic degenerative diseases (e.g., cancer and diabetes) and ailments of organs (e.g., kidney and lung) and systems (e.g., circulatory and gastrointestinal). The R. echinocarpa fruit contains water-soluble melanins (SM) that inhibit carbohydrate-digestive enzymes and show high antioxidant activity; thus, SM could be useful for the prevention and treatment of diabetes. This study showed that the SM structure contains melanin-bonding organic acids and carbohydrates, which could be associated with the SM solubility and higher yield, and that SMBT were innocuous in the acute and sub-acute assays in mice. Thus, the R. echinocarpa SMBT could be used as safe potential ingredients to develop functional products. K E Y W O R D Sdietary supplements, elemental analysis, functional food, melanin, solid-state carbon-13 magnetic resonance spectroscopy, thermogravimetry, toxicity 2 of 12 | GIL-AVILÉS et AL.

Water-Soluble Melanoidin Pigment as a New Antioxidant Component of Fermented Willowherb Leaves (Epilobium angustifolium)

“…Melanoidins of non-fermentation origin typical for the original seed coats, fruit shells, or root epidermis from Castanea mollissima [ 65 ], Echinacea purpurea [ 66 ], Nigella sativa [ 67 ], Randia echinocarpa [ 68 ], Sesamum indicum [ 69 ], and Helianthus anuus [ 70 ] showed slightly different values. The value of the atomic ratio H/C (0.89) indicated the predominance of aromatic fragments in the EAM structure, and the value of O/C (0.48) showed the presence of oxygen functional groups.…”

Phytochemical composition and biological activities of the plants of the genus Randia

“…Thus, R. echinocarpa extracts have antioxidant, immunomodulatory, and antimutagenic activities that have been considered essential to treat various diseases, including malaria and cancer (Munialo et al 2019), and support the traditional uses of the species. Supporting the potential of R. echinocarpa as a source of phytotherapeutic compounds, toxicity assays in mice showed that soluble melanins from fruit were innocuous, and treated mice showed normal behavior, weight, and healthy organs (Gil-Avilés et al 2019).…”

Rescue potency of Eucalyptus oil against gamma-rays induced gastric ulceration

“…No approved prophylaxis or therapy exists for these toxicities (2) . Considering the high toxicity of the radiation treatment to the gastrointestinal tract, studies revealing natural radio protectors that regulate the gastrointestinal tract response to injury following irradiation are extremely beneficial (3)(4)(5) . The genus Eucalyptus L'Heritier comprises about 300 species contains volatile essential oil in their leaves (6) .…”