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Melanins of Vitex mollis fruit with differences in water‐solubility show high inhibition of carbohydrate digestive enzymes and antioxidant activity
Author(s) -
PíoLeón Juan Fernando,
MontesAvila Julio,
LópezAngulo Gabriela,
DíazCamacho Sylvia Páz,
VegaRios Alejandro,
LópezValenzuela José Ángel,
DelgadoVargas Francisco
Publication year - 2018
Publication title -
journal of food biochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.507
H-Index - 47
eISSN - 1745-4514
pISSN - 0145-8884
DOI - 10.1111/jfbc.12509
Subject(s) - abts , chemistry , dpph , antioxidant , extraction (chemistry) , tyrosinase , food science , nutraceutical , water extraction , solubility , methanol , aqueous solution , enzyme , chromatography , biochemistry , organic chemistry
The fruit of Vitex mollis Kunth contains water‐soluble melanin (SM), whose properties have been poorly described. This study determined physicochemical characteristics, the inhibition of carbohydrate digestive enzymes (amylase and α‐glucosidase), and antioxidant activity (ABTS, DPPH, ORAC, and β‐carotene bleaching) of SM (partially purified, aqueous extraction), water‐insoluble melanin (IM) (pure, alkali‐acid extraction), and organic (i.e., methanol, ethanol, and methanol : water 8:2 vol/vol) and aqueous extracts of V. mollis fruit. SM and IM were characterized by UV and IR spectroscopy, and their spectra showed signals characteristic of melanins. They also showed similar antioxidant (1,321–2,664 μmol TE/g), and α‐glucosidase inhibitory (IC 50 1.48–0.022 mg/mL) activities, values that were better than those of the organic extracts (ABTS < 746 µmol TE/g and IC 50 > 4.87 mg/mL, respectively). In addition, SMs showed higher extraction yields than IMs. Therefore, SM shares nutraceutical properties with IM and can be obtained by simple and environmentally friendly methods. Practical applications Melanins show biological activities (e.g., antioxidant, immunostimulatory, UV‐, and radiation‐protective) and their consumption has been associated with health benefits. However, studies of plant melanins are scarce because their extraction involves harsh pH conditions and the yields are usually low. The results showed that melanin was the main pigment in Vitex mollis fruit and water‐soluble. Moreover, the extraction method was simple, ecological, and produced high yields. Both water‐soluble and water‐insoluble melanins showed similar biological activities (antioxidant and α glucosidase inhibition). Species of Vitex are commonly employed as food and in folk medicine (e.g., premenstrual and gynecological disorders, gastrointestinal problems and inflammation, bacterial infections). Soluble melanins of V. mollis could be used as food supplement or in pharmaceutical preparations.