Antioxidant, antibacterial properties and the light barrier assessment of raw and purified melanins isolated from Citrullus lanatus (watermelon) seeds

The nutritive value and terapeuthic activity of watermelon seeds is known, but up to day no studies on isolation and characterisation of their melanin were conducted. The aim of the study was to evaluate the antioxidant, antibacterial and light barrier properties of raw and purified melanins isolated from watermelon seeds. Native melanin was isolated from seeds by alkaline extraction. Obtained pigment was purified by acid hydrolysis. Chemical tests and FT-IR analysis were conducted to determine the melanin nature of the isolated pigments. UV-Vis, transmittance and colour properties were evaluated spectrophotometrically. Antioxidant activity was determined using ABTS and antibacterial activity through a well diffusion method. The results of the study demonstrated that melanins isolated from watermelon seeds had antioxidant, light barrier and antibacterial properties. A purified form of melanin had higher antioxidant activity and light barrier properties than the raw form. Both melanins inhibited the growth of and Watermelon seeds may be considered as a promising source of natural melanin which possess remarkable therapeutic action that can support the traditional use of this plant in the ethnomedicine.