Abstract
Black soybean germination or fermentation increases active ingredient bioavailability and anti-oxidative activity. This study investigated the effects of fermented and germinated black soy milk on anti-oxidation and melanogenesis inhibition. The total phenolic content (TPC; 42.66 ± 1.65 mg gallic acid equivalent/g) and total flavonoid content (TFC; 5.43 ± 0.54 mg quercetin equivalent (QE)/g) in ethanol extracts from Lactobacillus plantarum TWK10 (TWK10)-fermented nongermination black soy milk (FNGB) were significantly (p < 0.05) higher than those in ethanol extracts from nonfermented-nongermination black soy milk (NNGB). Although the TPC of ethanol extracts from nonfermented-germination black soy milk (NGB) and fermented-germination black soy milk (FGB) were not significantly different (p > 0.05), the TFC of FGB (1.79 ± 0.08 mg QE/g) was significantly higher than that of NGB (p < 0.05). The 1,1-diphenyl-2-picrylhydrazyl radical scavenging activity of ethanol extracts from NNGB, FNGB, NGB, and FGB was significantly higher than that of water extracts at 10 mg/mL (p < 0.05). Furthermore, ethanol extracts from both FNGB and FGB significantly reduced the melanin content in zebrafish embryos at 100 µg/mL (p < 0.05) without causing death, malformation or bradycardia. Overall, the antioxidant activity of black soy milk significantly increased after TWK10 fermentation; moreover, ethanol extracts from FNGB and FGB could inhibit melanogenesis, indicating their potential as whitening ingredients.
Highlights
Melanin biosynthesis is an important metabolic process in the body
According to the minimum germination rate of soybean seeds of 80% as specified by the Association of Official Seed Certifying Agencies (AOSCA) [38], the black soybeans were well germinated under the cultivation conditions used in this study
The results showed that the DPPH free radical scavenging capacity of the water extracts of nongermination black soy milk (NNGB), fermented nongermination black soy milk (FNGB), nonfermented-germination black soy milk (NGB), and fermented-germination black soy milk (FGB) increased with the increase in sample concentration and had a dose-response relationship (p < 0.05; Table 2)
Summary
Melanin biosynthesis is an important metabolic process in the body. It has been demonstrated that melanocytes generate melanin that determines the color of skin, hair, and eyes in humans [1,2]. An increase in tyrosinase activity promotes melanin biosynthesis, as do excessive UV irradiation and oxidative stress. Several animal models are used to study the inhibition of melanogenesis, such as zebrafish, mice, rats, guinea pigs, or humans. Detection of important indicators that affect melanogenesis, such as tyrosinase activity, in the zebrafish embryo model is feasible [10]. The appearance of zebrafish embryos and heart rate can be used to evaluate the toxicity of samples [9]. Because of these advantages, this study used the zebrafish embryo model in in vivo experiments
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