The polyphenol content of common buckwheat, Tartary buckwheat, buckwheat leaves, sea tangle, sea mustard ears, and fusiformis were analyzed. Among these, buckwheat leaves exhibited the highest polyphenol content. Hot water extraction followed by treatment with plantase enzyme increased the polyphenol yield by 56% for buckwheat leaves and by 34% for sea tangle. Cytotoxicity test performed on 3T3-L1 pre-adipocytes for seaweeds and buckwheat leaves revealed no significant cytotoxic effects compared to that of the control group at 1 mg/mL. Additionally, when examining the effects of buckwheat leaf and sea tangle extracts on the pre-adipocytes differentiation, into adipocytes confirmed that buckwheat leaf extract inhibited fat differentiation at 10 mg/mL and sea tangle at 0.1 mg/mL. Buckwheat/sea tangle enzyme food had 6.5 times higher amylase activity, 27 times higher protease activity, and more than twice as high dietary fiber, polyphenol, and DPPH scavenging ability as brown rice enzyme foods. Buckwheat/sea tangle enzyme-supplemented food contained more than 30% more phlorotannins and 7.8% more alginic acid than brown rice enzyme-supplemented food.

Buckwheat leaves have the best antioxidant properties, including flavonoids, rutin, and 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging ability compared to common buckwheat and tartary buckwheat. The total dietary fiber content of the powder extracted by mixing buckwheat leaves and sea tangle was 30.5%. To manufacture bread containing mixed buckwheat flour, 10, 20, and 30% buckwheat flour was mixed in to produce buckwheat bread. The bread’s characteristics underwent significant changes with varying levels of buckwheat flour. As the buckwheat content increased, the size of the bread decreased, but its hardness, gumminess, and chewiness tended to increase. The sensory characteristics of the bread were not improved due to the addition of gluten in the case of bread mixed with 20% buckwheat flour. When the buckwheat flour content was mixed at 20%, and the mixed extract of buckwheat leaves and sea tangle were added at 0.4% and 1.0%, there was no significant difference in the appearance of the buckwheat bread. Still, regarding sensory properties, the preference was higher in the sample with 1.0% added buckwheat flour.