Antioxidant and Anti-Adipogenic Activities of Trapa japonica Shell Extract Cultivated in Korea

Trapa japonica shell contains phenolic compounds such as tannins. Studies regarding the antioxidant and anti-adipogenic effects of Trapa japonica shell cultivated in Korea are still unclear. Antioxidant and anti-adipogenic activities were measured by in vitro assays such as 2,2-diphenyl-1-picrylhydrazy (DPPH) radical scavenging activity, 2,2'-azinobis( 3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) radical scavenging activity, ferric reducing ability of plasma assay, reducing power, superoxide dismutase-like activity, and iron chelating ability in 3T3-L1 cells. We also measured the total phenol and flavonoids contents (TPC and TFC, respectively) in Trapa japonica shell extract. Our results show that TPC and TFC of Trapa japonica shell extract were 157.7±0.70 mg gallic acid equivalents/g and 25.0±1.95 mg quercetin equivalents/g, respectively. Trapa japonica shell extract showed strong antioxidant activities in a dose-dependent manner in DPPH and ABTS radical scavenging activities and other methods. Especially, the whole antioxidant activity test of Trapa japonica shell extract exhibited higher levels than that of butylated hydroxytoluene as a positive control. Furthermore, Trapa japonica shell extract inhibited lipid accumulation and reactive oxygen species production during the differentiation of 3T3-L1 preadipocytes. Trapa japonica shell extract possessed a significant antioxidant and anti-adipogenic property, which suggests its potential as a natural functional food ingredient.