Identification of Sinapic Acid Derivatives from Petit Vert Leaves and Their Effects on Glucose Uptake in C2C12 Murine Myoblasts.

Petit vert (scientific name: Brassica oleracea var. gemmifera DC. × Brassica oleracea var. acephala DC.) is a new variety of vegetable created by crossbreeding kale and brussel sprouts (Brassica oleracea species). The present study aimed to identify biologically active compounds in extracts of the outer leaves of Petit vert by purification and to examine their biological activities. The dried and powdered outer leaves of Petit vert were extracted, fractionated, and purified to isolate active compounds. Mass spectrometry (MS) was used to identify the compounds, and nuclear magnetic resonance (NMR) spectroscopy was performed to elucidate their structures. The compounds isolated from Petit vert leaves were glycosides that contained kaempferol, quercetin (flavonol), or sinapic acid (phenylpropanoid). Glucose uptake in cultured C2C12 murine myoblasts in the absence of insulin was significantly increased by these compounds, kaempferol, sinapic acid, and ferulic acid, while uptake in the presence of insulin was also significantly increased by compounds 3 and 4, kaempferol, and sinapic acid. The effect was not necessarily concentration-dependent, and some agents decreased the glucose uptake at higher concentrations. The present study reports for the first time the isolation of five compounds containing sinapic acid from the outer leaves of Petit vert and their stimulation of glucose uptake in cultured C2C12 murine myoblasts. The results obtained herein suggest the potential of these compounds to effectively attenuate hyperglycemia and maintain muscle strength by promoting glucose metabolism in muscle cells.