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Watermelon produces many byproducts (watermelon rind and skin) even though those components contain various bioactive compounds, including citrulline. This study evaluated the citrulline concentration, total phenolic content, and antioxidant activity (DPPH and FRAP assays) of different parts of watermelon and investigated the bioavailability of citrulline from different parts of watermelon using an in vitro human intestinal epithelial Caco-2 cell monolayer model. Solid-phase extracted watermelon flesh, rind, and skin samples were treated on a Caco-2 cell monolayer for 1, 2, and 4 h. The collected basolateral solution at each time point was analyzed for the percentage of citrulline transport. Watermelon flesh had the highest citrulline content, but the watermelon skin had the highest total phenolic content and antioxidant activity compared to other watermelon parts. The citrulline bioavailability showed greater % transport in watermelon skin than in watermelon flesh, rind, and L-citrulline standard. It may be due to the different food matrices of watermelon parts. This suggests that the utilization of watermelon by-products such as skin would help develop value-added products with better bioavailability of citrulline. However, since this study was conducted with an in vitro cell model, more extensive research with in vivo studies will be needed.

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Objectives Excessive fat accumulation in the body, indicated as obesity causes development of other metabolic diseases, such as diabetes and cardiovascular diseases. Due to limitations of current strategies such as long-term engagement and high cost, new strategies to reduce the prevalence of obesity are needed. Garlic scape (Allium sativum L.) is the flower bud of the garlic plant that is removed to promote the growth of the bulb. Although most of garlic scape are trashed as a byproduct of garlic in the farm, it is still edible and includes various phytochemicals to improve human health. The purpose of this study was to investigate anti-obesity effect of garlic scape and its mechanism using 3T3-L1 cells. Methods Garlic scape extract (GSE) was prepared by solvent extraction using 80% methanol (v/v). 3T3-L1 cells, mouse embryonic fibroblast cells that mimic preadipocytes, were incubated with GSE during the differentiation. Total RNA and proteins from the cells were extracted. The expression of genes related to lipid metabolism such as peroxisome proliferator-activated receptor (PPAR) γ, CCAAT/enhancer-binding protein (C\EBP) α and β, adipocyte protein (aP) 2, acetyl CoA carboxylase (ACC), fatty acid synthase (FAS), sterol regulated element binding protein (SREBP) 1c, and carnitine palmitoyltransferase (CPT) 1α was determined using a quantitative PCR. The expression of proteins such as hormone sensitive lipase (HSL), ACC, and AMPK-activated protein kinase (AMPK) was measured using a western blot. Effect of GSE on lipid accumulation were visualized and quantified using Oil Red O staining. Results GSE decreased the expression of genes related to adipogenesis (PPARγ, C\EBPα, and C\EBPβ) and lipogenesis (ACC, FAS, and SREBP1c) whereas HSL and CPT1α genes and proteins related to lipolysis and fatty acid oxidation were not changed. Phosphorylation on both AMPK and ACC were increased. Adipocytes that were treated with GSE showed reduced lipid accumulation. Conclusions GSE inhibits fat accumulation in white adipocytes by decreasing adipogenesis and lipogenesis through possibly a AMPK pathway. Garlic scape may be a potential candidate to improve obese conditions. Funding Sources This work was supported by USDA.

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