Recently, research on antioxidants has become increasingly active in various fields.Antioxidants react through free radical or molecular oxygen quenching, being capable to either delay or inhibit the oxidation processes that occur under the influence of molecular oxygen or reactive oxygen species. Accordingly, assays developed to evaluate the antioxidant activity of food constituents vary. Therefore, to investigate the antioxidant activity of chemical(s), choosing an adequate assay based on the properties of chemical(s) is critical. Antioxidant assays may be broadly classified as electron transfer (ET)-based assays and hydrogen atom transfer (HAT)-based assays. ET-based assays include ABTS assay, DPPH assay, ferrous oxidation-xylenol orange assay, ferric thiocyanate assay, ferric reducing/antioxidant power assay, potassium ferricyanide reducing power assay, and cupric reducing antioxidant power assay. HAT-based assays include oxygen radical absorbance capacity assay, total peroxyl radical-trapping antioxidant parameter assay, thiobarbituric acid assay, -carotene bleaching assay, and cellular antioxidant activity assay. In this guideline, assays used recently were selected for extended discussion, including the mechanisms underlying each assay as well as the practice of antioxidant capacity assessment.

Edible flowers contain numerous phytochemicals which contribute to their health benefits, and consumption of edible flowers has increased significantly in recent years. While many researchers have been conducted, no literature review of the health benefits of common edible flowers and their phytochemicals has been compiled. This review aimed to present the findings of research conducted from 2000 to 2015 on the species, traditional application, phytochemicals, health benefits, and the toxicology of common edible flowers. It was found in 15 species of common edible flowers that four flavonols, three flavones, four flavanols, three anthocyanins, three phenolic acids and their derivatives were common phytochemicals and they contributed to the health benefits such as anti-oxidant, anti-inflammatory, anti-cancer, anti-obesity, and neuroprotective effect. Toxicology studies have been conducted to evaluate the safety of common edible flowers and provide information on their dosages and usages.

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The free and bound phenolic compounds in 10 common Chinese edible flowers were investigated using reversed phase high-performance liquid chromatography. Their antioxidant capacities were evaluated using 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical-scavenging activity, 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) radical-scavenging activity, oxygen radical absorption capacity (ORAC), ferric reducing antioxidant power (FRAP), and cellular antioxidant activity (CAA). Free factions were more prominent in phenolic content and antioxidant capacity than bound fractions. Paeonia suffruticosa and Flos lonicerae showed the highest total phenolic content (TPC) 235.5 mg chlorogenic acid equivalents/g of dry weight and total flavonoid content 89.38 mg rutin equivalents/g of dry weight. The major phenolic compounds identified were gallic acid, chlorogenic acid, and rutin. P. suffruticosa had the highest antioxidant capacity in the DPPH, ABTS, and ORAC assays, which were 1028, 2065, 990 μmol Trolox equivalents/g of dry weight, respectively, whereas Rosa chinensis had the highest FRAP value (2645 μmol Fe(2+) equivalents /g of dry weight). The P. suffruticosa soluble phenolics had the highest CAA, with the median effective dose (EC50 ) 26.7 and 153 μmol quercetin equivalents/100 g of dry weight in the phosphate buffered saline (PBS) and no PBS wash protocol, respectively. TPC was strongly correlated with antioxidant capacity (R = 0.8443 to 0.9978, P < 0.01), which indicated that phenolics were the major contributors to the antioxidant activity of the selected edible flowers.

CmTST2 is a tonoplast sugar transporter that is highly expressed during melon fruit development, and its overexpression also increases sugar accumulation in strawberry and cucumber fruits.