Cytotoxic, Antioxidant, and Antidiabetic Activities versus UPLC-ESI-QTOF-MS Chemical-Profile Analysis of Ipomoea aquatica Fractions

Ipomoea aquatica is a common green leafy vegetable that has numerous uses in traditional medicine. This study focused on the determination of the cytotoxic, antiradical, and antidiabetic properties of various fractions of the I. aquatica methanolic extract, as well as on the tentative identification of some bioactive compounds in the same fractions. The cytotoxicity was determined by the brine shrimp lethal test. The antioxidant activities of the I. aquatica fractions were investigated through 3 assays. The antidiabetic activity (in vitro) was measured by α-glucosidase and α-amylase inhibition assays. Phytochemical qualitative analyses demonstrated the presence of alkaloids, terpenoids, phenols, and flavonoids in the ethyl acetate-methanol and methanol fractions. The total phenolic and total flavonoid contents were found to be highest in the ethyl acetate-MeOH fractions. The evaluation of the cytotoxicity showed that the hexane-dichloromethane fraction is the most toxic, while the others are moderately toxic. The antioxidant activity assays showed that the ethyl acetate-MeOH fractions are the most potent, while the α-glucosidase and α-amylase assays revealed that the hexane-dichloromethane fraction might contain a potent antidiabetic agent. Some bioactive substances in the MeOH fractions, such as salicylic acid glucoside, 1-O-sinapoyl-β-D-glucose derivative, and dihydroferulic acid derivative, were tentatively identified. To the best of our knowledge, this is the first report to detect and identify these compounds in this species. Based on the results of this study, it may be concluded that I. aquatica is a potent antioxidant agent and could be a good candidate as a natural antioxidant in food and therapeutics.

Production of Defense Phenolics in Tomato Leaves of Different Age

Phenolics play an essential role in the defense reaction of crop plants against pathogens. However, the intensity of their production induced by infection may differ during the life of a plant. Here, we identified age-related differences in phenolic biosynthesis in the pathosystem Solanum lycopersicum cv. Amateur and Pseudomonas syringae pv. tomato DC3000. We analyzed concentrations of total phenolics, phenolic profiles, and concentrations of selected phenolic acids. The influence of bacterial infection, together with leaf and plant age, was assessed. The changes in concentrations of caffeic acid, 4-hydroxybenzoic acid, and salicylic acid glucoside caused by infection were found to be influenced by age. In concrete, the increases in the concentrations of these metabolites were all evident only in young plants.

Salicylic Acid Glucoside Acts as a Slow Inducer of Oxidative Burst in Tobacco Suspension Culture

Salicylic acid β-glucoside (SAG) is a storage form of a defense signal against pathogens, releasing free salicylic acid (SA), to meet the requirements in plants. Since excess SA induces locally restricted cell death following oxidative burst and Ca2+ influx in plants, the effects of SAG on cell viability, Ca2+ influx, and generation of superoxide (O•−) were examined in suspension-cultured tobacco BY-2 cells expressing aequorin. Among SA-related chemicals tested, only SAG induced the slow and long-lasting O2•− generation, although SAG was less active in acute O2•− generation, Ca2+ influx and induction of cell death. The prolonging action of SAG is likely due to gradual release of SA and the data suggested that a peroxidasedependent reaction is involved. Notably, pretreatment with low-dose SA (50 μm) enhanced the response to SAG by 2.5-fold. There are four possible secondary messengers in early SA signaling detectable in the BY-2 culture, namely O2•−, H2O2, Ca2+ and protein kinase (PK). If these messengers are involved in the low-dose SA-dependent priming for SAG response, they should be inducible by low-dose SA. Among the four SA-inducible signaling events, PK activation was excluded from the low-dose SA action since a much higher SA dose (> 0.4 mм) was required for PK activation.