UGT89AC1-mediated quercetin glucosylation is induced upon herbivore damage and enhances Camellia sinensis resistance to insect feeding

Quercetin is a key flavonol in tea plants (Camellia sinensis (L.) O. Kuntze) with various health benefits, and it often occurs in the form of glucosides. The roles of quercetin and its glucosylated forms in plant defense are generally not well-studied, and remain unknown in the defense of tea. Here, we found higher contents of quercetin glucosides and a decline of the aglucone upon Ectropis grisescens (E. grisescens) infestation of tea. Nine UGTs were strongly induced, among which UGT89AC1 exhibited the highest activity toward quercetin in vitro and in vivo. The mass of E. grisescens larvae that fed on plants with repressed UGT89AC1 or varieties with lower levels of UGT89AC1 was significantly lower than that of larvae fed on controls. Artificial diet supplemented with quercetin glucoside also reduced the larval growth rate, whereas artificial diet supplemented with free quercetin had no significant effect on larval growth. UGT89AC1 was located in both the cytoplasm and nucleus, and its expression was modulated by JA, JA-ILE, and MeJA. These findings demonstrate that quercetin glucosylation serves a defensive role in tea against herbivory. Our results also provide novel insights into the ecological relevance of flavonoid glycosides under biotic stress in plants.

Effect of quercetin glucosides from Allium extracts on HepG2, PC-3 and HT-29 cancer cell lines

The present study investigated the effects of quercetin glucosides, which were isolated from the Chinese onion (Allium chinense), garlic (Allium sativum), onion (Allium cepa L.) and the Welsh onion (Allium fistulosum L.) in HepG2, HT-29 and PC-3 cancer cell lines. Quercetin-3,4'-di-O-glucoside (3,4'-Qdg) and quercetin-4'-O-glucoside (4'-Qmg) comprise ~98% of the flavonoids in the methanol extract of onion. A small amount of 3,4'-Qdg is present in the Welsh onion and Chinese onion, whereas 4'-Qmg is also present in the Welsh onion. In HepG2 cells, 4'-Qmg was demonstrated to exhibit more significant growth inhibition compared with 3,4'-Qdg and quercetin 3-β-D-glucoside, but exhibited less inhibitory effects in PC-3 and HT-29 cells. These results suggest the anti-proliferative potential of 4'-Qmg in various cancer cell lines and the health benefits of the genus Allium. The findings indicate the potential of 4'-Qmg as an anticancer agent for further development.

Effects of Oral Administration of Moringa oleifera Lam on Glucose Tolerance in Goto-Kakizaki and Wistar Rats

Medicinal plants constitute an important source of potential therapeutic agents for diabetes. In the present study, we investigated the effects of Moringa oleifera (MO) Lam, Moringacea, on glucose tolerance in Wistar rats and Goto-Kakizaki (GK) rats, modeled type 2 diabetes. Major polyphenols in MO powder were quercetin glucosides, rutin, kaempferol glycosides and chlorogenic acids by HPLC analysis. As the results of glucose tolerance test, MO significantly decreased the blood glucose at 20, 30, 45and 60 min for GK rats and at 10, 30 and 45 min for Wistar rats (p<0.05) compared to the both controls after glucose administration. The area under the curve of changes in the blood glucose was significantly higher in the GK control group than in the GK plus MO group (p<0.05) in the periods 30–60 min and 60–120 min. Furthermore, MO significantly decreased stomach emptying in GK rats (p<0.05). The results indicated that MO has an ameliorating effect for glucose intolerance, and the effect might be mediated by quercetin-3-glucoside and fiber contents in MO leaf powder. The action of MO was greater in GK rats than in Wistar rats.

Effect of cinnamoyl and flavonol glucosides derived from cherry blossom flowers on the production of advanced glycation end products (AGEs) and AGE-induced fibroblast apoptosis

Cherry blossom flowers are familiar to the Japanese, and some species of the flowers soaked in salty vinegar are used as processed foods. The constituents of aqueous ethanol extract from cherry blossom (Prunus lannesiana) flowers (CBE) were examined and cinnamoyl and flavonol glucosides were isolated. To elucidate the pharmacological functions of CBE and its constituents, their effects on the production of advanced glycation end products (AGEs) and on AGE-induced fibroblast damage were examined. CBE and 1-O-(E)-caffeoyl-β-D-glucopyranoside (CaG), a principal compound in CBE, significantly suppressed the production of AGEs derived from glucose and albumin at 100 μg/mL. Among the flavonol glucosides, quercetin 3-O-β-D-glucopyranoside (QG) exhibited potent suppressive activity (IC50 : 30 μg/mL). CBE and CaG suppressed glyoxal-induced AGE production in fibroblasts at 10 μg/mL, but QG did not. In addition, CBE and CaG recovered collagen lattice formation consisting of collagen and glycated fibroblasts at 10 μg/mL. Moreover, CBE and its constituents, except kaempferol 3-O-(6″-malony)-β-D-glucopyranoside, significantly suppressed fibroblast apoptosis induced by carboxymethyl lysine-collagen at 10 μg/mL. These results show that cinnamoyl and flavonol glucosides of cherry blossom flowers suppress AGE production and AGE-induced fibroblast apoptosis. Cherry blossom flowers may be effective against skin AGE production and fibroblast damage by AGEs.