This study aimed to develop a convenient model to investigate the senescence of host defenses and the influence of food and nutrition. A small soil nematode, Caenorhabditis elegans, was grown for 3 days from hatching on a lawn of Escherichia coli OP50 as the normal food source, and subsequently some of the nematodes were fed lactic acid bacteria (LAB). The life spans of worms fed LAB were significantly longer than the life spans of those fed OP50. To investigate the effect of age on host defenses, 3-to 7-day-old worms fed OP50 were transferred onto a lawn of Salmonella enterica serovar Enteritidis for infection. The nematodes died over the course of several days, and the accumulation of salmonella in the intestinal lumen suggested that the worms were infected. The 7-day-old worms showed a higher death rate during the 5 days after infection than nematodes infected at the age of 3 days; no clear difference was observed when the worms were exposed to OP50. We then investigated whether the LAB could exert probiotic effects on the worms' host defenses and improve life span. Seven-day-old nematodes fed LAB from the age of 3 days were more resistant to salmonella than worms fed OP50 until they were infected with salmonella. This study clearly showed that LAB can enhance the host defense of C. elegans and prolong life span. The nematode appears to be an appropriate model for screening useful probiotic strains or dietetic antiaging substances.

Seven flavonoid profiles, some of which were reported to show antiallergic activity in vitro, were surveyed in 28 kinds of tea. Flavonoids were extracted with hot water, hydrolyzed to aglycons, and determined by HPLC. The hydrolysis time needed to obtain the maximum for each aglycon was examined. Flavonols quercetin and kaempferol were found in 17 kinds of tea infusions, as well as Japanese green tea infusions. Myricetin was found in jasmine and pu-erh tea infusions. A flavon, luteolin, was found in 5 kinds of tea infusions including great plantain tea. Apigenin was found in 4 kinds of tea infusions including perilla leaf tea, and scutellarein was found in 3 kinds of tea infusions. Scutellarein, which is a potent antiallergic and low cytotoxic flavonoid, is found in great plantain tea and was detected in perilla leaf and safflower tea infusions at concentrations of approximately 2 mg/g and 0.3 mg/g in dried whole tea leaves, respectively. The presence of scutellarein in both samples was confirmed by LC/MS. Keywords: Tea; green tea; flavonoids; quercetin; kaempferol; scutellarein

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