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Because of the high mortality, prevention of arterial thrombotic disease has top priority in developed countries. As inappropriate diet is known to predispose to acute thrombotic events, regular intake of an anti-thrombotic diet may offer a convenient and effective method of prevention. As part of a systematic investigation into the anti-thrombotic effect of fruits and vegetables, strawberry varieties were tested in this study. An in vitro platelet function test (haemostatometry) was used for screening strawberry filtrates. Those that showed significant antiplatelet effect were further assessed with a laser-induced thrombosis test in mice. Measurement of flow-mediated vasodilation in the femoral artery of mice reflected the effect on the vascular endothelium. Correlation between the effects on platelet reactivity in vitro and the antioxidant activity (hypoxanthine/xanthine oxidase test) or phenolic compound content was assessed. Strawberry varieties KYSt-4 (Nohime), KYSt-11 (Kurume IH-1) and KYSt-17 (Kurume 58) showed significant antiplatelet activity both in vitro and, after oral administration, in vivo. Both KYSt-11 and KYSt-17, but not KYSt-4, significantly reduced flow-mediated vasodilation; that is, caused endothelial dysfunction. Antiplatelet activities were heat stable. Significant correlation was found between antiplatelet and antioxidant activities (P=0.049, R=0.23) or total phenolic compounds (P=0.0096, R=0.36). Of the tested strawberry varieties, KYSt-4, KYSt-11 and KYSt-17 showed significant anti-thrombotic effect. The dual mechanism of the effect may involve a direct inhibition of both platelet function and antioxidant activities.

The aim of this study was to determine the optimum photoperiod of supplemental lighting to obtain high fruit yields in forcing culture of strawberry. Strawberry plants were illuminated with supplemental lighting provided by high-irradiance light-emitting diodes with photoperiods of 24, 16, 14, or 12-h daily under the controlled air temperature conditions set the ventilation starting temperature at 26°C and minimum air temperature at 6°C from October to May. Compared with plants in the other treatments and the control, those in the 12-h photoperiod treatment showed a significant increase in leaf photosynthesis and earlier differentiation of flower buds on the second inflorescence. These physiological changes resulted in the large amounts of carbon translocation from leaf to fruit, leading to the fruit quality improvement and the highest marketable yield among all of the treatments. When the photoperiod of supplemental lighting exceeded 12 h per day, flower opening on the first inflorescence was accelerated, but flower bud initiation on the second inflorescence was inhibited. This inhibition caused a decrease in leaf photosynthesis, leading to excessive carbohydrate accumulation in the leaves, resulting in lower total fruit yield than that from plants in the 12-h photoperiod treatment. These data show that a 12-h photoperiod of supplemental lighting is appropriate to obtain high yields in forcing culture of strawberry.