Eisuke Kuraya

This study characterized leaf extracts of Cymbopogon flexuosus (Ryukyu Lemongrass Corporation, Okinawa, Japan) and evaluated the bioaccessibility and bioactivities of phenolic compounds following a simulated in vitro gastrointestinal model of digestion (in vitro GID) of plant material. Undigested (controls, AqC, EtC) and digested aqueous (AqD) and ethanolic (EtD) extracts were analyzed. Control extracts contained higher total phenolics and flavonoids than digested ones, with EtC showing the highest values. UHPLC-QToF-MS (ultra-high-performance liquid chromatography system coupled to a quadrupole time-of-flight mass spectrometer) identified 32 compounds, including phenolic acids, flavone aglycones, C-glycosides, and derivatives. Hydroxybenzoic acids, coumaric acid, caffeic esters, flavones, tricin derivatives, vitexin, and isoorientin exhibited reduced recovery, while coumaric acid hexoside, ferulic acid hexoside, and isoschaftoside/schaftoside exceeded 100% recovery, suggesting release from the matrix. Some compounds were absent from AqD, and many were found in the pellet, indicating potential colonic metabolism. Antioxidant activity (DPPH, reducing power, β-carotene/linoleic acid) was stronger in controls but always weaker than BHT/ascorbic acid. Extracts mildly inhibited α-amylase but more strongly inhibited α-glucosidase as shown with applied enzyme inhibition assays, especially EtD (76.93% at a concentration of 10 mg/mL), which showed stronger activity than controls but remained below acarbose (87.74% at 1 mg/mL). All extracts promoted HaCaT keratinocyte growth and reduced HCT-116 colon cancer cell viability at 250 µg/mL, with the strongest effects in AqC and AqD. Overall, GID decreased antioxidant activity but enhanced antidiabetic potential, confirming the safety and selective anticancer effects of C. flexuosus extracts.

Essential oils (EOs) from Abies sachalinensis (Sakhalin fir), a conifer species found in Sakhalin Island and Hokkaido in Japan, effectively remove nitrogen dioxide and possess antifungal activity. EOs also exert a relaxing effect and enhance air quality. Underwater shock waves generate instantaneous high pressure that ruptures cell walls, enhancing the performance of steam distillation and oil extraction. In this study, we aimed to increase the yield and quality of A. sachalinensis extracts using shockwaves. Leaves and branches were subjected to shockwave pretreatment or left untreated before EO extraction by steam distillation. EO yield of untreated dried leaves was 2.4 g/kg of dry leaf weight (DW). Upon application of a 3.0 kV, 3.6 kJ shockwave, the yield increased with the number of shockwave cycles. After ten cycles, yield increased 13.6-fold. Pretreatment with shockwaves for 10 cycles resulted in approximately 6- and 13-fold reductions in total energy consumption relative to fresh and dried leaves, respectively. Antioxidant activity increased more than 30-fold in shockwave-pretreated leaves than in untreated dried leaves after 10 cycles. This novel process can significantly reduce the energy used for EO extraction in steam distillation, thereby contributing to the development of a sustainable, low-energy EO production system.

Probiotic bacteria continue to receive increasing attention in the food and feed industries. However, the production of Bifidobacterium and Lactobacillus at an industrial scale is challenging because of specific nutrient requirements and conditions, which are complicated and costly. We developed low-cost culture media by modifying the carbon and nitrogen sources for Bifidobacterium animalis subsp. lactis KMP-H9-01 and Lactobacillus reuteri KMP-P4-S03 from available food grade components. Sucrose (15 g/l) was selected as a suitable carbon source for both strains because it was the most economic and facilitated bacterial growth that was equal to that of glucose. The Bifidobacterium strain required beef extract as a nitrogen source to multiply. The fermentation of both strains using the modified media formula in 5-L and 50-L bioreactors showed that the highest cell counts of L. reuteri and B. animalis subsp. lactis were 9 and 9.8 log CFU/ml after 12–15 h, respectively. The concentration (g/l) ratio between lactate and acetate obtained from B. animalis subsp. lactis was 7:7.4 at 12 h and 11.4:10.6 at 40 h; the ratio was similar at both time points (6.9: 1.1) for L. reuteri. Thus, this economically modified food-grade medium for the large-scale fermentation of two probiotic bacteria was efficient.

Bicontinuous microemulsion (BME)-based hydrogel films were integrated with screen-printed electrodes (SPEs) comprising working, counter, and reference electrodes to form stand-alone, semi-solid-state electrochemical systems that do not require an outer electrolyte solution. The gel network of the BME hydrogel only exists in the micro-aqueous phase, and retains the structure of the entire BME gel. Following gelation, a micro-aqueous phase with suffi-cient ionic strength ensured effective ionic conductivity, even in thin gel films. This enabled the electrochemical reac-tion to proceed using a thin gel film as an electrolyte solution. However, an intact micro-oil phase with no gel network enabled efficient extraction from an external oil solution, and exhibited rapid electrochemistry that was comparable to that of a BME solution. Cyclovoltammetries of lipophilic redox species in oil using the gel-integrated SPE system demonstrated successfully in the oil itself, and in the air with dropped oil onto the system.

本研究では，我々が開発したシマグワ葉パウダーの血糖値上昇抑制効果を明らかにすることを目的とした．実験の結果，シマグワ葉パウダーは，その製造過程において，1-DNJ含有量は低下，スクラーゼに対するIC50 値は増加するものの，スクラーゼ阻害活性を保持していることが示された．また，同パウダーを摂取することで，スクロース負荷後の血糖値上昇を抑制でき，それに伴い，インスリン分泌を節減できることが示唆された．本研究から，シマグワ葉パウダーの血糖値上昇抑制効果が明らかとなった．

In this study, we have established a novel pretreatment system that improves the juice extraction volume and nutritional value of plant material using underwater shockwaves. The optimum treatment conditions for plant materials were obtained by conducting batch experiments using simple-structured underwater shockwave treatment equipment. From these results, a continuous underwater shockwave processing device was designed. Moreover, we have been demonstrated the applicability and reliability of underwater shockwave pretreatment in improving the yield of functional ingredients and fruit juice from plants. The instantaneous high-pressure dynamic control using underwater shockwaves is applicable to a wide range of extraction processes such as extraction of juices or ingredients from other naturally occurring foods and medicinal plants.

Distyly is usually rare or not observed in species thriving on oceanic islands. The rarity of this breeding system is probably because of the difficulty of colonization for distylous plants and the paucity of pollinators on oceanic islands. However, the endemic and endangered tree Psychotria homalosperma has maintained its distylous nature in the oceanic Bonin Islands, Japan. To understand how the distylous breeding system of P. homalosperma has been maintained on these islands and to characterize the reproduction systems, we studied the pollination and reproductive biology of this species. Specifically, we observed current flower visitors and estimated their effects on plant reproduction. We also examined the floral traits and floral volatiles of P. homalosperma to infer its original pollinators, because plant–pollinator relationships in the Bonin Islands have recently been disrupted by anthropological activities. Finally, we examined the fruit set and pollen tube growth in the stigmas under hand and open pollination. Although original pollinators were presumed to be moths with long proboscises, the introduced honeybee, Apis mellifera , was the most common flower visitor. The honeybee carried pollen grains only unidirectionally, from the short‐ to long‐styled morphs, because it could not reach the hidden stigmas of the short‐styled flowers, and long‐styled flowers set fruits 1.7–38 times more than short‐styled ones. This case study indicates that the instability of pollinator fauna can cause distylous species to be rare on oceanic islands.

The essential oil of A. zerumbet, obtained from the leaves through steam distillation, has a distinct aroma and shows antioxidant activity. In this study, we evaluated the yields, antioxidant activity, and volatile compound composition of essential oils extracted from the leaves of A. zerumbet to better understand how these characteristics may vary among individual plants, and how they may differ with location of growth and season in which leaves are harvested. Gas chromatography–mass spectrometry (GC/MS) and principal component analysis (PCA) revealed that chemical composition in each individual plant was not affected by harvest season or growth area. Furthermore, GC/MS and antioxidant activity assays revealed that although the antioxidant activity and yield of these essential oils differed significantly between individual plants and collecting seasons, there was a strong inverse correlation between the yields of essential oils and their antioxidant activity. The yield, the major volatile compound compositions, the enantiomeric ratio of the few monoterpenes, and the antioxidant activities of A. zerumbet essential oil varied significantly among individual plants, and probably reflected the genetic variability within the species. This suggests the plausibility of selecting lineages of A. zerumbet to optimize future production of valuable essential oils.