Oligomeric proanthocyanidins from rabbiteye blueberry leaves inhibits the proliferation of human T-cell lymphotropic virus type 1-associated cell lines via apoptosis and cell cycle arrest

Comparison of Proanthocyanidin Content in Rabbiteye Blueberry (Vaccinium virgatum Aiton) Leaves and the Promotion of Apoptosis against HL-60 Promyelocytic Leukemia Cells Using 'Kunisato 35 Gou' Leaf Extract

Polyphenol-rich rabbiteye blueberry (Vaccinium virgatum Aiton) leaves have attracted attention as a food material. In this study, we compared the total polyphenols, total proanthocyanidin content, and antioxidant activity of the leaves of 18 blueberry varieties and investigated the seasonal variation in polyphenols. We also evaluated the anti-cancer cell proliferation properties of the rabbiteye blueberry leaf specific cultivar 'Kunisato 35 Gou'. Rabbiteye blueberry leaves had significantly higher total polyphenol and total proanthocyanidin values than northern highbush blueberry and southern highbush blueberry leaves. The antioxidant activity of blueberry leaves was highly positively correlated with both the total polyphenol and total proanthocyanidin content. Variations were observed in the total polyphenol and total proanthocyanidin content of rabbiteye blueberry leaves harvested at different points in the growing season; leaves collected in fall to winter contained more epicatechin in addition to proanthocyanidins. In the evaluation of anti-cancer cell proliferation properties against HL-60 promyelocytic leukemia cells, the September-harvested extracts of rabbiteye blueberry 'Kunisato 35 Gou' showed strong properties, and the use of an FITC Annexin V apoptosis detection kit with propidium iodide confirmed that this HL-60 cell death occurred via apoptosis. Limiting the harvest time would make rabbiteye blueberry leaves a more functional food ingredient.

Inhibition of ATL cell proliferation by polymerized proanthocyanidin from blueberry leaves through JAK proteolysis

We have previously reported that the proanthocyanidin (PAC) fraction of blueberry leaf extract (BB-PAC) inhibits the proliferation of human T lymphotropic retrovirus (HTLV-1)-infected adult T-cell leukemia (ATL) by inducing apoptosis. In the present study, we further analyzed the structure of BB-PAC and elucidated the molecular mechanism underlying the inhibitory function of HTLV-1 infected and ATL cells. After hot water extraction with fractionation with methanol-acetone, BB-PAC was found to be concentrated in fractions 4 to 7 (Fr 7). The strongest inhibition of ATL cell growth was observed with Fr7, which contained the highest BB-PAC polymerization degree of 14. The basic structure of BB-PAC is mainly B-type bonds, with A-type bonds (7.1%) and cinchonain I units as the terminal unit (6.1%). The molecular mechanism of cytotoxicity observed around Fr7 against ATL cells was the degradation of JAK1 to 3 and the dephosphorylation of STAT3/5, which occurs by proteasome-dependent proteolysis, confirming that PAC directly binds to HSP90. JAK degradation was caused by proteasome-dependent proteolysis, and we identified the direct binding of PAC to HSP90. In addition, the binding of cochaperone ATPase homolog 1 (AHA1) to HSP90, which is required for activation of the cofactor HSP90, was inhibited by BB-PAC treatment. Therefore, BB-PAC inhibited the formation of the HSP90/AHA1 complex and promoted the degradation of JAK protein due to HSP90 dysfunction. These results suggest that the highly polymerized PAC component from blueberry leaves has great potential as a preventive and therapeutic agent against HTLV-1 infected and ATL cells.

Vaccinium virgatum Aiton Leaves Extract Suppressed Lipid Accumulation and Uric Acid Production in 3T3-L1 Adipocytes

Blueberry (Vaccinium virgatum Aiton; Kinisato 35 Gou) leaves have recently attracted increasing attention as a useful material for the prevention of lifestyle diseases. Here, we examined the effects of the hot water extract of blueberry leaves (BLEx) on lipogenesis and uric acid production in 3T3-L1 adipocytes. The results showed that BLEx suppressed lipid accumulation and the mRNA expression of differentiation markers in 3T3-L1 adipocytes. A fractionation study showed that the highly polymerized proanthocyanidin-rich fraction was responsible for this effect. Upon maturation to adipocytes, 3T3-L1 cells produced uric acid and tumor necrosis factor-α, and hypoxia stimulated the production of uric acid and xanthine oxidoreductase activity. BLEx suppressed the production of uric acid under these conditions. Although BLEx inhibited the enzymatic activity of xanthine oxidase, this activity was observed in several fractions containing catechin, epicatechin, chlorogenic acid, rutin, and low molecular weight proanthocyanidins. Taken together, these results indicate that BLEx contains various compounds with the ability to suppress lipid accumulation and uric acid production in adipocytes.

Comparison on chemical compositions and antioxidant capacities of the green, oolong, and red tea from blueberry leaves

Blueberry leaves, by‐products of the blueberry industry, could be explored as source of functional foods, such as teas. Three different types of tea, including nonfermented green tea, semifermented oolong tea, and fully fermented red tea from blueberry leaves, were investigated on their chemical compositions and antioxidant capacities here. The contents of individual amino acids in three types varied, while the total amounts retained constant. A total of 167 volatiles were detected with alcohols, alkenes, and aldehydes as the dominant. More volatiles produced in the fermented teas. The total phenolic/flavonoid contents were highest in the green tea and decreased significantly in the oolong and red teas, correlating inversely with the fermentation degree. The highest levels of representative phenolics, that is, phenolic acids and flavonol glycosides, contributed to the strongest antioxidant capacity in the green tea. These indicated that blueberry leaves provided promising and prospective potential to develop new teas beneficial for health.

Walnut Polyphenol Extract Attenuates Immunotoxicity Induced by 4-Pentylphenol and 3-methyl-4-nitrophenol in Murine Splenic Lymphocyte

4-pentylphenol (PP) and 3-methyl-4-nitrophenol (PNMC), two important components of vehicle emissions, have been shown to confer toxicity in splenocytes. Certain natural products, such as those derived from walnuts, exhibit a range of antioxidative, antitumor, and anti-inflammatory properties. Here, we investigated the effects of walnut polyphenol extract (WPE) on immunotoxicity induced by PP and PNMC in murine splenic lymphocytes. Treatment with WPE was shown to significantly enhance proliferation of splenocytes exposed to PP or PNMC, characterized by increases in the percentages of splenic T lymphocytes (CD3+ T cells) and T cell subsets (CD4+ and CD8+ T cells), as well as the production of T cell-related cytokines and granzymes (interleukin-2, interleukin-4, and granzyme-B) in cells exposed to PP or PNMC. These effects were associated with a decrease in oxidative stress, as evidenced by changes in OH, SOD, GSH-Px, and MDA levels. The total phenolic content of WPE was 34,800 ± 200 mg gallic acid equivalents/100 g, consisting of at least 16 unique phenols, including ellagitannins, quercetin, valoneic acid dilactone, and gallic acid. Taken together, these results suggest that walnut polyphenols significantly attenuated PP and PNMC-mediated immunotoxicity and improved immune function by inhibiting oxidative stress.