Depigmenting effect of <Emphasis Type="Italic">Cinnamomum cassia</Emphasis> Presl in B16F10 melanoma cells

To find efficient depigmenting agents, we examined several Chinese herbs for melanogenesis inhibition and toxicity. Cinnamomum cassia Presl exhibited low cytotoxicity at even high concentration (200 μg/ml). The effects on melanogenesis of cultured B16 melanoma cells, mushroom tyrosinase activity, and free radical scavenging activity were further assessed. The methanol extracts of this plant showed the suppression of melanin synthesis. Melanin content was dose-dependently decreased by this herb extract as compared with control cells. It also showed good anti-oxidative activity (IC₅₀=3.7 μg/ml) but no inhibition of mushroom tyrosinase activity. This result showed that Cinnamomum cassia Presl extract might be useful and safe as a new whitening agent in cosmetics.     

Inhibition of melanogenesis by Erigeron canadensis via down-regulating melanogenic enzymes in B16F10 melanoma cells

The effects of Erigeron canadensis extract on melanogenesis and cell toxicity in cultured B16F10 mouse melanoma cells were investigated. E. canadensis extract down regulated melanin synthesis effectively at a non-toxic concentration. Its extract was fractionated by using a recycling HPLC with GS310 column (21.5×500 mm, 10–15 μM) into five fractions. The fraction 1 showed melanin inhibition by 48.0% at 100 mg/ml which was 2.5 times more efficient than the depigmenting effect of commercial arbutin (17.5%) and also did not show cell toxicity. To elucidate the depigmenting mechanism of fraction 1, in vitro and cellular tyrosinase activity, antioxidant activity, and protein level of the main melanogenic enzymes, such as tyrosinase, TRP-1 and TRP-2 were evaluated. Fraction 1 inhibited melanin synthesis in B16F10 melanoma cells by decreasing protein levels of melanogenic enzymes, especially tyrosinase. In conclusion, we suggest that this fraction may be a safe and effective depigmentation agent.     

Melanogenesis inhibitory effect of dehydroevodiamine isolated from fruits of <Emphasis Type="Italic">Evodia rutaecarpa</Emphasis>

Dehydroevodiamine, an alkaloid, was isolated from the fruit of Evodia rutaecarpa and melanin production, and tyrosinase inhibition in B16F10 melanoma cells treated with the isolated dehydroevodiamine was investigated. The compound decreased melanin synthesis significantly without promoting cytotoxicity. The IC₅₀ value of dehydroevodiamine for melanogenesis and cell viability were 59.8 μM and 90.0 μM, respectively. The L-dopa oxidase activity of mushroom tyrosinase was reduced after dehydroevodiamine treatment by about 22.4% at a concentration of 33.2 μM. However, there was no effect on cellular tyrosinase activity. These results indicate that the observed decrease in melanin content after treatment with dehydroevodiamine was attributed to the direct inhibition of tyrosinase activity, rather than the suppression of tyrosinase gene expression. Dehydroevodiamine may be a promising new agent for use in cosmeceutical application.     

<Emphasis Type="Italic">Nelumbo nucifera</Emphasis> extracts as whitening and anti-wrinkle cosmetic agent

Water extract from Nelumbo nucifera was tested for possible functional cosmetic agent. Whitening effect was measured by tyrosinase inhibition assay and DOPA-oxidase inhibition assay, and anti-wrinkle effect was checked by elastase inhibition assay. DOPA-oxidase inhibition effect (whitening effect) of Nelumbo nucifera’s leaf, seed and flower extract was 59%, 57% and 50%, respectively. Nelumbo nucifera’s leaf, seed and flower extract showed 56%, 49%, and 54% elastase inhibition (anti-wrinkle effect) at 200 μg/ml, while adenosine indicated 26% inhibition. Water cream including Nelumbo nucifera’s root, leaf, flower, stem extract did not cause significant skin irritation. Water cream including 4% Nelumbo nucifera extract was stable for 30 days under various temperature conditions. From the study, Nelumbo nucifera’s leaf, flower and seed extracts showed strong possibility for whitening and anti-wrinkle functional cosmetic agent.     

Potential application of acetone extract of <Emphasis Type="Italic">Astragalus sinicus</Emphasis> Linne seed to functional cosmetics

For the functional cosmetic agent using acetone extract of A. sinicus Linne seed, the effects of whitening, wrinkling, and safety were investigated. Cell viabilities of Raw 264.7 up to 60 mg/mL did not appear to have any significant direct cytotoxic effect. The melanin concentration was decreased up to 62.1% at 20 mg/mL. When the acetone extract concentration of A. sinicus Linne seed was increased from 5 to 20 mg/mL, the inhibitory activity of tyrosinase was sharply increased from 61.3 to 93.8%. However, above 30 mg/mL, it did not increase. The inhibition effects of elastase and collagenase were increased with the extract concentration. Especially, when acetone extract concentration of A. sinicus Linne seed was increased from 25 to 200 μg/mL, the inhibition effect of elastase was increased from 60.2 to 97.5%. The inhibition effect of collagenase was increased from 35.0 to 99.0% when increased from 50 to 300 μg/mL. The indexes of pigment and coarseness were 28.56 MI and 18.45R-value, respectively, after 8 weeks of clinical trial using cream pack containing 0.2% of acetone extract of A. sinicus Linne seed. The indexes of elasticity and moisture were 64.5Ur/Uf and 55.2AU, respectively, after 8 weeks of clinical trial. These results demonstrate that acetone extract of A. sinicus Linne seed may be useful as a potential agent for functional cosmetics.     

Porcine amniotic fluid as possible antiwrinkle cosmetic agent

Porcine amniotic fluid was investigated for use as a functional cosmetic ingredient. From safety tests by MTT (5-diphenyltetrazolium bromide) assay, cell viability was above 90% for 50–1,000 μg/mL concentration and porcine amniotic fluid was safe for cosmetic ingredient. From stability tests, cream containing 1% porcine amniotic fluid maintained constant physical properties for color, pH and viscosity during 28 days, and porcine amniotic fluid was stable for a cosmetic agent. Efficacy tests were done for antiwrinkle (elastase inhibition and collagenase synthesis inhibition), whitening (tyrosinase inhibition and DOPA (3,4-Dihydroxy-L-phenyl-alanine) oxidation inhibition) and antioxidation. At 500 μg/mL concentration, elastase inhibition of porcine placenta amniotic fluid was 33%, whereas that of adenosine as reference was 14%. However, porcine amniotic fluid showed relatively insignificant effect on collagenase synthesis inhibition, whitening and antioxidation activity. From this study, porcine amniotic fluid showed potential for a future antiwrinkle cosmetic agent.     

Antibacterial Activity of Essential Oil and Extracts of <Emphasis Type="Italic">Cleistocalyx operculatus</Emphasis> Buds Against the Bacteria of <Emphasis Type="Italic">Xanthomonas</Emphasis> spp.

This study was undertaken to assess the antibacterial efficacy of the essential oil and extracts of Cleistocalyx operculatus buds against plant pathogenic bacteria of Xanthomonas spp. The diameter of inhibition zones of oil (1,000 μg/disc) and extracts (1,500 μg/disc) against the tested bacteria were found in the range of 7–23 mm. The MIC and MBC values of the oil and extracts against the tested Xanthomonas spp. ranged from 31.25–125 to 62.5–250 μg/ml and 125–500 and 250–1,000 μg/ml, respectively. The cell viability study demonstrated a potential detrimental effect of the oil (1,000 μg/ml) and hexane extract (250 μg/ml) on the tested Xanthomonas spp. Also the oil displayed significant antibacterial effects in vivo against Xoo KX019 and Xsp SK12 conducted on greenhouse-grown oriental melon plants (Cucumis melo L. var. makuwa). The results of this study suggest that C. operculatus-derived essential oil and extracts could be used as natural bactericides in the food and agriculture industries.     

Antimicrobial Activity of Essential Oils Isolated from Phlomis crinita Cav. ssp. mauritanica Munby

The essential oil extracted from the leaves and flowers of Phlomis crinita Cav. ssp. mauritanica Munby were obtained by steam distillation and analyzed by gas chromatography coupled with mass spectrometry. The major constituents of flower oil were β-caryophyllene (58.1%) and germacrene D (35.1%). This oil inhibited the growth of Staphylococcus aureus, Enterococcus faecalis, and Salmonella typhimurium with minimal inhibition concentrations (MIC) varying between 39 and 625 μg/ml. The essential oil obtained from the leaves was mainly composed of trans-caryophyllene (40.8%) and germacrene D (39.1%) and exhibited an antimicrobial profile against the same strains mentioned above with MIC between 156 μg/ml and 2.5 mg/ml.     

Antifungal Activity of Leaf Essential Oil and Extracts of <Emphasis Type="Italic">Metasequoia glyptostroboides</Emphasis> Miki ex Hu

Plant diseases constitute an emerging threat to global food security. Many of the currently available antifungal agents for agriculture are highly toxic and nonbiodegradable and cause extensive environmental pollution. Moreover, an increasing number of phytopathogens are developing resistance to them. Therefore, the aim of this study was to assess the antifungal efficacy of the leaf essential oil and the leaf extracts of Metasequoia glyptostroboides against Fusarium oxysporum, Fusarium solani, Phytophthora capsici, Colletotrichum capsici, Sclerotinia sclerotiorum, Botrytis cinerea and Rhizoctonia solani. The oil (1,000 μg/disc) and the extracts (1,500 μg/disc) revealed a remarkable antifungal effect against the tested plant pathogenic fungi with a radial growth inhibition percentage of 41.3–66.3% and 13.4–54.4%, respectively along with their respective MIC values ranging from 62.5 to 1,000 μg/ml and 500–4,000 μg/ml. The oil had a strong detrimental effect on spore germination of all the tested plant pathogens along with the concentration as well as time-dependent kinetic inhibition of Botrytis cinerea. Also, the oil exhibited a potent in vivo antifungal effect against Phytophthora capsici on greenhouse grown pepper plants. The results of this study indicate that the oil and extracts of M. glyptostroboides leaves could become natural alternatives to synthetic fungicides to control certain important plant fungal diseases.     

Eicosapentaenoic acid inhibits tube formation of vascular endothelial cellsin vitro

We previously have described a quantitative angiogenesisin vitro model, in which endothelial cells are cultured between two layers of type I collagen gel and become organized into tube-like structures. Using this model, the effect of eicosapentaenoic acid (20∶5n−3) on tube formation was investigated. When the endothelial cells isolated from bovine carotid artery were treated for 2 days with 5 μg/mL of arachidonic acid (20∶4n−6), eicosapentaenoic acid or docosahexaenoic acid (22∶6n−3), these polyunsaturated fatty acids were extensively incorporated into cellular phospholipids. The content of arachidonic, eicosapentaenoic and docosahexaenoic acid increased from 9.58% to 23.29%, from 0.98% to 11.76% and from 6.88% to 18.40%, respectively. When the eicosapentaenoic acid-treated cells were cultured between collagen gels, the tube-forming ability of the cells was markedly inhibited. The inhibition was dose-dependent between 1.0 and 5.0 μg/mL of eicosapentaenoic acid. At 5.0 μg/mL of eicosapentaenoic acid the inhibition reached 76%. By contrast, arachidonic acid increased tube formation, and docosahexaenoic acid had no effect. To elucidate the mechanism of eicosapentaenoic acid induced inhibition ofin vitro tube formation, we examined the effect of the acid on the proliferation of endothelial cells. Eicosapentaenoic acid at any dose (<5.0 μg/mL) had no effect on the proliferation of endothelial cells cultured on plastic plates without collagen gel. However, when the cells were cultured between collagen gels, eicosapentaenoic acid inhibited cell growth in a dose-dependent manner with maximum inhibition being observed at 2.5 μg/mL. These data suggest that eicosapentaenoic acid suppresses tube formation of endothelial cells, at least in part,via its inhibitory effect on cellular proliferation. Thus eicosapentaenoic acid may act as an endogenous inhibitor of angiogenesis under various pathological conditions, including tumor growth and chronic inflammation.     

Inhibition of 12- and 15-lipoxygenase activities and protection of human and tilapia low density lipoprotein oxidation by I-Tiao-Gung (<Emphasis Type="Italic">Glycine tomentella</Emphasis>)

I-Tiao-Gung, Glycine tomentella, has been used extensively as a traditional herbal medicine to relieve physical pain, but its bioactivity has not been studied systematically. Ninety-five percent ethanol extracts of G. tomentella (GT-E) showed antioxidant activity in human plasma by prolonging the lag phase (+T_lag) of Cu²⁺-induced, LDL oxidation and were dose dependent. The+T_lag of LDL combined with 3.2 μg/mL GT-E was similar to that with 2.0 μM (ca. 0.5 μg/mL) Trolox. A similar inhibitory effect was found toward tilapia plasma LDL. In addition, GT-E inhibited tilapia thrombocyte (nucleated platelet), 5-, 12-, and 15-lipoxygenase (LOX). The IC₅₀ values were 0.43, 0.72, and 0.42 μg/mL, respectively, whereas the IC₅₀ values for nordihydroguaiaretic acid (NDGA) on 5-, 12-, and 15-LOX were 2.3, 1.6, and 1.7 μg/mL, respectively. The IC₅₀ value for cyclooxygenase-2 (COX-2) inhibition by GT-E was 42.0 μg/mL, whereas the IC₅₀ value by indomethacin as a positive control was 0.61 μg/mL. The prevention of LDL oxidation and the dual inhibition of LOX and COX-2 are indicative of the possible roles of I-Tiao-Gung in antiatherosclerosis and anti-inflammation.     

Effect of tocotrienols on the growth of a human breast cancer cell line in culture

The tocotrienol-rich fraction (TRF) of palm oil consists of tocotrienols and some α-tocopherol (α-T). Tocotrienols are a form of vitamin E having an unsaturated side-chain, rather than the saturated side-chain of the more common tocopherols. Because palm oil has been shown not to promote chemically-induced mammary carcinogenesis, we tested effects of TRF and α-T on the proliferation, growth, and plating efficiency (PE) of MDA-MB-435 estrogen-receptor-negative human breast cancer cells. TRF inhibited the proliferation of these cells with a concentration required to inhibit cell proliferation by 50% of 180 μg/mL, whereas α-T had no effect at concentrations up to 1000 μg/mL as measured by incorporation of [³H]thymidine. The effects of TRF and α-T also were tested in longer-term growth experiments, using concentrations of 180 and 500 μg/mL. We found that TRF inhibited the growth of these cells by 50%, whereas α-T did not. Their effect on the ability of these cells to form colonies also was studied, and it was found that TRF inhibited PE, whereas α-T had no effect. These results suggest that the inhibition is due to the presence of tocotrienols in TRF rather than α-T. Based on a paper presented at the PORIM International Palm Oil Congress (PIPOC) held in Kuala Lumpur, Malaysia, September 1993.     

新型功能性植物盐美白功效的体外评价

对松盐、梅盐与竹盐的美白功效进行了体外评价,分别研究其对体外酪氨酸酶的单酚酶和二酚酶活性的抑制作用,并以熊果苷为阳性对照,采用体外培养的B16黑素瘤细胞模型探究其对胞内酪氨酸酶活性、细胞增殖及迁移的影响。结果表明,植物盐元素组成丰富,且水溶液呈碱性,松盐、竹盐、梅盐对酪氨酸酶活性表现出极显著的浓度依赖的抑制作用(p0.01),当这3种植物盐水溶液的质量浓度为50.0 g/L时,它们对酪氨酸酶单酚酶抑制率分别为97.1%、94.8%、48.2%,对二酚酶的抑制率均高于92.0%;与原盐相比,5.0g/L的植物盐对B16细胞生长抑制作用不明显,但会抑制其横向迁移;植物盐对B16细胞胞内酪氨酸酶活性抑制作用优于熊果苷,5.0g/L的梅盐组的细胞内酪氨酸酶活性仅有8.76%,抑制效果好于松盐、竹盐。所研究的植物盐可以抑制酪氨酸酶的活性,且对B16细胞无附加毒性,显示出作为一种无机酪氨酸酶抑制剂的潜力,在人体美白方面有较好的潜在应用价值。     

The effect of two isomeric octadecenoic acids on alkyl diacyl glycerides and neutral glycosphingolipids of Novikoff hepatoma cells

The addition of 150 μg ofcis-6-octadecenoic acid (6–18∶1) per milliliter to the growth medium of Novikoff hepatoma cells reduced the rate of multiplication of these cells, whereas the same level ofcis-9-octadecenoic acid (9–18∶1) was without effect. The quantity of alkyl diacyl glycerols in cells grown in medium containing 100 μg/ml of either 6–18∶1 or 9–18∶1 was reduced to about 10% of that observed in cells grown in unsupplemented media. The presence of 6–18∶1 acid led to an increase in the concentration of the dihexosyl ceramide and a corresponding decrease in that of the monohexosyl ceramides of the cells; whereas the presence of 9–18∶1 resulted in an increase in the relative amount of tetraglycosyl ceramide and corresponding reductions in those of mono- and dihexosyl ceramide. Possible causes for these changes are discussed.     

Tocotrienols inhibit the growth of human breast cancer cells irrespective of estrogen receptor status

Potential antiproliferative effects of tocotrienols, the major vitamin E component in palm oil, were investigated on the growth of both estrogen-responsive (ER+) MCF7 human breast cancer cells and estrogen-unresponsive (ER-) MDA-MD-231 human breast cancer cells, and effects were compared with those of α-tocopherol (αT). The tocotrienol-rich fraction (TRF) of palm oil inhibited growth of MCF7 cells in both the presence and absence of estradiol with a nonlinear dose-response but such that complete suppression of growth was achieved at 8 μg/mL. MDA-MB-231 cells were also inhibited by TRF but with a linear dose-response such that 20 μg/mL TRF was needed for complete growth suppression. Separation of the TRF into individual tocotrienols revealed that all fractions could inhibit growth of both ER+ and ER- cells and of ER+ cells in both the presence and absence of estradiol. However, the γ- and δ-fractions were the most inhibitory. Complete inhibition of MCF7 cell growth was achieved at 6 μg/mL of γ-tocotrienol/δ-tocotrienol (γT₃/δT₃) in the absence of estradiol and 10μm/mL of δT₃ in the presence of estradiol, whereas complete suppression of MDA-MB-231 cell growth was not achieved even at concentrations of 10μg/mL of δT₃. By contrast to these inhibitory effects of tocotrienols, αT had no inhibitory effect on MCF7 cell growth in either the presence or the absence of estradiol, nor on MDA-MB-231 cell growth. These results confirm studies using other sublines of human breast cancer cells and demonstrate that tocotrienols can exert direct inhibitory effects on the growth of breast cancer cells. In searching for the mechanism of inhibition, studies of the effects of TRF on estrogen-regulated pS2 gene expression in MCF7 cells showed that tocotrienols do not act via an estrogen receptor-mediated pathway and must therefore act differently from estrogen antagonists. Furthermore, tocotrienols did not increase levels of growth-inhibitory insulin-like growth factor binding proteins (IGFBP) in MCF7 cells, implying also a different mechanism from that proposed for retinoic acid inhibition of estrogen-responsive breast cancer cell growth. Inhibition of the growth of breast cancer cells by tocotrienols could have important clinical implications not only because tocotrienols are able to inhibit the growth of both ER+ and ER- phenotypes but also because ER+ cells could be growth-inhibited in the presence as well as in the absence of estradiol. Future clinical applications of TRF could come from potential growth suppression of ER+ breast cancer cells otherwise resistant to growth inhibition by antiestrogens and retinoic acid.     

Regulation of Cell Division and Growth in Roots of <Emphasis Type="Italic">Lactuca sativa</Emphasis> L. Seedlings by the <Emphasis Type="Italic">Ent</Emphasis>-Kaurene Diterpenoid Rabdosin B

Rabdosin B, an ent-kaurene diterpenoid purified from the air-dried aerial parts of Isodon japonica (Burm.f) Hara var. galaucocalyx (maxin) Hara, showed a biphasic, dose-dependent effect on root growth and a strong inhibitory effect on root hair development in lettuce seedlings (Lactuca sativa L.). Lower concentrations of rabdosin B (20–80 μM) significantly promoted root growth, but its higher levels at 120–200 μM, by contrast, had inhibitory effects. Additionally, all tested concentrations (10–40 μM) inhibited root hair development of seedlings in a dose-dependent manner. Further investigations on the underlying mechanism revealed that the promotion effect of rabdosin B at the lower concentrations resulted from increasing the cell length in the mature region and enhancing the mitotic activity of meristematic cells in seedlings’ root tips. In contrast, rabdosin B at higher concentrations inhibited root growth by affecting both cell length in the mature region and division of meristematic cells. Comet assay and cell cycle analysis demonstrated that the decrease of mitotic activity of root meristematic cells was due to DNA damage induced cell cycle retardation of the G₂ phase and S phase at different times.     

Antioxidant Activity of Raisin Extracts in Bulk Oil,Oil in Water Emulsion,and Sunflower Butter Model Systems

The antioxidant activities of the raisin extract (RE) in stripped corn oil, stripped corn oil emulsions, and sunflower butter stored at 60 °C for up to 15 days was evaluated. Peroxide values and hexanal content were measured on a half day, 2 or 3 day basis for the emulsion, sunflower butter, and bulk oil, respectively. The RE had the best antioxidant activity in the bulk oil system. Statistical contrasts indicated the oxidation of bulk corn oil treated with RE was significantly (p < 0.001 and p = 0.044) lower than bulk oil and bulk oil treated with tertiary-butylhydroquinone (TBHQ), respectively. No differences (p = 0.15) in hexanal concentrations were observed in stored bulk oils treated with RE and TBHQ. However, both these materials inhibited hexanal formation better (p < 0.001) when compared to the control corn oil. In contrast, 200 μg/g TBHQ had better (p = 0.0004) antioxidant activity than 3,000 μg/g RE in the oil in water(o/w) emulsion. No significant differences (p = 0.1637) in hexanal formation were observed in the emulsions treated with RE and TBHQ. However, the data indicated that the RE treated emulsion did undergo more secondary oxidation than the emulsion treated with TBHQ beyond 110 h. The 3,000 μg/g RE had antioxidant activity in sunflower butter, but was less effective than the 200 μg/g TBHQ and a lower RE concentration (200 μg/g). The observations supported the hypothesis that RE has antioxidant activity in the multiple model systems.     

Inhibition of acylcoenzyme A:Cholesterol acyltransferase activity by PD128O42: Effect on cholesterol metabolism and secretion in CaCo-2 cells

The regulation of cholesterol uptake and secretion by acylcoenzyme A:cholesterol acyltransferase (ACAT) was investigated in the human intestinal cell line, CaCo-2. A new ACAT inhibitor, PD128042 (CI-976), was first characterized. The addition of the fatty acid anilide to membranes prepared from CaCo-2 cells inhibited ACAT activity without altering the activities of HMG-CoA reductase, fatty acid Co-A hydrolase, or triglyceride synthetase. PD128042 was a competitive inhibitor of ACTA with 50% inhibition occurring at a concentration of 0.2 μg/mL. When added to the medium of CaCo-2 cells at a concentration of 5 μg/mL, PD128042 inhibited oleate incorporation into cholesteryl oleate by 92% and increased oleate incorporation into triglycerides and phospholipids by 51% and 38%, respectively. After incubating CaCo-2 cells with the ACAT inhibitor, the rate of newly synthesized cholesterol decreased by 75% and membranes prepared from these cells contained significantly less HMG-CoA reductase activity. PD128042 significantly decreased the basolateral secretion of newly synthesized cholesteryl esters without affecting the secretion of newly synthesized triglycerides or phospholipids. The inhibitor decreased the esterification of labeled exogenous cholesterol which was taken up by the cell from bile salt micelles. Moreover, after 16 hr of ACAT inhibition, less labeled unesterified micellar cholesterol was associated with the cell. The esterification of cholesterol in CaCo-2 cells plays an integral role in the uptake of cholesterol through the apical membrane and its eventual secretion at the basolateral membrane.     

Low concentration of oxidized low density lipoprotein suppresses platelet reactivity <Emphasis Type="Italic">in vitro</Emphasis>: An intracellular study

The intracellular mechanisms underlying oxidized low density lipoprotein (oxLDL)-signaling pathways in platelets remain obscure and findings have been controversial. Therefore, we examined the influence of oxLDL in washed human platelets. In this study oxLDL concentration-dependently (20–100 μg/mL) inhibited platelet aggregation in human platelets stimulated by collagen (1 μg/mL) and arachidonic acid (60 μM), but not by thrombin (0.02 U/mL). The activity of oxLDL was greater at 24 h in inhibiting platelet aggregation than at 12 h. At 24 h, oxLDL concentration-dependently inhibited intracellular Ca²⁺ mobilization and thromboxane B₂ formation in human platelets stimulated by collagen. In addition, at 24 h oxLDL (40 and 80 μg/mL) significantly increased the formation of cyclic AMP, but not cyclic GMP or nitrate. In an ESR study, 24 h-oxLDL (40 μg/mL) markedly reduced the ESR signal intensity of hydroxyl radicals (OH⁻) in both collagen (2 μg/mL)-activated platelets and Fenton reaction (H₂O₂+Fe²⁺). The inhibitory effect of oxLDL may induce radical-radical termination reactions by oxLDL-derived lipid radical interactions with free radicals (such as hydroxyl radicals) released from activated platelets, with a resultant lowering of intracellular Ca²⁺ mobilization followed by inhibition of thromboxane A₂ formation, thereby leading to increased cyclic AMP formation and finally inhibited platelet aggregation. This study provides new insights concerning the effect of oxLDL in platelet aggregation.