Tyrosinase and α-glucosidase inhibitory potential of compounds isolated from Quercus coccifera bark: In vitro and in silico perspectives

Bark of Quercus coccifera is widely used in folk medicine. We tested tyrosinase and α-glucosidase inhibitory effects of Q. coccifera bark extract and isolated compounds from it. The extract inhibited tyrosinase with an IC₅₀ value of 75.13 ± 0.44 µg/mL. Among the isolated compounds, polydatin (6) showed potent tyrosinase inhibition compared to the positive control, kojic acid, with an IC₅₀ value of 4.05 ± 0.30 µg/mL. The Q. coccifera extract also inhibited α-glucosidase significantly with an IC₅₀ value of 3.26 ± 0.08 µg/mL. (-)-8-Chlorocatechin (5) was the most potent isolate, also more potent than the positive control, acarbose, with an IC₅₀ value of 43.60 ± 0.67 µg/mL. According to the kinetic analysis, 6 was a noncompetitive and 5 was a competitive inhibitor of tyrosinase, and 5 was a noncompetitive α-glucosidase inhibitor. In the light of these findings, we performed in silico molecular docking studies for 5 and 6 with QM/MM optimizations to predict their tyrosinase inhibition mechanisms at molecular level and search for correlations with the in vitro results. We found that the ionized form of 5 (5i) showed higher affinity and more stable binding to tyrosinase catalytic site than its neutral form, while 6 bound to the predicted allosteric sites of the enzyme better than the catalytic site.     

Polydatin prevents angiotensin II-induced cardiac hypertrophy and myocardial superoxide generation

Our studies and others recently demonstrate that polydatin, a resveratrol glucoside, has antioxidative and cardioprotective effects. This study aims to investigate the direct effects of polydatin on Ang II-induced cardiac hypertrophy to explore the potential role of polydatin in cardioprotection. Our results showed that in primary cultured cardiomyocytes, polydatin blocked Ang II-induced cardiac hypertrophy in a dose-dependent manner, which were associated with reduction in the cell surface area and [³H]leucine incorporation, as well as attenuation of the mRNA expressions of atrial natriuretic factor and β-myosin heavy chain. Furthermore, polydatin prevented rat cardiac hypertrophy induced by Ang II infusion, as assessed by heart weight-to-body weight ratio, cross-sectional area of cardiomyocyte, and gene expression of hypertrophic markers. Further investigation demonstrated that polydatin attenuated the Ang II-induced increase in the reactive oxygen species levels and NADPH oxidase activity in vivo and in vitro. Polydatin also blocked the Ang II-stimulated increases of Nox4 and Nox2 expression in cultured cardiomyocytes and the hearts of Ang II-infused rats. Our results indicate that polydatin has the potential to protect against Ang II-mediated cardiac hypertrophy through suppression of NADPH oxidase activity and superoxide production. These observations may shed new light on the understanding of the cardioprotective effect of polydatin.     

虎杖苷抗百草枯中毒肺纤维化作用及机制的研究进展

百草枯(Paraquat,PQ)对人畜均有很强的毒性,可引起肺组织不可逆的弥漫性纤维化,最终导致患者因呼吸衰竭而死亡。虎杖苷(Polydatin,PD)是蓼科植物虎杖的干燥根茎中分离出来的一种芪类有机化合物,也是其发挥药理作用的主要成分,具有抗氧化、抗肿瘤、抗炎、清除自由基、降低肺纤维化进程等丰富的药理活性。目前研究表明PD治疗PQ中毒肺纤维化比较明确的机理可归纳为抗氧化应激、调节细胞因子网络调控失衡以及抗基质金属蛋白酶(MMPs)/金属蛋白酶组织抑制因子(TIMPs)的失衡。本文主要对PD抗PQ中毒肺纤维化作用机制的研究进展进行了综述。     

Purification and functional characterization of the first stilbene glucoside-specific β-glucosidase isolated from Lactobacillus kimchi

This study aimed to develop viable enzymes for bioconversion of resveratrol-glucoside into resveratrol. Out of 13 bacterial strains tested, Lactobacillus kimchi JB301 could completely convert polydatin into resveratrol. The purified enzyme had an optimum temperature of 30–40 °C and optimum pH of pH 5.0 against polydatin. This enzyme showed high substrate specificities towards different substrates in the following order: isorhaponticin >> polydatin >> mulberroside A > oxyresveratrol-3-O-glucoside. Additionally, it rarely hydrolyzed astringin and desoxyrhaponticin. Based on these catalytic specificities, we suggest this enzyme be named stilbene glucoside-specific β-glucosidase. Furthermore, polydatin extracts from Polygonum cuspidatum were successfully converted to resveratrol with a high yield (of over 99%). Stilbene glucoside-specific β-glucosidase is the first enzyme isolated from lactic acid bacteria capable of bio-converting various stilbene glucosides into stilbene.     

Targeting the ROS/PI3K/AKT/HIF‐1α/HK2 axis of breast cancer cells: Combined administration of Polydatin and 2‐Deoxy‐d‐glucose

It is well established that cancer cells depend upon aerobic glycolysis to provide the energy they need to survive and proliferate. However, anti‐glycolytic agents have yielded few positive results in human patients, in part due to dose‐limiting side effects. Here, we discovered the unexpected anti‐cancer efficacy of Polydatin (PD) combined with 2‐deoxy‐D‐glucose (2‐DG), which is a compound that inhibits glycolysis. We demonstrated in two breast cell lines (MCF‐7 and 4T1) that combination treatment with PD and 2‐DG induced cell apoptosis and inhibited cell proliferation, migration and invasion. Furthermore, we determined the mechanism of PD in synergy with 2‐DG, which decreased the intracellular reactive oxygen (ROS) levels and suppressed the PI3K/AKT pathway. In addition, the combined treatment inhibited the glycolytic phenotype through reducing the expression of HK2. HK2 deletion in breast cancer cells thus improved the anti‐cancer activity of 2‐DG. The combination treatment also resulted in significant tumour regression in the absence of significant morphologic changes in the heart, liver or kidney in vivo. In summary, our study demonstrates that PD synergised with 2‐DG to enhance its anti‐cancer efficacy by inhibiting the ROS/PI3K/AKT/HIF‐1α/HK2 signalling axis, providing a potential anti‐cancer strategy.     

Reactive oxygen species-mediated endoplasmic reticulum stress and mitochondrial dysfunction contribute to polydatin-induced apoptosis in human nasopharyngeal carcinoma CNE cells

Previous studies revealed that polydatin, a natural small compound, possessed protective effect against ischemia/reperfusion injury and inflammation. However, the action and molecular mechanism of its potent anti-cancer activity remain poorly understood. In the present study, polydatin significantly killed several human tumor cell lines in a dose- and time-dependent manner. The compound also dose-dependently caused mitochondrial apoptosis in human nasopharyngeal carcinoma CNE cells. In addition, polydatin triggered endoplasmic reticulum (ER) stress and down-regulated the phosphorylation of Akt in CNE cells, while knock-down of CCAAT/enhancer-binding protein homologous protein (CHOP) dramatically abrogated the inactivation of Akt and reversed the pro-apoptotic effect of polydatin. Furthermore, polydatin provoked the generation of reactive oxygen species in CNE cells, while the antioxidant N-acetyl cysteine almost completely blocked the activation of ER stress and apoptosis, suggesting polydatin-induced reactive oxygen species is an early event that triggers ER stress mitochondrial apoptotic pathways in CNE cells. Taken together, these findings strongly suggest that polydatin might be a promising anti-tumor drug and our data provide the molecular theoretical basis for clinical application of polydatin.     

Polydatin Induces Apoptosis and Inhibits Growth of Acute Monocytic Leukemia Cells

Polydatin (PD), a component isolated from Polygonum cuspidatum, has various activities such as inhibiting platelet aggregation, lowering level of blood lipid, reducing lipid peroxidation, and so on. However, the antitumor activity of PD has been poorly reported. In the present study, effect of PD on cell proliferation was evaluated by Cell Counting Kit‐8, and cell cycle and apoptosis were investigated by flow cytometry. Meanwhile, the protein expression level of Bc1‐2, Bax, cyclin A, cyclin B, and cyclin D1, which associated with apoptosis and cell cycle were analyzed by Western blotting. Results show that PD could effectively inhibit the growth, arrest cells in S phase, and induce apoptosis of acute monocytic leukemia cell line THP‐1; meanwhile, expression of cyclin D1 and Bc1‐2 decreased significantly, and expression of Bax and cyclin A increased notably. All results suggest that PD maybe a potential therapeutic strategy for acute monocytic leukemia.     

光强对毛脉酸模根中白藜芦醇和白藜芦醇苷的影响

在人工控制条件下,观察了光强对毛脉酸模根中白藜芦醇和白藜芦醇苷的影响.结果表明,较短时期的遮荫使毛脉酸模根中白藜芦醇和白藜芦醇苷含量随着遮荫程度的增加而增加,较长时期的遮荫则使白藜芦醇和白藜芦醇苷含量降低;随遮荫程度和遮荫时间的增加,根中白藜芦醇和白藜芦醇苷含量显著降低.根中白藜芦醇产量在8月份达最大值、白藜芦醇苷产量在9月份达最大值,遮荫降低根中白藜芦醇和白藜芦醇苷的产量.在毛脉酸模生长后期给予短期深度遮荫可以提高白藜芦醇和白藜芦醇苷产量.     

白藜芦醇甙减轻高糖所致心肌微血管内皮细胞损伤的作用及机制研究

目的:探讨白藜芦醇甙在高糖处理的大鼠心肌微血管内皮细胞损伤中的作用及其可能调控机制。方法:酶消法分离大鼠CMECs,高糖处理CMECs建立细胞损伤模型,实验随机分为6个组:对照组(葡萄糖浓度为5.5 mmol/L)、白藜芦醇甙组、高糖组(葡萄糖浓度为33 mmol/L)、高糖+白藜芦醇甙组、高糖+白藜芦醇甙+3-MA(自噬抑制剂)组和高糖+雷帕霉素(自噬诱导剂)组。白藜芦醇甙组和高糖+白藜芦醇甙组分别加入10μmol/L的白藜芦醇甙孵育24 h,高糖+白藜芦醇甙+3-MA组加入10μmol/L的白藜芦醇甙和10μmmol/L 3-MA孵育24 h,高糖+雷帕霉素组加入100 nmol/L的雷帕霉素孵育24小时。CCK-8实验检测大鼠CMECs增殖;Tunel法检测大鼠CMECs凋亡;FITC-葡聚糖清除实验检测单层CMECs通透性;Western blot检测LC3Ⅱ和p62的表达。结果:与对照组和白藜芦醇甙组相比,高糖组CMECs增殖能力降低(P<0.05),凋亡率显著增加(P<0.05),细胞通透性增加(P<0.05),LC3Ⅱ表达降低(P<0.05),p62的表达增加(P<0.05);与高糖组相比,高糖+白藜芦醇甙组和高糖+雷帕霉素组CMECs增殖能力增加(P<0.05),凋亡率显著降低(P<0.05),细胞通透性降低(P<0.05),LC3Ⅱ表达增加(P<0.05),p62的表达降低(P<0.05);与高糖+白藜芦醇甙组相比,高糖+白藜芦醇甙+3-MA组CMECs增殖能力降低(P<0.05),凋亡率显著增加(P<0.05),细胞通透性增加(P<0.05),LC3Ⅱ表达降低(P<0.05),p62的表达增加(P<0.05)。结论:白藜芦醇甙通过增加自噬减轻高糖处理的大鼠心肌微血管内皮细胞损伤。     

Microbial transformation of polydatin and emodin-8-β-d-glucoside of Polygonum cuspidatum Sieb. et Zucc into resveratrol and emodin respectively by Rhizopus microsporus

Rhizopus microsporus isolated by our laboratory was able to transform polydatin into resveratrol and emodin-8-β-d-glucoside into emodin, respectively, through the fermentation of Polygonum cuspidatum Sieb. et Zucc. The fermentation products were separated and purified by H1020 resin and silica gel column chromatography. Thin layer chromatography (TLC) and high performance liquid chromatography (HPLC) were used to identify the products and evaluate the transformation efficiency. A variety of parameters of submerged state fermentation, including the growth characteristics, the change of β-glucosidase activity and the amount of polydatin, resveratrol, emodin-8-β-d-glucoside, emodin, and the dissolved oxygen, were monitored simultaneously. The amount of resveratrol yielded increased dramatically from 0.04 g/l at the beginning to the maximum value of 0.34 g/l at 36 h of fermentation, and emodin was from 0.4 g/l to 0.65 g/l at 80 h. The transformation rate of glycosides reached 98% and the purity of both resveratrol and emodin was 95%.