Antioxidant product analysis of Folium Hibisci Mutabilis

Folium Hibisci Mutabilis, a new member of Chinese Pharmacopoeia, can treat some diseases induced by reactive oxygen species. The study prepared a lyophilized aqueous extract of Folium Hibisci Mutabilis (LAFHM). LAFHM was found to enrich eight flavonoids (i.e., quercetin, luteolin, hyperoside, isoquercitrin, rutin, kaempferol, tiliroside, and vitexin) by HPLC analysis. These flavonoids were further compared using antioxidant assays, where triliroside and vitexin always exhibited higher IC₅₀ values than the others. In ultra-performance liquid chromatography coupled with electrospray ionization quadrupole time-of-flight tandem mass spectrometry analysis, these flavonoids could basically give two characteristic m/z values (226 and 196) and their corresponding double m/z values (i.e., 602, 570, 926, 926, 570, 1186, and 862), when treated by 1,1-diphenyl-2-picryl-hydrazl radical (DPPH^?). Finally, the coupling products of DPPH^?-treated triliroside were investigated using computational chemistry. It was found that the –OH in para-coumaroyl moiety to have the lowest bond disassociation energy among all phenolic -OHs in the triliroside. In conclusion, Folium Hibisci Mutabilis contains the above eight antioxidant flavonoids. Despite of the different antioxidant levels, they can generally produce flavonoid-radical coupling product and flavonoid-flavonoid homodimer during antioxidant process. Especially, tiliroside uses para-coumaroyl as linker to construct a tiliroside-radical coupling product at the meta-carbon atom.     

Comparison of Ferroptosis-Inhibitory Mechanisms between Ferrostatin-1 and Dietary Stilbenes (Piceatannol and Astringin)

Synthetic arylamines and dietary phytophenolics could inhibit ferroptosis, a recently discovered regulated cell death process. However, no study indicates whether their inhibitory mechanisms are inherently different. Herein, the ferroptosis-inhibitory mechanisms of selected ferrostatin-1 (Fer-1) and two dietary stilbenes (piceatannol and astringin) were compared. Cellular assays suggested that the ferroptosis-inhibitory and electron-transfer potential levels decreased as follows: Fer-1 >> piceatannol > astringin; however, the hydrogen-donating potential had an order different from that observed by the antioxidant experiments and quantum chemistry calculations. Quantum calculations suggested that Fer-1 has a much lower ionization potential than the two stilbenes, and the aromatic N-atoms were surrounded by the largest electron clouds. By comparison, the C4′O-H groups in the two stilbenes exhibited the lowest bond disassociation enthalpies. Finally, the three were found to produce corresponding dimer peaks through ultra-performance liquid chromatography coupled with electrospray ionization quadrupole time-of-flight tandem mass spectrometry analysis. In conclusion, Fer-1 mainly depends on the electron transfer of aromatic N-atoms to construct a redox recycle. However, piceatannol and astringin preferentially donate hydrogen atoms at the 4′-OH position to mediate the conventional antioxidant mechanism that inhibits ferroptosis, and to ultimately form dimers. These results suggest that dietary phytophenols may be safer ferroptosis inhibitors for balancing normal and ferroptotic cells than arylamines with high electron-transfer potential.     

Ferroptosis-Inhibitory Difference between Chebulagic Acid and Chebulinic Acid Indicates Beneficial Role of HHDP

The search for a safe and effective inhibitor of ferroptosis, a recently described cell death pathway, has attracted increasing interest from scientists. Two hydrolyzable tannins, chebulagic acid and chebulinic acid, were selected for the study. Their optimized conformations were calculated using computational chemistry at the B3LYP-D3(BJ)/6-31G and B3LYP-D3(BJ)/6-311 + G(d,p) levels. The results suggested that (1) chebulagic acid presented a chair conformation, while chebulinic acid presented a skew-boat conformation; (2) the formation of chebulagic acid requires 762.1729 kcal/mol more molecular energy than chebulinic acid; and (3) the 3,6-HHDP (hexahydroxydiphenoyl) moiety was shown to be in an (R)- absolute stereoconfiguration. Subsequently, the ferroptosis inhibition of both tannins was determined using a erastin-treated bone marrow-derived mesenchymal stem cells (bmMSCs) model and compared to that of ferrostatin-1 (Fer-1). The relative inhibitory levels decreased in the following order: Fer-1 > chebulagic acid > chebulinic acid, as also revealed by the in vitro antioxidant assays. The UHPLC–ESI-Q-TOF-MS analysis suggested that, when treated with 16-(2-(14-carboxytetradecyl)-2-ethyl-4,4-dimethyl-3-oxazolidinyloxy free radicals, Fer-1 generated dimeric products, whereas the two acids did not. In conclusion, two hydrolyzable tannins, chebulagic acid and chebulinic acid, can act as natural ferroptosis inhibitors. Their ferroptosis inhibition is mediated by regular antioxidant pathways (ROS scavenging and iron chelation), rather than the redox-based catalytic recycling pathway exhibited by Fer-1. Through antioxidant pathways, the HHDP moiety in chebulagic acid enables ferroptosis-inhibitory action of hydrolyzable tannins.     

Chemical Study on Protective Effect Against Hydroxyl‐induced DNA Damage and Antioxidant Mechanism of Myricitrin

Excessive reactive oxygen species (ROS) can oxidatively damage DNA to cause severe biological consequences. In the study, a natural flavonoid, myricitrin (myricetin‐3‐O‐α‐L‐rhamnopyranoside), was found to have a protective effect against hydroxyl‐induced DNA damage (IC₅₀ 159.86 ± 54.24 μg/mL). To investigate the mechanism, it was determined by various antioxidant assays. The results revealed that myricitrin could effectively scavenge ·OH, ·O₂^?, DPPH· (1,1‐diphenyl‐2‐picrylhydrazyl radical), and ABTS⁺· (2,2′‐Azino‐bis(3‐ethylbenzothiazoline‐6‐sulfonic acid) radicals (IC₅₀ values were respectively 69.71 ± 5.93, 69.71 ± 5.93, 25.34 ± 2.14, and 1.71 ± 0.09 μg/mL), and bind Cu²⁺ (IC₅₀ 27.33 ± 2.36 μg/mL). Based on the mechanistic analysis, it can be concluded that: (i) myricitrin can effectively protect against hydroxyl‐induced DNA oxidative damage via ROS scavenging and deoxynucleotide radicals repairing approaches. Both approaches can be attributed to its antioxidant. From a structure‐activity relationship viewpoint, its antioxidant ability can be attributed to the ortho‐dihydroxyl moiety, and ultimately to the stability of its oxidized form ortho‐benzoquinone; (ii) its ROS scavenging is mediated via metal‐chelating, and direct radical‐scavenging which is through donating hydrogen (H·) and electron (e); and (iii) its protective effect against DNA oxidative damage may be primarily responsible for the pharmacological effects, and offers promise as a new therapeutic reagent for diseases from DNA oxidative damage.     

Herba Ecliptae Protects against Hydroxyl Radical‐induced Damages to DNA and Mesenchymal Stem Cells via Antioxidant Mechanism

Herba Ecliptae (HE) is a typical Chinese herbal medicine used in China for 1500 years. In the study, HE was extracted by various solvents to prepare five HE extracts. They were observed to possess a protective effect against ×OH‐induced DNA damage, and scavenging effects on ×OH radical, ×O₂^? radical, DPPH×(1,1‐diphenyl‐2‐picrylhydrazyl) radical, and ABTS×⁺ (2,2′‐azino‐bis(3‐ethyl‐benzothiazoline‐6‐sulfonic acid) radical, and reduce Cu²⁺ ion. The contents of total phenolics and wedelolactone in five extracts were determined respectively using Folin‐Ciocalteu method and HPLC method. To identify which chemical component can be responsible for its effects, the correlation graphs between chemical contents and antioxidant abilities (1/IC₅₀ values) were plotted to calculate correlation coefficients (R values). Finally, MTT assay revealed that two HE extracts could effectively protect mesenchymal stem cells (MSCs) against ×OH‐induced damage at 3‐30 μg/mL. On the basis of mechanistic analysis, we concluded that: (i) HE can effectively protect against ×OH‐induced damages to DNA and MSCs, thereby HE may have a therapeutic potential in MSCs transplantation or prevention of many diseases; (ii) the effects can be mainly attributed to total phenolics (R = 0.678) especially wedelolactone (R = 0.618); (iii) they exert antioxidant action via hydrogen atom transfer (HAT) and sequential electron proton transfer (SEPT) mechanisms.     

(E)-N-芳基-3-[2-(8-羟基喹啉基)-乙烯基]咔唑的合成、抗氧化活性及促进鼠骨髓间质干细胞增殖的研究

设计合成了3-[2-(8-羟基喹啉基)-乙烯基]-N-对甲苯基咔唑(8)和3-[2-(8-羟基喹啉基)-乙烯基]-N-对甲氧苯基咔唑(9)两个新的化合物, 用IR, MS, 1H NMR和元素分析确认其结构. 并利用DPPH•方法, 超氧阴离子自由基( )法, 羟基自由基HO•法和噻唑蓝比色法(MTT法)分别测定了目标产物的抗氧化活性和调控鼠骨髓间质干细胞(MSCs)的作用. 结果表明, 这两种化合物对DPPH•自由基、超氧阴离子自由基和羟基自由基具有较强的抗氧化活性, 化合物9在低浓度时对鼠骨髓间质干细胞增殖有很好的促进作用.     

黑海参多糖组成的研究

通过酶降解、酒精沉淀、DEAE柱纯化和脱色精制四步，从黑海参体壁中制得黑海参多糖的纯品。经电泳法及凝胶拉法鉴定，所得样品为均一组分，是一种典型的动物酸性杂多糖，内含硫酸酯基。样品经水解后用HPLC检测，得葡萄糖（36．7％）、岩藻糖（16．4％）、葡萄糖醛酸（34．2％）、木糖（7．22％）及一些未知成分（5．47％）。经Smith降解及一些波谱特征表明，单糖之间苷键是α-型，主要为1-2和1-3连结。凝胶往法测定其平均分子量约是96×104。     

Evaluation of antioxidant activity of isoferulic acid in vitro

Isoferulic acid (3-hydroxy-4-methoxycinnamic acid, IFA), the isomer of ferulic acid (4-hydroxy-3-methoxycinnamic acid), is a rare phenolic acid occurring in Rhizoma Cimicifugae. Unlike ferulic acid, which has been well investigated, the antioxidant activity of IFA has not been measured. In this study, IFA was systematically evaluated for its in vitro antioxidant activity for the first time. IC50 values were calculated of 7.30 +/- 0.57, 4.58 +/- 0.17, 1.08 +/- 0.01, 8.84 +/- 0.43, 7.69 +/- 0.39, 1.57 +/- 0.2, 13.33 +/- 0.49 microg/mL, respectively, for lipid peroxidation, DPPH (1,1-diphenyl-2-picrylhydrazyl radical) and ABTS (3-ethylbenzthiazoline-6-sulfonic acid diammonium salt) radical scavenging, reducing power on Fe3+ and CU2+ ions, and hydroxyl and superoxide anion radical scavenging. Comparison with the IC50 values with those of the positive controls, Trolox and butylated hydroxyanisole (BHA), it can be concluded that isoferulic acid is an effective natural antioxidant in both lipid and aqueous media.     

Ferroptosis-Inhibitory Effect and Possible Mechanisms of Ellagitannin Geraniin

The search for safe and effective ferroptosis-inhibitors has become an important topic. Geraniin, an ellagitannin bearing hexahydroxydiphenoyl (HHDP) and dehydrohexahydroxydiphenoyl (DHHDP) groups, was observed to inhibit erastin-induced ferroptosis in bone marrow-derived mesenchymal stem cells (bmMSCs). To determine the mechanism, geraniin was further analyzed using UV-vis spectra and several colorimetric assays, where its IC₅₀ values were always much lower than that of the Trolox positive control. When interacted with several free radicals, geraniin gave no radical adduct formation (RAF) peak in the ultra-performance liquid chromatography coupled with electrospray ionization quadrupole time-of-flight tandem mass spectrometry. In conclusion, geraniin exhibits ferroptosis-inhibitory potential towards erastin-treated bmMSCs; such potential may mainly stem from its strong lipid peroxidation (LPO)-inhibition, Fe²⁺-chelating, and antioxidant actions. Geraniin gives neither dimer nor radical adduct, owing to the bulky HHDP (or DHHDP) group; thus, it is considered as a safe and effective ferroptosis-inhibitor.     

N-(2-Phenoxy)ethyl imidazo[1,2-a]pyridine-3-carboxamides containing various amine moieties: Design,synthesis and antitubercular activity

Seven 2,6-disubstituted N-(2-phenoxy)ethyl imidazo[1,2-a]pyridine-3-carboxamide series containing various amine moieties were designed and synthesized as new anti-TB agents.Many of them show excellent in vitro activity against both drug-sensitive MTB strain H37Rv and two MDR-MTB clinical isolates(MIC:<0.002-0.030 μg/mL).Compounds 2f,5e and 5g display acceptable safety and pharmacokinetic profiles,opening a new direction for further development.