Two Phenolic Diterpenes as Antioxidants

1 INTRODUCTION Experimental studies in recent years show thatphenolic diterpenes are potent antioxidants with highbio-activities of anti-tumor, anti-HIV and anti-mi-crobes[1～4], and they have been developed and ap-plied in medicine, cosmetics, and keeping foods fresh.However, the exact mechanism in which phenolicditerpenes act as those bio-activities are still unex-plored. A series of compounds with similar struc-tures, including carnosol, rosmanol, isorosmanol andso on, were isolated f…     

Antioxidant and Antimicrobial Evaluation and Chemical Investigation of Rosa gallica var. aegyptiaca Leaf Extracts

Rosa gallica var. aegyptiaca is a species of flowering plant belonging to the Rosaceae family that plays an important role as a therapeutic agent for the treatment of specific types of cancer, microbial infections, and diabetes mellitus. This work presents the first report on the evaluation of the antioxidant and antimicrobial potential along with the phytochemical analysis of Rosa gallica var. aegyptiaca leaves. Five leaf extracts of hexane, chloroform, methanol, hydromethanol 80%, and water were prepared. Assessment of antioxidant activity was carried out via DPPH radical scavenging assay. Antimicrobial activity against five foodborne pathogenic bacteria—including Listeria monocytogenes, Bacillus subtilis, Staphylococcus aureus, Escherichia coli, and Salmonella enteritidis—and the fungus Candida albicans, was examined using the disc diffusion method. Total phenolic content and total flavonoid content were determined using the Folin–Ciocalteu reagent and aluminum chloride methods, respectively. Isolation, identification, and quantification of phenolic compounds were performed using HPLC-DAD analysis. Amongst the five leaf extracts that were investigated, hydromethanol 80% extract possessed the highest extraction yield, antioxidant activity, total phenolic content, and antimicrobial activity against all tested microbial strains. Moreover, this extract furnished six active phenolic compounds: gallic acid (1), (+) catechin (2), chlorogenic acid (3), (–) epicatechin (4), quercetin-3-O-α-d-(glucopyranoside) (5), and quercetin (6). This study provides an alternative utilization of R. gallica var. aegyptiaca leaves as a readily accessible source of natural antioxidants and antimicrobials in the food and pharmaceutical industries.     

Artificial Intelligence Assisted Ultrasonic Extraction of Total Flavonoids from Rosa sterilis

Flavonoids in Rosa sterilis were studied. The flavonoids in Rosa sterilis were extracted by ultrasonic method, and the extraction conditions were modeled and optimized by response the surface methodology and the artificial intelligence method. The results show that the ultrasonic method can effectively extract total flavonoids, and the extraction rate is close to the prediction value of ANN-GA algorithm, which proves the rationality of the model. The order of the effects of the parameters on the experiment was material liquid ratio > extraction power > extraction time > ethanol concentration. In addition, the scavenging effects of flavonoids on DPPH, O²⁻· and ·OH were also determined, and these indicated that flavonoids have strong antioxidant activities. The kinetics of the extraction process was studied by using the data of the extraction process, and it was found that the extraction process conformed to Fick’s first law.     

Microwave-Assisted and Conventional Extractions of Volatile Compounds from Rosa x damascena Mill. Fresh Petals for Cosmetic Applications

Rosa x damascena Mill. essential oil is mainly used in the cosmetics and perfumery industry, but it also finds application in the food industry as a flavoring agent. The chemical composition of essential oils is affected by environment, soil, harvesting technique, storage condition, and extraction methods. Nowadays, the study and design of greener, more efficient, and sustainable extractive procedures is the main and strategic focus in the chemical research and development of botanical derivatives, especially as regards fragrances and essential oils. Several technologies are available, and the best method to use depends on the desired chemicals, but conventional extractive processes are often laborious and time-consuming, involve large amounts of solvents, and may cause the partial loss of volatiles, affecting the quality of the final product. In the last decade, microwave irradiation has been successfully applied to classical techniques, often improving the general extractive efficiency and extract quality. In the present paper, as a preliminary analytical screening approach, two microwave-mediated techniques, Solvent-Free Microwave Extraction (SFME) and Microwave Hydrodiffusion and Gravity (MHG), and two conventional procedures, Hydrodistillation (HD) and Steam Distillation (SD), were applied and compared for the extraction of volatile compounds from R. x damascena fresh petals to highlight differences and advantages of the selected procedure and of the obtained extracts useful in a cosmetic context as fragrances or active ingredients. The chemical composition of the extracts was investigated by GC-MS and GC-FID. Sixty-one components, distributed in the four techniques, were identified. SD and HD are dominated by oxygenated terpenes (59.01% and 50.06%, respectively), while MHG and SFME extracts are dominated by alcohols (61.67% and 46.81%, respectively). A relevant variability in the composition of the extracts relating to the extraction techniques used was observed. To point out the correlation between the process and composition of the obtained natural products, principal component analysis (PCA) of the data extracted from GC-FID was used. Taking into account a cosmetic application, SFME shows several advantages when compared with the other procedures. The extract (obtained in a significantly higher amount) contains a meaningful lower level of potential fragrance allergenic compounds and quite a double amount of benzyl alcohol and 2-phenyl ethanol that can also enhance the preservative action in personal care products.     

Two New Flavonoids from Retama raetam

Two new furanoflavonoids, retamasins A and B ( 1 and 2 , resp.), along with five known flavonoids, 3 – 7 , were isolated from the aerial parts of Retama raetam. Their structures were determined on the basis of extensive spectroscopic (IR, MS, and 1D‐ and 2D‐NMR) analyses and by comparison with the literature data. This is the first report of the isolation of new furanoflavonoids 1 and 2 from Retama genus, while compounds 3, 5 , and 6 were found for the first time from R. raetam. Antioxidant and anti‐inflammatory activities of the isolated compounds were also evaluated. Compounds 2, 3 , and 5 – 7 exhibited potent inhibitions of iNOS activity with IC₅₀ values of 2.9, 5.0, 3.1, 1.2, and 4.8 μg/ml, respectively. All compounds inhibited NF‐κB except 1 and 5 . Compound 6 was most active in inhibiting iNOS and NF‐κB activity, as well as in decreasing oxidative stress.     

Two New Flavonoids from Derris eriocarpa How

Two new flavonoids, 1 and 2 , together with two known flavonoids, tephrosin ( 3 ) and 12a‐hydroxy‐α‐toxicarol ( 4 ), were isolated from the whole herb of Derris eriocarpa How . The structures and absolute configurations of the new compounds were elucidated on the basis of their MS, NMR, and ECD data. The structures of the known compounds were established by extensive spectroscopic (MS, 1D‐ and 2D‐NMR) analyses and comparison with the literature data. All compounds were isolated from D. eriocarpa for the first time. Compound 3 showed modest inhibitory activities against the growth of human cancer cells HEL and A549 with the IC₅₀ values of 15.03 ± 0.62 and 13.27 ± 0.39 μm , respectively.     

Microwave-Assisted Green Synthesis of Non-Cytotoxic Silver Nanoparticles Using the Aqueous Extract of Rosa santana (rose) Petals and Their Antimicrobial Activity

Green methods using biological extracts, in particular plant-based solutions, have shown great potential for silver nanoparticle synthesis. A microwave-assisted single-step phytosynthesis of silver nanoparticles is described in the present study. The aqueous extract obtained from the Rosa santana (rose) petals was used for the first time in the synthesis. The synthesized nanoparticles obtained after optimized microwave conditions for time and temperature were analyzed by ultraviolet–visible spectroscopy (UV–Vis), Fourier-transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), and Zeta-size analysis. The results obtained from the characterization studies showed that the synthesized nanoparticles were nearly spherical in shape with sizes from 6.52?nm to 25.24?nm with an average particle size of 14.48?nm with a face-centered cubic structure. The antibacterial activities of the synthesized nanoparticles were evaluated and revealed that the silver nanoparticles displayed good inhibition against both Gram-negative and Gram-positive bacteria. Also, the cytotoxic effect of the silver nanoparticles on a mouse fibroblast cell line (L929) was studied by a cell viability assay. The results showed that phytosynthesized silver nanoparticles were nontoxic to the healthy normal cell line at all tested concentrations.     

Two Novel Antibacterial Flavonoids from Myrsine Africana L.

Two novel flavonoids, myrsininone A （1）, an isoflavone and myrsininone B （2）, a flavanone, with very strong antibacterial activities, were isolated from the stems of Myrsine africana L. Their structures were elucidated by extensive spectroscopic analyses. The antibacterial activities were determined by modified Resazuric MIC methods.     

Two New Flavonoids from the Rhizomes of Abacopteris penangiana

A new flavan‐4‐ol glycoside, abacopterin K ( 1 ), and a new dihydrochalcone glycoside, abacopterin L ( 2 ), were isolated from the rhizomes of Abacopteris penangiana. Their structures were elucidated on the basis of various spectroscopic analyses and chemical evidences. The novel glucosylation pattern of abacopterin K consisting of two ‘glucose‐fused’ dioxepine ring moieties is found for the first time within natural flavonoids.     

Two New Triterpenoid Glycosides from the Roots of Rosa cymosa Tratt.

Two new triterpenoid glycosides, 3α,19α,23α‐trihydroxy‐2‐oxo‐12‐ursen‐28‐O‐β‐d ‐glucopyranoside ( 1 ) and 3α,19α,23α‐trihydroxy‐2‐oxoolean‐12‐en‐28‐O‐β‐d ‐glucopyranoside ( 2 ) as well as three known compounds, 2α,3α,19α‐trihydroxyolean‐12‐en‐28‐O‐β‐d ‐glucopyranoside ( 3 ), 2α,3α,19α,23‐tetrahydroxy‐12‐ursen‐28‐O‐β‐d ‐glucopyranoside ( 4 ), and 2α,3β,19α,23‐tetrahydroxyurs‐12‐en‐28‐oic acid ( 5 ) were isolated from 75% EtOH extract of Rosa cymosa. Their structures were elucidated by extensive spectroscopic methods. All the isolated compounds displayed moderate inhibitory activity against LPS‐induced NO production in macrophages.     

Comparison of Two On-Line Analysis Techniques Used for the Screening of Antioxidants in EGb 761

In order to perform on-line screening procedures for antioxidants in the Ginkgo biloba extract (EGb761), a comparison was carried out between LC–DAD–DPPH analysis used for the determination of DPPH^· bleaching and LC–DAD–CL determination applied for the detection of H₂O₂ and O ₂ ^?· scavenging activities. The results demonstrated that 15 antioxidants in EGb 761 could be identified by LC–DAD–CL, while only 10 antioxidants were detected under LC–DAD–DPPH conditions. Furthermore, it was found that both sensitivity and reproducibility of the LC–DAD–CL method were superior. The results indicated that the combination of the two methods might provide useful information for the prediction of antioxidants in herbal medicines.     

Effects of Micelle on Pyrazoles as Antioxidants in Radical-induced Oxidation of DNA

Effects of 4-(1,3-diphenyl-1H-pyrazol-5-yl)phenol(APP), 4-(1,5-diphenyl-1H-pyrazol-3-yl)phenol(BPP) and 4-(3,5-diphenyl-1H-pyrazol-1-yl)phenol(CPP) on 2,2'-azobis-(2-amidinopropane hydrochloride)(AAPH)-induced oxidation of DNA were measured in the presence of various concentrations of Triton X-100, cetyltrimethylammonium bromide(CTAB), or sodium dodecyl sulfate(SDS) in order to clarify the influence of neutral, cationic and anionic microenvironments on antioxidant capacities of APP, BPP and CPP. Although these surfactants can protect DNA against AAPH-induced oxidation, the pyrazoles in the presence of these surfactants functioned as prooxidants when the concentrations of Triton X-100 and CTAB increased. However, CPP exhibited antioxidant property with the increase of the concentration of CTAB. On the contrary, APP, BPP and CPP were antioxidants in the presence of various concentrations of SDS. The added surfactants resulted in the complication of the microenvironments around DNA, pyrazoles and peroxyl radical(ROO^·) derived from AAPH. The anionic charge of SDS was beneficial to enhancing the antioxidant effectiveness of these pyrazoles. It can be concluded that the charge property of surfactants markedly influenced the behavior of an antioxidant in AAPH-induced oxidation of DNA.     

Improved Synthesis of Asymmetric Curcuminoids and Their Assessment as Antioxidants

In this paper, the syntheses of twelve asymmetric curcumin analogs using Pabon’s method are reported. Generally, the previously reported yields of asymmetric curcuminoids, such as 9a (53%), 9c (38%), and 9k (38%), have been moderate or low. Herein, we propose that the low yields were due to the presence of water and n-BuNH₂ in the reaction media. To prove this formulated hypothesis, we have demonstrated that the yields can be improved by adding molecular sieves (MS) (4 Å) to the reaction mixture, thus reducing the interference of water. Therefore, improved yields (41–76%) were obtained, except for 9b (36.7%), 9g (34%), and 9l (39.5%). Furthermore, compounds 9b, 9d, 9e, 9f, 9g, 9h, 9i, 9j, and 9l are reported herein for the first time. The structures of these synthetic compounds were determined by spectroscopic and mass spectrometry analyses. The free radical scavenging ability of these synthetic asymmetric curcuminoids was evaluated and compared to that of the positive control butylated hydroxytoluene (BHT). Among the synthesized asymmetric curcuminoids, compounds 9a (IC₅₀ = 37.57 ± 0.89 μM) and 9e (IC₅₀ = 37.17 ± 1.76 μM) possessed effective 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging abilities, and compounds 9h (IC₅₀ = 11.36 ± 0.65 μM) and 9i (IC₅₀ = 10.91 ± 0.77 μM) displayed potent 2,2’-azinobis-(3-ethylbenzthiazoline-6-sulphonate) (ABTS) radical scavenging abilities comparable to that of curcumin (IC₅₀ = 10.14 ± 1.04 μM). Furthermore, all the synthetic asymmetric curcuminoids were more active than BHT.     

Flavonoids as Inhibitors of Bacterial Efflux Pumps

Flavonoids are widely occurring secondary plant constituents, and are abundant in vegetable and fruit diets as well as herbal medicines. Therapeutic treatment options for bacterial infections are limited due to the spread of antimicrobial resistances. Hence, in a number of studies during the last few years, different classes of plant secondary metabolites as resistance-modifying agents have been carried out. In this review, we present the role of flavonoids as inhibitors of bacterial efflux pumps. Active compounds could be identified in the subclasses of chalcones, flavan-3-ols, flavanones, flavones, flavonols, flavonolignans and isoflavones; by far the majority of compounds were aglycones, although some glycosides like kaempferol glycosides with p-coumaroyl acylation showed remarkable results. Staphylococcus aureus NorA pump was the focus of many studies, followed by mycobacteria, whereas Gram-negative bacteria are still under-investigated.     

高分子抗氧化剂研究进展

过量自由基可造成人体的多种损伤,加速人的衰老.抗氧化剂可以清除或转化多余的自由基,对人体起到保护作用.本文从天然高分子及合成高分子两方面对抗氧化剂的研究进展进行了综述.在天然高分子抗氧化剂中,超氧化物歧化酶(SOD)、过氧化氢酶(CAT)及谷胱甘肽过氧化物酶等的结构与功能已经较为清晰;金属硫蛋白、血红蛋白、短肽及多糖等...     

Kinetic Evaluation of Reactivity of Phenolic Derivatives as Antioxidants for Polypropylene

Reactivity of commercial phenols as antioxidants for plastics, especially polypropylene, was examined under kinetic considerations. Inhibitive rate constants, k_inh, were found to decrease in the order: SWP ? Topanol CA ? BMP > Ionox 330 > Irganox 1076 > Irganox 1010, while numbers n′ of free radicals trapped by the phenolic moiety decreased in the order: Irganox 1076 > Irganox 1010 ? Ionox 330 > BMP ? Topanol CA > SWP (the structures of these antioxidants are given in the text). In practical use of phenols for polypropylene, it was found that effective phenols are not those having higher values of of k_inh., but n′ values nearly two. The effect of substituents, especially para substituents, of phenols on their activities was elucidated.