Impact of superheated steam roasting on changes in antioxidant and microstructure properties of raw and processed cocoa cotyledon

This research focused on the roasting of cocoa beans at 184 °C for 16 min duration in a superheated steam oven using two separate modes of heating: convection mode and superheated steam mode. After roasting, the antioxidant properties of the cooked cocoa were assessed as ferric reducing antioxidant power activity (FRAP), DPPH radical scavenging activity, total flavonoid content (TFC) and total phenol content (TPC). The micro structural properties of raw and processed cocoa beans were observed using scanning electron microscopy (SEM). As discovered in the scan, conventional roasting showed a nearly complete rapture of the cytoplasmic network system and the destruction of the organelles, whereas superheated steam mode showed satisfactory images. Studies indicated that superheated steam roasting preserved significantly (p < 0.05) greater antioxidant properties as opposed to conventional method of roasting.     

Demethylation and degradation of phenylmethylethers by the sulfide-methylating homoacetogenic bacterium strain TMBS 4

Biochemical studies on anaerobic phenylme-thylether cleavage by homoacetogenic bacteria have been hampered so far by the complexity of the reaction chain involving methyl transfer to acetyl-CoA synthase and subsequent methyl group carbonylation to acetyl-CoA. Strain TMBS 4 differs from other demethylating homoacetogenic bacteria in using sulfide as a methyl acceptor, thereby forming methanethiol and dimethylsulfide. Growing and resting cells of strain TMBS 4 used alternatitively CO₂ as a precursor of the methyl acceptor CO for homoacetogenic acetate formation. Demethylation was inhibited by propyl iodide and reactivated by light, indicating involvement of a corrinoid-dependent methyltransferase. Strain TMBS 4 contained ca. 750 nmol g dry mass^-1 of a corrinoid tentatively identified as 5-hydroxybenzimidazolyl cobamide. A photometric assay for measuring the demethylation activity in cell extracts was developed based on the formation of a yellow complex of Ti³⁺ with 5-hydroxyvanillate produced from syringate by demethylation. In cell extracts, the methyltransfer reaction from methoxylated aromatic compounds to sulfide or methanethiol depended on reductive activation by Ti³⁺. ATP and Mg²⁺ together greatly stimulated this reductive activation without being necessary for the demethylation reaction itself. The specific activity of the transmethylating enzyme system increased proportionally with protein concentration up to 3 mg ml^-1 reaching a constant level of 20 nmol min^-1 mg^-1 at protein concentrations 10 mg ml^-1. The specific rate of activation increased in a non-linear manner with protein concentration. Strain TMBS 4 degraded gallate, the product of sequential demethylations, to 3 acetate through the phloroglucinol pathway as found earlier with Pelobacter acidigallici.Abbreviations BV benzyl viologen - CTAB cetyltrimethylammonium bromide - H₄folate tetrahydrofolate - MOPS 3-[N-morpholino]propanesulfonic acid - MV methyl viologen - NTA nitrilotriacetate - t_d doubling time - TMB 3,4,5-trimethoxybenzoate     

Antimicrobial activity of pleurocidin is retained in Plc-2, a C-terminal 12-amino acid fragment

An analysis of a series of five peptides composed of various portions of the pleurocidin (Plc) sequence identified a l2-amino acid fragment from the C-terminus of Plc, designated Plc-2, as the smallest fragment that retained a antimicrobial activity comparable to that of the parent compound. MIC tests in vitro with low-ionic-strength medium showed that Plc-2 has potent activity against Pseudomonas aeruginosa, Escherichia coli and Staphylococcus aureus but not against Enterococcus faecalis. The antifungal activity of the synthetic peptides against phytopathogenic fungi, such as Fusarium oxysporum, Colletotrichum sp., Aspergillus niger and Alternaria sp., also identified Plc-2 as a biologically active peptide. Microscopy studies of fluorescently stained fungi treated with Plc-2 demonstrated that cytoplasmic and nuclear membranes were compromised in all strains of phytopathogenic fungi tested. Together, these results identify Plc-2 as a potential antimicrobial agent with similar properties to its parent compound, pleurocidin. In addition, it demonstrated that the KHVGKAALTHYL residues are critical for the antimicrobial activity described for pleurocidin.     

Enhanced chemiluminescence of the luminol–AgNO3 system by Ag nanoparticles

The oxidation reaction of luminol with AgNO₃ can produce chemiluminescence (CL) in the presence of silver nanoparticles (NPs) in alkaline solution. Based on the studies of UV‐vis absorption spectra, photoluminescence (PL) spectra and CL spectra, a CL enhancement mechanism is proposed. The CL emission spectrum of the luminol–AgNO₃–Ag NPs system indicated that the luminophore was still 3‐aminophthalate. On injection of silver nanoparticles into the mixture of luminol and AgNO₃, they catalysed the reduction of AgNO₃ by luminol. The product luminol radicals reacted with the dissolved oxygen, to produce a strong CL emission. As a result, the CL intensity was substantially increased. Moreover, the influences of 18 amino acids, e.g. cystine, tyrosine and asparagine, and 25 organic compounds, including gallic acid, tannic acid and hydroquinone, on the luminol–AgNO₃–Ag NPs CL system were studied by a flow‐injection procedure, which led to an effective method for detecting these compounds. Copyright © 2011 John Wiley & Sons, Ltd.     

一株茄病镰刀菌的代谢产物研究

一株茄病镰刀菌（Fusarium solani）固体发酵培养物经柱层析分离得到10个化合物。通过波谱分析,分别鉴定为对羟基苯甲酸甲酯（1）、水杨酸甲酯（2）、水杨酸戊酯（3）、香草乙酮（4）、草夹竹桃苷（5）、2-甲氧基-4-乙烯苯基-β-D-吡喃葡萄糖苷（6）、1-O-β-D-glucopyranosyl-(2S,3R,8E)-2-[(2R)-2-hydroxylpalmitoylamino]-8-octadecene-1,3-diol（7）、1-O-β-D-glucopyranosyl-(2S,3R,4E,8E)-2-[(2R)-2-hydroxyhexadecanoylaino]-8-octadecene -1,3-diol （8）、脑苷脂D（9）和脑苷脂C（10）。所有化合物均为首次从茄病镰刀菌中分离得到,其中化合物6首次作为天然产物报道。     

Saliva affects the antifungal activity of exogenously added histatin 3 towards Candida albicans

Antifungal activity of histatin 3 against two Candida albicans clinical isolates was determined in assays containing rabbit submandibular gland saliva. Histatin 3 inhibited the cell growth and germination of both isolates dose-dependently (10-100 microg ml(-1)) with maximum inhibition occurring after 60 min incubation. Adding fresh histatin 3 after 60 min caused further reduction in the viable cell count. Higher histatin 3 concentrations (50-100 microg ml(-1)) and prolonged exposure to peptide were required to inhibit germination. Histatin 3 was rapidly degraded in rabbit submandibular gland saliva and this may explain why fresh addition of histatin 3 increases candidacidal activity.     

Bioactive aristolactams from Piper umbellatum

Four alkaloids named piperumbellactams A-D (1-4) were isolated from branches of Piper umbellatum together with known N-hydroxyaristolam II (5), N-p-coumaroyl tyramine (6), 4-nerolidylcatechol (7), N-trans-feruloyltyramine, E-3-(3,4-dihydroxyphenyl)-N-2-[4-hydroxyphenylethyl]-2-propenamide, beta-amyrin, friedelin, apigenin 8-C-neohesperidoside, acacetin 6-C-beta-d-glucopyranoside, beta-sitosterol, its 3-O-beta-d-glucopyranoside and its 3-O-beta-d-[6'-dodecanoyl]-glucopyranoside. Glycosidase inhibition, antioxidant and antifungal activities of these compounds were evaluated. Compounds 1-3 showed moderate alpha-glucosidase enzyme inhibition with IC50 values 98.07+/-0.44, 43.80+/-0.56 and 29.64+/-0.46, respectively. In DPPH radical scavenging assay, compounds 2, 3 and 6 showed potent inhibitory activity while compounds 4, 5 and 7 showed potent antifungal activity.     

红芒6号果实成熟阶段香气成分研究

对商熟期及完熟期的红芒6号芒果果实采用顶空固相微萃取法(HS-SPME)提取香气成分,以气相色谱—质谱分析进行鉴定。共检出22种香气成分,其中商熟期14种,完熟期10种,主要为萜烯类、醛类、酸类等。两个阶段都具有的成分是α-桂叶烯、α-蛇麻烯等;商熟期主要的香气成分是( )-2-蒈烯;完熟期的主要香气成分是δ-3-蒈烯。     

Anaerobic utilization of essential oils bydenitrifying bacteria

Plant volatile organic compounds are a major carbonsource in nature. We studied the degradability ofthese substances by anaerobic microorganisms inenrichment cultures with representative essential oilsas organic substrates and nitrate as electronacceptor. Lemon and pine needle oil supportedmicrobial growth in the presence of pure oil, whereasparsley seed, camphor, sage, fennel, and mint oilsupported growth only when the essential oils weredissolved in an overlying phase of2,2,4,4,6,8,8-heptamethylnonane. Thyme oil did notsupport denitrification. Analyses of the microbiallydegraded oils revealed the disappearance ofmonoterpenes, of several monoterpenoids, and ofmethoxy-propenyl-benzenes, including apiole andmyristicin. Most-probable-number determinations fordenitrifying communities in sewage sludge and forestsoil yielded 10⁶ to 10⁷monoterpene-utilizing cells ml^-1, representing0.7 to 100% of the total cultivablenitrate-reducing microorganisms. The utilization ofessential oils together with the common occurrence ofthis metabolic trait are indications for anenvironmentally important, but currently unexploredanaerobic turnover of plant volatile organic compoundsin soil.     

The combination effects of phenolic compounds and fluconazole on the formation of ergosterol in Candida albicans determined by high-performance liquid chromatography/tandem mass spectrometry

A liquid chromatography/tandem mass spectrometry (LC/MS) with atmospheric pressure chemical ionization (APCI) for the quantification of ergosterol, lanosterol, and squalene was developed to evaluate the combination effects of phenolic compounds with fluconazole on ergosterol biosynthesis in Candida albicans. The three analytes were separated by a column of C18 and were quantified without interference with each other using positive mode tandem mass spectrometry (MS/MS). Molecular ions of ergosterol and lanosterol were detected as the [M+H-H2O]+ ion species at m/z 380 and 410, whereas squalene appeared as the [M+H]+ ion species at m/z 412. On fragmentation of ergosterol, lanosterol, and squalene, the product ions at m/z 69, 149, and 109, respectively, were present as major fragments. These product ions were used for the quantification of them in multiple reaction monitoring acquisition mode. The relationship between signal intensity and the analytes' concentration was linear over the concentration range of 0.05-10 microg/ml. Following the treatment of C. albicans with fluconazole in combination with albicanyl caffeate, resveratrol, and 3,4'-difluorostilbene, respectively, the content of ergosterol in both the sensitive and resistant C. albicans showed depletion, whereas the squalene showed accumulation especially in the sensitive isolates determined with the method developed.