A critical comparison of methyl and ethyl esters production from soybean and rice bran oil in the presence of microwaves

Transesterification of vegetable oils (from soybeans and rice bran) into methyl and ethyl esters using a batch microwave system was investigated in this study. A critical comparison between the two alcohols was performed in terms of yields, quality, and reaction kinetics. Parameters tested were temperature (60, 70 and 80 °C) and time (5, 10, 15 and 20 min). At all tested conditions, more than 96% conversion rates were obtained for both ethanol and methanol. Use of microwave technology to assist the transesterification process resulted in faster reaction times and reduced catalyst requirement (about ten-fold decrease). Methanol required lower alcohol:oil ratios than normally used in conventional heating, whereas ethanol required higher molar ratios. All esters produced using this method met ASTM biodiesel quality specifications. Methanol performed better in terms of performance and costs, while ethanol may have some environmental and safety benefits.     

Identification of hotspot regions of MurB oxidoreductase enzyme using homology modeling,molecular dynamics and molecular docking techniques

Despite the availability of effective chemotherapy and a moderately protective vaccine, new anti-tuberculosis agents are urgently needed to decrease the global incidence of tuberculosis (TB) disease. The MurB gene belongs to the bacterial cell wall biosynthesis pathway and is an essential drug target in Mycobacterium tuberculosis (Mtb) that has no mammalian counterparts. Here, we present an integrated approach involving homology modeling, molecular dynamics and molecular docking studies on Mtb-MurB oxidoreductase enzyme. A homology model of Mtb-MurB enzyme was built for the first time in order to carry out structure-based inhibitor design. The accuracy of the model was validated using different techniques. The molecular docking study on this enzyme was undertaken using different classes of well known MurB inhibitors. Estimation of binding free energy by docking analysis indicated the importance of Tyr155, Arg156, Ser237, Asn241 and His304 residues within the Mtb-MurB binding pocket. Our computational analysis is in good agreement with experimental results of site-directed mutagenesis. The present study should therefore play a guiding role in the experimental design of Mtb-MurB inhibitors for in vitro/in vivo analysis.     

Structurally conserved interaction of Lgl family with SNAREs is critical to their cellular function

The Lethal giant larvae (Lgl) tumor suppressor family is conserved from yeast to mammals and plays a critical yet controversial role in cell polarity. Studies on Drosophila Lgl suggest that its function in polarity is through regulation of the acto-myosin cytoskeleton. In contrast, studies on the yeast Lgl homologs, Sro7/Sro77, suggest a function in exocytosis through interaction with the t-SNARE Sec9. Using yeast/mammalian Lgl chimeras, we demonstrate that the overall architecture of Lgl proteins is highly conserved and that the C-terminal domain is the major site of SNARE interaction within both yeast and mammalian homologs. Importantly, we find that the ability of Lgl chimeras to function as the only source of Lgl in yeast correlates precisely with the ability to interact with the yeast t-SNARE. We report a novel interaction between Sro7 and the yeast myosin V, Myo2. However, we find that interactions with either Myo2 or Myo1 (myosin II) cannot account for the dramatic functional differences observed for these chimeras in yeast. These results provide the first demonstration that the interaction of an Lgl family member with a specific effector is critical to its function in vivo. These data support the model that the Lgl family functions in cell polarity, at least in part, by regulating SNARE-mediated membrane delivery events at the cell surface.     

Crystal structures of nitroalkane oxidase: insights into the reaction mechanism from a covalent complex of the flavoenzyme trapped during turnover

Nitroalkane oxidase (NAO) from Fusarium oxysporum catalyzes the oxidation of neutral nitroalkanes to the corresponding aldehydes or ketones with the production of H(2)O(2) and nitrite. The flavoenzyme is a new member of the acyl-CoA dehydrogenase (ACAD) family, but it does not react with acyl-CoA substrates. We present the 2.2 A resolution crystal structure of NAO trapped during the turnover of nitroethane as a covalent N5-FAD adduct (ES*). The homotetrameric structure of ES* was solved by MAD phasing with 52 Se-Met sites in an orthorhombic space group. The electron density for the N5-(2-nitrobutyl)-1,5-dihydro-FAD covalent intermediate is clearly resolved. The structure of ES was used to solve the crystal structure of oxidized NAO at 2.07 A resolution. The c axis for the trigonal space group of oxidized NAO is 485 A, and there are six subunits (1(1)/(2) holoenzymes) in the asymmetric unit. Four of the active sites contain spermine (EI), a weak competitive inhibitor, and two do not contain spermine (E(ox)). The active-site structures of E(ox), EI, and ES* reveal a hydrophobic channel that extends from the exterior of the protein and terminates at Asp402 and the N5 position on the re face of the FAD. Thus, Asp402 is in the correct position to serve as the active-site base, where it is proposed to abstract the alpha proton from neutral nitroalkane substrates. The structures for NAO and various members of the ACAD family overlay with root-mean-square deviations between 1.7 and 3.1 A. The homologous region typically spans more than 325 residues and includes Glu376, which is the active-site base in the prototypical member of the ACAD family. However, NAO and the ACADs exhibit differences in hydrogen-bonding patterns between the respective active-site base, substrate molecules, and FAD. These likely differentiate NAO from the homologues and, consequently, are proposed to result in the unique reaction mechanism of NAO.     

Trophoblasts regulate the placental hematopoietic niche through PDGF-B signaling

The placenta is a hematopoietic organ that supports hematopoietic stem/progenitor cell (HSPC) generation and expansion without promoting differentiation. We identified PDGF-B signaling in trophoblasts as a key component of the unique placental hematopoietic microenvironment that protects HSPCs from premature differentiation. Loss of PDGF-B or its receptor, PDGFRβ, induced definitive erythropoiesis in placental labyrinth vasculature. This was evidenced by accumulation of CFU-Es and actively proliferating definitive erythroblasts that clustered around central macrophages, highly reminiscent of erythropoiesis in the fetal liver. Ectopic erythropoiesis was not due to a requirement of PDGF-B signaling in hematopoietic cells but rather in placental trophoblasts, which upregulated Epo in the absence of PDGF-B signaling. Furthermore, overexpression of hEPO specifically in the trophoblasts in vivo was sufficient to convert the placenta into an erythropoietic organ. These data provide genetic evidence of a signaling pathway that is required to restrict erythroid differentiation to specific anatomical niches during development.     

Antibacterial and phytochemical studies on Calotropis gigantia (L.) R. Br. latex against selected cariogenic bacteria

In vitro antibacterial potential of the chloroform, ethyl acetate, hexane, methanol and aqueous extracts of Calotropis gigantia (L.) R. Br. was evaluated by using five cariogenic bacteria, Actinomyces viscosus, Lactobacillus acidophilus, Lactobacillus casei, Streptococcus mitis and Streptococcus mutans. Agar well diffusion method and minimum inhibitory concentration (MIC) were used for this purpose. The chloroform extracted fraction of latex showed inhibitory effect against S. mutans and L. acidophilus with MIC value of 0.032 and 0.52 mg/mL, respectively. Qualitative investigation on structure elucidation of bioactive compound using IR, NMR and GC–MS techniques revealed the presence of methyl nonanoate, a saturated fatty acid.     

Microbial secondary metabolites ameliorate growth, <Emphasis Type="Italic">in planta</Emphasis> contents and lignification in <Emphasis Type="Italic">Withania somnifera</Emphasis> (L.) Dunal

In the present investigation, metabolites of Streptomyces sp. MTN14 and Trichoderma harzianum ThU significantly enhanced biomass yield (3.58 and 3.48 fold respectively) in comparison to the control plants. The secondary metabolites treatments also showed significant augmentation (0.75–2.25 fold) in withanolide A, a plant secondary metabolite. Lignin deposition, total phenolic and flavonoid content in W. somnifera were maximally induced in treatment having T. harzianum metabolites. Also, Trichoderma and Streptomyces metabolites were found much better in invoking in planta contents and antioxidants compared with their live culture treatments. Therefore, identification of new molecular effectors from metabolites of efficient microbes may be used as biopesticide and biofertilizer for commercial production of W. somnifera globally.     

Cumulative role of bioinoculants on growth,antioxidant potential and artemisinin content in <Emphasis Type="Italic">Artemisia annua</Emphasis> L. under organic field conditions

Artemisia annua L. is mostly known for a bioactive metabolite, artemisinin, an effective sesquiterpene lactone used against malaria without any reputed cases of resistance. In this experiment, bioinoculants viz., Streptomyces sp. MTN14, Bacillus megaterium MTN2RP and Trichoderma harzianum Thu were applied as growth promoting substances to exploit full genetic potential of crops in terms of growth, yield, nutrient uptake and particularly artemisinin content. Further, multi-use of the bioinoculants singly and in combinations for the enhancement of antioxidant potential and therapeutic value was also undertaken which to our knowledge has never been investigated in context with microbial application. The results demonstrated that a significant (P < 0.05) increase in growth, nutrient uptake, total phenolic, flavonoid, free radical scavenging activity, ferric reducing antioxidant power, reducing power and total antioxidant capacity were observed in the A. annua treated with a combination of bioinoculants in comparison to control. Most importantly, an increase in artemisinin content and yield by 34 and 72 % respectively in the treatment having all the three microbes was observed. These results were further authenticated by the PCA analysis which showed positive correlation between plant macronutrients and antioxidant content with plant growth and artemisinin yield of A. annua. The present study thus highlights a possible new application of compatible bioinoculants for enhancing the growth along with antioxidant and therapeutic value of A. annua.     

Coagulanolide, a withanolide from Withania coagulans fruits and antihyperglycemic activity

One new withanolide, (17S,20S,22R)-14alpha,15alpha,17beta,20beta-tetrahydroxy-1-oxowitha-2,5,24-trienolide) named coagulanolide (4) along with four known withanolides 1-3 and 5 have been isolated from Withania coagulans fruits and their structures were elucidated by spectroscopic techniques. The compounds 1-5 showed significant inhibition on postprandial rise in hyperglycemia post-sucrose load in normoglycemic rats as well as streptozotocin-induced diabetic rats. The compound 5 also showed significant fall on fasting blood glucose profile and improved the glucose tolerance of db/db mice. Further compound 5 showed antidyslipidemic activity in db/db mice. The median effective dose of the compound 5 was determined to be around 25 mg/kg in streptozotocin-induced diabetic rats, which is comparable to the standard antidiabetic drug metformin. Our results provide further support to explain the traditional use of W. coagulans as antihyperglycemic cum antidyslipidemic agent by the traditional medical practitioners.