Molecular modeling studies and anti-TB activity of trisubstituted indolizine analogues; molecular docking and dynamic inputs

A series of trisubstituted indolizine analogues has been designed as a result of a fragment-based approach to target the inhibition of mycobacterial enoyl-acyl carrier protein reductase. Anti-tuberculosis (TB) screening of the characterized compounds by a resazurin microplate assay method revealed that ethyl group at second position of indolizine nucleus exhibited activity against susceptible and multidrug-resistant strains of Mycobacterium tuberculosis at concentration of 5.5 and 11.3 μg/mL, respectively. A molecular docking study was also conducted to evaluate the stability of the active compounds, and compound with ethyl substitution at second position of indolizine nucleus showed the highest free binding energy of ΔG ?24.11 (kcal/mol), a low clash score of 3.04, and high lipo score of ?13.33. Indolizine analog with ethyl substitution at second position demonstrated Molecular Mechanics/Generalized Born Surface Area (?23.85 kcal/mol). Two molecular dynamics studies were computed (100 ps and 50 ns) to calculate the relationship between the potential and kinetic energies of the active anti-TB compound with time and temperature. The discovery of this lead may have a positive impact on anti-TB drug discovery.     

Growth stimulation and inhibition by salt in relation to Na<Superscript>+</Superscript> manipulating genes in xero-halophyte <Emphasis Type="Italic">Atriplex halimus</Emphasis> L.

In the present study, Na⁺ manipulating genes could contribute not only to ion homeostasis but also to growth stimulation with exposing the halophyte Atriplex halimus L. to moderate NaCl concentration. The stimulation of growth was attributed to Na⁺ accumulation inside the vacuole leading to increase leaf cell size as well as accelerate leaf cell division. Increasing the assimilatory surface could result in enhancing the photosynthetic rate. The reduction of A. halimus growth compared to optimum growth at 50 and 200 mM NaCl could be attributed to osmotic effect rather than the ionic one of salt stress. The inhibition of photosynthesis seemed to be resulted from limitation of CO₂ due to the osmotic effect on stomatal conductance rather than the activity loss of photosynthetic machinery. The depletion of starch content along with the increase in sucrose content could imply that photosynthesis may be a limiting for A. halimus growth. The fast coordinate induction of Na⁺ manipulating genes could reveal that the tolerance of A. halimus to high concentrations evolved from its ability to regulate and control Na⁺ influx and efflux. V-H ⁺-PPase may play a vital role in A. halimus tolerance to osmotic and/or ionic stress due to its kinetics of induction. It seemed that H⁺-ATPase plays a pivotal role in A. halimus tolerance to stress due to the increase in its protein level was detected with all NaCl concentrations as well as with PEG treatments. Both of these genes might be useful in improving stress tolerance in transgenic crops.     

Benzothiazole analogs as potential anti-TB agents: computational input and molecular dynamics

Biotin is very important for the survival of Mycobacterium tuberculosis. 7,8-Diamino pelargonic acid aminotransaminase (DAPA) is a transaminase enzyme involved in the biosynthesis of biotin. The benzothiazole title compounds were investigated for their in vitro anti-tubercular activity against two tubercular strains: H37Rv (ATCC 25,177) and MDR-MTB (multidrug-resistant M. tuberculosis, resistant to isoniazid, rifampicin, and ethambutol) by an agar incorporation method. The possible binding mode and predicted affinity were computed using a molecular docking study. Among the synthesized compounds in the series, the title compound {2-(benzo[d]thiazol-2-yl-methoxy)-5-fluorophenyl}-(4-chlorophenyl)-methanone was found to exhibit significant activity with minimum inhibitory concentrations of 1 μg/mL and 2 μg/mL against H37Rv and MDR-MTB, respectively; this compound showed the highest binding affinity (–24.75 kcal/mol) as well.     

An <i>in Vitro</i> Approach to Investigate the Role of Abscisic Acid in Alleviating the Negative Effects of Chilling Stress on Banana Shoots

Banana is a tropical crop cultivated in warm places. Chilling stress in Egypt is making banana crops less productive. Abscisic acid (ABA), a key plant hormone, regulates metabolic and physiological processes and protects plants from a variety of stresses. In vitro growing banana shoots were pre-treated with ABA at four concentrations (0, 25, 50, and 100 mM) and chilled at 5°C for 24 h, followed by a six-day recovery period at 25°C. By comparing ABA treatments to both positive and negative controls, physiological and biochemical changes were investigated. Chilling stress (5°C) caused a considerable increase in lipid peroxidation and ion leakage and reduced photosynthetic pigments in cold-treated plantlets. Increasing the concentration of ABA to 100 µM enhanced the response to chilling stress. ABA had a major effect on mitigating chilling injury in banana shoots by keeping cell membranes stable and lowering the amount of ion leakage and lipid peroxidation. Also, ABA significantly maintained the photosynthetic pigment concentration of banana shoots; accumulated higher amounts of total soluble carbohydrates and proline; and increased DPPH radical scavenging activity. Furthermore, ABA treatment enhanced cold tolerance in chilling-stressed banana shoots through the regulation of antioxidant enzyme activity. Overall, the results show that ABA is a good choice for protecting banana shoots from the damage caused by chilling stress.     

Antimycobacterial,docking and molecular dynamic studies of pentacyclic triterpenes from Buddleja saligna leaves

Buddleja saligna (family Buddlejaceae) is a medicinal plant endemic to South Africa. Two isomeric pentacyclic triterpenes, oleanolic acid and ursolic acid, were isolated from the leaves of B. saligna using silica gel column chromatography. Compounds oleanolic acid and ursolic acid were subjected to derivatization with acetic anhydride in the presence of pyridine to obtain oleanolic acid-3-acetate and ursolic acid-3-acetate, respectively. The structures of these compounds were fully characterized by detailed nuclear magnetic resonance (NMR) investigations, which included ¹H and ¹³C NMR. Molecular docking studies predicted the free binding energy of the four triterpenes inside the steroid binding pocket of Mycobacterium tuberculosis fadA5 thiolase compared to a reported inhibitor. Thus, their ability to inhibit the growth of M. tuberculosis was predicted and was confirmed to possess significant antimycobacterial activity when tested against Mycobacterium smegmatis, M. tuberculosis H₃₇Rv (ATCC 25177), clinical isolates of multi-drug-resistant M. tuberculosis (MDR-TB) and extensively drug-resistant M. tuberculosis (XDR-TB) using the Micro Alamar Blue Assay. Ursolic acid was isolated from this plant for the first time.     

Ecology of the rampant weed Nymphaea lotus L. Willdenow in natural and ricefield habitats of the Nile delta, Egypt

In a field study conducted around Lake Manzala (Egypt) during 1995–1996, the distribution of the floating-leafed lotus (Nymphaea lotus L.) in irrigation canals and ricefields was analyzed by classification and ordination methods. Environmental factors associated with its abundance and distribution were evaluated. A data set of 30 stands of lotus and nine environmental variables was analyzed by Canonical Correspondence Analysis (CCA) ordination relating environmental factors to the occurrence of the weed. Ordination analysis detected a strong association between soil organic matter and fine sediment (silt + clay) in the distribution of lotus. Water variables were less important. The density of lotus averaged 3.3±0.49 plants m−2 in the irrigation canals and 6.6±1.4 plants m−2 in the ricefields. The phytomass of lotus ranged from 877 g m−2 in the pure stands to 226 g m−2 in ricefield habitats. The highest proportion of lotus phytomass was allocated to leaf blade, with values reaching 40% of total phytomass in the infested ricefields. Allocation proportions to other plant organs varied between natural and ricefield habitats. Lotus plants allocated more dry matter to vegetative reproduction than to sexual reproduction. The ratio of vegetative to sexual reproduction ranged from 3.48 in the pure stands to 9.63 in infested ricefields. Populations of lotus showed wider variation in leaf area classes in pure stands than in rice stands. Presence of lotus as a weed in ricefields significantly reduced the growth and grain yield of the crop, indicating the risk of its spreading as an invasive weed. This revised version was published online in July 2006 with corrections to the Cover Date.     

Psidium guajava Linn leaf ethanolic extract: In vivo giardicidal potential with ultrastructural damage,anti-inflammatory and antioxidant effects

Introduction and aimConsidering the magnitude of giardiasis problem, the side-effects of the used anti-giardia drugs and the resistance posed against them, the current study aimed to evaluate the in-vivo giardicidal effect of Psidium guajava leaf extract (PGLE).MethodsFor fulfilling this aim, five Swiss-albino mice groups were included; GI: non-infected, GII: Giardia-infected and non-treated, GIII: Giardia-infected and metronidazole-treated, GIV: Giardia-infected and PGLE-treated, and GV: Giardia-infected and treated with both metronidazole and PGLE. Treatment efficacy was assessed via; Giardia cyst viability and trophozoite count, trophozoite electron microscopic ultrastructure, duodenal histopathological scoring, immunohistochemistry for TNF-α and duodenal scanning electron microscopy. Moreover, mice serum liver enzymes, total bilirubin, albumin, lipid profile including; total cholesterol, HDL, LDL and triglycerides were assessed. Additionally, hepatic oxidative stress markers including; malondialdehyde (MDA), nitric oxide (NO), reduced glutathione (GSH) and superoxide dismutase (SOD) were measured.ResultsResults showed that PGLE whether alone or combined with metronidazole has induced significant trophozoite count reduction and major architectural changes. Duodenal histological improvement, and local protective anti-inflammatory effect were confirmed. PGLE has also helped in healing of Giardia-induced gut atrophy. Thus, offered a comprehensive therapy for both the pathogen and the resultant pathological sequalae. Serum markers showed favorable hepatoprotective effect. Total cholesterol, LDL and triglycerides levels were less in PGLE-treated group than in metronidazole-treated group. Hepatic oxidative stress markers revealed the promising extract antioxidant effect. This study highlights, the promising in-vivo giardicidal PGLE activity, that was comparable to metronidazole, thus, the extract would be an ideal strongly recommended treatment for giardiasis. When combined with metronidazole, the extract potentiated its therapeutic effect. Besides, having hepatoprotective, anti-inflammatory, and antioxidant properties, the extract can combat the major side effects of metronidazole therapy.     

Stress degradation studies on betahistine and development of a validated stability-indicating assay method

The purpose of this work was to study the stability of betahistine (BET) at different stress conditions and to develop a sensitive stability-indicating high-performance liquid chromatographic (HPLC) assay method. The stress conditions applied were including the effect of heat, moisture, acid-base, and ultra-violet (UV) light. Betahistine and its decomposition products were derivatized by reaction with dansyl chloride (Dan-Cl) and analyzed by HPLC equipped with fluorescence detector (FL) set at 336 and 531 nm as excitation and emission wavelengths, respectively. The drug was particularly labile at UV light and oxygen rich media. Two potential degradation products could be separated and identified by spectral methods. The chromatographic method involved Zorbax Eclipse XDB-C(18) column kept at 30+/-2 degrees C and a gradient elution with mobile phase composed of acetonitrile and 0.02 mol L(-1) sodium acetate. The response factor of dansylated BET monitored by fluorescence detection was 32 times more than its UV response. The calibration curve of BET in bulk form was linear from 0.005 to 4.2 ng microL(-1). Intraday and interday precision were less than 0.04% (CV), and accuracy was between 99.2% and 100.9% over 2.0 ng microL(-1). The limit of detection was 0.002 ng microL(-1). The method was also validated for sample stability during reaction, robustness and selectivity. The method was applied for purity testing of betahistine in tablet form.