Pazilah Ibrahim

Antioxidant, anti-TB activities, phenolic and amide contents of standardised extracts of Piper sarmentosum Roxb

Ethanol and aqueous extracts of the different parts of Piper sarmentosum were analysed by HPLC for marker compounds to standardise these extracts. The standardised extracts were investigated for antioxidant activity (β-carotene linoleate model and DPPH model), anti-TB activity (microplate tetrazolium assay), and estimation of total phenolic and amide contents. The extracts of the different parts exhibited different antioxidant activity, phenolic and amide contents (p < 0.01). The ethanol extracts exhibited better antioxidant activity as compared to the aqueous extracts. The leaf ethanol extract was further investigated for dose response relationship and its EC50 was found to be 38 µg mL−1. All the extracts have exhibited anti-TB activity with MIC/MBC 12.5 µg mL−1. The leaf methanol extract was fractionated and the ethyl acetate fraction exhibited anti-TB activity with MIC/MBC 3.12 µg mL−1 while MIC/MBC of isoniazid (INH) was found to be 0.5 µg mL−1. A positive correlation was found between antioxidant activity and total polyphenols, flavonoids and amides, in the β-carotene linoleate model (p = 0.05) and in the DPPH model (p = 0.01). The analytical method was found to have linearity >0.9922, coefficient of variance <5% and accuracy 95.5 ± 5 to 96.9 ± 5. This plant possesses promising antioxidant as well as anti-TB properties.

Elucidating Isoniazid Resistance Using Molecular Modeling

The continuing rise in tuberculosis incidence and the problem of drug resistance strains have prompted the research on new drug candidates and the mechanism of drug resistance. Molecular docking and molecular dynamics simulation (MD) were performed to study the binding of isoniazid onto the active site of Mycobacterium tuberculosis enoyl-acyl carrier protein reductase (InhA) in an attempt to address the mycobacterial resistance against isoniazid. Results show that isonicotinic acyl-NADH (INADH) has an extremely high binding affinity toward the wild type InhA by forming stronger interactions compared to the parent drug (isoniazid) (INH). Due to the increase of hydrophobicity and reduction in the side chains volume of A94 of mutant type InhA, both INADH and the mutated protein become more mobile. Due to this reason, the molecular interactions of INADH with mutant type are weaker than that observed with the wild type. However, the reduced interaction caused by the fluctuation of INADH and the mutant protein only inflected minor resistance in the mutant strain as inferred from free energy calculation. MD results also showed there exists a water-mediated hydrogen bond between INADH and InhA. However, the bridged water molecule is only present in the INADH-wild type complex, reflecting the putative role of the water molecule in the binding of INADH to the wild type protein. The results support the assumption that the conversion of prodrug isoniazid into its active form INADH is mediated by KatG as a necessary step prior to target binding on InhA. Our findings also contribute to a better understanding of INH resistance in mutant type.

Standardization and in vivo antioxidant activity of ethanol extracts of fruit and leaf of Piper sarmentosum.

The present study aimed to investigate standardized ethanol extracts of fruit and leaves of Piper sarmentosum for their in vivo antioxidant activity in rats using a CCl (4)-induced oxidative stress model. The standardization was based on the quantification of the markers pellitorine, sarmentine and sarmentosine by high performance liquid chromatography (HPLC), and determination of total primary and secondary metabolites. The rats, divided into 7 groups each (n = 6), were used as follows: group 1 (CCl (4), negative control), group 2 (untreated, control), groups 3 and 4 (fruit extract 250 and 500 mg/kg, respectively), groups 5 and 6 (leaf extract 250 and 500 mg/kg, respectively) and group 7 (vitamin-E 100 mg/kg, positive control). The doses were administered orally for 14 days; 4 h following the last dose, a single dose of CCl (4) (1.5 mg/kg) was given orally to all the groups except group 2, and after 24 h, blood and liver of each animal were obtained. Analysis of plasma and liver homogenate exhibited significant preservation of markers of antioxidant activity, total plasma antioxidant activity (TPAA), total protein (TP), superoxide dismutase (SOD), catalase (CAT), and thiobarbituric acid reactive species (TBARS), in the pretreated groups as compared to the CCl (4) group (p < 0.05). Histology of the liver also evidenced the protection of hepatocytes against CCl (4) metabolites in the pretreated groups. The results of this study indicate the IN VIVO antioxidant activity of both extracts of the plant, which may be valuable to combat diseases involving free radicals.

(E)-N′-[(E)-3-(4-Hydr­oxy-3-methoxy­phen­yl)allyl­idene]isonicotinohydrazide

In the title compound, C16H15N3O3, the dihedral angle between the pyridine and benzene rings is 7.66 (5)°. The crystal packing is consolidated by intermolecular C—H⋯O and O—H⋯N interactions, which link the molecules into zigzag chains propagating along [010]. The chains are further linked into a three-dimensional network by N—H⋯O, C—H⋯N, C—H⋯O and C—H⋯π interactions.

(E)-N'-(2,4,5-Trifluorobenzyl-idene)isonicotinohydrazide monohydrate.

In the Schiff base molecule of the title compound, C13H8F3N3O·H2O, the benzene ring and the pyridine ring are nearly coplanar, making a dihedral angle of 6.64 (7)°. The molecule exists in an E configuration with respect to the C=N double bond. In the crystal structure, molecules are linked via the water molecules into two-dimensional planes parallel to the ab plane through intermolecular N—H⋯O, O—H⋯O O—H⋯N and C—H⋯O hydrogen bonds.

(E)-N′-(2,4,5-Trimethoxy­benzyl­idene)isonicotinohydrazide dihydrate

The asymmetric unit of the title compound, C16H17N3O4·2H2O, contains one Schiff base molecule and two water molecules. The Schiff base molecule exists in an E configuration with respect to the C=N double bond and is essentially planar, the dihedral angle between the benzene and pyridine rings being 5.48 (8)°. The three methoxy groups are also coplanar with the benzene ring [C—O—C—C torsion angles = 3.9 (2), 178.51 (15) and 0.8 (2) Å]. In the crystal structure, the water molecules link the molecules into a three-dimensional network via intermolecular N—H⋯O, O—H⋯O, O—H⋯N and C—H⋯O hydrogen bonds.

Analysis of differentially expressed proteins in late‐stationary growth phase of Mycobacterium tuberculosis H37Rv

Mycobacterium tuberculosis is a causative agent of tuberculosis (TB). The ability of M. tuberculosis to be quiescent in the cell has caused the emergence of latent infection. A comprehensive proteomic analysis of M. tuberculosis H37Rv over three growth phases, namely mid‐log (14‐day culture), early stationary (28‐day culture), and late stationary (50‐day culture), was performed in order to study the change in proteome from the mid‐log phase to late‐stationary phase. Combination methods of two‐dimensional electrophoresis (2‐DE) and tandem mass spectrometry were used to generate proteome maps of M. tuberculosis at different growth phases. Ten proteins were detected differentially expressed in the late‐stationary phase compared with the other two phases. These proteins were SucD, TrpD, and Rv2161c, which belong to metabolic pathway proteins; FadE5, AccD5, DesA1, and Rv1139c are proteins involved in cell wall or lipid biosynthesis, whereas TB21.7 and Rv3224 are conserved hypothetical proteins with unknown function. A surface antigen protein, DesA1, was not detectable in the late‐stationary phase, although present in both log and early‐stationary phases. The changes in the expression levels of these proteins were in line with the growth environment changes of the bacteria from mid‐log phase to late‐stationary phase. The information gathered may be valuable in the intervention against latent TB infection.

(E)-N′-(2-Benzyl­oxybenzyl­idene)isonicotinohydrazide methanol solvate monohydrate

The title compound, C20H17N3O2·CH4O·H2O, was synthesized by the condensation reaction of 2-benzyloxybenzaldehyde with isoniazid (isonicotinic acid hydrazide). The tricyclic compound displays a trans configuration with respect to the C=N double bond. The central benzene ring makes dihedral angles of 8.83 (7) and 70.39 (8)° with the pyridine ring and the terminal benzene ring, respectively. The dihedral angle between the pyridine ring and the terminal benzene ring is 73.11 (8)°. In the crystal structure, molecules are connected by intermolecular N—H⋯O, O—H⋯O, O—H⋯(N,N) and C—H⋯O hydrogen bonds, forming a two-dimensional network perpendicular to the a axis.

Effects of Isoniazid on Viability, Cell Morphologies and Acid Fastness Properties of Mycobacterium avium NCTC 8559 during the Growth Cycle

Our previous study demonstrated that the effects of isoniazid (INH) on Mycobacterium tuberculosis at the cellular level varied according to the growth phases. In this study, the variations in the INH action on M. avium strain NCTC 8559 are reported. M. avium cells grown on Middlebrook 7H10 agar were harvested at different stages of their growth cycle, exposed to the minimum inhibitory concentration of INH, stained with acid-fast staining for morphological changes and acid fastness properties, and the number of colonies were evaluated for viability studies. The study demonstrated that M. avium NCTC 8559 cells at the initial and fragmentation stages of the growth cycle were most susceptible to INH.

Bis{(E)-N'-[2,4-bis(trifluoro-meth-yl)benzyl-idene]isonicotinohydrazide} monohydrate.

The asymmetric unit of the title compound, 2C15H9F6N3O·H2O, contains two independent Schiff base molecules and one water molecule. Both Schiff base molecules exist in an E configuration with respect to the C=N double bonds and the dihedral angles between the benzene and the pyridine rings in the two molecules are 17.53 (12) and 20.62 (12)°. In the crystal structure, molecules are linked by intermolecular N—H⋯O and C—H⋯O hydrogen bonds into infinite one-dimensional chains along the a axis. In addition, intermolecular O—H⋯N, O—H⋯F, C—H⋯F and C—H⋯O hydrogen bonds further link these chains into a three-dimensional network. Weak π–π interactions with centroid–centroid distances in the range 3.6495 (17)–3.7092 (16) Å are also observed.