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Gentamicin is a broad spectrum antibiotic employed for the cure of infections caused by both Gram-positive and Gram-negative bacteria. It is eliminated through urine in the unmetabolized and microbiologically active form, leading to the emergence of gentamicin-resistant bacteriocoenosis. Green synthesis of methyl gallate conjugated silver nanoparticles (MG–AgNPs) is reported in this study. The synthesized MG–AgNPs were found to be stable at high temperature, in the pH range 4 to 8, and with up to 100 mM NaCl concentration in the solution. Further, the synthesized MG–AgNPs were employed as a selective and sensitive probe for the detection of gentamicin. The proposed colorimetric aggregation sensor significantly detected gentamicin over a wide range of concentrations in the presence of other interfering drugs and metal ions. UV-visible spectroscopy, FTIR, and atomic force microscopy were employed to confirm the sensing phenomenon. The binding ratio of MG–AgNPs with gentamicin was found to be equimolar. The limit of detection and quantification were found to be 0.29 μM and 1 μM, respectively, in the concentration range of 1–100 μM. The proposed sensor significantly detects gentamicin in environmental waters, human blood plasma, serum, and urine.

Three biologically active new Schiff bases, 2-[(3-hydroxybenzylidene)amino]phenol 5 , 2-[(4-hydroxybenzylidene)amino]phenol 6 and 4-[(2-hydroxyphenylimino)methyl]benzene-1,3-diol 7 , were synthesized by the reaction of 2-aminophenol 1 with three different hydroxyl-benzaldehydes 2 – 4 . They were characterized by spectroscopic analysis (IR, 1 H NMR, EI-MS) along with elemental analyses. The products were biological screened out for antioxidant, lipoxygenase inhibition, antibacterial and urease inhibition activities. The compounds 5 and 6 showed potent while 7 showed moderate antioxidant activity. Compound 6 showed potent whereas 5 and 7 showed significant lipoxygenase inhibition activity. All the target compounds showed excellent activities against Staphylococcus intermedius , Bacillus subtilis , Staphylococcus aureus, Escherichia coli and Salmonella typhi bacteria. All the compounds showed non-significant activity against urease enzyme.

A ligand L has been synthesized by the condensation of 4-chlorobenzaldehyde and 2-amino-5-chlorobenzophenone. The complexes 1–5 of Pb+2, Ni+2, Co+2, Cu+2 and Cd+2 with ligand were prepared. The newly synthesized ligand L and its complexes 1–5 were characterized on the basis of elemental analyses, molar conductance, 1H NMR, IR and MS spectral data. The ligand was also characterized by X-ray crystallography. By electronic spectra and magnetic moment data, the square planar geometry for complex 1 and the octahedral geometry for complexes 2–5 were proposed. The conductivity data suggests non-electrolytic nature of the complexes 1–5. The complexes have higher antibacterial activity than the parent ligand L.

Schiff bases, 2-{[(2-hydroxyphenyl)methylidene]amino}phenol (4) and 2-{[3-4-(dimethylamino)phenyl-2-propenylidene]amino}phenol (5), have been synthesized by the condensation of 2-aminophenol (1) with 2-hydroxybenzaldehyde (2) and 4-dimethylaminocinnamaldehyde (3), respectively. They showed good lipoxygenase inhibition and antioxidant activities, as compound 4 showed potent antioxidant activity. The products also showed good activities against Gram-positive: S. intermedius, B. subtilis and S. aureus, and Gram-negative: E. coli and S. typhi bacteria, as compounds 5 and 4 are excellent active against B. subtilis and S. typhi, respectively. These good to potent activities may be due to the presence of free hydroxyl and amino groups. They showed non-significant urease inhibition activity.

Steroidal galactoside 1 and aryl esters 2 and 3 have been isolated from Buddleja crispa, along with ginipin 4, gardiol 5, 1-heptacosanol 6, and methyl benzoate 7, isolated for the first time from this species. The structures of all of the compounds were determined by spectroscopic techniques and chemical studies. The steroidal galactoside 1 is an inhibitor of lipoxygenase. Compounds 1- 3 displayed inhibitory activity against butyrylcholinesterse, while compounds 2 and 3 further showed inhibition against acetylcholinesterase

Two new lignans trivially named negundins A (1) and B (2), were isolated along with (+)-diasyringaresinol (3), (+)-lyoniresinol (4), vitrofolal E (5) and vitrofolal F (6), reported for the first time from this species. The structures of the new compounds were established through spectral studies. Compound 2 showed potent inhibitory activity against lipoxygenase enzyme, while 5 showed moderate activity against butyryl-cholinesterase.

Three C-alkylated flavonoids 7-O-alpha-D-glucopyranosyl-3,5-dihydroxy-3'-(4"-acetoxyl-3"-methylbutyl)-6,4'-dimethoxyflavone (1), 7-O-alpha-D-glucopyranosyl-3,4'-dihydroxy-3'-(4"-acetoxyl-3"-methylbutyl)-5,6-dimethoxyflavone (2), 3,7,4'-trihydroxy-3'-(8"-acetoxy-7"-methyloctyl)-5,6-dimethoxyflavone (3) and a trans-clerodane type diterpenoid (-)-6beta-hydroxy-5beta,8beta,9beta,10alpha-cleroda-3,13-dien-16,15-olid-18-oic acid (4) are reported from Duranta repens along with (+)-hardwickiic acid (5) and (+)-3,13-clerodadien-16,15-olid-18-oic acid (6), isolated for the first time from this species. Their structures were established on the basis of the spectral methods, especially two dimensional (2D) NMR spectroscopy.

Isoprenylated flavonoids 5,7-dihydroxy-3'-(2-hydroxy-3-methyl-3-butenyl)-3,6,4'-trimethoxyflavone (1), 3,7-dihydroxy-3'-(2-hydroxy-3-methyl-3-butenyl)-5,6,4'-trimethoxyflavone (2) and an isoprenylated acetophenone derivative (3) have been isolated from Duranta repens along with known compounds, 5-hydroxy-3,6,7,4'-tetramethoxyflavone (4), rosenonolactone (5), 6,7-dimethoxycoumarin (6), 5alpha,8alpha-epidioxyergosta-6,22-dien-3beta-ol (7) and 5alpha,8alpha-epidioxyergosta-6,9(11),22-trien-3beta-ol (8), isolated for the first time from this species. Their structures and the relative configuration were determined by spectroscopic methods (1H- and 13C-NMR, IR, UV and MS) and two-dimensional (2D)-NMR experiments. The compounds 1-5 showed inhibitory activity against prolyl endopeptidase while 4 and 5 were also active against thrombin.

About 24 species of the genus Galium are reported from Pakistan, distributed from plains to mountains. In Flora of Pakistan, Nazimuddin et al. recognized two subspecies of Galium tricornutum, i.e., subsp. tricornutum and subsp. longipedanculatum [1]. Most species of the genus have medicinal properties, and reports showed that cleavers (Galium) have anti-elastase and anti-collagenase activities [2]. In traditional Chinese medicine, Galium verum L. is often used in the treatment of hepatitis and phlebophlogosis [3]. Literature reveals that the medicinal plants of the genus Galium are widely used in the folk medicine of various countries [4] for the treatment of jaundice [5], as an antitumor, antimicrobial, and antiinflammatory [6], and for the treatment of gout and epilepsy [7]. Medicinal plant species of the genus Galium have been used as a source of dye, therapeutics, and food for years. Literature reviews show reports on the essential oil content of members of this genus [8–10]. A thorough review of the literature shows that our report is the first report on the essential oil composition of the Galium tricornutum subspecies longipedanculatum. A voucher specimen (SHPC-024) has been deposited in the Herbarium, Department of Botany, Shaheed Benazir Bhutto University, Sheringal and at the Herbarium of the University of Karachi (No. 7399). GC and GC/MS analysis showed that the oil is composed of eucalyptol (20.8%), L-camphor (13.9%), L-borneol (11.6%), myrtenol (5%), 2-methyl-2-adamantanol (3.0%), and -cubene (2.6%), as shown in Table 1.

Paeonins A and B, new monoterpene galactosides have been isolated from the chloroform-soluble fraction of the roots of Paeonia emodi and showed potent lipoxygenase inhibitory activity. The structures of 1 and 2 have been assigned on the basis of spectral analysis including one- and two-dimensional NMR techniques.

Hispidone, a new flavanone, has been isolated from Onosma hispida and assigned the structure (2S)-5,2'-dihydroxy-7,4',5'-trimethoxyflavanone (1) by spectroscopic methods. In addition, (2S)-5,2'-dihydroxy-7,5'-dimethoxyflavanone (2), benzoic acid (3), and 4-hydroxy benzoic acid (4) are also reported for the first time from this species.

In the title compound, C(19)H(18)N(4)O(3), the pyrazole ring is oriented at dihedral angles of 41.12 (7) and 12.25 (10)°, respectively, with respect to the planes of the phenyl and benzene rings. Intra-molecular N-H⋯O and O-H⋯O hydrogen bonds generate seven- and six-membered S(7) and S(6) ring motifs, respectively.

The molecule of the title Schiff base compound, C20H13ClN2O3, assumes an E configuration about the C=N bond. The aromatic rings of the nitrobenzene and chlorobenzene groups are twisted by 13.89 (13)° and form dihedral angles of 76.38 (13) and 84.64 (13)°, respectively, with the phenyl ring. In the crystal, molecules are linked into chains parallel to the b axis by C—H...π interactions.

The title Schiff base compound, C20H14ClNO2, adopts an E configuration about the azomethine bond. The phenol and chlorobenzene rings form dihedral angles of 84.71 (9) and 80.70 (8)°, respectively, with the phenyl ring and are twisted by 15.32 (8)° with respect to one another. The molecular conformation is stabilized by an intramolecular O—H...N hydrogen bond, which forms an S(6) ring motif. In the crystal, molecules are linked by C—H...O hydrogen bonds, forming columns parallel to the a axis.

There are one-and-a-half independent molecules in the asymmetric unit of the title compound, C18H20N2O4. One molecule is centrosymmetric with the mid-point of the N—N bond located on a center of inversion. In the other, which lies on a general position, the benzene rings are aligned at 21.6 (1)°. Weak intermolecular C—H...O hydrogen bonding is present in the crystal strcture.

In the title compound, C15H12N2O2, the seven-membered ring bearing the three methylene C atoms displays a puckered conformation, with the methylene C atoms deviating from the plane of the benzene ring by 0.05 (1), 0.98 (1) and 1.04 (1) Å. The phenanthroline unit is not planar; the dihedral angles between this benzene ring and the other pyridyl rings are 9.62 (4) and 9.31 (4)°. The crystal packing is stabilized by π–π interactions between two phenanthroline ring systems, forming a centrosymmetric dimer with a centroid–centroid distance of 3.656 (1) Å.

Crispins A (1) and B (2), two new glycosphingolipids, were isolated from the whole plant Buddleja crispa, along with three known compounds: alpha-amyrin, linoleic acid, and stigmasterol. Their structures were elucidated by chemical and spectroscopic techniques. Both 1 and 2 showed significant inhibitory activity against alpha-chymotrypsin in a concentration-dependent manner.

The title compound, C18H16O7·H2O, is a flavonoid isolated from Dodonaea viscosa. The benzopyran ring system of the flavonoid is essentially planar [maximum deviation = 0.025 (2) Å] and inclined at 5.83 (2)° to the attached benzene ring. The water of hydration is involved in extensive hydrogen bonding, assembling the molecules into a supramolecular network via classical intermolecular O—H...O hydrogen bonding. The crystal structure is further stabilized by π–π stacking interactions [centroid–centroid distance between benzene rings = 3.564 (3) Å].

In the title compound, C14H13NO2, the azomethine double bond adopts an E conformation and the benzene rings form a dihedral angle of 77.70 (7)°. In the crystal, molecules are linked by O—H...N and C—H...O hydrogen bonds and arranged in a zigzag fashion, forming infinite chains parallel to the c axis, resulting in a graph-set R22(9) motif.

In the title compound, [Cu(C(12)H(18)N(2)O(2))]·0.25H(2)O, the coordination of the O,N,N',O'-tetra-dentate ligand results in a cis-CuN(2)O(2) square-planar geometry for the metal ion and the presence of two six-membered and one five-membered chelate rings. The complete complex mol-ecule is close to planar (r.m.s. deviation = 0.047 Å). The uncoordinated water mol-ecule (O-atom site symmetry 2) was modelled as half occupied. In the crystal, C-H⋯O(w) and O(w)-H⋯O (w = water) hydrogen bonds link the components into layers parallel to ab plane.

In the title compound, C20H13Cl2NO, the C=N bond adopts an E conformation. The chloro-substituted rings form a dihedral angle of 11.99 (9)° with each other and form dihedral angles of 74.95 (9) and 83.26 (10)° with the unsubstituted ring. In the crystal, molecules are connected into dimers by pairs of weak C—H...O hydrogen bonds and the dimers are arranged in columns parallel to the a axis.

In the title compound, C20H13BrClNO, the azomethine double bond [C=N = 1.246 (4) Å] adopts an E conformation. The bromo- and chlorophenyl rings are inclined to one another by 13.70 (11)°, and form dihedral angles of 76.68 (10) and 74.24 (7)°, respectively, with the phenyl ring. In the crystal, molecules are linked by C—H...O hydrogen bonds to form double stranded chains propagating along the b-axis direction.

The asymmetric unit of the title compound, C(47)H(58)N(6)O(6), comprises three independent mol-ecules, in one of which one tert-butyl group is disordered in a 1:1 ratio. The mol-ecule is a di(ar-yl)methane having two aliphatic and one N-heterocyclic substituent in each aryl ring. For the mol-ecule having the disordered tert-butyl group, the aryl rings make an angle of 115.3 (2)° at the methyl-ene carbon; one aryl ring is aligned at 42.0 (1)° with respect to the N-heterocyclic substituent and the other at 48.7 (1)° with respect to its substituent. The two ordered mol-ecules are disposed about a pseudo center of inversion. The pairs of twist angles in these two mol-ecules differ [52.7 (1) and 61.7 (1)°, and 29.1 (1) and 58.5 (1)°].

In the title compound, C(47)H(54)N(6)O(2), the C-C-C bond angle between the rings is 108.40 (13)°. One aryl ring aligned at 38.5 (1)° with respect to the N-heterocyclic substituent and the other at 56.0 (1)° with respect to its substituent. In the crystal, adjacent mol-ecules are linked by C-H⋯N hydrogen bonds, forming a chain extending along the a axis.

In the title molecule, C12H15NO5, the nitrophenoxy portion is approximately planar (r.m.s. deviation = 0.034 Å) and makes an angle of 84.8 (1)° with respect to the –CH2–C(=O)–O–C fragment. In the crystal, π–π stacking is observed between nearly parallel benzene rings of adjacent molecules, the centroid–centroid distance being 3.6806 (10) Å. Weak intermolecular C—H...O hydrogen bonding is present in the crystal structure.

The molecule of the title compound, C19H14Cl2O2, has two benzene rings connected to a methylene C atom, and the rings are aligned at 66.3 (1)°. Intermolecular C—H...π and π–π stacking interactions are observed in the crystal structure, the centroid–centroid distances between parallel benzene rings being 3.7529 (12) and 3.6201 (12) Å, respectively.

In the title compound, C(33)H(36)O(6), two naphthalene ring systems are connected through a methyl-ene linkage [C-C-C = 114.9 (2)°]; the ring systems are aligned at an angle of 76.5 (1)°. Of the two -O-CH(2)-C(=O)-C(CH(3))(3) substituents, one adopts an extended conformation whereas the other is U-shaped. In the crystal, mol-ecules are linked via weak C-H⋯O hydrogen bonding, forming supra-molecular chains running along the c axis.

In the title compound, C(20)H(22)O(6), the mean planes through the benzene rings make a dihedral angle of 59.82 (7)° with each other. Weak inter-molecular C-H⋯O inter-actions together with π-π stacking inter-actions [centroid-centroid distance = 3.830 (1) Å] between benzene rings are observed in the crystal packing.

In the title compound, C13H12N4O6, the mean plane through the nitrobenzene forms a dihedral angle of 37.38 (15)° with the plane through the imidazole ring. The crystal packing is stabilized by weak intermolecular C—H...O and C—H...N interactions together with π–π stacking interactions between nitrobenzene rings [centroid–centroid distance = 3.788 (3) Å] and between imidazole rings [centroid–centroid distance = 3.590 (2) Å].

The molecule of the title compound, C13H12BrN3O4, is non-planar, as indicated in the dihedral angle of 59.5 (4)° formed between the least-squares planes through the imidazole and benzene rings. In the crystal, molecules are connected via C—H...O contacts, forming a supramolecular chain.

The three independent mol-ecules of the title compound, C(15)H(14)O(4), have similar orientations of their aromatic rings, the dihedral angles between the rings being 57.0 (1), 58.1 (1) and 58.2 (1)°. In each mol-ecule, the hydr-oxy group forms an intra-molecular hydrogen bond to the carbonyl O atom, forming an S(10) ring motif.

The title molecule, C21H26Br2O2, is a substituted diphenylmethane derivative whose angle at the methylene carbon is 115.0 (2)°.