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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.

Antioxidant and anticholinesterase activities of twelve flavonoids i.e. santin ( 1 ), penduletin ( 2 ), viscosine ( 3 ), 6,7-dimethylkaempferol ( 4 ), kaempferol-​3-​methylether ( 5 ), 3,4′-dimethoxy-5,7-dihydroxyflavone ( 6 ), 5,7,4′-trihydroxy-3′-(3-hydroxymethylbutyl)-3,6-dimethoxyflavone ( 7 ), 5,7-dihydroxy-3′-(2-hydroxy-3-methyl-3-butenyl)-3,6,4′-trimethoxy-flavone ( 8 ), 5,7-dihydroxy-3′-(3-hydroxy-methylbutyl)-3,6,4′-trimethoxyflavone ( 9 ), 5,7-dihydroxy-3′-(4′′-acetoxy-3′′-methylbutyl)-3,6,4′-trimethoxy flavone ( 10 ), aromadendrin, (2S,3S) 3,4′,5,7-tetrahydroxyflavanone ( 11 ), and pinocembrin ( 12 ), together with monohydrated crystal ( 1A ) of 1 and anhydrous crystal ( 3A ) of 3 – isolated from Dodonaea viscosa – were studied. The results are given as 50% inhibition concentrations (IC 50 ). Their structure–activity relationships are discussed for both activities. Flavonoids 3 and 10 showed higher antioxidant activity in all tests. 3 Also showed moderate acetylcholinesterase (IC 50 : 182.97 ± 1.25 μM) and significant butyrylcholinesterase (IC 50 : 47.07 ± 0.54 μM) inhibitory activities. Compounds 2 (IC 50 : 55.78 ± 1.01 μM) and 3A (IC 50 : 58.72 ± 1.02 μM) were also moderate anticholinesterase agents against butyrylcholinesterase enzyme. Monohydrate crystal ( 1A ) showed better antioxidant and anticholinesterase activities than its amorphous form ( 1) . In contrast, the amorphous 3 exhibited better activity than the anhydrous crystal ( 3A ). In hydrous crystal, the water molecule might be responsible for better activity. These natural flavonoids can be used as pharmaceuticals and/or preservatives in respective industries.

Six Schiff bases 8–13 were synthesized by condensation of 2-aminophenol (1) with various chloro- and nitro-benzaldehydes (2–7), characterized, and evaluated for antioxidant, antibacterial, lipoxygenase, and urease inhibitory potentials. All Schiff bases except 11 showed potent antioxidant activity with IC50 values ranging between 17.2 and 33.1 μM when compared with standard BHA (IC50 = 44.2 μM); especially, compound 10 (IC50 = 17.2 μM) and compound 13 (IC50 = 18.6 μM) exhibited much better potential than the standard BHA. In lipoxygenase inhibition activity, all products except 8 showed excellent-to-good potential with IC50 values ranging from 22.5 to 110.5 μM while comparing with standard baicalein (IC50 = 22.6 μM). Compound 10 (IC50 = 22.5 μM) showed lipoxygenase potential comparable to the standard baicalein (IC50 = 22.6 μM), and molecular docking simulations showed that nitro group of 10 penetrated deeply into a pocket surrounded by basic amino acid residues which revealed the excellent activity of 10. All products also showed good potential against all gram-positive S. intermedius, B. subtilis, and S. aureus, and moderate activity against gram-negative E. coli and S. typhi bacteria. However, the products showed nonsignificant inhibitory potential 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.

New dimeric and a trimeric coumarin glucosides namely Daphneretusin A (1) Daphneretusin B (2) along with three known oligomers (3-5) were obtained as a result of bioassay guided fractionation of Daphne retusa Hemsl. Fractions (n-hexane, CHCl3, AcOEt, CH3OH and water) exhibited potent radical scavenging activity in relevant non-physiological bioassays. The structures of isolated compounds were elucidated by UV, IR, EIMS, FAB-MS, 1D, and 2D NMR spectroscopic analysis.

Two new coumarins, murrmeranzin (1) and murralonginal (2), together with four known compounds minumicrolin (3), murrangatin (4), meranzin hydrate (5) and hainanmurpanin (6) have been isolated from the aerial parts of Murraya paniculata. The structures of these compounds were determined through spectral analysis. Minumicrolin (3) showed mild butyrylcholinesterase inhibition activity.

Two new oxindole alkaloids isatinone A (1) and B (2) have been isolated from Isatis costata, along with the known trisindoline. Their structures have been assigned on the basis of spectroscopic techniques and chemical studies. Both new compounds showed significant antifungal 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

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.

Emodinol, a new oleane type triterpene, has been isolated from the chloroform soluble fraction of Paeonia emodi. The structure 1beta, 3beta, 23-trihydroxyolean-12-en-28-oic acid 1 has been assigned on the basis of spectral studies including 2D NMR. It showed significant beta-glucuronidase inhibitory activity. In addition benzoic acid and 3-hydroxybenzoic acid have also been reported for the first time from this species.

A new methylene-bridged bisflavonoid, methylenebissantin (1), and nine known compounds, including flavonoids (2–5), diterpenoids (6 and 7), and phenol derivatives (8–10) were isolated from the aerial parts of Dodonaea viscosa Jacq. The structure elucidation was based on spectroscopic data analyses. The isolated compounds were evaluated for the inhibition of Plasmodium falciparum enoyl-ACP reductase (PfENR). Methylenebissantin (1) exhibited a moderate inhibition (IC50 91.13 μM) against PfENR.

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.

Two new oleanane triterpenes; 2alpha,3alpha,24-trihydroxyolean-12-ene-28,30-dioic acid ([structure: see text]) and 2alpha,3alpha,24,28-tetrahydroxyolean-12-ene ([structure: see text]) have been isolated from the roots of Atropa acuminata. Anti-oxidant p-hydroxyphenethyl trans-ferulate ([structure: see text]), beta-sitosterol-3-O-beta-D-glucopyranoside ([structure: see text]) and oleanolic acid ([structure: see text]) have also been reported for the first time from this species. The structures were determined by spectroscopic studies including 2D-NMR.

Patuletin isolated from Tagetes patula was used as a capping and reducing agent to synthesize in one pot gold nanoparticles capped with patuletin. Conjugation of gold with patuletin was confirmed by FT-IR and UV–visible spectroscopy and amount of patuletin conjugated to gold nanoparticles was found to be 63.2% by weight. Particle sizes were measured by atomic force microscopy (AFM) and were found to have a mean diameter of about 45 nm. Patuletin-coated gold nanoparticles were found to be highly fluorescent. To examine their potential as chemical sensors, they were contacted with fourteen different drugs. Of these drugs, only one, piroxicam, was found to quench luminescence. Quenching obeyed Beer's law in a concentration range of 20–260 µM. Important for molecular recognition applications, fluorescence quenching by piroxicam was not affected by pH variation, elevated temperatures, addition of other drugs and addition of blood plasma to the colloidal suspensions.

The C-alkylated flavonoids 3,7,4′-trihydroxy-3′-(4-hydroxy-3-methylbutyl)-5,6-dimethoxyflavone (1), 3,7-dihydroxy-3′-(4-hydroxy-3-methylbutyl)-5,6,4′-trimethoxyflavone (2) and the trans-clerodane diterpenoids 6β-hydroxy-15,16-epoxy-5β,8β,9β,10α-cleroda-3,13(16),14-trien-18-oic acid (3) and 2β-hydroxy-15,16-epoxy-5β,8β,9β,10α-cleroda-3,13(16),14-trien-18-oic acid (4) were isolated from Duranta repens. Their structures and the relative configuration of 3 and 4 were determined by spectroscopic methods (1H- and 13C-NMR, IR, and MS) and 2D-NMR experiments. The known flavonoid 5 is also reported for the first time from this species. The compounds 1, 3, and 5 showed significant enzyme-inhibitory activity against thrombin.

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.

Viscosine was isolated from Dodonaea viscosa, which showed significant lipoxygenase inhibitory activity (IC50: value 39 ± 0.17). Molecular docking simulations were conducted to explore molecular binding mode, and to help elucidate molecular mechanism behind its significant inhibitory activity. Molecular interactions of viscosine with catalytic triad (His523, His518, Ile875) inside active site of lipoxygenase via hydrogen bonding, seems to be the major factor involved in its significant lipoxygenase inhibitory activity.

Microbial transformation of clerodane lactone ( 1 ) by a plant pathogen fungus, Rhizopus stolonifer , resulted in the production of metabolites 3 and 4 . While incubation of clerodane methyl ester ( 2 ) by R. stolonifer yielded metabolites 5 – 8 . The structures of the transformed products were determined by the spectroscopic techniques and compounds 4 , 7 and 8 were found. The antibacterial activity of clerodane diterpenoids 1 and 2 and their metabolites 3 – 8 were also studied. The metabolites 3 – 7 showed moderate activities against both Gram-positive and Gram-negative organisms. While metabolite 8 showed a moderate activity against Gram-positive organisms and a good activity against Gram-negative organisms.

A new C-alkylated flavonoid (5,7-dihydroxy-3′-(4″-acetoxy-3″-methylbutyl)-3,6,4′-trimethoxyflavone (1), along with two known C-alkylated flavonoids (5,7-dihydroxy-3′-(3-hydroxymethylbutyl)-3,6,4′-trimethoxyflavone (2), 5,7,4′-trihydroxy-3′-(3-hyroxymethylbutyl)-3,6-dimethoxyflavone (3) and two new source C-alkylated flavonoids (5,7-dihydroxy-3′-(2-hydroxy-3-methyl-3-butenyl)-3,6,4′-trimethoxyflavone (4), 5,7,4′-trihydroxy-3,6-dimethoxy-3′-isoprenyl-flavone (5) were isolated from the aerial parts of Dodonaea viscosa. The structures of all compounds were established on the basis of 1D and 2D NMR spectroscopy and mass spectrometry. The isolated compounds were evaluated for their inhibitory effect on urease and α-chymotrypsin enzyme. All the compounds (1–5) exhibited mild inhibition against urease but remained recessive in case of α-chymotrypsin.

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.

Two new lupane derivatives, 3beta,6alpha-dihydroxylup-20(29)-ene (1) and 6alpha-hydroxylup-20(29)-en-3beta-octadecanoate (2), have been isolated from the stems of Periploca aphylla, in addition to beta-sitosterol and lupeol. The structures of 1 and 2 were determined by spectral and chemical methods. Compound 1 showed strong inhibition of alpha-glucosidase type VI and a moderate antibacterial activity.

Rosenones A (1) and B (2), new anthraquinone derivatives, have been isolated from the ethyl acetate soluble fraction of Aitchisonia rosea along with 1,3,6-trihydroxy-2-methylanthraquinone (3) reported for the first time from this species.

A new steroid leucisterol (1) and a new peroxy acid urticic acid (2) along with methoxybenzyl benzoate (3), 4-hydroxy benzoic acid (4), beta-sitosterol (5), and ursolic acid (6), have been isolated from the chloroform soluble fraction of the whole plant of Leucas urticifolia. Their structures were elucidated on the basis of nuclear magnetic resonance (1D and 2D NMR) spectral data. Leucisterol showed potent inhibitory activity against butyrylcholinesterase enzyme.

Haloxylase, the triglyceride (1), unsaturated fatty acid (2), and saturated fatty acid methyl ester (3) have been isolated from the chloroform-soluble fraction of Haloxylon recurvum. Their structures have been elucidated through spectroscopic studies and chemical transformation. All these compounds showed significant inhibitory activity against the enzyme chymotrypsin in a concentration dependent fashion.

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.

A new triterpene named as alysinol 3alpha, 22beta-dihydroxyolean-12-ene [structure: see text] along with known compounds usnic acid, methyl 2,4-dihydroxy-3,6-dimethyl benzoate, 3-hydroxy benzoic acid, stigmasterol, poriferasterol and ursolic acid have been isolated from Alysicarpus monolifer. The structure of [structure: see text] has been established through spectroscopic techniques.

Sphingolipid 1 and its corresponding beta-D-glucopyranoside derivative 2 have been isolated from the ethylacetate fraction of Conyza canadensis along with beta-sitosterol 3, stigmasterol 4, beta-sitosterol 3-O-beta-D-glucoside 5 and harmine 6, reported for the first time from this species. The structures of 1 and 2 were elucidated through spectroscopy including two-dimensional NMR.

Buddlejosides A (1) and B (2), new iridoid galactosides, and buddlejone (3), a benzofuran type sesquiterpene, have been isolated from the EtOAc fraction of Buddleja crispa together with β-sitosterol (4) and ursolic acid (5). Their structures have been assigned on the basis of spectral analyses including I D and 2D NMR spectral techniques.

Durantins A-C (1-3), new coumarinolignoids together with three known compounds cleomiscosins A (4), 6,7,8-trimethoxycoumarin (5) and 5,4'-dihydroxy-3,6,7-trimethoxyflavone (6) have been isolated from a CHCl 3 soluble fraction of Duranta repens. Their structures were assigned on the basis of spectral studies. Compounds (1, 3 and 4) showed inhibitory activity against phosphodiesterase enzyme.