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The title salt, C(8)H(20)N(+)·C(22)H(27)O(3)S(-), is a proton-transfer compound derived from the recently reported parent carb-oxy-lic acid [Alhadi et al. (2010). Acta Cryst. E66, o1787] by the addition of a second equivalent of di-n-butyl-amine, yielding the di-n-butyl-ammonium carboxyl-ate salt. The structure of the carboxyl-ate anion resembles that of the parent carb-oxy-lic acid. The main difference lies in the position of the H atom in the 4-hy-droxy group. In the anion the O-H bond is perpendicular, rather than parallel, to the benzyl ring. This position appears to facilitate hydrogen bonding to an O atom of the carboxyl-ate group of a symmetry-related anion. In addition, there are three N-H⋯O hydrogen bonds. In contrast, the neutral species hydrogen bonds via a carboxylic acid dimer. The dihedral angle between the benzene rings in the anion is 79.19 (7)°.

In the title compound, C(22)H(28)O(3)S, the dihedral angle between the two aromatic rings is 80.56 (6)°. The hy-droxy group is shielded by the two sterically hindered tert-butyl groups and therefore is not involved in any hydrogen bonding. The C-O-H fragment is coplanar with the aromatic ring, the dihedral angle between them being 7(5)°. In the crystal structure, pairs of mol-ecules are hydrogen bonded across crystallographic centers of symmetry.

Antioxidants interact with free radicals, terminating the adverse chain reactions and converting them to harmless products. Antioxidants thus minimize the oxidative stress and play a crucial role in the treatment of free radicals-induced diseases. However, the effectiveness of natural and/or synthetic antioxidants is limited due to their poor absorption, difficulties to cross the cell membranes, and degradation during delivery, hence contributing to their limited bioavailability. To address these issues, antioxidants covalently linked with nanoparticles, entrapped in nanogel, hollow particles, or encapsulated into nanoparticles of diverse origin have been used to provide better stability, gradual and sustained release, biocompatibility, and targeted delivery of the antioxidants with superior antioxidant profiles. This review aims to critically evaluate the recent scientific evaluations of nanoparticles as the antioxidant delivery vehicles, as well as their contribution in efficient and enhanced antioxidant activities. [ABSTRACT FROM AUTHOR]

The title compound, 2C(16)H(13)N(3)O(4)·C(18)H(14)N(4)·2CH(4)O, was crystallized from the reaction between 3,4,5-trihydroxy-benzoyl-hydrazine and indole-2-carbaldehyde in a mixture of ethanol and methanol. The compound is a stoichiometric 2:1 cocrystal of the methanol-solvated reaction product, 3,4,5-trihydr-oxy-N'-(1H-indol-2-ylmethyl-idene)benzohydrazide and 1H-indole-2-carbaldehyde azine that arose unexpectedly during the synthesis. The former mol-ecules are linked by O-H⋯O hydrogen bonds and also by π-π stacking inter-actions between benzoyl-hydrazide rings into a two-dimensional network. The methanol solvent mol-ecules are hydrogen bonded to this network. The centrosymmetric azine mol-ecules are not engaged in hydrogen bonding.

The title compound, C(16)H(16)N(2)O(6)·C(2)H(5)OH, was synthesized from 3,4,5-trihydroxy-benzoyl-hydrazide and 2,4-dimethoxy-benzaldehyde in ethanol. The compound is not planar, with the two aromatic planes of the two aromatic rings twisted by 15.6 (1)°. The hydr-oxy groups are involved in both intra-molecular O-H⋯O and inter-molecular O-H⋯N and O-H⋯O hydrogen bonds and a C-H⋯O interaction also occurs.

The benzohydrazide mol-ecule of the title compound, C(14)H(10)BrClN(2)O(5)·CH(3)OH, is non-planar, the two aromatic rings at either side of the -C(=O)-NH-N=CH- unit being twisted by 5.9 (1)°. The benzohydrazide mol-ecule is linked to the solvent mol-ecule by an O-H⋯O hydrogen bond. Mol-ecules are connected by further O-H⋯O hydrogen bonds and an N-H⋯O link into a two-dimensional array.

The benzohydrazide mol-ecule of the title compound, C(14)H(11)N(3)O(7)·H(2)O, is planar (r.m.s. deviation = 0.068 Å). The benzohydrazide mol-ecule and the uncoordinated water mol-ecule inter-act through O-H⋯O hydrogen bonds; these together with O-H⋯N and N-H⋯O hydrogen bonds form a three-dimensional network.

The benzohydrazide mol-ecule in the title dihydrate, C(14)H(11)ClN(2)O(5)·2H(2)O, is non-planar, with the two aromatic rings at either side of the -C(=O)-NH-N=CH- unit forming a dihedral angle of 29.7 (2)°. The benzohydrazide mol-ecule is linked to the water mol-ecules by O-H⋯O and N-H⋯O hydrogen bonds, with other O-H⋯O hydrogen bonds leading to a layer structure.

The mol-ecule of the title compound, C(8)H(8)N(4)O(3)S, is planar. Adjacent mol-ecules are linked through O-H⋯S, N-H⋯S and N-H⋯O hydrogen bonds into a three-dimensional network.

The title compound, C(14)H(11)BrN(2)O(5)·2H(2)O, crystallizes as hydrogen-bonded sheets. The 2-hydr-oxy group on the benzyl-idene group forms an intra-molecular hydrogen bond to the N atom of the C=N double bond. The amino N atom is a hydrogen-bond donor to a water mol-ecule. The hydr-oxy group on the benzohydrazide group is a hydrogen-bond donor to one acceptor site, whereas each water mol-ecule is a hydrogen-bond donor to two acceptor sites.