Mechanism behind the degradation of aqueous norbixin upon storage in light and dark environment.

Buffered aqueous solutions of norbixin were stored in light and dark, and analyzed using mass spectrometry. Compounds with both higher and lower masses than norbixin were detected, suggesting the formation of oxidation products and oxidative cleavage products of norbixin. The norbixin oxidation products included compounds containing several oxidations. The amounts of oxidation products of norbixin increased during storage in both light and dark, but in light, the development accelerated. Scavengers of superoxide radical anion (superoxide dismutase), hydrogen peroxide (catalase), hydroxyl radicals (mannitol) and singlet oxygen (sodium azide) and carbon-centered radicals (DMPO) were tested to determine if any of the reactive species were involved in the degradation of norbixin. Of these, only DMPO decreased the bleaching of norbixin indicating the involvement of carbon-centered radicals. Multiple oxidations of norbixin might be a result of a radical chain reaction involving peroxyl and carbon-centered radicals even though not detectable with electron spin resonance.

Incorporation of bixin in aqueous media: Self-formulation with sorbitol ester of norbixin.

We have previously reported how the natural food colorant, bixin, was enzymatically modified by appending sorbitol to the bixin scaffold. The resulted product, sorbitol ester of norbixin (SEN) was expected to be more hydrophilic. The present study aimed to investigate the physical behaviour of SEN in aqueous media. The property of SEN was studied together with non-reacted bixin as separation of the two compounds was unsuccessful. The SEN molecules behaved as a bolaamphiphile in aqueous media, underwent self-association and develop a hydrophilic aggregate. SEN-aggregates could uptake the non-reacted bixin molecules inside its hydrophobic moiety and dispersed it in aqueous media. Aggregation of SEN molecules with incorporated bixin resulted in a hypsochromic shift of the absorption spectra indicting H-aggregation. Dynamic light scattering showed the formation of aggregates with an average hydrodynamic radius 38 ±â€¯2 nm. The dispersibility of the aggregates was affected by pH and the ionic strength of the media.

Hydrophilization of bixin by lipase-catalyzed transesterification with sorbitol.

Bixin is one of the most used yellow-orange food colorants in the food industry. The polyene chain of bixin makes it highly hydrophobic and less suitable for water-based food formulations. Lipase-catalyzed reactions of bixin with sorbitol were studied to synthesize a new derivative of bixin with potential hydrophilic properties. Interestingly, we show that the lipase-catalyzed reaction of bixin leads to a transesterification reaction and formation of a transesterified product, sorbitol ester of norbixin (SEN). The reaction efficiency was optimized with various immobilized lipases at different water activity levels in the organic solvent, 2-methyl-2-butanol. Among the examined lipases, immobilized Candida antarctica lipase B (Novozyme 435) provided the highest reaction yield at a water activity close to zero. Tetrahydrofuran (THF) was used as co-solvent to improve bixin solubility. The optimization of the reaction conditions with 20% THF lead to a total reaction yield of 50% of SEN.

Allotwinning in a molecular crystal: (1R,3S)-dimethyl 2-oxocyclohexane-1,3-dicarboxylate.

Two polytypic modifications of (1R,3S)-dimethyl 2-oxocyclohexane-1,3-dicarboxylate intergrow to form allotwins. One phase shows monoclinic symmetry, Cc, while the other is orthorhombic Pmc21. The structures may be considered as two different modes of superstructure ordering of an underlying, disordered structure. Considered in the same metrically orthorhombic unit cell a = 37.8883, b = 4.7233, c = 11.6835 Å, the two can be conveniently distinguished by their non-standard centering, Cc being represented as Xc with the centering vectors (0 0 0); (½ 0 ½); (» ½ ¾); (¾ ½ »); and Pmc21 as Xmc21 with the centering vectors (0 0 0); (½ 0 0). The difference between the allotwin domains lies only in the relationship between next-nearest neighbors along the stacking direction 100 and hence the conformations and packing efficiencies are identical for both phases and all three domains. The stacking sequences for the two phases correspond to ABAB for the orthorhombic stacking and ABA'B'/AB'A'B for the two (equivalent) monoclinic stackings. The monoclinic phase dominates comprising ca 80% of the total volume. Within the monoclinic phase, the ratio between the two possible orientations is highly unbalanced (6:1) indicating relatively large domains. The allotwinning detected in this sample may appear exotic in molecular compounds, but we suggest that the rarity of such examples in the literature is a reflection of the paucity of software that can identify and handle such cases. It is easy to overlook the possibility that a complex diffraction pattern originates from allotwinning and assume that normal mono-component twinning is the cause. The underlying mechanism in this case is the formation of two-dimensional layers of molecules that allow for two equivalent, but in terms of absolute geometry, different, ways of stacking.

(6R*,10R*)-Dimethyl 1,4-dioxaspiro-[4.5]decane-6,10-dicarboxyl-ate.

The title compound, C(12)H(18)O(6), is in the usual chair conformation with the two ester functions in a 1,3-trans orientation. With a value of 1.439 (2) Å, the pseudo-axial C-O bond of the 1,3-dioxolane ring is slightly longer than the corresponding equatorial C-O bond of 1.424 (3) Å. The O-C-O angle of the dioxolane ring is 106.25 (17)°.