Photochemistry in everyday life: The effect of spontaneous emulsification on the photochemistry of trans-anethole

Sensitized Photooxidation of Ortho-prenyl Phenol: Biomimetic Dihydrobenzofuran Synthesis and Total 1 O2 Quenching

The sensitized photooxidation of ortho-prenyl phenol is described with evidence that solvent aproticity favors the formation of a dihydrobenzofuran [2-(prop-1-en-2-yl)-2,3-dihydrobenzofuran], a moiety commonly found in natural products. Benzene solvent increased the total quenching rate constant (k_T ) of singlet oxygen with prenyl phenol by ~10-fold compared to methanol. A mechanism is proposed with preferential addition of singlet oxygen addition to prenyl site due to hydrogen bonding with phenol OH group, which causes a divergence away from the singlet oxygen 'ene' reaction toward the dihydrobenzofuran as the major product. The reaction is a mixed photooxidized system since an epoxide arises by a type I sensitized photooxidation.

Antiviral and Antioxidant Components from the Fruits of Illicium verum Hook.f. (Chinese Star Anise)

Illicium verum Hook.f. (Chinese star anise), a known Chinese traditional spice, is commonly applied in Chinese cuisine and cooking in Southeast Asia. As a kind of medicinal and edible resource, the fruit of I. verum has attracted great attention for its chemical constituents and physiological activities. In this work, the phytochemical study of the fruits of I. verum led to the isolation and identification of 20 compounds, including 6 new lignans and phenylpropanoids (1-6) and 14 known ones (7-20). Their structures were characterized by extensive analysis of spectroscopic data (IR, UV, high-resolution electrospray ionization mass spectrometry (HR-ESI-MS), one-dimensional (1D) and two-dimensional (1D) NMR), electronic circular dichroism (ECD) calculation, and by comparison with literature data. Meanwhile, all compounds (1-20) were evaluated for their antiviral and antioxidant activities. Especially, compound 7 [(-)-bornyl p-coumarate] showed strong antiviral activities against influenza virus A/Puerto Rico/8/34 H1N1 (PR8) with an IC₅₀ value of 1.74 ± 0.47 μM, which is much better than those of Tamiflu (IC₅₀ = 10.01 ± 0.92 μM) and ribavirin (IC₅₀ = 10.76 ± 1.60 μM). The antiviral activity against PR8 of compound 7 was reported for the first time, which was sufficiently confirmed by cell counting kit 8 (CCK-8), cytopathic effect (CPE) reduction, and immunofluorescence assays. In this study, the discovery of antiviral and antioxidant components from the fruits of I. verum could benefit the further development and utilization of this plant.

Anethole Stability in Aniseed Spirits: Storage Condition Repercussions on Commercial Products

Background: trans-anethole is the main component of anise, and its flavor is characteristic of all the aniseed spirits. It is known that trans-anethole oil/ethanol/water solution could result in the undesirable emulsion effect called the “ouzo effect”. Moreover, trans-anethole can undergo chemical decay, producing unhealthy compounds, mainly cis-anethole and para-anisaldehyde. In this work, the trans-anethole stability was challenged simulating commercial products’ long-term storage. Methods: Anethole standard solutions and two Italian aniseed spirits, namely Sambuca and Mistrà, were used to evaluate the trans-anethole response to light (both ultraviolet and visible) and its stability under thermal stress. Anethole decay was monitored by trans-anethole quantification using an HPLC method. Results: Light and high-temperature exposure affect the trans-anethole content of aniseed spirits during the storage, but sucrose revealed a role in the trans-anethole protection. Conclusions: as transport and storage are involved in the anethole decay, the Regulations on the minimum of the anethole that must be a guarantee in the aniseed spirits should be revised.

Changes in Volatile Compounds during Aging of Sweet Fennel Fruits-Comparison of Hydrodistillation and Static Headspace Sampling Methods

Two extraction methods for subsequent gas chromatographic (GC) determination of volatiles from freshly harvested and aged fennel fruit samples ( Foeniculum vulgare Mill.,ssp. vulgare var. dulce) have been compared. Hydrodistillation followed by GC-FID and GC-MS analysis was used as a standard method for essential oil characterization, while static headspace followed by GC (SHS-GC-FID) was used as a comparative method for determination of volatile components. As the fennel fruit ages, there is a gradual loss of the volatile components as indicated by the lower yield of essential oil and lower content of volatiles, as indicated by the alternative SHS-GC-FID analysis. Slight differences observed for the main components ( trans-anethole, estragole, fenchone, and limonene) using the two methods are negligible, indicating that these volatiles did not undergo chemical transformation during the sample preparation procedures. A difference in anisaldehyde content was observed when the composition of the hydrodistilled essential oil was compared with the SHS-GC-FIDanalysis of volatiles and explanation for the variation of anisaldehyde content and the origin of other compounds was suggested. Comparison of the obtained results showed that limonene oxides, carvone and carveolare detectable in SHS-GC-FID analysis of the aged fennel fruits, while in hydrodistilled samples analyzed by GC-FID they were not present. Another observed difference was the appearance of products in significant amounts with higher retention times than trans-anethole, namely threo- and erythro-anethole β-hydroxymethylether and anethole glycol that are not detectable in the essential oil obtained by hydrodistillation. So, the relative abundance of the major components is comparable between these two methods for fennel seed up to 3 years from harvest and they can be used interchangeably depending on the purpose and amount of material. Furthermore, SHS-GC-FID can be used for assessment of maximum storage time and quality of fennel fruit suitable for human consumption.

Flavonoids protecting food and beverages against light

Flavonoids, which are ubiquitously present in the plant kingdom, preserve food and beverages at the parts per million level with minor perturbation of sensory impressions. Additionally, they are safe and possibly contribute positive health effects. Flavonoids should be further exploited for the protection of food and beverages against light-induced quality deterioration through: (1) direct absorption of photons as inner filters protecting sensitive food components; (2) deactivation of (triplet-)excited states of sensitisers like chlorophyll and riboflavin; (3) quenching of singlet oxygen from type II photosensitisation; and (iv) scavenging of radicals formed as reaction intermediates in type I photosensitisation. For absorption of light, combinations of flavonoids, as found in natural co-pigmentation, facilitate dissipation of photon energy to heat thus averting photodegradation. For protection against singlet oxygen and triplet sensitisers, chemical quenching gradually decreases efficiency hence the pathway to physical quenching should be optimised through product formulation. The feasibility of these protection strategies is further supported by kinetic data that are becoming available, allowing for calculation of threshold levels of flavonoids to prevent beer and dairy products from going off. On the other hand, increasing understanding of the interplay between light and matrix physicochemistry, for example the effect of aprotic microenvironments on phototautomerisation of compounds like quercetin, opens up for engineering better light-to-heat converting channels in processed food to eventually prevent quality loss.