Enhancement of Antioxidant Activity in O/W Emulsion and Cholesterol-Reducing Capacity of Epigallocatechin by Derivatization with Representative Phytosterols

Remarkable Enhancement of Antioxidant Activity of the Ovalbumin-EGCG Conjugate through a Novel Preceding Selective Protection Grafting Strategy

Conventional radical grafting of proteins with catechins consumed the most antioxidant-active hydroxyls during grafting, thus failing to effectively retain antioxidant activity in conjugates. In this study, a novel strategy of selective protection of the most reactive hydroxyls before grafting was developed to preserve the most reactive hydroxyls and effectively retain antioxidant activity in conjugates. Selective protection of the most reactive hydroxyls of (-)-epigallocatechin-3-gallate (EGCG) was successfully realized in a yield of 87% applying trimethyl orthopropionate and catalytic calcium triflate at 40 °C. The novel ovalbumin (OVA)-EGCG conjugate with 93% grafting ratio was prepared by radical grafting with the selectively protected EGCG and subsequent deprotection. Substantially enhanced antioxidant performance of the novel OVA-EGCG conjugate in liposomes was unveiled with notably reduced curcumin degradation and leakage. The strategy and approaches developed in this study will be valuable to effectively improve the antioxidant activities of protein-catechin grafting conjugates.

Soy proteins as vehicles for enhanced bioaccessibility and cholesterol-lowering activity of phytosterols

BACKGROUND

The formulation of phytosterol (PS)-enriched functional foods has attracted increasing interest in the recent years, owing to its potential health effects. However, the poor solubility and bioavailability greatly limit PS application in this regard. This study investigated whether soy protein isolate (SPI) could effectively perform as a nanocarrier for improving the water solubility, bioaccessibility, and cholesterol-lowering activity of PSs.

RESULTS

In this work, we fabricated SPI-PS nanocomplexes, which not only can enhance the stability and bioaccessibility of PS, but also improve the cholesterol-lowering ability of SPI. This improvement was mainly due to the formation of protein-active substance complexes, through hydrophobic interactions. The complexation with PSs resulted in formation of nanosized particles with greater sizes, lower ζ-potential, and higher surface hydrophobicity. The encapsulation efficiency, loading amount, and solubility of PS were closely related to the applied PS concentration in the mixed dispersions, and the maximal PS solubility in the aqueous phase reached about 1.63 mg mL^-1 at the highest PS concentration (2.0 mg mL^-1 ). The PS molecules in the nanocomplexes were mainly present in the amorphous form. The enhanced in vitro cholesterol-lowering activity of PS nanocomplexes relative to free PS seemed to be closely related to its higher bioaccessibility.

CONCLUSION

The findings are of relevance for the development of food-grade PS ingredients suitable for the formulations of PS-enriched functional foods. © 2022 Society of Chemical Industry.

Effects of Growth Period and Storage Methods on Primary Metabolite Contents and Antioxidant Activities of Morus alba L. Leaf

(1) Background: Mulberry leaves have been widely consumed due to their richness in bioactive substances and high antioxidant activity. The choice of storage method to ensure the quality of mulberry leaves is a challenge in the supply process. (2) Methods: The differences in primary metabolites of freeze-dried mulberry leaf powder after 30 days of storage under different storage conditions (i.e., vacuum or non-vacuum, 4 °C or room temperature) were investigated. (3) Results: A low temperature and vacuum had better preservation effects on the types and activity of the primary metabolites of mulberry leaves, with vacuum preservation being the best. However, the types of primary metabolites in mulberry leaves were significantly reduced after non-vacuum storage at room temperature compared to those with other storage methods. Among the metabolites detected, including dehydroascorbic acid, various phenolic acids, amino acids, lipids, and carbohydrates showed a significant decrease in their contents of more than 40%, and there was a significant increase in the contents of various compounds of the muconic acid biosynthetic pathway compared to those in other storage methods. Moreover, the antioxidant activity of mulberry leaves stored at room temperature under non-vacuum conditions was also significantly reduced. (4) Conclusions: Vacuum storage is the most ideal storage method for preserving mulberry leaves.

Enhanced antioxidant capacity of lipoic acid in different food systems through lipase-mediated esterification with phytosterols

BACKGROUND

α-Lipoic acid has excellent antioxidant activity, but its poor lipid solubility greatly limits its practical application. This study was undertaken (i) to develop a novel and efficient enzymatic synthesis of lipophilic lipoic acid esters using Candida sp. 99-125 lipase as a catalyst; and (ii) to systematically evaluate their antioxidant potential against bulk oil, oil-in-water emulsion (O/W) and cooked ground meat.

RESULTS

Lipophilic lipoic acid esters were successfully and efficiently synthesized using phytosterols as acyl receptor in the presence of Candida sp. 99-125 lipase. The product was identified as phytosterol lipoate by mass spectrometry, Fourier transform infrared spectroscopy and nuclear magnetic resonance. The maximum conversion of phytosterol lipoate surpassed 90% within 12 h and its final yield exceeded 81%. Interestingly, the oil solubility of lipoic acid was increased at least 25-fold and other physicochemical properties were significantly improved. Most importantly, phytosterol lipoate exhibited higher antioxidant activity than lipoic acid in bulk oil, O/W emulsions and cooked ground meat.

CONCLUSION

The antioxidant capacity of lipoic acid can be significantly enhanced by esterification with phytosterols. Therefore, phytosterol lipoate could be further developed as a new antioxidant for use in oil- and fat-based foods. © 2022 Society of Chemical Industry.

Fatty acids and nutritional components of the seed oil from Wangmo red ball Camellia oleifera grown in the low-heat valley of Guizhou, China

Wangmo red ball Camellia oleifera is the main Camellia species cultivated for oil in the low-heat valley of Guizhou, China. In this study, we evaluated the comprehensive nutritional value of Wangmo C. oleifera seed oil through fatty acid and nutritional component analyses. Twenty excellent Wangmo C. oleifera plants with stable yield and disease resistance were selected from the Camellia oleifera germplasm resource garden in the low-heat valley site of Guizhou University. The unit crown yield, fatty acid content of the seed oil, fatty acid composition and functional nutrients were determined, and the oil quality was comprehensively evaluated using principal component analysis. The fatty acid content of C. oleifera seed oil was 35.03–53.47%, suggesting likely popularization and wide application prospects. The fatty acids included SFAs, MUFAs and PUFAs, and the oleic acid content was 80%, indicating a highly stable and nutritious oil. The oil was also rich in carotenoids, polyphenols, flavonoids, β-sitosterol, squalene and α-Ve, with average content of 7.404 mg/kg, 16.062 mg/kg, 0.401 g/100 g, 265.087 mg/kg, 129.315 mg/kg and 21.505 mg/100 g, respectively. However, the correlations among the nutritional indices were weak. PCA showed that germplasms GH7, GH43, GH28, GH8 and GH31 exhibited the top five nutritional qualities. The rankings in this study provide data for identifying excellent Wangmo C. oleifera plants with high nutritional quality. Additionally, this study provides a valuable reference for the research and development of high-end edible oil and a theoretical basis for the development of economic forest species in low-heat valley areas across the world.

Development of a Gemini Interfacial Antioxidant for Oil in Water Emulsion with Gallic Acid and Dodecyl Gemini Chains

In this study, development of the gemini gallate (GG) interfacial antioxidant for oil in water (O/W) emulsion was performed employing Steglich esterification with gallic acid and dodecyl gemini chains through a prepacked column and peristaltic pump-based purification system. The structural identity and purity of the prepared GG and monogallate (MG) were confirmed by NMR, Fourier transform infrared spectroscopy, and high-performance liquid chromatography-mass spectrometry. Further evaluation revealed that the GG possessed excellent radical scavenging activity and superior antioxidant activity in an O/W emulsion relative to the MG, especially under the condition of a reduced amount of the emulsifier. Microscopic investigation by a fluorescent probe and transmission electron microscopy (TEM) unveiled that the extraordinary antioxidant performance in the O/W emulsion was presumably attributed to preferable interfacial location because of the unique gemini molecular architecture. The superior antioxidant activity of the gemini antioxidant holds great promise for antioxidation in O/W emulsions.

Effect of thermosonication pre-treatment on mung bean (Vigna radiata) and white kidney bean (Phaseolus vulgaris) proteins: Enzymatic hydrolysis, cholesterol lowering activity and structural characterization

Protein hydrolysates have attained great attention due to a good nutritive food ingredient and higher biological activities. In this study, thermosonication, ultrasound and heat were used as a pre-treatment to obtain (<3KDa) hydrolysate from mung bean and white kidney bean to understand the mechanism of cholesterol absorption into micelle and inhibition of 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMG-CoA) activity. Size exclusion high performance liquid chromatography (SE-HPLC) results of mung bean showed that the concentration of peptides (0.5KDa-1KDa and 1-3KDa) in the hydrolysate were significantly (p < 0.05) increased after thermosonication while, the peptides concentration (1-3KDa) in white kidney bean was significantly (p < 0.05) decreased. Thermosonication of mung bean hydrolysate exhibited higher inhibition of cholesterol solubilization, hydrophobicity and antioxidant activities. In addition, there was no difference observed in HMG-CoA activity and hydrophobicity between ultrasound alone and ultrasound combined with heat i.e. thermosonication treated hydrolysate of white kidney bean. Changes in secondary and tertiary structures were also analyzed under different processing conditions with maximum change due to thermosonication. Results indicated that mung bean hydrolysate had a great potential for inhibition of cholesterol synthesis and its solubility in the micelle, antioxidant activity and also convinced for its application in food and nutraceutical industries.

Forecasting structure of natural products through color formation process by thin layer chromatography

With booming of computer technology, it is feasible to quantitatively extract valuable information from readily available image of objects, which dramatically reduces the cost and improves the efficiency. In this work, a structural classification method, based on data extracted from color formation process on thin layer chromatography (TLC) plates through computer processing, was established for natural products. Representative natural products exhibited good clustering and separation according to the extracted color feature, and structure of natural products can be classified by the distribution region in the color system. This method provides structural information for typical types of natural products directly from the formed color on TLC, which is very efficient and make portable device-based structure analysis of natural products possible. In addition, a general mechanism of color formation was proposed. This method is free from special instrument, high-throughput, and would facilitate large-scale screening of bioactives from natural sources.