Evaluation of novel green walnut liqueur as a source of antioxidants: Multi-method approach

The Effect of Adding Spices to Green Walnut Tinctures on Their Polyphenolic Profile, Antioxidant Capacity and Action on Renal Cells

Green walnuts—unripe fruits of Juglans regia L. are known for their many biological activities and therapeutic potential. Tinctures based on unripe walnuts (samples 1 and 2) and tinctures with the addition of spices (ginger, cloves, bay leaves, juniper fruit: samples 3–6) were tested for polyphenol profile and antioxidant capacity. The effect on a normal monkey kidney epithelial cell line (VERO) was evaluated. For monitoring the changes in cell proliferation, real-time cell analysis (xCELLigence system) was employed and cell viability was measured by the MTS test. All tinctures showed the presence of polyphenols, mainly phenolic acids, flavonoids, and naphthoquinones, and in the sample with cloves, eugenol was found. Addition of spices increased the antioxidant capacity. Tinctures show a dose-dependent cytotoxic effect. The lowest concentrations (125 µg mL−1) of both tinctures without additives (1 and 2) and with bay leaves (4) did not adversely affect (p > 0.05) and even supported cell proliferation (p < 0.05) in comparison to the control cells without treatment. Viability was lower in all cells except for the cells treated with tincture with cloves addition (p > 0.05). It indicates the beneficial effect of cloves enrichment and supports the assumption that the appropriate dosage of tinctures is necessary to be safe for the consumers.

Tailored Functionalization of Natural Phenols to Improve Biological Activity

Phenols are widespread in nature, being the major components of several plants and essential oils. Natural phenols' anti-microbial, anti-bacterial, anti-oxidant, pharmacological and nutritional properties are, nowadays, well established. Hence, given their peculiar biological role, numerous studies are currently ongoing to overcome their limitations, as well as to enhance their activity. In this review, the functionalization of selected natural phenols is critically examined, mainly highlighting their improved bioactivity after the proper chemical transformations. In particular, functionalization of the most abundant naturally occurring monophenols, diphenols, lipidic phenols, phenolic acids, polyphenols and curcumin derivatives is explored.