Antioxidant Activity and Mechanism of Resveratrol and Polydatin Isolated from Mulberry (Morus alba L.)

Natural stilbenes have unique physiological effects, such as anti-senile dementia, anti-cancer, anti-bacterial, lowering blood lipid, and other important biological functions, which have attracted great attention from scholars in recent years. In this study, two stilbene compounds, resveratrol (RES) and polydatin (PD), were isolated from Mulberry (Morus alba L.), and their antioxidant activity and mechanism were investigated. The results showed that the contents of RES and PD in mulberry roots were 32.45 and 3.15 μg/g, respectively, significantly higher than those in mulberry fruits (0.48 and 0.0020 μg/g) and mulberry branches (5.70 and 0.33 μg/g). Both RES and PD showed high antioxidant potential by DPPH, ABTS free-scavenging methods, and ORAC assay, and provided protection against oxidative damage in HepG2 cells by increased catalase (CAT) activity, superoxide dismutase (SOD) activity, and Glutathione (GSH) content, and decreasing generation of reactive oxygen species (ROS), lactate dehydrogenase (LDH) level, and malondialdehyde (MDA) content. Therefore, RES and PD treatment could be effective for attenuating AAPH-induced oxidative stress in HepG2 cells. This study will promote the development and application of stilbene compounds. Furthermore, the RES and PD could be used as antioxidant supplements in functional foods, cosmetics, or pharmaceuticals, contributing to health improvement.

The Influence of Iron Ions on Optical Brighteners and Their Application to Cotton Fabrics

The influence of iron ions at concentrations of 0.2, 0.5, and 1.0 g/L on optical brighteners of the groups stilbene and biphenyl in solution and on cotton fabric was investigated. Both groups of optical brighteners are intended for detergent formulations. The influence of iron ions was studied by absorption and fluorescence spectra in solution and by whiteness degree, identifying color differences using CIEL*a*b* coordinates and Ultraviolet Protection Factor (UPF) of cotton fabrics. The obtained results in solutions and cotton fabrics showed different behavior of optical brighteners stilbene and biphenyl in the presence of iron. Stilbene compounds with metal ions produced new species capable of absorbing in the UV-B region of the spectrum. A biphenyl compound in combination with iron had no effect on the absorption properties. Both optical brighteners were influenced by iron ions in the sense of fluorescence quenching. The influence of iron ions in single- and two-bath treatments of cotton fabrics after one cycle on whiteness degree and UPF was negligible.

Impact of Environmental Factors on Stilbene Biosynthesis

Stilbenes are a small family of polyphenolic secondary metabolites that can be found in several distantly related plant species. These compounds act as phytoalexins, playing a crucial role in plant defense against phytopathogens, as well as being involved in the adaptation of plants to abiotic environmental factors. Among stilbenes, trans-resveratrol is certainly the most popular and extensively studied for its health properties. In recent years, an increasing number of stilbene compounds were subjected to investigations concerning their bioactivity. This review presents the most updated knowledge of the stilbene biosynthetic pathway, also focusing on the role of several environmental factors in eliciting stilbenes biosynthesis. The effects of ultraviolet radiation, visible light, ultrasonication, mechanical stress, salt stress, drought, temperature, ozone, and biotic stress are reviewed in the context of enhancing stilbene biosynthesis, both in planta and in plant cell and organ cultures. This knowledge may shed some light on stilbene biological roles and represents a useful tool to increase the accumulation of these valuable compounds.

Glycosylation of Stilbene Compounds by Cultured Plant Cells

Oxyresveratrol and gnetol are naturally occurring stilbene compounds, which have diverse pharmacological activities. The water-insolubility of these compounds limits their further pharmacological exploitation. The glycosylation of bioactive compounds can enhance their water-solubility, physicochemical stability, intestinal absorption, and biological half-life, and improve their bio- and pharmacological properties. Plant cell cultures are ideal systems for propagating rare plants and for studying the biosynthesis of secondary metabolites. Furthermore, the biotransformation of various organic compounds has been investigated as a target in the biotechnological application of plant cell culture systems. Cultured plant cells can glycosylate not only endogenous metabolic intermediates but also xenobiotics. In plants, glycosylation reaction acts for decreasing the toxicity of xenobiotics. There have been a few studies of glycosylation of exogenously administrated stilbene compounds at their 3- and 4′-positions by cultured plant cells of Ipomoea batatas and Strophanthus gratus so far. However, little attention has been paid to the glycosylation of 2′-hydroxy group of stilbene compounds by cultured plant cells. In this work, it is described that oxyresveratrol (3,5,2′,4′–tetrahydroxystilbene) was transformed to 3-, 2′-, and 4′-β-glucosides of oxyresveratrol by biotransformation with cultured Phytolacca americana cells. On the other hand, gnetol (3,5,2′,6′–tetrahydroxystilbene) was converted into 2′-β-glucoside of gnetol by cultured P. americana cells. Oxyresveratrol 2′-β-glucoside and gnetol 2′-β-glucoside are two new compounds. This paper reports, for the first time, the glycosylation of stilbene compounds at their 2′-position by cultured plant cells.

Induced extracellular production of viniferins in grapevine cell culture medium by elicitation with methyl jasmonate and stevioside

We report the high production of stilbenes, including resveratrol and viniferins, in grapevine (Vitis labruscana L.) cell cultures through elicitation with methyl jasmonate (MJ) and stevioside (STE). Methyl-β-cyclodextrin (CD-M) is widely used as a solubilizer for resveratrol production. For the first time, we used STE as a solubilizer for stilbene production in plant cell cultures. MJ was most effective in activating VvSTS expression and stimulating stilbene biosynthesis and induced accumulation of trans-piceid in the cells. High levels of trans-resveratrol and δ-viniferin production were observed in the culture medium when CD-M and STE, respectively, were used as solubilizers, but neither were significantly elevated within the cells. Maximum production of trans-resveratrol (12.2 mg/L) and δ-viniferin (892.2 mg/L) was observed 5 days after elicitation of cells with MJ and STE in shake flask cultures. Notably, predominant production of δ-viniferin and trans-resveratrol was observed in shake and static flask culture medium, respectively. Furthermore, stilbene compounds of resveratrol, e-viniferin, and δ-viniferin were mainly produced in a 3 L bioreactor culture following elicitation of cells with MJ and STE. These results provide new strategies for conditional, high-level production of resveratrol and viniferins in cell cultures by utilizing the solubilizing properties of STE or CD-M.

Stilbene Compounds Inhibit Tumor Growth by the Induction of Cellular Senescence and the Inhibition of Telomerase Activity

Cellular senescence is a state of cell cycle arrest characterized by a distinct morphology, gene expression pattern, and secretory phenotype. It can be triggered by multiple mechanisms, including those involved in telomere shortening, the accumulation of DNA damage, epigenetic pathways, and the senescence-associated secretory phenotype (SASP), and so on. In current cancer therapy, cellular senescence has emerged as a potent tumor suppression mechanism that restrains proliferation in cells at risk for malignant transformation. Therefore, compounds that stimulate the growth inhibition effects of senescence while limiting its detrimental effects are believed to have great clinical potential. In this review article, we first review the current knowledge of the pro- and antitumorigeneic functions of senescence and summarize the key roles of telomerase in the regulation of senescence in tumors. Second, we review the current literature regarding the anticancer effects of stilbene compounds that are mediated by the targeting of telomerase and cell senescence. Finally, we provide future perspectives on the clinical utilization of stilbene compounds, especially resveratrol and pterostilbene, as novel cancer therapeutic remedies. We conclude and propose that stilbene compounds may induce senescence and may potentially be used as the therapeutic or adjuvant agents for cancers with high telomerase activity.