Ocular tissues and fluids oxidative stress in hares fed on verbascoside supplement

The potential benefits of polyphenols for corneal diseases

The cornea functions as the primary barrier of the ocular surface, regulating temperature and humidity while providing protection against oxidative stress, harmful stimuli and pathogenic microorganisms. Corneal diseases can affect the biomechanical and optical properties of the eye, resulting in visual impairment or even blindness. Due to their diverse origins and potent biological activities, plant secondary metabolites known as polyphenols offer potential advantages for treating corneal diseases owing to their anti-inflammatory, antioxidant, and antibacterial properties. Various polyphenols and their derivatives have demonstrated diverse mechanisms of action in vitro and in vivo, exhibiting efficacy against a range of corneal diseases including repair of tissue damage, treatment of keratitis, inhibition of neovascularization, alleviation of dry eye syndrome, among others. Therefore, this article presents a concise overview of corneal and related diseases, along with an update on the research progress of natural polyphenols in safeguarding corneal health. A more comprehensive understanding of natural polyphenols provides a novel perspective for secure treatment of corneal diseases.

Preventive Efficacy of an Antioxidant Compound on Blood Retinal Barrier Breakdown and Visual Dysfunction in Streptozotocin-Induced Diabetic Rats

In diabetic retinopathy (DR), high blood glucose drives chronic oxidative stress and inflammation that trigger alterations of the neurovascular balance finally resulting in vascular abnormalities and retinal cell death, which converge towards altered electroretinogram (ERG). In the last years, a growing body of preclinical evidence has suggested that nutrients with anti-inflammatory/antioxidant properties can be able to hamper DR progression since its very early stages. In the present study, we used a streptozotocin-induced rat model of DR, which mimics most aspects of the early stages of human DR, to test the preventive efficacy of a novel compound containing cyanidin-3-glucoside (C3G), verbascoside and zinc as nutrients with antioxidant and anti-inflammatory properties. Western blot, immunofluorescence and electroretinographic analyses demonstrated a dose-dependent inhibition of oxidative stress- and inflammation-related mechanisms, with a significant counterpart in preventing molecular mechanisms leading to DR-associated vasculopathy and its related retinal damage. Preventive efficacy of the compound on dysfunctional a- and b-waves was also demonstrated by electroretinography. The present demonstration that natural compounds, possibly as a consequence of vascular rescue following ameliorated oxidative stress and inflammation, may prevent the apoptotic cascade leading to ERG dysfunction, adds further relevance to the potential application of antioxidants as a preventive therapy to counteract DR progression.

Dietary Intervention With a Targeted Micronutrient Formulation Reduces the Visual Discomfort Associated With Vitreous Degeneration

Purpose

To investigate the impact of supplementation with a targeted micronutrient formulation on the visual discomfort associated with vitreous degeneration.

Methods

In this clinical trial, 61 patients with symptomatic vitreous floaters were randomized to consume daily, the active supplement consisting of 125 mg L-lysine, 40 mg vitamin C, 26.3 mg Vitis vinifera extract, 5 mg zinc, and 100 mg Citrus aurantium or placebo for 6 months. Change in visual discomfort from floaters, assessed with the Floater Disturbance Questionnaire, was the primary outcome measure. Secondary outcome measures included best-corrected visual acuity, letter contrast sensitivity, photopic functional contrast sensitivity with positive and negative contrast polarity, and quantitative vitreous opacity areas.

Results

After supplementation, the active group reported a significant decrease in their visual discomfort from floaters (P < 0.001), whereas the placebo group had no significant change in their visual discomfort (P = 0.416). At 6 months, there was a significant decrease in vitreous opacity areas in the active group (P < 0.001) and an insignificant increase in vitreous opacity areas in the placebo group (P = 0.081). Also, there was a significant improvement in photopic functional contrast sensitivity with positive contrast polarity in the active group after supplementation (P = 0.047).

Conclusions

The findings of this study indicate improvements in vision-related quality of life and visual function of patients suffering from vitreous floaters after supplementation with a formulation of antioxidative and antiglycation micronutrients. Notably, these improvements were confirmed by the decrease in vitreous opacity areas in the active group.

Translational Relevance

This targeted dietary intervention should be considered to support patients with symptomatic vitreous degeneration.

Dietary Supplementation of Antioxidant Compounds Prevents Light-Induced Retinal Damage in a Rat Model

Light-induced retinal damage (LD) is characterized by the accumulation of reactive oxygen species leading to oxidative stress and photoreceptor cell death. The use of natural antioxidants has emerged as promising approach for the prevention of LD. Among them, lutein and cyanidin-3-glucoside (C3G) have been shown to be particularly effective due to their antioxidant and anti-inflammatory activity. However, less is known about the possible efficacy of combining them in a multicomponent mixture. In a rat model of LD, Western blot analysis, immunohistochemistry and electroretinography were used to demonstrate that lutein and C3G in combination or in a multicomponent mixture can prevent oxidative stress, inflammation, gliotic and apoptotic responses thus protecting photoreceptor cells from death with higher efficacy than each component alone. Combined efficacy on dysfunctional electroretinogram was also demonstrated by ameliorated rod and cone photoreceptor responses. These findings suggest the rationale to formulate multicomponent blends which may optimize the partnering compounds bioactivity and bioavailability.

Cistanches Herba, from an endangered species to a big brand of Chinese medicine

Cistanches Herba (CH, Chinese name: Roucongrong), is a very precious, tonic Chinese medicine. Cistanche deserticola and Cistanche tubulosa are the two commonly used species and authenticated in Chinese Pharmacopoeia. Due to the parasitic nature of Cistanche plants, the wild source was once endangered and listed in the Appendix II of Convention on International Trade in Endangered Species of Wild Fauna and Flora. However, after continuously struggling in the past decades, CH has grown up to a big brand of Chinese medicine featured with the cultivation area as 1.26 million mu, the annual output as 6000 tons, and the related industrial output value as more than 20 billion China Yuan, attributing to large-scale cultivation and in-depth phytochemical and pharmacological investigations. Noteworthily, great achievements have reached concerning the research and development of relevant products, such as modern drugs, traditional Chinese medicine prescriptions, and dietary supplements. The current review summarizes the research progresses concerning the distribution and cultivation, phytochemistry, pharmacology, metabolism and product development of CH in the past decades, and the emerging challenges and developing prospects are discussed as well.

Reaction-diffusion model as framework for understanding the role of riboflavin in “eye defence” formulations

Analysis of UV-visible spectra, performed on commercial riboflavin-based eye drops, showed that absorbance is a saturating function of vitamin concentration. This implies a threshold concentration, C_t, such that for riboflavin concentration > C_t the absorbance remains constant and the effectiveness of the eye drops is independent of the dose used. These experimental results were combined with a diffusion–reaction model to elucidate the mechanism of action within the cornea. The model predicts that the eye drops have a low effectiveness on UVB and UVC, while they have a good performance for UVA. Indeed, at the center of the cornea the transmittance is significantly reduced and after 1 h it is reduced by about 70% compared to a cornea devoid of eye drops.

Analysis of UV-visible spectra, performed on commercial riboflavin-based eye drops, showed that absorbance is a saturating function of vitamin concentration.

Vitreous Antioxidants, Degeneration, and Vitreo-Retinopathy: Exploring the Links

The transparent vitreous body, which occupies about 80% of the eye’s volume, is laden with numerous enzymatic and non-enzymatic antioxidants that could protect the eye from oxidative stress and disease. Aging is associated with degeneration of vitreous structure as well as a reduction in its antioxidant capacity. A growing body of evidence suggests these age-related changes may be the precursor of numerous oxidative stress-induced vitreo-retinopathies, including vision degrading myodesopsia, the clinically significant entoptic phenomena that can result from advanced vitreous degeneration. Adequate intravitreal antioxidant levels may be protective against vitreous degeneration, possibly preventing and even improving vision degrading myodesopsia as well as mitigating various other vitreo-retinopathies. The present article is, therefore, a review of the different antioxidant molecules within vitreous and the inter-relationships between vitreous antioxidant capacity and degeneration.

Relationships Between Chemical Structure and Antioxidant Activity of Isolated Phytocompounds from Lemon Verbena

Over the last few years, people have been concerned about the narrow relationship between nutrition and health leading to an increasing demand of nutraceutical products and functional food. Lemon verbena (Lippia citriodora Kunth) has been traditionally used for respiratory, digestive, and muscular diseases, showing effects that are promoted by the antioxidant activity of its phytoconstituents. The antioxidant power of several lemon verbena extracts has been tested but its isolated compounds activity has not been described. The aim of the present work was to isolate phytochemicals from a commercial lemon verbena extract through a semi-preparative high-performance liquid chromatography approach for further evaluation of its individual antioxidant activity using three different methods. The structure-antioxidant activity relationships revealed the influence of substitutions in the strong antioxidant power exerted by glycosylated phenylpropanoids, in contrast to the low antioxidant capacity showed by iridoids. Development of enriched extracts in these compounds could lead to greater antioxidant effects and improved functional ingredients to prevent chronic diseases.

Aloysia citrodora Paláu (Lemon verbena): A review of phytochemistry and pharmacology

ETHNOPHARMACOLOGICAL RELEVANCE

Aloysia citrodora Paláu (Lippia citriodora Kunth), commonly known as "lemon verbena" is a medicinal plant native to South America, North Africa, and South of Europe which is used by native people for several indications such as diarrhea, flatulence, insomnia, and rheumatism.

AIM OF THE REVIEW

Despite the wide biological activities of lemon verbena, there is no current review summarizing medicinal properties of the plant; thus, this paper aims to discuss current state of the art regarding the phytochemistry, pharmacology, and therapeutic applications of A. citrodora considering in vitro, in vivo, and clinical studies.

MATERIALS AND METHODS

Electronic databases including PubMed, Scifinder, Cochrane library, Scopus, and Science direct were searched with the scientific name of the plant and its synonyms, as well as the common name. All studies on the ethnobotany, phytochemistry, pharmacology, and clinical application of the plant until October 2017 were included in this review.

RESULTS

Despite the few number of studies on the ethnopharmacology of the plant, A. citrodora is widely assessed regarding its phytochemistry and biological activities. Neral and geranial are the main ingredients of the essential oil; whereas verbascoside is the most significant component of the extract. Biological activities such as antioxidant, anxiolytic, neuroprotective, anticancer, anesthetic, antimicrobial, and sedative effects are proved in cell cultures, as well as animal studies.

CONCLUSIONS

Several pharmacological activities have been reported for A. citrodora; however, the plant is not fully assessed regarding its safety and efficacy in human. Future well-designed human studies are essential to confirm the therapeutic benefits of this plant in clinical settings.

Corneal epithelial wound healing promoted by verbascoside-based liposomal eyedrops

Different liposomal formulations were prepared to identify those capable of forming eyedrops for corneal diseases. Liposomes with neutral or slightly positive surface charge interact very well with the cornea. Then these formulations were loaded with verbascoside to heal a burn of corneal epithelium induced by alkali. The cornea surface affected involved in wound was monitored as a function of time. Experimental results were modeled by balance equation between the rate of healing, due to the flow of phenylpropanoid, and growth of the wound. The results indicate a latency time of only three hours and furthermore the corneal epithelium heals in 48 hours. Thus, the topical administration of verbascoside appears to reduce the action time of cells, as verified by histochemical and immunofluorescence assays.