Quercetin belongs to a group of plant pigments called flavonoids, which are a polyphenol group of biochemicals that give many fruits, flowers, and vegetables their colors (www.mountsinai.org/ health-library/supplement/quercetin ). Flavonoids such as quercetin are antioxidants. Antioxidants scavenge free radicals that are produced by normal metabolism (mitochondrial respiration).

Free radicals (reactive oxygen species [ROS]) are implicated in various conditions that damage cell membranes, tamper with DNA, and cause cell apoptosis. To extrapolate, the free-radical theory of aging suggests that organisms age because cells accumulate free-radical damage over time (https://en.wikipedia.org/wiki/Free-radical_theory_of_aging ).

Oxidative Stress and the Eye

Oxidative stress, a disturbance in the balance between the production of ROS and antioxidant defenses, has been proposed as a mediator of ocular surface disease. Hyperosmolar conditions, inflammatory factors, and matrix-remodeling factors stimulate ocular oxidative stress and are also related to the production of ROS (Favero et al, 2021). In addition, aging and the decline of cellular functions underlie many diseases, particularly those of the eye. Furthermore, long-term exposure to such insults as ultraviolet light, visible light, ionizing radiation, chemotherapeutics (including glaucoma drops), and environmental toxins contribute to oxidative damage in ocular tissues and increase the risk of pathological consequences of oxidative stress in aging eyes (Saccà et al, 2018). Importantly, ROS play a role in various points of the ocular inflammation cycle underlying ocular surface disease (Seen and Tong, 2018).

Antioxidants to the Rescue

Polyphenols are natural molecules that exhibit positive activity/effects in counteracting the main pathologic mechanisms of dry eye disease (DED) and in reducing its symptoms (Favero et al, 2021). They are natural compounds characterized by one or more phenol rings. This structure makes them effective antioxidant molecules that can reduce the production of free radicals. A review of the literature suggests that topically applied polyphenols present promising outcomes against DED (Favero et al, 2021).

Additionally, polyphenols showed therapeutic effects in various fields of medicine. The molecules that have been studied the most include epigallocatechin gallate (EGCG), resveratrol, quercetin, betaine, pterostilbene, and curcumin (Favero et al, 2021; Berman et al, 2017; Bielory and Tabliago, 2020; and others; full list available at www.clspectrum.com ).

Flavonoids account for around 60% of all polyphenols and are found in foods such as apples, onions, dark chocolate, and red cabbage. Other polyphenols include resveratrol in red wine, ellagic acid in berries, curcumin in turmeric, and lignans in flax seeds, sesame seeds, and whole grains (Petre, 2019). Quercetin is a potent antioxidant flavonoid found mostly in onions, grapes, berries, cherries, broccoli, and citrus fruits (Anand David et al, 2016). It has been used as a nutritional supplement and may be beneficial against a variety of diseases, with effects such as cardiovascular protection, anticancer, antitumor, anti-ulcer, anti-allergy, anti-viral, and anti-inflammatory activity, and anti-diabetic, gastroprotective, antihypertensive, immunomodulatory, and anti-infective effects (Lakhanpal and Rai, 2007).

Many patients inquire as to what they can do to address their visual and other ocular symptoms. I generally suggest that caring for the body will care for the eye. A goal of overarching good health, including exercise, smoking cessation, adequate body hydration, and diet management, is in order. The medicine of plants is a safe adjunct to standard therapies when used in moderation.

Be sure to investigate the research and to recommend supplements that have appropriately balanced ingredients in managing ocular surface disease. More on quercetin and ocular surface disease to come. CLS

For references, please visit www.clspectrum.com/references and click on document #316.