Introduction

Mamey sapote is a tropical fruit that is scientifically known as Pouteria sapota. It belongs to the sapodilla family( Sapotaceae) and is a climatic fruit type.¹ This species of Mamey sapote is originally from southern Mexico and most of Central  America. Later, it was imported as a crop to Florida, Hawaii, the Bahamas and northern South America.² The description of the fruit is as follows

The shape of the fruit is ovoid, 20 centimetres in length and 7-12 centimetres in diameter, with a thick and rough brown peel and a soft, sweet pulp with a colour ranging from dark coffee brown to deep red or pink. Seeds make up 15 to 25% of the fruit overall and have several applications.² The unique sweet flavour of the pulp makes it popular among its consumers. It can be eaten fresh, frozen or dehydrated.² Besides its delicious taste, it is healthy and enriched with nutrients. Sapote mamey contains more carotenoids than other tropical fruits like papaya, jobo, etc. Mamey sapote is usually consumed as fruit, and the pulp can be used to make milkshakes, ice-creams-sweets and the seeds are used for beverage preparation. In traditional indigenous medicine, the extracted oil was used for alopecia, as an analgesic,  removing kidney stones, rheumatism and digestion-related problems. Additionally, the seed latex was used for dermal problems.³

Nutritional elements in mamey sapote that are beneficial for vision health

Vitamins

• Vitamin A: It is vital for the human visual and immune system.⁴ The basic role of Vitamin A is to support the functioning of the cornea and the conjunctival membranes⁵ 
• Vitamin C: Vitamin C helps in scavenging the reactive oxidative species(ROS), which are the causative agents for oxidative stress.⁶ Several studies have demonstrated that Vitamin C protects the cornea, lens and other ocular tissues from oxidative damage. It has also been proven effective in safeguarding the reducing capacities of antioxidants.⁷ Also, Vitamin C can protect the lens against light-induced oxidative damage to the Na+ K+-ATPase pump⁸ and from lipid peroxidation⁹
• Vitamin E: Vitamin E is an effective antioxidant that is naturally available in food and protects the body against free radicals.⁵ Since almost 65% of the fatty acids in the membrane of photoreceptors are polyunsaturated, they are particularly susceptible to oxidative damage through peroxidation.¹⁰ Over time, exposure to bright light causes phototoxic damage to this portion as well, which is seen as lipofuscin granules. Vitamin E can lower lipid peroxidation; therefore, it can contribute towards the reduction of phototoxic damage¹⁰ 

Carotenoids

• Beta-carotene: It is essential for maintaining eye health, and it is the precursor of vitamin A. Carotenoids are a class of pigments that includes beta-carotene. It is present in many fruits and vegetables and is transformed into vitamin A by the body.¹¹ Carotenoids are considered potent antioxidants at low partial pressures of oxygen, which are the conditions encountered in the lens of the eye. The available data from the conducted research conclude an inverse relationship between blood beta-carotene levels and cataract risk¹²
• Lutein and Zeaxanthin: Beta carotene, lutein and zeaxanthin are the pigments shown in many clinical and pre-clinical trial investigations slowing down the progression of eye diseases. This is mostly due to their ability to squelch free radicals and stop oxidative-related damage to the retina¹³

Antioxidant properties

Explanation of oxidative stress and its impact on vision

As a result of an imbalance in the antioxidant defence system, the accumulation of reactive oxygen species ( ROS ) leads to oxidative stress.¹⁵ ROS play various physiological roles, including cell signalling and are typically produced as the byproduct of oxygen metabolism. Nevertheless, xenobiotics and environmental stressors like UV, ionising radiation, pollutants and heavy metals greatly increase ROS production. Some examples of ROS are superoxide, singlet oxygen, and hydrogen peroxide. etc.¹⁴

Protection of eye cells against oxidative damage by the antioxidants present in the mamey sapote

According to phytochemical characterisation studies, the presence of phenolic and carotenoid compounds signifies the inherent antioxidant properties in the mamey fruit.¹⁶ The antioxidant property of the edible flesh of the fruit has been evaluated, and various phenolic compounds, flavanols and carotenoids have been identified and are recommended to be incorporated in the diet.¹⁷ 

The nutritional content of the Mamey sapote fruit is as follows-

• Energy- 124Kcal
• Carbohydrates - 32.1g
• Protein - 1.45g
• Dietary fibre - 5.4g
• Folates - 7µg
• Niacin - 1.432g
• Pantothenic acid - 0.397mg
• Pyridoxine - 0.720mg
• Riboflavin - 0.116mg
• Thiamine - 0.013 mg
• Vitamin A - 143 IU
• Vitamin C- 23 mg
• Sodium - 7 mg
• Potassium - 454 mg
• Calcium - 18 mg
• Copper - 0.213 mg
• Iron - 0.78 mg
• Magnesium - 11 mg
• Phosphorus - 26mg
• Beta- carotene - 82µg
• Lutein-Zeaxanthin - 204µg
• Lycopene - 199 µmg

Based on the available nutrition chart of Mamey sapote, the fruit is enriched with a higher concentration of Vitamin C, which helps the body to scavenge dangerous oxygen radicals developed in the susceptible areas. Additionally, it includes a good concentration of health-promoting flavonoids and polyphenolic antioxidants, including lutein, zeaxanthin, lycopene and beta-carotene.¹⁸ All of them together function in reducing the oxidation stress and eradicating  ROS. Likewise, these protect the damaged areas of the eye tissues and prevent them from damage from oxidative stress.¹⁸ 

Anti-inflammatory effects

Importance of managing inflammation for eye health

The term “inflammatory eye disease” refers to a broad range of ailments, from minor problems to life-threatening situations. Ocular inflammation can affect any eye region and can arise as a complication of systemic inflammatory disease.¹⁹ The most prevalent type of inflammatory eye illness is uveitis, whose symptoms include redness, pain, blurred vision and light sensitivity. If left untreated, it will result in irreversible vision loss and eye tissue damage. The shape of the eye might be disturbed because of the small size of the eye; even a slight swelling can result in a big impact, leading to visual acuity.²⁰

Inflammation is also connected to other inflammatory disorders of the eyes, like dry eye syndrome. Prolonged inflammation can reduce the amount and quality of tears produced, creating a vicious cycle in which dry eyes aggravate inflammation, further harming the surface of the eyes and increasing the risk of infections and corneal abrasions.^21,22

Anti-inflammatory properties of mamey sapote and their contribution to reducing eye inflammation

Mamey sapote’s anti-inflammatory qualities are mainly ascribed to the high concentration of vitamins C and E and other antioxidants. They can greatly aid in lowering ocular inflammation and promoting general eye health. Vitamin C is a major source of antioxidants that reduce oxidative stress and inflammation. This might prove that it can be used in treating eye inflammation and also helps to strengthen the immune system. It also contributes to the manufacturing of collagen, which is essential for preserving the ocular tissues.^23,24 Mamey sapote also consists of Vitamin E,  essential for lowering the risk of inflammatory eye disorders.²⁴

Support for macular health

Role of lutein and zeaxanthin in maintaining macular health

Because of their capacity to accumulate in the macula and their antioxidant properties, lutein and zeaxanthin are vital for preserving retinal health and lowering the risk of age-related macular degeneration. Two tissues, the macula and the lens, play a vital role in vision. The carotenoids lutein and zeaxanthin are mostly found in these tissues. They perform the function of shielding the eyes from harmful radiation exposure. They absorb visible blue light, which is extremely reactive and may exacerbate photooxidative degeneration of the retina.²⁵

How mamey sapote's nutrients support the prevention of macular degeneration

Nutrients associated with the prevention of macular degeneration are anthocyanins, carotenoids( lutein, zeaxanthin and beta-carotene ), vitamin A, vitamin C, vitamin E, zinc and selenium. Lutein and zeaxanthin are the most effective antioxidants for preventing the risk of age-related macular degeneration.²⁶ 

Mamey sapote’s antioxidant, vitamin and mineral content synergistically supports eye health and reduces inflammation. Therefore, its consumption could prove essential for the prevention of macular degeneration.

Research and studies

Overview of existing research on mamey sapote and vision health

Studies conducted demonstrate the plant’s potential advantages as anti-amyloidogenic and anti-tumorigenic.  A range of carotenoids, including keto carotenoids like cryptoxanthin and sapotexin xin are found in the fruit. So the 3’-deoxy-k-end group of sapote xanthin has been shown to be a significant source of provitamin A, which is necessary for preserving cognitive function and vision.²⁷ 

Although a few specific studies clearly relate mamey sapote to the prevention of macular degeneration. Also, the existing research indicates that the rich abundance of antioxidants and anti-inflammatory qualities supports eye health and prevents oxidative damage, but further research is expected in this regard.

Summary

Mamey sapote, known by its scientific name Pouteria sapota, is a tropical fruit known for its nutritional benefits, which include promoting eye health. It is enriched with nutrients such as Vitamin A, Vitamin C, beta-carotene, lutein-zeaxanthin and lycopene. Lutein and zeaxanthin are the carotenoids which are mostly found in the macula and lens of the eye and help to protect these tissues from photo-oxidative reactions and thus oxidative stress. These substances also minimise the incidence of cataracts and age-related macular degeneration by shielding the retina against oxidative stress.28 Vitamin A is required for the formation of rhodopsin, a pigment in the retina which aids the eye in adapting to low-light conditions. Additionally, it is essential to preserve corneal health.⁴ Overall, mamey sapote has proven to be beneficial in improving eye health, but future research is expected to explore this further. 5