Introduction

Synsepalum dulcificum is commonly known as a miracle fruit, miracle plant or magic fruit. It resembles a fresh cranberry and is nearly tasteless fruit to humans. The name "miracle fruit" originated from the word "miraculin" - a protein found in the fruit responsible for taste alteration. The fruit has a unique taste-modifying feature that results in an increase in sweetness and a decrease in sourness. If a person chews or holds the berry on their tongue for a short time, it causes sour foods to taste sweet.¹

This taste-modifying function of the fruit had been regarded as a miracle. The taste-altering effect lasts approximately thirty minutes. In the 17th century, it was first discovered by European explorers in West and Central Africa. The Indian variety of miracle berry is known as Gymnema sylvestris with botanical synonyms: Asclepias geminata, Periploca sylvestris and Marsdenia sylvestris. It is also known by the name Gdmar or sugar destroyer. This fruit can be consumed raw or processed. This fruit has potential applications in the food industries, cosmetics industries and pharmaceutical industries.²

Brief overview of its taste-altering properties

Miraculin is a protein found in the miracle fruit plant (Synsepalum dulcificum). Instead of not having a sweet taste, it has the ability to change the taste perception of a sour substance to sweet. Its taste-modifying action results from binding sweet taste receptors. Under acidic conditions, it transforms sour taste into sweetness through an unknown molecular process, while it lacks flavor neutrality at neutral pH levels.³

Miraculin consists of two glycosylated 191-amino-acid polypeptides linked by disulfide bonds, forming a homodimer with a molecular weight of approximately 24,000 Da. The sweet taste receptor is a heterodimer consisting of T1R2 and T1R3, both having a sweet ligand binding site. T1R2 is for small molecules and T1R3 is for larger molecules.¹

The exact mechanism of miraculin action is not entirely clear. However, a theoretical model designed to understand how miraculin alters taste perception suggests that miraculin directly binds to the sweet taste receptor T1R2-T1R3 of the tongue. Miraculin only activates the receptor in the presence of acid, thus rendering sour foods to be perceived as sweet. In other words, when anyone first eats a Miracle Fruit and then consumes anything sour (e.g., a lemon wedge) taste receptors get activated and the individual does not perceive the sourness, instead perceives the sour substance as sweet.¹

Nutritional value

Miracle fruit contains different vitamins, proteins, lipids, and dietary phytochemicals providing nutritional and health benefits. It is a good source of important vitamins required for healthy living. It contains vitamin A for good vision, healthy bone formation and the immune system. Vitamin C is essential to avoid infections. Vitamin E is helpful for healthy vision, fertility and maintenance of cellular integrity and vitamin K which is vital for blood clotting and bone health.

Barriers are also a good source of essential and non- essential amino acids, including tryptophan (8.06%), histidine (0.4%), isoleucine (0.7%), leucine (0.6%), lysine (0.6%), methionine (1.05%), phenylalanine (0.7%), threonine (1.1%), and valine (0.69%). The bright red colour of the fruit is indicative of the presence of beneficial, antioxidant flavonoids, especially anthocyanins, which have been reported as anti-cancer and chemopreventive agents.⁵

Miracle fruit was reported to contain potent antioxidants phytochemicals like epicatechin, rutin, quercetin, myricetin, kaempferol, gallic, ferulic, syringic acid, delphinidin glucoside, cyanidin galactoside and malvidin galactoside, a-tocotrienol, c-tocopherol and lutein. The fruit offers a significant nutritional and health advantage through its taste-modifying capability, attributed to miraculin. Miraculin is currently under investigation as a potential low-calorie sweetener.⁴

Health uses of synsepalum dulcificum

In the traditional herbal medicine system of many countries, all portions of the S. dulcificum plant are used to treat or manage a number of human diseases and disorders. Earlier literature suggests that diabetes and sexually related diseases are two major ailments for which this plant is used. Different part of the plant is used for different purposes which includes:²

• Leaves are used for diabetes, malaria, hyperthermia, enuresis, asthma, male infertility, weight loss, cancer and also as appetizer and sweetener
• Bark of the tree is used to cure prostate problems, 
• Branches are consumed to treat oral and dental problems, and erectile dysfunction 
• Root is used to treat gonorrhea 
• Fruit has traditionally been used in diabetic and obese patients and to sweeten sour dishes and beverages

Pharmacological activities of S. dulcificum

Miracle fruit's plant has been reported to show a variety of pharmacological actions, which include:

Anticonvulsant activity

S. dulcificum seed extract has anticonvulsant activity due to a specific phytochemicals, which have mild affinity for the gamma-aminobutyric acid (GABA) receptor's picrotoxin (PTX) binding site.

Antioxidant activity

S. dulcificum fruits, leaves, roots and seeds are reported to have antioxidant phytochemicals such as flavonoids, phenols, terpenoids and amides, all of which are capable of boosting health by protecting against the harmful effects of oxidative stress.⁷

Hypolipidemic activity

Ethanolic extract of S. dulcificum seed, leaves and dry pulp decrease total cholesterol levels in plasma, which is due to the presence of active triterpenoids in the extract.

Anti-alopecia activity

S. dulcificum seed oil was studied in healthy women, with the conclusion that it is a very safe and effective option for strengthening and repairing damaged hair.²

Insulin resistance 

The lyophilised powder of Miracle Fruit was given through an oral route for male Wister rats. he result indicated a decrease in the glucose-insulin index, hence it reports a production of insulin resistance in rats delayed by the administration of Miracle fruit orally.⁶

Antidiabetic activity

Research was done in Wistar albino rats to find antidiabetic activity of flavonoid-rich and methanolic leaf extracts of Miracle Fruit in type 2 diabetes. Results showed a great reduction in serum glucose level in diabetic animals treated, so Miracle fruit is seen to have antidiabetic properties.⁶

Anticancer activity

Antioxidant properties of miracle fruit help to inhibit malignant cell proliferation. S. dulcificum contains chemicals (þ-syringaresinol and þ-epi-syringaresinol), which exhibit inhibitory effects on human skin cancer cells. The effect of aqueous leaf extracts of miracle fruit was studied and reported that the mutagenicity was inhibited. The effect of S. dulcificum berry and stem extracts on the expression of early apoptotic genes, c-fos and c-jun, on colorectal cancer cells. Human colon cancer cell, as well as their cytotoxic action on colorectal cancer cells has also been reported.

Antihyperuricemic activity

In the study on hyperuricemic mice induced by potassium salt, the butanol extract from S. dulcificum fruits reduced the elevated levels of serum uric acid in the treated animals.⁴

Exploration of its potential role in reducing sugar intake and promoting a balanced diet

High sugar consumption is harmful for health,which results in several chronic diseases. So natural sweeteners provide a better alternative, such as miracle fruit, because this tropical plant has the unique ability of changing a sour taste into sweet. A study has been performed, which aimed to characterise the temporal profile of miracle fruit and assess its sugar substitute power in sour beverages through time-intensity and temporal dominance of sensation tests. Results showed that miracle fruit seems to be a good sugar substitute, since it provides high intensity sweetness, reduced product sourness and absence of an aftertaste. Miracle fruit provided a sensory profile similar to that established and recognised sugar substitute in the market, so it is a good alternative for a natural substance, as a sweetening agent.⁸

Summary

Synsepalum dulcificum, commonly known as Miracle Fruit, offers a unique taste-altering property, making sour foods taste sweet. Beyond its novelty, it possesses nutritional value and has shown promising pharmacological properties, including antioxidant activity, anti-hyperuricemia effects, and potential improvements in insulin resistance. Moreover, its application in enhancing food palatability for chemotherapy patients and as a natural alternative to artificial sweeteners highlights its diverse health uses. Further research is warranted to fully understand its pharmacological potential and optimise its utilisation in various health contexts.