Miracle fruit - Synsepalum dulcificum or Richadella dulcifica ?

Miracle fruit is a fruit  native to West Africa and has been known to Westerners since the 18th century.

Sour is sweet
Miracle fruit contains a protein called miraculin, which binds with the taste buds and acts as a sweetness inducer when it comes in contact with acids. During the 1970s, the Food and Drug Administration an extract of miraculin to be marketed as a sugar substitute. A no calorie sugar substitute to consider is
stevia sweetener.

Miracle fruit side effects
No side effects have yet been reported with miracle fruit in the medical literature.

Improvement of insulin resistance by miracle fruit ( Synsepalum dulcificum ) in fructose-rich chow-fed rats.
Phytother Res. 2006 Nov. Department of Emergency Medicine, Mackay Memorial Hospital and College of Oral Medicine, Taipei Medical University, Taipei City, Taiwan 10401, ROC.
In an attempt to probe a new target to improve insulin resistance, miracle fruit was employed to investigate the effect on insulin resistance induced by fructose-rich chow in rats. Single oral administration of the powder of Miracle fruit decreased the plasma glucose in a dose-dependent manner for 150 min in rats fed fructose-rich chow for 4 weeks. Oral administration of Miracle fruit (0.2 mg/kg) to fructose-rich chow fed rats, three times daily for 3 days, reversed the raised value of the glucose-insulin index, indicating that miracle fruit has the ability to improve insulin sensitivity. In conclusion, the results suggest that Miracle fruit may be used as an adjuvant for treating diabetic patients with insulin resistance because this fruit has the ability to improve insulin sensitivity.

Cortical representation of taste-modifying action of miracle fruit in humans.
Neuroimage. 2006 Dec;33(4):1145-51. Yamamoto C, Nagai H, Takahashi K, Nakagawa S, Yamaguchi M, Tonoike M, Yamamoto T. Department of Behavioral Physiology, Graduate School of Human Sciences, Osaka University, 1-2 Yamadaoka, Suita, Osaka 565-0871, Japan.
Red berries of a tropical plant called miracle fruit, Richadella dulcifica, reduce the sour and aversive taste of acids and add sweet and palatable taste. To elucidate the brain mechanism of this unique action of miracle fruit, we recorded taste-elicited magnetic fields of the human cerebral cortex. The initial taste responses were localized in the fronto-parietal opercular / insular cortex reported as the primary taste area. The mean latency of the response to citric acid after chewing miracle fruit was essentially the same as that for sucrose and was 250-300 ms longer than that for citric acid. Since it is known that stimulation with acids after the action of miracle fruit induces both sweetness and sourness responses in the primate taste nerves, the present results suggest that the sourness component of citric acid is greatly diminished at the level of subcortical relays, and mostly sweetness information reaches the cortical primary taste area.