Grapefruit is a subtropical citrus tree grown for its bitter fruit, which was originally named the “forbidden fruit of Barbados. The fruit was first documented in 1750 by Rev. Griffith Hughes describing specimens from Barbados. Currently, the grapefruit is said to be one of the “seven wonders of Barbados” [1].

Grapefruit is very useful in removing or dissolving inorganic calcium which may have formed in the cartilage of the joint as in arthritis, as a result of excessive consumption of devitalized white floor products (Wainwright and Martin, 2004) [1]. Grapefruit mercaptan, a sulfur-containing terpene, is one of the substances which have a strong influence on the taste and odour of grapefruit, compared with other citrus fruits [2].

A study in 2007 found a correlation between eating a quarter of grapefruit daily and a 30% increase in risk for breast cancer in postmenopausal women. The study points to the inhibition of CYP3A4 enzyme by grapefruit, which metabolizes estrogen. However, there is a study showing that grapefruit consumption may net increase breast cancer risk. Furthermore, related studies showed a significant decrease breast cancer risk with greater intake of grapefruit in women who never used hormone therapy [3]. Grapefruit can have a number of interactions with drugs, often increasing the effective potency of compounds. Grapefruit contains naringin, bergamottin and dihydroxybergamottin, which inhibit the protein isoform CYP3A4 predominantly in the small intestine rather than liver. It is via inhibition of this enzyme that grapefruit increases the effects of a variety of drugs by increasing their bioavailability. The effect of grapefruit juice with regard to drug absorption was originally discovered in 1989. However, the effect became well-policized after being responsible for a number of deaths due to overdosing on medication [4-6].

Experimental animals

Twenty mature male Wistar rats (160-225 g) obtained from an animal house in Ladoke Akintola University, Ogbomoso, Nigeria were acclimatized for two weeks in well ventilated animal house with a constant 12 hour light: 12 hour dark lighting schedule and comfortable temperature of 27 ± 2°C. The animals were housed in wire gauzed cage with wood chip beddings. They were fed with growers’ marsh pellet diet (obtained from Bendel Feeds Limited, Ilorin, Kwara State) and water was given ad libitunm.

Extract preparation

Citrus paradisi was purchased from local commercial sources. Botanical identification and authentication was done at the Botany department of the University of Ilorin. The fruits were cut into two halves and a juice extractor was used to extract the juice. The extracted juice was then sieved to obtain a clear sample of the juice. The extract was evaporated to reduce the water content of the juice and obtain a desired concentrate. The pH of the extract before evaporation was 3.48 at 30.1°C and was 2.9 at 30.1°C after evaporation.

Experimental design

Twenty adult male Wistar rats were divided into four groups:

Group A: 0.6 ml/gBW/day orally for 14 days

Group B: 0.8 ml/gBW/day orally for 14 days

Group C: 1.0 ml/gBW/day orally for 14 days

Group D: Control- Water only

Animal sacrifice

The rats were sacrificed twenty four hours after the administration of the last dose. The skulls of the rats were opened up using a bone crusher and the cerebellum was carefully dissected out and quickly fixed in 10% formal saline for routine histological study using H/E stain.

Histological

The cerebellum of the control group showed normal histological features, illustrating a well defined molecular, granular and Purkinje layers and presence of numerous closely packed small cells in the granular layer as well a large Purkinje cells in the Purkinje cell layer. The cerebellum of experimental group B and C (Figure 2 and 3) showed a dose dependent cellular degeneration and atrophy thus leading to a decrease in number of cells in the granular and Purkinje layers respectively. These changes were most pronounced in the group with the highest dose (group C which received 1 ml/gBW/day) of grapefruit juice extract, followed by the group with the medium dose (group B which received 0.8 ml/gBW/day) of the extract. The group that received the least dose of the extract (group B which received 0.6 ml/gBW/ day) showed a normal cytoarchitecture of the cerebellum with a slight increase in number of granule cells in the granular layer.

The results of the Haematoxylin and eosin staining (H & E) reactions showed (Figure 1 and 4) a dose dependent cellular degeneration of the granular layer. Atrophic changes were observed in the Purkinje cells and granule cells; these were more pronounced in those that received 1.0 ml/gBW/day of grapefruit extract. The increase in cellular degeneration of the granule and Purkinje cells in the experimental groups as reported in this study might have been as a result of cellular atrophy; its mechanism is not yet clear. The actual mechanism by which grapefruit juice extract induced cellular degeneration observed in this experiment needs further investigation.

Figure 1: Showing photomicrograph of the Cerebellum of an adult male Wistar rat (Group A) given 0.6ml of grapefruit juice. Using H&E stain (Mag. X400). GL: granule layer.

Figure 2: Showing photomicrograph showing of the Cerebellum of an adult male Wistar rat (Group B) given 0.8ml of grapefruit juice. Using H&E stain (Mag. X400). GC: granule cell.

Figure 3: Showing photomicrograph of the Cerebellum of an adult male Wistar rat (Group C) given 1.0ml of grapefruit juice. Using H&E stain (Mag. X400).

Figure 4: Showing photomicrograph of the Cerebellum of an adult male Wistar rat (Group D) distilled water. Using H&E stain (Mag. X400). WM: white matter PCL: Purkinje cell layer; PC: Purkinje cell; ML: molecular layer.

Degenerative changes have been reported to result in cell death, which is of two types, namely apoptotic and necrotic cell death. These two types differ morphologically and biochemically [7]. Pathological or accidental cell death is regarded as necrotic and could result from extrinsic insults to the cell such as osmotic, thermal, toxic and traumatic effects.

In this experiment grapefruit juice could have acted as toxins to the cells of the cerebellum. The process of cellular necrosis involves disruption of the structural and functional integrity which was a landmark of this experiment. In cellular necrosis, the rate of progression depends on the severity of the environmental insults. The greater the severity of insults, the more rapid the progression of cellular injury [8]. It may be inferred from the present results that high dose of grapefruit juice extract resulted in a dose-dependent toxic effects on the cerebellum.