THE EFFECT OF Kigelia africana FRUIT EXTRACTS ON TOTAL SERUM BILIRUBIN LEVEL

ABSTRACT

Kigelia africana has long been used by rural and African countries to treat various illnesses. The antioxidant activity of the flavonoid-rich extract and methanol extract of Kigelia africana fruit was determined by evaluating the Ferric Reducing Antioxidant Power (FRAP) of the extracts using a modified method of Benzie and Strain (1996). Results revealed that the methanol extract had a significantly higher ability to reduce Fe3+ to Fe2+ than the flavonoidrich extract (p<0.05) at lower concentrations. At a concentration of 0.1mg/ml and 0.2mg/ml the methanol extract had a significantly higher (p<0.05) ability to reduce Fe3+ to Fe2+ (420 ± 0.00 and 580 ± 0.00mg Fe(II)/g extract) than the flavonoid-rich extract (260 ± 0.00 and 440 ± 0.00mg Fe(II)/g extract, respectively). There was no significant difference (p>0.05) between the FRAP values of the methanol extract and the flavonoid-rich extract at concentrations of 0.4mg/ml to 1.0mg/ml. Both extracts showed reducing capacity in a concentration dependant manner with the higher concentrations exhibiting higher reducing potential. There was no significant difference (p>0.05) between the FRAP value of the methanol extract at concentration 0.4mg/ml (800 ± 0.00mg Fe(II)/g extract) and the FRAP values at concentrations of 0.6mg/ml (820 ± 0.00mg Fe(II)/g extract), 0.8mg/ml (840 ± 0.00mg Fe(II)/g extract) and 1.0mg/ml(860 ± 0.00mg Fe(II)/g extract). The Fe(II) reduction potential of the flavonoid-rich extract showed no significant difference (p>0.05) at concentration 0.4mg/ml (690 ± 0.00mg Fe(II)/g extract) and at concentrations of 0.6mg/ml (780 ± 0.00mg Fe(II)/g extract), 0.8mg/ml (800 ± 0.00mg Fe(II)/g extract) and 1.0mg/ml (820 ± 0.00mg Fe(II)/g extract). The effect of Kigelia africana fruit extracts on bilirubin level of rats induced with complete Freund’s adjuvant (CFA) was investigated in this study. Adult Sprague Dawley rats weighing 100–230g of either sex were divided into ten experimental groups and used in this investigation. The groups include a normal control group, positive control group, negative control group, groups treated with dexamethasone or diclofenac (reference drugs), group treated with quercetin (standard flavonoid) and groups treated with varying doses of the flavonoid-rich extract and methanol extract of Kigelia africana fruit. Administration of complete Freund’s adjuvant significantly elevated total serum bilirubin level of the rats compared to normal and positive control rats. Methanol extract of Kigelia africana administered at the doses of 200 and 400mg/kg, significantly decreased the levels of total bilirubin in the serum by 32.22% and 21.51% respectively, compared to the negative control. Flavonoid-rich extract of Kigelia africana administered at the doses of 100 and 200mg/kg significantly decreased the levels of total bilirubin in the serum by 37.75% and 30.27% respectively, compared to the negative xi control. Reference drugs, dexamethasone and diclofenac sodium reduced the total bilirubin levels significantly by 36.71% and 29.37% respectively, compared to the negative control. Quercetin (a standard flavonoid) exhibited the highest percentage of inhibition (49.68%) compared to the negative control. Injection of CFA resulted in increased paw diameter of the rats as a result of inflammation. Treatment of rats with Kigelia africana fruit extracts significantly reduced oedema of the inflamed hindpaw compared to arthritic rats (negative control) thus indicating the anti-inflammatory effect of the extracts. The plant extracts showed a higher percentage of inhibition of paw oedema than the reference drugs, dexamethasone and diclofenac sodium. It was observed that higher doses of the extracts showed lower degree of inhibition. The flavonoid-rich extract of Kigelia africana administered at the dose of 100mg/kg showed a higher percentage of inhibition of paw oedema (37.36%) than the methanol extracts administered at the doses of 200 and 400mg/kg which showed 26.16% and 19.94% inhibition respectively, compared to the negative control. Quercetin (standard flavonoid) showed the greatest degree of inhibition of paw oedema. The presence of flavonoids in the fruit extract of Kigelia africana may be partly responsible for its antioxidant activity. The anti-inflammatory effects of the flavonoid-rich and methanol extract of Kigelia africana fruit may be as a result of their antioxidant characteristics and ability to suppress proinflammatory mediators. The results suggested that Kigelia africana may be beneficial in reducing serum bilirubin levels as well as oxidative stress in inflammatory diseases. However, further studies on the extracts of Kigelia africana fruit are required to understand the mechanism of its effect on serum bilirubin levels, its ameliorative effect on inflammatory diseases and to ascertain the safe doses of the fruit extracts in the management of inflammatory diseases.