Biochemical studies on the effects of polyphenols from fermented and unfermented acetone extracts of cocoa (Theobroma cacao L.) seeds on antioxidant enzymes of streptozotocin-induced diabetic rats

Abstract

This study was carried out to investigate both the in vivo and in vitro antioxidant effects of polyphenols extracted from fermented and unfermented Theobroma cacao seeds with a view to using the extract in the management of hyperglycaemia-related conditions. Phytochemical screening of the aqueous extracts, total phenol and flavonoid quantifications were carried out using standard methods. DPPH free radicals scavenging, lipid peroxidation, reducing power and membrane stabilizing activities of the fermented (FP) and unfermented (UP) polyphenols were carried out in vitro. The effect of FP (which was the most potent from the in vitro assays) on antioxidant enzymes and liver function indices (150 mg/kg bwt and 300 mg/kg bwt) were investigated in diabetic and non-diabetic rats, with 2 mg/ kg bwt glimepiride as the reference drug. The FP and UP activities for DPPH radical scavenging were 93.72 ± 0.00 % and 77.69 ± 1.67 % at 50 μg/ml (IC50 23.94 ± 0.005/31.07 ± 0.570 μg/ml) which compared favourably with the reference chemical ascorbic acid (96.35 ± 0.03 %, IC50 17.43 ± 0.70 μg/ml), reducing power 1.17 ± 0.066 and 0.85 ± 0.023 at 300 μg/ml (Ascorbic acid 2.10 ± .008), lipid peroxidation 63.06 ± 4.17 % ,IC50 0.469  0.080 mg/ml and 70.45 ± 2.18 %, IC500.489  0.039 mg/ ml at 1000 μg/ml (with reference to BHT 63.20 ± 4.55 %, IC50 0.68 ± 0.064 mg/ml) and membrane stabilizing potential 33.25 ± 3.41 % and 28.17 ± 0.08 % at 350 μg/ml (with reference to ibuprofen 43.73 ± 2.98 %). The antioxidant and anti-diabetic activities of acetone extract of the fermented cocoa seeds on experimental rats compared favourably with the reference drug. However, the effects on antioxidant enzymes and liver function tests revealed that the 150 mg/kg bwt of the extract was quite effective.