BIOCHEMICAL, NUTRITIONAL AND TOXICOLOGICAL STUDIES ON THREE VARIETIES OF LABLAB PURPUREUS (L.) SWEET SEEDS

Abstract

Lablab purpureus is a lesser-known legume in Southwest Nigeria that could meet the protein requirement of people in the tropics. There is a need for investigation to ascertain its full potential. The biochemical, nutritional and toxicological effects of three varieties of Lablab purpureus seeds were investigated in male albino Wistar rats. The three varieties of the seeds used were Rongai Brown, P₁ 509 114 (RB), Rongai White, NAPRI 4 (RW) and Highworth Black, Grif 12293 (HB). Proximate composition, Anti-nutritional Factors (ANF) and protein quality were determined using standard analytical procedures. Sixty-five male albino Wistar rats divided into control, RB, RW and HB groups were used for the studies. Changes in the haematological, serum biochemical and histological parameters following ad libitum feeding of L purpureus were used as indices of toxicity with standard biomarkers and analytical procedures. Biomarkers of oxidative injury to the liver, kidney and testes were also used to assess the level of toxicity. The control group received standard feed. The biochemical characterization of L. purpureus seed proteins was done using Sodium Dodetyl Sulphate Polyacrylamide Gel Electrophoresis (SDS-PAGE). Data were analysed using Analysis of Variance (ANOVA) and Student t-test at p=0.05. The three varieties of L. purpureus contained crude protein ranging from 22.8% to 24.2% and the crude fibre were appreciably high ranging from 12.7% to 13.1%. Trypsin inhibitors, haemaglutinnins, cyanogenic glucosides, oxalates, phytates, tannins, saponins and alkaloids were found in the three varieties or L. purpureous. All the rats placed on the three raw L. purpureous diets had low values of protein efficiency ratios, net protein ratio and protein retention efficiency. Compared with the control group, feeding the RB, RW and HB seeds for seven days produced, significant reductions in the concentrations of red blood cells (5.0±0.4. 6.5±0.4 and 5.8±0.2x10¹²/L), haemoglobin (9.0±0.7, 11.6±0.5 and 10.7±0.2g/dL) and packed cell volume (30.4 ± 1.5, 35.4±1.5 and 32.4±1.8%) respectively. The RB, RW and HD seeds produced significant increases in the activities of serum alanine aminotransferase (74.5±4.7, 40.8±3.5 and 53.8±1.9 U/L), aspartate aminotransferase (266.5±21.7, 173.3±11.1 and 235.5 ±10.1 U/L), alkaline phosphatase (341.8±35.4, 155.0±2.9 and 177.0±6.4 U/L) and gamma glutamyl transferase (29.8±3.0, 13.8±1.6 and 21.5 ±0.6U/L). Similarly, there was an increase in urea (89.0±5.0, 45.7±1.5 and 65.5±3.9mg/dl) and creatinine (1.1±0.1, 0.5±0.1 and 0.8±0.1 mg/dl) levels. Histology of the rat liver revealed mild congestion of hepatic blood vessels and severe diffuse hepatic necrosis. The kidneys showed moderate congestion of blood vessels with focal haemorrhages, while the testes showed degeneration and necrosis of seminiferous epithelial cells. Lablab purpureous could be a good source of protein for poor countries of the world. However, it induced alterations in the hepatic, nephrotic and testicular antioxidant systems, impaired testicular and epididymal sperm function. Proper processing is necessary to reduce the anti-nutritional factors.