Phenolic constituents and neuroprotective properties of African basil (Ocimum gratissimum Linn.) leaf and seed extracts in manganese-induced neurotoxicity in fruit flies (Drosophila melanogaster Meigen) model
摘要
Exposure to metals like manganese is often used to induce neurotoxicity in fruit flies. The leaves of African basil (AB) (Ocimum gratissimum Linn.) have been reported to possess neuroprotection, however, scientific data on protective property of AB seed is not sufficient. Hence, this study focuses on neuroprotective properties of AB leaf and seed aqueous extracts in manganese chloride (MnCl2)-induced neurotoxicity in fruit flies. Phenolics constituents of AB leaf and seed were determined using HPLC. Effects of treatment with AB leaf and seed extracts on survival and locomotor performance, respective activities and levels of glutathione S-transferase (GST), superoxide dismutase (SOD), catalase, total thiol, reactive oxygen species (ROS), thiobarbituric acid reactive species (TBARS), acetylcholinesterase (AChE) and monoamine oxidase (MAO) were determined. Syringic acid (104.30 mg/100 g and 108.82 mg/100 g), naringenin (118.92 mg/100 g and 124.20 mg/100 g) and isorhamnetin (120.61 mg/100 g and 113.86 mg/100 g) were the most dominant phenolic constituents in both AB leaf and seed; however, gallic acid (45.82 mg/100 g), protocatechuic acid (26.12 mg/100 g), rutin (59.82 mg/100 g) and quercetin (65.13 mg/100 g) were more prominent in leaf while P-coumaric acid (149.52 mg/100 g) and vanillic acid (23.87 mg/100 g) were more abundant in AB seed. Manganese caused significantly (P < 0.05) reduced survival (60.08%) and locomotor rates (63.17%) in flies, however, treatment with both AB leaf (84.19% and 82.68%) and seed (82.08%, 81.96% and 88.63%) increased these parameters. The significantly (P < 0.05) reduced GST (0.012 mmol/min/mg protein), SOD (14.86 µmol/min/mg protein), catalase (0.014 mmol H2O2 consumed/mg protein) and total thiol (0.24 mmol/mg protein) coupled with elevated ROS (3.12 µmol H2O2 produced/mg protein), TBARS (1.98 mmol/mg protein), AChE (0.24 µmol/min/mg protein) and MAO (1.92 mmol/mg protein) obtained in MnCl2-diet fed flies were positively reversed by treatment with both AB leaves and seeds extracts. Both leaves and seeds of AB had relatively same antioxidative and neuroprotective activities; hence, they could be consumed as food and explored as potent nutraceutical agents to alleviate oxidative stress related diseases, particularly, neurodegeneration.