The novel phytocomponent asiaticoside-D isolated from Centella asiatica exhibits monoamine oxidase-B inhibiting potential in the rotenone degenerated cerebral ganglions of Lumbricus terrestris

Abstract

Background: Centella asiatica (CA) is one of the most valuable herbal medicines widely being used for the treatment of various neurological ailments that are challenging for health-care providers and also is deemed to be safe and effective.Purpose: Monoamines (MAs) are neurotransmitters and neuromodulators that play a significant role in the neural communication, regulation of motor and cognitive functions in the brain. Neurodegeneration is associated with elevated levels of MAO-B that can lead to damaging reactive oxygen species (ROS) in the brain. The current study, evaluated the effects of asiaticoside-D (AD) from neuroprotective CA, on the levels and activities of monoamine oxidase A and B (MAO-A and B), in addition to the behavioral analysis.Methods: Qualitative and quantitative analyses of various solvent extracts of CA were performed. The extracts were screened for antioxidant potential using 1,1-diphenyl-2-picryl hydroxyl (DPPH), 2,2′-azinobis-3-ethylbenzothiozoline-6-sulfonic acid (ABTS), hydrogen peroxide (H2O2) radical, nitric oxide (NO) radical inhibition, lipid peroxidation (LPO) and ferric reducing antioxidant power (FRAP) assays. The purification of AD was done by column, thin layer and high-performance liquid chromatographies followed by structural elucidation using IR, HR–MS, 1H and 13C NMR spectra. Docking studies were performed to assess the impact of AD on MAO-A and B.In vivo, Lumbricus terrestris were exposed to 0.4 ppm rotenone (ROT) of medium for 7 days and were subjected to co-treatment along with 15 ppm of AD from CA. At the end of experiment period, the neuronal behavior of worms was assessed. Cerebral ganglions (CGs) were removed and the m-RNA levels of MAO-A and B were analyzed by Semi Q-PCR and their activities were also analyzed.Results: The ethanolic extracts exhibited higher antiradical activity against DPPH, ABTS, H2O2, LPO, FRAP, NO and vitamin C with EC50 value of 20.2, 20.9, 20.4, 22.0, 24.9, 28.1, 25.5 and 22.0 µg/ml respectively. Structural analysis by IR, HR-MS, 1H and 13C NMR spectrum have shown the structure of the isolated compound as (2α, 3β)-2,3–dihydroxyurs-12-en-28-oicacid-O-α-L-rhamnopyranosyl-(1→4)-O-β-d-glucopyranosyl (1→6)-β–copyranosyl ester and was represented as AD. In silico interaction of AD with MAO-A and B residues Lys312 at distances of 1.84 Å and 2.44 Å respectively was found to exhibit high binding energy of -9.4 and 7.4 kcal. The neuronal behavior using L. terrestris showed significant improvement against (p < 0.001) ROT impaired behavior (group II) on AD supplementation (p < 0.05). Further, the m-RNA levels and activities of MAO-A and B which were significantly altered (p < 0.001) by ROT could be effectively maintained on AD supplementation.Conclusion: AD was found to exert its negative impact on the levels and activities of MAO-A and B in CGs of rotenone- induced changes in L. terrestris, the property which is considered to be crucial against ROT induced neurodegenerative pathology like -Parkinsonism.