In vitro evaluation of the neuroprotective potential of Olea dioica against Aß peptide-induced toxicity in human neuroblastoma SH-SY5Y cells.

Alzheimer's disease (AD) is a type of neurodegenerative disease, associated with the hastening of ROS, acetylcholinesterase (AChE) activity, and amyloid ß peptides plaques in the brain. The limitations and side effects of existing synthetic drugs incline toward natural sources. In the present communication active principles of methanolic extract of Olea dioica Roxb, leaves are explored as an antioxidant, AChE inhibitor, and anti-amyloidogenic. Furthermore, neuroprotection against the amyloid beta-peptide has been studied. The bioactive principles were identified by GC-MS and LC-MS and further subjected to antioxidant (DPPH and FRAP) and neuroprotection (AChE inhibition, ThT binding, and MTT assay, DCFH-DA and lipid peroxidation (LPO) assay using neuroblastoma (SHSY-5Y) cell lines) assays. Methanolic extract of O. dioica Roxb, leaves was found to contain polyphenols and flavonoids. In vitro assays exhibited potential antioxidant and anti-AChE (˃50%) activities. ThT binding assay indicated protection against amyloid-beta aggregation. MTT assay, Aß1-40 (10 µM) with extract increase the cell viability (˃50%) and showed significant cytotoxicity to SHSY-5Y cells. ROS level (˃25%) significantly decreased in the Aß1-40 (10 µM) + extract (15 and 20 µM/mL) and LPO assay (˃50%) suggesting prevention of cell damage. Results advocate that O. dioica leaves are a good source of antioxidants, anti-AChE, and anti-amyloidogenic compounds which may be further evaluated as a natural medicine for the treatment of AD.

Homology modeling and docking studies on oxidosqualene cyclases associated with primary and secondary metabolism of Centella asiatica.

Centella asiatica is a well-known medicinal plant, produces large amount of triterpenoid saponins, collectively known as centelloids, with a wide-spectrum of pharmacological applications. Various strategies have been developed for the production of plant secondary metabolites in cell and tissue cultures; one of these is modular metabolic engineering, in which one of the competitive metabolic pathways is selectively suppressed to channelize precursor molecules for the production of desired molecules by another route. In plants the precursor 2,3-oxidosqualene is shared in between two competitive pathways involved with two isoforms of oxidosqualene cyclases. One is primary metabolic route for the synthesis of phytosterol like cycloartenol by cycloartenol synthase; another is secondary metabolic route for the synthesis of triterpenoid like ß-amyrin by ß-amyrin synthase. The present work is envisaged to evaluate specific negative modulators for cycloartenol synthase, to channelize the precursor molecule for the production of triterpenoids. As there are no experimentally determined structures for these enzymes reported in the literature, we have modeled the protein structures and were docked with a panel of ligands. Of the various modulators tested, ketoconazole has been evaluated as the negative modulator of primary metabolism that inhibits cycloartenol synthase specifically, while showing no interaction with ß-amyrin synthase. Amino acid substitution studies confirmed that, ketoconazole is specific modulator for cycloartenol synthase, LYS728 is the key amino acid for the interaction. Our present study is a novel approach for identifying a suitable specific positive modulator for the over production of desired triterpenoid secondary metabolites in the cell cultures of plants.