Accelerated identification of serine racemase inhibitor from Centella asiatica

Komal Rani,Annaian Shanmugam,Akanksha Singh,Saroj Kumar,Krishna Dalal,Alagiri Srinivasan,Mitali Tyagi,Mohit Mazumder,Manoj Pillai,Gourinath Samudrala

doi:10.1038/s41598-020-61494-1

Abstract

Serine racemase (SR) converts the free form of L-serine into D-serine (DS) in the mammalian brain. The DS functions as a co-agonist of N-methyl D-aspartate (NMDA) receptor. The over- activation of NMDA receptor leads to many neurological disorders like stroke, amyotrophic lateral sclerosis, Alzheimer’s disease and an effective inhibitor of SR could be a corrective method for the receptor over-activation. We report for the first time here a rapid way of purifying and identifying an inhibitor from medicinal plants known to have the neuro-protective effect. We have purified SR inhibitor from the methanolic extract of Centella asiatica by affinity method. High resolution mass spectrometry and infrared spectroscopy were used to identify the ligand to be madecassoside. We have shown the madecassoside binding in silico and its inhibition of recombinant human serine racemase in vitro and ex vivo.

Highlights

Serine racemase (SR) converts the free form of L-serine into D-serine (DS) in the mammalian brain
The identity of SR was confirmed by western blot analysis and mass spectrometry (Fig. 1, panels C and D)
As the Centella asiatica (CA) extract bound to SR, an increase in response units is seen when compared to buffer

Summary

Introduction

Serine racemase (SR) converts the free form of L-serine into D-serine (DS) in the mammalian brain. The over- activation of NMDA receptor leads to many neurological disorders like stroke, amyotrophic lateral sclerosis, Alzheimer’s disease and an effective inhibitor of SR could be a corrective method for the receptor over-activation. We report for the first time here a rapid way of purifying and identifying an inhibitor from medicinal plants known to have the neuro-protective effect. We have shown the madecassoside binding in silico and its inhibition of recombinant human serine racemase in vitro and ex vivo. The free DS functions as a co-agonist of N-methyl-D aspartate (NMDA) receptor in the brain[1], retina[2], keratinocytes[3] and in chondrocytes[4]. Inhibition of SR is another way to regulate the NMDA receptor transmission and is the only way to prevent serine isomerization occurring in proteins in certain pathological conditions including the AD. The triterpenoids of Centella asiatica (CA) and their derivatives have been shown to exert neuro-protective effects in the experimental model of AD30–32

Methods

Results

Conclusion