Analgesic and acetylcholinesterase inhibition potential of polyphenols from Scolopia crenata (Flacourtiaceae): An endemic medicinal plant of India

Abstract

Scolopia crenata (Wight & Arn.) Clos. (Flacourtiaceae), an endemic Indian medicinal tree is used traditionally to alleviate musculo-skeletal pain, to treat wounds and as sedatives in herbal formulations. In the present study, various solvent extracts from stem bark and leaves of S. crenata were quantified for bioactive secondary metabolites (total phenolics, tannins, total flavonoids, total proanthocyanidins, total monomeric anthocyanins and vitamin E) and assessed for radical scavenging and acetylcholinesterase (AChE) inhibitory abilities in vitro. The methanol extracts of stem bark and leaf showing promising activity was further assessed for in vivo analgesic activity employing acetic acid induced writhing and hot plate tests in mice. From the results, the methanol extracts from stem bark and leaf contained higher amounts of bioactive secondary metabolites and scavenged DPPH and ABTS+ effectively in vitro. They also showed a remarkable inhibition of AChE in vitro (IC50 9.20 and 5.64μg/ml, respectively). The mode of AChE inhibition was found to be non-competitive in leaf while competitive for stem bark extract. The methanol extracts of both leaf and stem bark significantly (p<0.05) reduced the number of writhing in acetic acid induced writhing test and prolonged the latency response in hot plate in a dose dependent manner. The plants extracts also showed a decreased analgesic effect in the presence of antagonists (atropine and mecamylamine) in the cholinergic system. HPLC analysis revealed the presence of phenolic acids (caffeic acid, p-coumaric acid, ferulic acid and gallic acid), flavonoids (apigenin, catechin, quercetin, luteolin, kaempferol and rutin) and a pentacyclic triterpeniod, betulinic acid in the methanol extracts of stem bark and leaf of S. crenata. The findings of the present study highlight the association of analgesic activity with AChE enzyme inhibition, involvement in cholinergic system and free radical scavenging potential of S. crenata as a choice for various pharmaceutical applications.