Crystal structure, phytochemical study and enzyme inhibition activity of Ajaconine and Delectinine

Abstract The Crystal structure, comparative DFT study and phytochemical investigation of atisine type C-20 diterpenoid alkaloid ajaconine ( 1 ) and lycoctonine type C-19 diterpenoid alkaloid delectinine ( 2 ) is reported here. These compounds were isolated from Delphinium chitralense . Both the natural products 1 and 2 crystallize in orthorhombic crystal system with identical space group of P 2 1 2 1 2 1 . The geometric parameters of both compounds were calculated with the help of DFT using B3LYP/6-31+G (p) basis set and HOMO-LUMO energies, optimized band gaps, global hardness, ionization potential, electron affinity and global electrophilicity are calculated. The compounds 1 and 2 were screened for acetyl cholinesterase and butyryl cholinesterase inhibition activities in a dose dependent manner followed by molecular docking to explore the possible inhibitory mechanism of ajaconine ( 1 ) and delectinine ( 2 ). The IC 50 values of tested compounds against AChE were observed as 12.61 μM (compound 1 ) and 5.04 μM (compound 2 ). The same experiments were performed for inhibition of BChE and IC 50 was observed to be 10.18 μM ( 1 ) and 9.21 μM ( 2 ). Promising inhibition activity was shown by both the compounds against AChE and BChE in comparison with standard drugs available in the market such as allanzanthane and galanthamine. The inhibition efficiency of both the natural products was determined in a dose dependent manner.