Studies on Phytochemicals of Wedelia chinensis (Asteraceae) and Their Anticholinesterase & Antioxidant Activities

Abstract

This dissertation describes the results of phytochemical and Anticholinesterase & Antioxidant activities on the medicinal plant of the Wedelia chinensis. The whole research work has been divided into two parts. Part-A comprises with the chemical investigation of the Wedelia chinensis. Part-B deals with the study on biological activities on the fractions and isolated pure compounds. Extraction of the dried powder of whole plant of Wedelia chnensis was done by cold extraction method with methanol as solvent. Crude methanolic extract (CME) of the plant was further fractionated into four fractions; petroleum ether fraction (PEF), Chloroform fraction (ClF), Ethyl acetate fraction (EAF) and Dia-ion resin fraction (DRF). Chromatographic separation techniques were applied to isolate compounds from these fractions. The structures of these compounds were elucidated with the help of extensive spectroscopic techniques. The work has resulted in the isolation of seven compounds, out of which two were found to be new and one is isolated for the first time from this plant. From chemical investigation of the Dia-ion resin (DRF) and Ethyl acetate fraction (EAF), seven compounds were isolated and characterized; DFC-1, DFC-2, DFC-3, DFC-4, DFC-5, EFC-1, EFC-2. Among the isolated compounds, compounds DFC-4 and DFC-5 are new one. Compound DFC-1 was first time isolated from this plant, previously reported from Achyranthes Aspera.

In Part-B, Anticholinesterase & Antioxidant activities of the fractions as wel as pure compounds have been investigated. Results found are shown in decreasing order as follows: Reducing power capacity: Catechin ˃ DRF ˃ EAF ˃ CME ˃ CLF ˃ PEF. Catechin ˃ EFC-1 ˃ EFC-2. DFC-3 ˃ DFC-4 ˃ Catechin ˃ DFC-2 ˃ DFC-5 ˃ DFC-1 Total antioxidant activity DRF > EAF > Catechin > CME > CLF > PEF. EFC-1 > Catechin > EFC-2. DFC-3 > DFC-4 > Catechin > DFC-1 > DFC-5 > DFC-2 DPPH radical scavenging activity: Catechin ˃ EAF ˃ DRF ˃ CME ˃ CLF ˃ PEF. EFC-1 ˃ catechin ˃ EFC-2 . DFC-3 > Catechin ≈ DFC-4 > DFC-5 > DFC-2 > DFC-1. Hydroxyl radical scavenging activity DRF > Catechin > EAF > CME. EFC-1 > Catechin > EFC-2 . DFC-3 > Catechin ≈ DFC-2 > DFC-4 > DFC-1 > DFC-5. Lipid peroxidation inhibitory activity DRF > Catechin > EAF > CME. EFC-2 > Catechin > EFC-1. DFC-3 > DFC-4 > Catechin > DFC-2 > DFC-1 > DFC-5. Butyrylcholinesterase inhibitory activity  The results demonstrated that DRF and EAF exhibited strong enzyme inhibition activity among the other fractions evaluated. The compound EFC-2 has strong enzyme inhibition activity than EFC-1.  Butyrylcholinesterase inhibitory activity of isolated compounds (DFC-1, DFC- 2, DFC-3, DFC-4 and DFC-5) from dia-ion resin fraction has been investigated and IC50 (g/mL) values were found at 78, 48, 20, 45 and 22.5 μg/mL respectively.  From the IC50 (g/mL) values, it was evident that compound DFC-3 & DFC-5 are Butyrylcholinesterase inhibitory active. Acetylcholinesterase inhibitory activity  The results demonstrated that dia-ion resin fraction and ethyl acetate fraction exhibited strong enzyme inhibition activity among the other fractions.  From the result, it was evident that the compounds are acetylcholinesterase inhibition active and their activity decreases in the following order: Donepezol > EFC-2 > EFC-1 Dopenezol > DFC-3 > DFC-4 > DFC-5 > DFC-2 > DFC-1.