Isolation of secondary metabolites from leaves of Globimetula oreophila parasitizing Azadirachta indica: a spectroscopic study

Abstract

Globimetula oreophila is a hemiparasitic plant commonly called mistletoe, found growing on several dicotyledonous trees using them as a host for its root-like structure called haustoria. Globimetula oreophila has been used to cure various ailments, including diarrhea, stomachache, headache, and malaria. This research study aims to isolate and characterize some phytochemical constituents in the ethyl acetate, n-butanol, and n-hexane fractions of Globimetula oreophila leaves. The powdered plant material was extracted with 70% ethanol using cold maceration. The crude extract was fractionated with n-hexane, chloroform, ethyl acetate, and n-butanol to produce the corresponding fractions. Physical and chemical tests, FTIR, UV–visible spectroscopy, 1D, and 2D NMR analysis elucidated the structures of the compounds. Column chromatographic separation of the n-butanol fraction led to the isolation of a yellowish amorphous substance coded DG1 and DG5 as 5, 7, 3’, 4’-tetrahydroxy-quercetin-3-O-α-L-rhamnopyranoside and 3, 5, 7, 3’, 4’-pentahydroxy flavones. Column chromatographic separation of the ethyl acetate fraction also led to the isolation of a white amorphous substance coded DG2 and a yellowish amorphous substance coded DG3 as 3,5-dimethoxy-4'-O-(2'',3''-dihydroxy-3-methyl-butyl)-dihydrostilbene and 2',4-dihydroxy-4'-methoxy chalcone. Compound DG4 was isolated as a white amorphous powder through the column separation of the n-hexane fraction and was found to be stigmasterol. Based on the findings of this study, it has been determined that the leaves of G. oreophila are a rich source of phytochemical constituents. These five compounds were isolated and reported for the first time in the plant with two being new to the genus, contributing to the chemical taxonomy of the plant.