Chemical Constituents from Macaranga lowii King ex Hook.f. (Euphorbiaceae) and Their Effects on Antioxidant Activity

The genus Macaranga comprises about 300 species worldwide and is commonly distributed in the tropical region of Africa, Southeast Asia, China and India. The plant of this genus was reported to possess various medicinal properties which have been traditionally used to treat various illnesses such as fungal infection, malaria, stomachache, and diarrhoea. This genus also contains many phenolic compounds, particularly prenylated flavonoids and stilbenoids, followed by terpenoids and tannins. The phytochemical study on the crude acetone extract from the stem bark of Macaranga lowii was carried out to isolate chemical constituents using several chromatographic techniques and characterise the structure of the isolated compounds using various spectroscopic methods. The powdered stem bark of M. lowii (2.05 kg) was macerated in acetone for 24 hours at room temperature and repeated three times. The crude extract (38.8 g) was dissolved in methanol (200 mL) and fractionated with diethyl ether to reduce tannin and yield a crude extract with less tannin (10.9 g). The crude extract was subjected to vacuum liquid chromatography (VLC) to give nine semi-purified fractions (ML1-9). Fractionation and purification of fraction ML2 (448 mg) yielded compound 1 (6.2 mg) and 3 (0.3 mg). Fraction ML7 (220 mg) was subjected to radial chromatography (RC) to give a pure compound 2 (2.1 mg). The compounds were elucidated using Nuclear Magnetic Resonance (NMR), Ultraviolet-Visible (UV-Vis), Infrared (IR) and Mass spectrometry (MS), as well as comparison with the previous literature. Two phenolic compounds namely pentadecyl ferulate (1) and scopoletin (2) together with a sterol known as stigmasterol (3) were purified successfully from the stem bark of M. lowii. Scopoletin (2) exhibited moderate activity against DPPH radical scavenging with the IC50 value of 34.82 mM.