Chemical Constituents from the Leaves of Macaranga heynei I.M. Johnson (Euphorbiaceae)

Prenylated flavonoids, stilbenoids and terpenoids are abundantly found in the genus of Macaranga, which belongs to the Euphorbiaceae family. This genus has been traditionally used to alleviate chest and hypochondrium pain. In 2018 and 2019, we have reported the discovery of four new compounds and three known compounds from Macaranga heynei which demonstrated significant activity on anticholinesterase and DPPH radical scavenging. Hence, an extensive investigation was carried out on this species to purify other chemical constituents with promising bioactivities. Two kilograms of M. heynei leaves were macerated in methanol for 24 hours at room temperature to obtain a crude methanolic extract (300 g). The crude extract was dissolved in 80% methanol:20% water, and partitioned with n-hexane and ethyl acetate. The crude ethyl acetate extract (150 g) was fractionated using vacuum liquid chromatography (VLC) with n- hexane:ethyl acetate gradient to give seven fractions (MH1-7). Fraction MH2 (360 mg) was subjected to column chromatography (CC) using the eluent chloroform:ethyl acetate in ascending polarity to afford a pure compound (1) (54.7 mg). Two pure compounds, (2) (4.0 mg) and (3) (0.5 mg), were obtained from fraction MH3 (11 g) after fractionation and purification using VLC (n-hexane:ethyl acetate), sephadex, radial chromatography and CC (chloroform:ethyl acetate). Based on the spectroscopic analyses and comparison with the literature data, the compounds were elucidated as macarubiginosin B (1) and two new compounds Y (2) and Z (3) ([Fig. 1]).

Fig. 1 Structure of compounds 1-3.

Funding This research is funded under Fundamental Research Grant Scheme (FRGS/1/2021/STG04/UITM/01/1).