Bioassay Guided Isolation and Identification of a Cytotoxic Compound from Azadirachta indica Leaves

This study aimed to investigate the structural features of the isolated flavonol glycoside, which might behave as a cytotoxic compound. The hexane, chloroform, ethyl acetate, and aqueous fractions of an 80% methanol solution of Neem (Azadirachta indica) (Family: Meliaceae) leaves were subjected to a cytotoxicity bioassay against brine shrimp, Artemia salina. The ethyl acetate fraction exhibited the highest cytotoxic effect, supported by the lowest lethal concentration, a LC₅₀ value of 1.35±0.40 ppm. A compound, Quercetin 3‐O‐β‐D‐glucopyranoside, was isolated from the most toxic fraction of the ethyl acetate via preparative liquid chromatography and then identified via ultraviolet‐visible (UV‐Vis), infrared (IR), mass spectrum (MS) and nuclear magnetic resonance (NMR) analyses. The compound was further confirmed by physical state, color, solubility, and melting point determination. The cytotoxic results suggest that the leaf ethyl acetate fraction consists of toxic compounds, which point towards the isolation of Quercetin 3‐O‐β‐D‐glucopyranoside.     

A New Megastigmane Palmitate and a New Oleanane Triterpenoid from Aster yomena Makino

A new megastigmane palmitate, 9‐oxomegastigm‐5(13)‐ene‐2β‐palmitate ( 1 ), and a new oleanane triterpenoid, (3β)‐3,23,28‐trihydroxyolean‐12‐en‐11‐one ( 2 ), together with three known oleanane‐type triterpenoids, β‐amyrin ( 3 ), erythrodiol ( 4 ), and (3β)‐olean‐12‐ene‐3,23,28‐triol ( 5 ), were isolated from the aerial parts of Aster yomena (Asteraceae). Their structures were identified based on 1D‐ and 2D‐NMR analysis, including ¹H,¹H‐COSY, HSQC, HMBC, and NOESY techniques.     

1H and 13C NMR assignments for two lignans from the heartwood of Streblus asper

In our ongoing investigation of the bioactive constituents from plants, two new lignans, magnolignan A-2-O-beta-D-glucopyranoside and strebluslignanol were isolated from heartwood of Streblus asper, along with three known lignans, magnolignan A, magnolol, and magnaldehyde D. 1D and 2D NMR experiments, including COSY, HMQC, and HMBC, and other spectroscopic methods, including UV, IR, and MS were used for the determination of the structures and NMR assignments. Primary bioassays showed that magnolignan A-2-O-beta-D-glucopyranoside and strebluslignanol have medium cytotoxic activity against HEp-2 and HepG2 cells, with IC(50) of 13.3 microM, 46.4 microM and 10.1 microM, 21.7 microM, respectively.