LIMONOIDS FROM AZADIRACHTA-EXCELSA

Activity-directed fractionation of a stem extract of Azadirachta excel sa using KB (human oral epidermoid carcinoma) cells led to the isolati on of four meliacin-type limonoids. Two of these constituents were nov el, namely, 2,3-dihydronimbolide and 3-deoxymethylnimbidate, and these were purified along with the known compounds, nimbolide and 28-deoxon imbolide. The structures of the new compounds were determined by spect roscopic methods. Nimbolide and 28-deoxonimbolide were broadly cytotox ic when evaluated against a panel of human cancer cell lines, while th e two novel compounds were inactive in this regard. The defection of n imbolide and 28-deoxonimbolide as cytotoxic constituents was facilitat ed by an electrospray LC/MS dereplication procedure. (C) 1998 Elsevier Science Ltd. All rights reserved.