New limonoids from Aphanamixis polystachya (Wall) R. Parker (Meliaceae) leaves

The Meliaceae family, with 50 genera and more than 1400 species, belongs to the Sapindales order, which is among the richest and most diverse sources of secondary metabolites in the Angiospermae. The most abundant metabolites in few families of Sapindales (Meliaceae, Rutaceae, Simaroubaceae, Cneoraceae) are the tetranorditerpenes, known as limonoids, consisting of compounds with variations of the triterpene core structure. Limonoids are mainly distributed in the Meliaceae with a fascinating structural diversity (1,2), including a large number of cycles oxidation and rearrangement. These derivatives exhibited a wide range of biological activities on humans such as antibacterial, antifungal, antimalarial, anticancer, antiviral and a number of other pharmacological activities (3). Aphanamixis is an important genus in the Meliaceae. A series of compounds were isolated from plants of this genus, such as triterpenes, limonoids, lignans, flavonoids, and alkaloids (4). In the present study, a phytochemical investigation of Aphanamixis polystachya (Wall) R. Parker syn. A. rohituka (Roxb.) Pierre leaves was performed. The dried and powdered plant material was sequentially extracted with n-hexane, CHCl3, CHCl3:MeOH (9:1) and MeOH. The n-hexane extract was partitioned between n-hexane and a MeOH-H2O (3:2) mixture and the aqueous portion was dried and subjected to flash chromatography through Biotage IsoleraTM. The CHCl3 extract was also chromatographed through Biotage Isolera™ while the CHCl3:MeOH extract was separated on Sephadex LH-20 column. Subsequently, the fractions obtained from both flash chromatography and Sephadex LH-20 column chromatography were submitted to RP-HPLC. A lignan and four mexicanolide-type limonoids, including two new natural products (1 and 2) were characterized by 1D- and 2D-NMR and MS analyses.