Isolation and Characterization of an Amide, (2S)2-Hydroxy-N-((3R,4R)-1,3,4-Trihydroxytridecan-2-YL)Undecamide, from the Root Bark of Ficus exasperata (Vahl)

Abstract

Silica gel (70-230 mesh ASTM) was packed into a column (45 cm × 3 cm) using the dry method. About 7 g of extract was mixed with 30 g of silica gel and allowed to dry. It was then loaded onto the column and successively eluted initially with pet ether 100%, followed by 10%, 20%, 40%, 60%, 80% chloroform in pet-ether; followed by 100% chloroform; 20%, 50% ethyl acetate in chloroform; followed by 100% ethyl acetate and then 20% and 50% methanol in ethyl acetate. 25 fractions were collected in 50 ml aliquots and bulked together according to their TLC profiles and Rf.  The bulked fraction was further column chromatographed over silica gel (70-230 mesh) using a pipette and isocratically eluting with pet-ether: chloroform: methanol 67:25:8. 30 fractions of 2 ml each were collected. Compound C-3 (200 mg) was obtained from the fractions 1-15 as an off-white amorphous powder. The combination of IR, 1HNMR, 13CNMR, gCOSY, HMBC, HSQC and Mass spectral data on this off-white powder has led to an unambiguous assignment and the compound, an amide, isolated from the bioactive fraction of F. exasperata has the chemical name (2S)2-hydroxy-N-((3R,4R)-1,3,4-trihydroxytridecan-2-yl)undecamide. The acclaimed medicinal uses of this plant such as antihypertensive, anti-inflammatory, anti-arthritic, anti-ulcerogenic, anti-microbial and anti-oxidant, among others made it attractive to the authors.