Extraction and characterization of Vernonia oil and synthesis of N-(aminoalkyl) vernolamides and N,N' polymethylene bis (vernolamides)

Abstract

Vernonia galamensis is an annual herb found growing as a common weed in most parts of Africa, but its center of diversity is in East Africa. The dry seed of this plant consists of about 40% naturally epoxidized oil that contains 72-80% vernolic acid (cis-12, 13epoxyoctadec-9-enoic acid). This makes this plant an excellent source of naturally epoxidized triglyceride oil. The present study reports on the extraction of vernonia oil and the preparation of epoxy-containing aminoamides and diamides. The oil was extracted from different varieties of vernonia plant (var. Nairobensis; var. Ethiopica; var.galamensis) using both soxhlet and cold extraction methods. Soxhlet extraction was found to yield more oil (36-40%) that contains low content of vernolic acid, while cold extraction gave a slightly lower yield of oil (20-39%) that contains a high content of vernolic acid. VarEthiopica gave the highest yield in both extraction methods (39-40%), while var. galamensis gave the lowest yield (20-26%). Vernonia oil was then reacted with 1,2-diaminoethane; 1,3-diaminopropane; 1,4-diaminobutane and 1,6-diaminohexane to give the corresponding aminoamides [N-(2aminoethyl)vernolamide, N-(3-aminopropyl )vernolamide, N-(4-aminobutyl)vernolamide, N-(6-aminohexyl)vernol-amide)] and diamides [N,N' -Ethylene bis(vernolamide), N,N'trimethylene bis(vernolamide), N,N' -tetramethylene bis (vernolamide) and N,N'hexamethylene bis(vernolamide)] ofvernolic acid. The reaction of vernonia oil with I,4-diaminobutane was used to study the following different parameters which influenced aminolysis of the triglyceride: (i) Molar ratios of vernonia oil to diamine (1: I; 1:2; 1:3; 1:5; 1:7 and 1:10) (ii) Temperatures (room temperature, 500C, 600C and 700C). (iii) Reaction period. (iv) Solvents (without solvent, chloroform, tetrahydrofuran, carbon tetrachloride, acetonitrile and ethanol).