Due to controversial reports on the component acids of Hibiscus sabdarifa seed fat and in anticipation of the co-occurrence of cyclopropene and epoxy acids in the seed oils of Malvaceae (especially in the genus Hibiscus)5,6 it was considered worthwhile to re-examine the seed oil of H . sabdarifla. Seed oil of H . sabduriflu (Malvaceae) contains myristic (2.1 %), palmitic (35.2 %), palmitoleic (2.0%), stearic (3.473, oleic (34.0 %), linoleic (14.6%) and three unusual HBr-reacting fatty acids. These acids are cis-12,13-epoxy-cis-9-octadecenoic (12,13-epoxyoleic), 4.5 %; sterculic, 2.9%; and malvalic, 1.3 %. Acetolysis of epoxide in the presence of cyclopropenes was effected by room temperature treatment with acetic acid-lO% sulphuric acid. Seed oils of Vernonia anthelmintica and Sterculia foetida were used as reference standards.

Seed oil ofPhyllanthus niruri (Euphorbiaceae) contains 1.2% ricinoleic (12‐hydroxy‐cis‐9‐octadecenoic) acid, previously unknown in the genusPhyllanthus. Identification is based on thin layer and gas liquid chromatography, infrared, nuclear magnetic resonance, and mass spectrometry analysis as well as chemical methods. Other major components of the oil are linoleic acid (21%) and linolenic acid (51.4%).

Seed oils ofSida acuta andSida rhombifolia were found to contain sterculic (11.0, 10.8%) and malvalic (1.7, 2.0%) acids respectively, in addition to the normal fatty acids. Co‐occurrence of these acids was established by gas liquid chromatography of the silver nitrate‐methanol‐treated methyl esters usingSterculia foetida esters as a reference standard. This gas liquid chromatography technique of quantitation was found most suitable to estimate these acids in low level cyclopropenoid acid‐containing seed oils.

Seed oils from seven species belonging to four botanical families have been analysed for their fatty acid composition by using chromatographic and spectroscopic techniques. Oils from six species are very interesting in containing high percentage (63.7–84.0%) of C18 unsaturated acids. Chemical screening of seed oils reveals that the species producing highly unsaturated oils merit attention for evaluation as perspective crops.

Seed oils of Mucuna pruriens (Leguminosae) and Urena lobatu (Malvaceae) were found to contain HBr-reacting acids to the extent of 1.3 and 10.8 "/D respectively.Acetylation of the M. pruriens seed oil, followed by saponification and separation of the acids, gave 12,13-dihydroxyoleic acid. From this and other evidence it is concluded that 12,13-epoxyoleic (vernolic) acid is present as aconstituent of the glycerides. On the other hand, the cyclopropenoid material in U. lobata oil was characterised as a mixture of malvalic (4.8 %) and sterculic (6 %) acids by the gas-liquid chromatography (g.1.c.) of the silver nitrate-methanol treated methyl esters. Seed oils of Vernoniu unthelminticu and Stercirlia foetidn were used as reference standards.