Chemical investigation of vegetable oils

Abstract

In this thesis are presented the author’s contributions towards the systematic analysis of some Indian vegetable oils and also the medicinal applications of some of them. These have been separated by combined fractionation and urea?adduct formation methods. The glyceride composition has also been determined. It is earnestly hoped that these studies would contribute to our knowledge of the chemistry and application of these oils.

The thesis consists of eleven chapters as detailed below:

Introduction This is a general introduction to the subject of the chemistry of oils and fats. It consists of a brief review of: (a) occurrence, (b) classification and nature, (c) extraction, (d) refining, (e) chemistry, and (f) requirements of Indian oils and fats.

A systematic study of the applicability of the Baudouin test for detecting adulteration in oils and ghee was undertaken with a Klett–Summerson photoelectric colorimeter. It is shown that adulteration of ghee to a minimum of 5 percent with commercial sesame oil can be detected by applying the Baudouin test. However, the Baudouin test is not applicable to heated oils.

Hydrogenation and Iodine Numbers The hydrogenation iodine numbers (HIN) of ten vegetable oils as well as of maleic acid monomethyl fumarate and methyl oleate have been determined using Powers’ micro?hydrogenation apparatus. This method gives a true degree of unsaturation of oils and is easier than the classical method of iodine value determination.

Mahua Oil (Madhuca indica) Mahua seed oil, available in plenty as a forest product, has a bad odour, dark red colour, and bitter taste. Soap prepared from this oil imparts a yellow colour to cloth. Attempts to refine this oil are recorded in this chapter. Mahua seed oil has been refined to a colourless, odourless, and tasteless oil by chromatography over alumina using carbon tetrachloride as eluent.

The chemical examination of the crude oil has been carried out. The mixed fatty acids of this oil consist of myristic (6.52%), palmitic (15.42%), stearic (13.44%), oleic (69.90%), and linoleic (13.21%) acids. The glyceride composition as determined by acetone–permanganate oxidation method is:

Trisaturated (6.3%),

Monounsaturated (18.3%),

Disaturated (55.5%),

Triunsaturated (19.9%).

Coconut Oil Coconut oil obtained by cold pressing of ripe, unacidified kernels has long been reputed to have medicinal properties. The mixed fatty acids consist of caprylic (8.57%), capric (10.14%), lauric (47.22%), myristic (22.54%), palmitic (7.72%), stearic (2.84%), oleic (0.07%), and linoleic (0.47%) acids. The glyceride composition is:

C3U (9.05%),

C2U (5.42%),

CU3 (85.53%).

Ponciana Oil This tree is abundant in India and its oil has not so far been completely investigated. The fatty acid composition has been determined both by ester?fractionation and urea?adduct methods. The mixed fatty acids consist of palmitic, oleic, and linoleic acids.

Other Oils (e.g., Cucurbita, Sesamum, etc.) Several other local oils have been examined for their chemical composition. Fatty acid composition was determined by ester?fractionation and urea?adduct methods.

Pharmacological Studies This chapter deals with the results obtained in pharmacological studies. Although sesamum oil does not show inhibitory action against common gram?positive and gram?negative bacteria, it is highly active in vitro against several strains of Mycobacterium tuberculosis. However, the results of in vivo studies with guinea pigs have not been successful.

Attempts Towards the Synthesis of Sesamin Experiments conducted towards the synthesis of sesamin are described. Of the five routes chalked out, one could be carried to the final stage. In this, p?hydroxybenzoylacetone was reduced with lithium aluminium hydride to give the corresponding compound which on cyclisation with polyphosphoric acid gave a chroman derivative resembling the skeleton structure of sesamin. Similar reactions with diethyl diphenylacetone gave two compounds (m.p. 145° and 155°) which are possibly two isomers of sesamin.

Collaborative Work Chapters VIII, IX, and X represent work done in collaboration with others.