Fatty acids and sterols of coffee and mint suspension cultures

The cells of two plants, Coffea arabica and an unknown Mentha species, were grown as suspension cultures in liquid media, in order to analyse and compare the fatty acids and sterols of the cell cultures to those found in the parent plants. The cell growth, the parameters of pH and conductivity of the media, and the composition of the neutral lipid fraction were examined. In the case of the coffee cell cultures, the cell growth and the media pH and conductivity were studied in three different media, two defined and one undefined, while the mint cell cultures were studied in one other defined medium. Both coffee and mint cell cultures were grown in the absence of light (normal cultural conditions) and in the presence of light. The coffee cells showed no differences in growth rate due to variations in media composition. Exposure to light affected neither the growth rate nor initiated chlorophyll formation in the coffee cell cultures, although a distinct green pigmentation formed in the mint cells. A plot of the ionic conductivity of coffee and mint cell suspension cultures was essentially a mirror image of the growth curve of the respective culture. The fatty acids present in the neutral lipid fraction of the cells were studied via gas chromatography, and were compared to the fatty acids found in the seeds and tissues of the parent plants. Palmitate, stearate, oleate, linoleate and linolenate were found in all coffee and mint cell cultures, independent of the composition of the media and of the presence of absence of light. The appearance of short chain fatty acids (less than C-l6) occurred during the dying phases of culture. The fatty acid composition of the coffee cell cultures resembled the analyses of the leaf and stem tissues of the coffee plant rather than the coffee bean. The cell cultures all contained linolenate, not found in the coffee bean, and lacked arachidate, which was present in the bean. In contrast to the coffee cell, the mint cell fatty acids resembled the fatty acid composition of the mint seed rather than the parent plant tissues which contained substantial quantities of the short chain fatty acids (less than C-16). The total fatty acid content of the coffee and mint cell cultures was lower than the seeds of the parent plant, but was comparable to parent plant tissues. A decrease in the total fatty acid content of the neutral lipid fraction of both cultures was noted during the death phase of culture. The total fatty acid content of the coffee cell cultures was not altered by changes in media composition, nor by growth of the cultures in the presence of light. However, the growth of mint cell cultures ln the presence of light had a marked effect on the fatty acid content, which increased approximately four fold in comparison to cultures grown in the dark. The sterol composition of the unsaponifiable lipid found in the extracts of coffee and mint cell cultures was investigated via gas chromatography and thin layer chromatography. The sterols present were compared to those found in the seeds of the parent plants. The sterols found in large concentration in the coffee cells werep -sitosterol, stigmasterol and campesterol, while in the mint cells only ϐ -sitosterol was conspicuous. The predominant sterols found in the seeds of the parent plants and in the plant cell cultures were identical. However, the cell cultures of both coffee and mint contained larger amounts of sterols in their saponified lipid extracts than found in the seeds. Furthermore, in comparison to the seeds, the lipid extracts of the cell cultures contained greater quantities of unesterified sterols. A wide variety of sterols other than desmethyl sterols were located in the seeds and cell cultures, but were not identified as they constituted only a minor portion of the total plant sterols present. A large portion of the unsaponiflables of the coffee bean was characterized as non-steroidal. This non-steroidal material was identified as a mixture of two diterpenold alcohols, cafestoi and kawheol, both known to be major constituents of the unsaponiflables of coffee bean oil. The coffee cell oil unsaponifiables were also found to contain these two diterpenoid alcohols.Land and Food Systems, Faculty ofGraduat